Maintenance of Remote Communication Facility (Rcf)

Home , Antenna farm, Antiresonance, Crystal oven, Fade margin, Independent sideband, Overmodulation

ORDER rlll,,

J MAINTENANCE OF REMOTE commucf~TIoN FACILITY (RCF) EQUIPMENTS

OCTOBER 16, 1989

U.S. DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION AbMINISTRATION

Distribution: Selected Airway Facilities Field Initiated By: ASM- 156 and Regional Offices, ZAF-600 10/16/89 6580.5

FOREWORD 1. PURPOSE. direction authorized by the Systems Maintenance Service. This handbook provides guidance and prescribes techni- Referenceslocated in the chapters of this handbook entitled cal standardsand tolerances,and proceduresapplicable to the Standardsand Tolerances,Periodic Maintenance, and Main- maintenance and inspection of remote communication tenance Procedures shall indicate to the user whether this facility (RCF) equipment. It also provides information on handbook and/or the equipment instruction books shall be special methodsand techniquesthat will enablemaintenance consulted for a particular standard,key inspection element or personnel to achieve optimum performancefrom the equip- performance parameter, performance check, maintenance ment. This information augmentsinformation available in in- task, or maintenanceprocedure. struction books and other handbooks, and complements b. Order 6032.1A, Modifications to Ground Facilities, Order 6000.15A, General Maintenance Handbook for Air- Systems,and Equipment in the National Airspace System, way Facilities. contains comprehensivepolicy and direction concerning the development, authorization, implementation, and recording 2. DISTRIBUTION. of modifications to facilities, systems,andequipment in com- This directive is distributed to selectedoffices and services missioned status. It supersedesall instructions published in within Washington headquarters,the FAA Technical Center, earlier editions of maintenance technical handbooksand re- the Mike Monroney Aeronautical Center, regional Airway lated directives . Facilities divisions, and Airway Facilities field offices having the following facilities/equipment: AFSS, ARTCC, ATCT, 6. FORMS LISTING. EARTS, FSS, MAPS, RAPCO, TRACO, IFST, RCAG, RCO, RTR, and SSO. a. Use FAA Form 6600-6, Technical Performance Record, VHF/UHF Air/Ground Receivers/Transmitters, to record the performance of very-high-frequency (vhf) and : 3. CANCELLATION. This order cancels Orders 6600.22A, Maintenance of ultra-high-frequency (uhf) transmitters, receivers, and Point-to-Point and Air-Ground Communication Transmitting transceivers.This form is available under NSN 0052-00-874- 2000, unit of issue: PD. and Receiving Equipment, and 6630.2A, Maintenance of Communication Antennas and Transmission Lines. b. Use FAA Form 6610-1, Technical Performance Record, SSB-AM Transmitter, High Frequency Point-to- 4. MAJOR CHANGES. Point/Broadcast, to record the performance of transmitters This handbook revises, updates,and combines the infor- using the 3MHz-to-30MHz frequency band. This order form ” mation previously contained in threeorders: Order 6600.22A, is available under NSN 0052-00-874-0000,unit of issue:PD. Maintenance of Point-to-Point and Air-Ground Communica- c. Use FAA Form 6620-1, Technical Performance tion Transmitting and Receiving Equipment:.Order 6630.2A, Record, SSB-AM Receiver, High Frequency Point-to- . Maintenanceof Communication Antennas and Transmission Point/Broadcast,to record the performanceof receivers using Lines; and canceled Order 6520.4A, Maintenance Concept the 3MHz-to-3OMHz frequency band. This form is available for Remote Transmitter/Receiver Class 0 (RTR-0) and under NSN 0052-00-874-1000, unit of issue: PD. RemoteCommunications Outlet Class0 @ZO-0) Facilities. (Order 6520.4A was canceledby the directives checklist WA d. Use FAA Form 6000-8, Technical Performance 0000.4G.) Record-Continuation or Temporary Record/ReportForm, to record miscellaneousperformance information prescribed in 5. MAINTENANCE AND MODIFICATION POLICY. chapter 4 of this order, for transmitters, receivers, a. Order 6000.15A, this handbook, and the applicable transceivers,or ancillary equipment. This form is available equipment instruction books shall be consulted and used under NSN 0052-00-686-0001, unit of issue: PD. together by the maintenancetechnician in all duties and ac- I tivities for the maintenance of remote communication e. Use FAA Form 6050-3, Frequency Interference facilities. The threedocuments shall be consideredcollective- Report, when needed. This form is available under NSN 0052-00-837-1000,unit of issue: SE. I) ly as the single official source of maintenance policy and f Page i 6580.5 1 O/l 6189

7. RECOMMENDATIONS FOR IMPROVEMENT. Clearance Procedures for Airway Facilities Maintenance Preaddressedcomment sheetsare provided at the back of Directives. Usersare encouraged to this handbookin accordancewith Order 1320.40B,Expedited for improvement.

I W. PeterKochis Director, Systems Maintenance Service

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TABLE OF CONTENTS

Chapter 1. GENERAL INFORMATION AND REQUIREMENTS

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1. Objective...... 1 2. Scope and Coverage ...... 1 3. Aircraft Accident ...... 1 4. Receiver Sensitivity and Transmitter Power ...... 2 Output Adjustment Policy 5. Certification Requirements ...... 2 Precautions When Using Test Tones ...... 2 ;- Nonstandard Facilities ...... 2 8: Authorized Emissions ...... 2 9.-l 9. Reserved.

Chapter 2. TECHNICAL CHARACTERISTICS . 20. PurposeorFunction ...... 5 21 e-23. Reserved.

Section 1. RCF DESCRIPTION

Subsection 1. HIGH-FREQUENCY (HF) RCF

24. HF Point-to-Point (PTP) and Air-to-Ground (A-G) ...... 9 25. HFVoiceBroadcast ...... -...... 9 26.-29. Reserved.

Subsection 2. VHF AND UHF RCF

Air Traffic Control/Service ...... , ...... 12 Extended Remote Center Air-to-Ground (ERCAG) ...... 12 Communication Facilities * 32. Remote Transmjtter/Receiver Class 0 (RTR-0 and ...... 12 Remote Communications Outlet Class 0 (RCO- b ) Communication Facilities 33. -35. Reserved. . Section 2. HF EQUIPMENTDESCRIPTION General E* Modes of Operation‘ l : : : : : : : : : : : : : : : : : : : : :I 38. -39: Reserved. Subsection 1. RF EQUIPMENT 40. HF Transmitters HF Receivers . . : : : : : : : : : : : : : : : : : : : : : : ii! 42. -:k Reserved. . Subsection 2. TRANSMISSION LINES 44::Generalreserved...... 20 Page Iii 1 o/23/95 : 6580.5 CHG 5

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Subsection 3. ANTENNAS

46. General ...... -.. 20 47. HF Point-to-Point and Broadcast Antennas ...... 20 48. Ground-Mobile Antennas ...... 27 49.40. Reserved.

Subsection 4. WAVE PROPAGATION

51. General ...... 35 52. Basic ...... ~. 35 53. Structure of the Ionosphere ...... 35 54. Skywave Transmission Geometry ...... 37 55. Groundwave and Scatter Propagation ...... 38 56. Ionospheric Variations ...... 38 57. Reliability of HF Circuits ...... 42 58.-59. Reserved.

Section 3. VHF AND UHF EQUIPVENT DESCRIPTION

60. General ...... 42 61.-62. Resewed.

Subsection 1. RF EQUIPMENT

63. ITT Models AN/GRT-21 (VHF) and AN/GRT-22 (UHF) Transmitters ...... 42 64. Wulfsberg Model WT-100 (VHF) Transmitters ...... 47 65. ITT Models AN/GRR-23 (VHF) and AN/GRR-24 (UHF) Receivers ...... 49 ” 66. Wulfsberg Model WR-100 (VHF) Receiver ...... 49 67. Motorola Models CM-200 UT and CM-200 VT Transmitters ...... 52 68. Motorola Models CM-200 UR and CM-200 VR Receivers ...... 52-2 * 69. Motorola Models CM-50 (VHF)/CM-51 (UHF) Linear Power Amplifiers (LPA). . . 52-3 *

Subsection 2. TRANSMISSION LINES

70. General ...... 52-3 71. Combiners and Multicouplers ...... 52 - 3 Subsection 3. ANTENNAS

72. General ...... 54 73. VHF Single Input Antennas ...... 54 74. UHF Single Input Antennas ...... 55 75. VHF Dual Input Antennas 55 76. UHF Dual Input Antennas .. 57 77. VHF/UHF Dual Input Antennas 57 78. VHF Omnidirectional Gain Antennas ;77 79. VHF Directional Gain Antennas...... 80.-81. Reserved. 82. Ground-Mobile and Base-Station Antennas ...... 57 83. Radio Link Antennas ...... 58

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84-89. Reserved.

Subsection 4. WAVE PROPAGATION

General ...... 59 Basic...... 59 WaveGeometry ...... 59 Factors Affecting Coverage ...... ; ...... 61 Coverage and Reliability Analysis ...... 61 Reserved.

Chapter 3. STANDARDS AND TOLERANCES

100. General ...... 65 101. Notes and Conditions ...... 65 102. References ...... 66 103.-l 09. Reserved.

Section 1. HIGH FREQUENCY EQUIPMENT

Subsection 1. TRANSMllTERS

110. Model 1330 5KW AM and Ssb Transmitter ...... 66 111. Model 1311 1 KW AM and Ssb Transmitter ...... 66 112. Model 127-l Converter-Driver 113. Model125-1Sband125-3IsbG;inerato;’::::::::::::::::::::::::: :; 114. Model GPT-1 OfQV AM and Ssb Transmitter...... 67 115-l 17. Reserved.

Subsection 2. RECEIVERS

118. Model 2210 AM and Ssb Receiver . . . y ...... 69 119.-123. Reserved.

Section 2. VHF AND UHF EQUIPMENT

Subsectidn 1. TRANSMITTERS

124. VHF and UHF Transmitters, Types AN/GRT-21, AN/GRT-22, ...... 70 and WT-100 125. Miscellaneous Parameters ...... m...... 71 126. High Power VHF Transmitter, Aerocom, Type 7023 ...... 71 127.-l 30. Reserved.

Subsection 2. RECEIVERS

131. VHF and UHF Receivers, Type AN/GRR-23 and AN/GRR-24 ...... 71 132. VHF Receiver, Type WR-100 ...... 73 133. High-Gain VHF Receiver, Aerocom, Type 8080 ...... 74 %- 134. VHF and UHF Receivers, Type CM-200 VR and CM-ZOO UR ...... 75 135.-139. Reserved. * Pagev 6580.5 CHG 4 212195

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Section 3. ANTENNAS AND TRANSMISSION LINES

140. Insulation Resistance, Antennas ...... 76-l 141. Insulation Resistance, Transmission Lines ...... 76-1 142. System Insulation Resistance ...... 76-l 143. SWRMeasuredatAntenna ...... 76-I 144. DC Series Resistance ...... 76-q 145. Transmission Line Loss ...... 76-q 146.-159. Reserved.

Chapter 4. PERIODIC MAINTENANCE

160. Get-h-al ...... 77 161.-l 64. Reserved.

Section 1. PERFORMANCE CHECKS

Subsection 1. HF TRANSMITTERS

165. Quarterly...... 77 166. Semiannuaily ...... 77 167. Annually ...... 77 168.-169. Reserved.

Subsection 2. HF RECEIVERS

170. Quarterly ...... 78 171. Semiannually ...... 78 172. Annually ...... 78 173.-l 74. Reserved.

Subsection 3. VHF AND UHF TRANSMITTERS * * 175. Withdrawn-CHG 4 . 176. Semiannua(ly...... 79 177.-l 79. Reserved.

Subsection 4. VHF AND UHF RECEIVERS

* -180. Withdrawn--C& 4 * . 181. Semiannua~y...... ~...... 80 182. Annuafly...... -~....~..~...~ 81 183.-l 84. Reserved.

Subsection 5. ANTENNAS AND TRANSMISSION LINES

185. Annually...... 81 186.-l 89. Reserved.

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Paragraph Page r Section 2. OTHER MAINTENANCE TASKS

Subsection 1. TRANSMITTERS

Quarterly...... 81 Semiannually ...... 82 Reserved.

Subsection 2. RECEIVERS * * 195. Quarterly ...... 82 196.-l 99. Reserved.

Subsection 3. ANTENNAS AND TRANSMISSION LINES

200. Annually ...... 82 20 1.224. Reserved.

Chapter 5. MAINTENANCE PROCEDURES

225. General ...... 85 226. Instruction Book References ...... 85 227. TestEquipment ...... 85 228. Physical Repair and Maintenance of Cables ...... 85 229.-234. Reserved.

Section 1. PERFORMANCE CHECK PROCEDURES

235. Technical Performance Records...... 88 236. Entries in Technical Performance Records ...... 88 237. Aural Monitoring ...... 93 238.-239. Reserved.

Subsection 1. TRANSMITTER CHECKS

240. Transmitter Output Power and Standing-Wave Ratio (SWR) ...... 94 241. Transmitter Audio Modulation Level and Percentage ...... 95 242. Spurious Emissions and Intermodulation Distortion ([MD) ...... 97 243. Frequency Stability ...... 97 244.-249. Reserved.

Subsection 2. RECEIVER CHECKS

250. Sensitivity ...... 99 251. SquelchThreshold ...... 100 252. Selectivity and Nonsymmetry Measurements ...... 100 253. Frequency Stability ...... 102 254. Automatic Volume Control (AVC) Action ...... 103 255.-259. Reserved. m Pagevii 6580.5 10/16/89

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Subsection 3. ANTENNAS AND TRANSMISSION LINES

260. Measuring Transmission Line Loss ...... 104 261. Measuring SWR on Coaxial Transmission Lines ...... 104 262. Measuring SWR on Open-Wire Transmission Lines ...... 107 263. Receiving Antenna and Transmission Line Tests ...... 108 264.-269. Reserved.

Section 2. OTHER MAINTENANCE TASKS PROCEDURES

Subsection 1. TRANSMllTERS

270. General ...... 108 271.-279. Reserved.

Subsection 2. RECEIVERS

280.-289. Reserved.

Subsection 3. ANTENNAS AND TRANSMISSION LINES

290. Measuring Insulation Resistance of Antennas ...... m_ ...... 108 291. Measuring tnsulation Resistance of Transmission Lines ...... 108 292. Measuring DC Series Resistance ...... I ...... - ...... 109 293. Alternative Checks for Shorted-Stub, Balun-Input _ ...... 109 TACO, DHV Antennas 294.-299. Reserved.

Section 3. SPECIAL MAINTENANCE PROCEDURES

300. Time-Domain Reflectometer Tests on Transmission Lines ...... 109 301. Testing for Stray Coaxial Line Radiation ...... 109 302. Open-Wire Transmission Line Balance ...... _ ...... 109 303. Radiation Pattern Ground Check ...... 110 304. SWR Loss Check of Old Coaxial Transmission Lines ...... 111 305-314. Reserved.

Chapter 6. FLIGHT INSPECTION

315. General ...... 113 316. Activities That May Require a Confirming Flight Inspection ...... _ . . 113 317. Activities Not Requiring a Confirming Flight Inspection ...... 113 318.-324. Reserved.

Chapter 7. MISCELLANEOUS

325. General ...... 115 326. Expansion and Contraction ...... 115 327. Interfacing AN/GRR-23 and AN/GRR-24 Type Receivers to . . = ...... II5 Telco Equipment

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APPENDIX 1. GLOSSARY

APPENDIX 2. BASIC TESTS FOR TRANSMITTERS AND RECEIVERS

1. General ...... 1 2. Transmitter Output Power ...... 1 3. Transmitter Modulation ...... 3 4. SpuriousEmission ...... *...... : 6 5. RF Signal Generators and the Communication Service...... 6 Monitor (CSM) Receiver Sensitivity ...... 7 Receiver Selectivity and IF Bandpass Symmetry ...... 7 Frequency Stability 7 MiscellaneousTests ...... 7 Figure 1. Three Methods for Metering Output Power in an Ssb Transmitter ...... 2 Figure 2. Correlation of Peak Envelope and Average Power in an Ssb Transmitter ...... 3 Figure 3. Spectrum Analyzer and Oscilloscope Patterns of Two-Tone Ssb Tests ...... 4 Figure 4. Relationship of Two-Tone Amplitudes to Carrier and Intermodulation Distortion in an Ssb Signal ...... 5 Figure 5. Typical Receiver IF Selectivity Response ...... 8

APPENDIX 3. TRANSMITTER AMPLITUDE MODULATION (AM) MEASUREMENTS

1. General ...... 1 2. The Trapezoidal Pattern ...... 1 3. The Envelope Pattern ...... 1 4. Modulation Adjustment Techniques ...... 1 Figure 1. Modulation Measurement by the Trapezoidal Pattern ..... 2 Figure 2. Modulation Measurement by the Envelope Pattern ...... 2 Figure 3. Production of Trapezoidal Pattern ...... 3 Figure 4. Various Trapezoidal Patterns ...... 4 Figure 5. Various Envelope Patterns ...... 4 Figure 6. Nomograph for Percentage of Modulation, 50 to 95 Percent 5 Figure 7. Nomograph for Percentage’of f&dulat~on,btd * ’ ’ ’ ’ ’ ’ ’ ’ 60 Percent ...... 6

APPENDIX 4. REFERENCE DATA FOR AUDIO FREQUENCY MEASUREMENTS

1. General ...... 1 2. DB-VU-DBM Unit Conversion ...... 1 3. RMS Volts to Power Level Conversion ...... 1 4. Meter Correction Graph ...... 1 5. Decibels Above and Below a 1 -Milliwatt ...... 1 Reference Level 6. Conversion of Noise Units ...... 2 Table 1. Decibels Above and Below a Reference Level of 1 mW into 600 Ohms ...... 2

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Figure 1. DB-VU-DBM Unit Conversion Chart 3 Figure 2. RMS Voltage to Power Level Conversion Chart ’ : : : : : : : 4 Figure 3. Meter Correction Graph ...... , ...... 5 Figure 4. Nomograph for Conversion of Noise Units, 0 dBm to -4OdBm ...... 6 Figure 5. Nomograph for Conversion of Noise Units, AOdBm to -90dBm ...... 7

APPENDIX 5. PRINCIPLES OF RF TRANSMISSION LINES

1. General ...... 1 Electrical Types of Lines ...... 1 3’. Standing-Wave Ratio ...... 1 4: TunedLines ...... 1 5. Open-Wire Line Spacing ...... 2 Characteristic Impedance of Matched Lines ...... 2 ;: Harmonic Suppression ...... 3 Open-Wire Line Requirements ...... 3 :: Sagging of Open-Wire Spans ...... 3 10. Rigid, Air-Dielectric Coaxial Lines ...... 4 11. Flexible, Solid-Dielectric Coaxial Lines ...... 4 12. Twisted-Pair Transmission Lines ...... 4 13. Transmission Lines at VHF and UHF Frequencies ...... 5 Coupling and Matching ...... 5 ;:I Transmitter Coupling ...... 5. InductiveCoupling ...... 5 :;: Direct Coupling ...... 8 18. Pi-Network Coupling ...... 8 19. LinkCoupling ...... 8 20. Receiver Coupling ...... 8 21. Matching Antenna to Line ...... 8 22. Antenna-Coupling Transformers ...... 8 Matching Line Sections ...... 9 E: Half-WaveLines ...... 10 25. MatchingStubs ...... 10 Balanced-to-Unbalanced Matching System ...... 10 Interference Suppression ...... 10 Figure 1. Standing Waves on Open-Circuited and ...... 1 Short-Circuited Lines Figure 2. Relation of Mismatch to SWR .... 2 Figure 3. Sectional View of Air-Insulated ... : : : : : : : : : : : : : 4 Coaxial Cable Figure 4. Sectional View of Solid-Dielectric ...... 5 Coaxial Cable Figure 5. Complete Transmitter-and-Receiver-to- ...... 6 Antenna Transmission System Figure 6. Transmitter Coupling Arrangements 7 Figure 7. Open-Wire Impedance-Matching Transformers ’ : 1 : : : : : 9 Figure 8. Coaxial Impedance-Matching Transformers ...... 9

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Figure 9. Stub-Line Impedance Matching ...... IO Figure 10. Graph for Quarter-Wave Stub Length and Positioning .... 11 Figure 11. Quarter-Wave and Half-Wave Balun ...... 11 Arrangements

APPENDIX 6. PRINCIPLES OF ANTENNAS

1. General ...... 1 2. Electrical Characteristics ...... 1 3. Radiation Pattern ...... 1 4. Effect of Radiation Pattern on Signal Intelligibility ...... 2 5. General Directional Requirements ...... 3 Strength of Field ...... 4 7 AntennaResistance ...... 4 8: Input Impedance-Radiation Resistance ...... 4 9. AntennaGain ...... 5 10. AntennaBandwidth ...... 5 11. Reciprocity ...... 6 12. Power Absorbed by Receiving Antennas- ...... 6 Effective Length Figure 1. Basic Forms of Conductor Antennas ...... 1 Figure 2. Radiated Field from a Short, Straight ...... 2 Conductor in Free Space Figure 3. Three-Dimensional Nature of Radiation ...... 2 Pattern

APPENDIX 7. ORIENTATION OF HIGH-FREQUENCY (HF) DIRECTIVE ANTENNA

1. General ...... 1 2. Preliminary Procedure ...... 1 3. Basic Formulas and Symbols for Calculations ...... 2 4. Surveying the Antenna ...... 2 Figure 1. Plan View of Rhombic Antenna ...... 2

APPENDIX 8. WORKING AND SUPPLEMENTARY DATA

1. General ...... 1 2. Formulas for Antenna and Transmission Line ...... 1 Calculations 3. ChartsandNomographs ...... 6 Table 1. RF Cable Data ...... 19 Figure 1. Metric Conversion Factors . . Figure 2. Two-Wire Line Characteristics ’ : : : : : : : : : : : : : : . . 2 Figure 3. SWR Chart of Forward Versus Reflected ...... 5 Power Figure 4. Reliability Nomograph ...... 7 Figure 5. Open-Wire Line Characteristic Impedance ...... 8 Figure 6. Quarter-Wave Matching Section ...... 9 Characteristic Impedance Figure 7. Radio and Optical Line-of-Sight ...... 10 Distances

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6580.5 10/16/89

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Figure 8. Line-of-Sight Distances for Elevated ...... 11 Antennas to 5,000 Feet Figure 9. Line-of-Sight Distances for Elevated ...... 12 Antennas to 50,000 Feet Figure 10. Path Attenuation at 150MHz ...... 13 Figure 11. Path Attenuation at 300MHz 14 Figure 12. Obstruction Loss Relative to Smooth’ : : : : : : : : : : : : : 15 Earth Figure 13. Graph of Additional Losses Caused by ...... 16 r Standing Waves Figure 14. Attenuation Characteristics for Coaxial 17 Cable Types RG-142/U, RG-214/U, RG-21’7/U, RG-223;U, - * . RG-331 /U, and RG-333/U Figure 15. System Losses in Air -Ground ...... 18 Communication

APPENDIX 9. FABRICATING EMERGENCY ANTENNAS AND FEED LINES

1. General ...... 1

Section 1. EMERGENCY SUPPORTS AND GUYING

2. SupportPoles ...... 1 3. Other Kinds of Supports ...... 9 4.-g. Reserved. 0 Section 2. EMERGENCY ANTENNA AND FEEDER FABRICATION

10. General ...... 9 11. HFAntennas...... 9 12. VHF and UHF Antennas ...... 10 13. ImprovisedFeeders ...... 15 14. Improvised Matching Transformers ...... 15 Table 1. Pole-Setting Depths ...... 1 . Figure 1. Methods of Raising and Setting Poles ...... 2 Figure 2. Guy Anchors 3 Figure 3.GuyAttachment’:::::::::::::::::::::::: 4 Figure 4. Serving Antenna Wire .. 5 L Figure 5. Tying Strain and Spreader Insulators...... : : : 6 Figure 6. Typical Emergency Half-Wave Dipole ...... 7 and Feeder Figure 7. Folding Mast Antenna Support ...... 8 Figure 8. Example of Butt Splice for Poles 9 Figure 9. Multiwire Doublet Antenna . : : : : : : : : : : : : : : : 11 Figure 10. Vertical V and Half-Rhombic Antennas ...... 12 Figure 11. Long-Wire Antenna 13 Figure 12. Whip Antenna ... 1 : 1 : : : : : : : : : : : : : : : : : : : 14 Figure 13. Vertical Half-Wave Dipole Antenna 14 Figurel4.VerticalJAntenna...... :::::::::::::: 14

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Figure 15. Open-Wire Line Construction ...... 14

APPENDIX 10. CONNECTING ADDITIONAL RECEIVERS TO A SINGLE ANTENNA

1. General ...... 1 Multipling of HF Receivers on One Antenna...... 1 :: Methods of Coupling Balanced-Input Receivers ...... 1 on One Antenna 4. Multipling VHF Unbalanced-Input Receivers ...... 2 on One Antenna

LIST OF TABLES

2-l. Regular Variations of Ionosphere ...... 39 Irregular Variations of Ionosphere ...... 40 52::: TestEquipment ...... 85

LIST OF ILLUSTRATIONS

Figure 2-l. Basic Functions of the Remote Communication Facility ...... 6 2-2. RCF A-G Radio Communication System ...... 7 2-3. The RCF and Its Tributary Facilities ...... 8 Typical IFSS Communication HF PTP A-G Network ...... 10 $12: Typical Antenna Farm for an IFSR RCF ...... 11 2-6. A-G Radio Communication System ...... 13 2-7. Block Diagram of an HF SSB Transmitter ...... 15 Single Sideband Generation ...... 16 g:;: Single Sideband Modulation Patterns ...... 17 2-l 0. Block Diagram of a High-Frequency SSB Receiver ...... 18 2-11. Typical Forms of Transmission Lines ...... 20 2-12. Long-WireAntenna ...... 22 2-13. Vertical V Antenna 23 2-14. Vertical Half-Rhombic’Ar;ten;;a:c’Ant&~a: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 23 2-15. Multiwire Doublet Antenna ...... 24 2-16. Transmitting Rhombic Antenna with Three-Wire Curtain ...... 25 and Dissipation Line 2-l 7. Typical Rhombic Antenna Horizontal and Vertical ...... 26 Plane Radiation Patterns 2-18. Terminated Sloping V Antenna ...... 27 2-l 9. Multiwire Broadband Antenna ...... 28 Z-20. Tanner Wire-Grid Lens Antenna ...... 29 2-21. Rotatable Log-Periodic Antenna ...... 29 2-22. Rotatable Yagi Antenna ...... 30 2-23. Rotatable Cubical Quad Antenna ...... 31 2-24. Vertical Monocone Antenna ...... 32 2-25. HFLoopAntennaArray ...... 32 2-26. Omnidirectional Base-Station Antennas ...... 33 2-27. Directional Base-Station Antennas ...... 34 2-28. Vehicular-Mounted Whip and Stub Antennas ...... 34 w ‘

6580.5 CHG 3 9128193

Figure Page

LIST OF ILLUSTRATIONS (CONTINUED)

2-29. Typical Great-Circle Spherical Triangles for Paths ...... 35 Above, Across, and Below the Equator 2-30. The Four Principle Layers of the Ionosphere ...... 36 2-31. Geometry of Ionospheric Propagation ...... 37 2-32. Block Diagram of the AN/GRT-21 (VHF) and ...... 43 AN/GRT-22 (UHF) Transmitters, lo-watt 2-33. Block Diagram of the AN/GRT-21 (VHF) and AN/GRT-22 ...... 46 (UHF) Linear Amplifier, 50-Watt 2-34. Block Diagram of the WT-100 (VHF) Transmitter ...... 48 2-35. Block Diagram of the AN/GRR-23 (VHF) and ...... 50 AN/GRR-24 (UHF) Receivers * 2-36. Block Diagram of WR-100 (VHF) Receiver ...... 51 2-36.1. Block Diagram of CM-200 VT and CM-200 UT ...... 52-l 2-36.2. Block Diagram of CM-200 VR and CM-200 UR ...... 52-3 * 2-37. Coaxial Cable Transmission Lines ...... 53 2-38. General View of TACO Antenna ...... ' ...... 54 2-39. VSWR and Radiation Patterns, VHF and UHF Dipole Antennas ...... 56 2-40. TACO Model Yl02B-130V VHF Yagi Antenna ...... 58 2-41. Corner-Reflector Antenna for Radio Link ...... 59 2-42. Typical Air-Ground Communication Service Volume ...... 60 2-43. Components of VHF and UHF Wave Propogation ...... 60 2-44. Lobing, Obstructions, and Absorption Effects ...... 62 5-l. Sample FAA Form 661 O-l ...... 89 0 5-2. Sample FAA Form 6620-l ...... 90 5-3. Sample FAA Form 6600-6 ...... 91 5-4. Sample FAA Form 6000-8 ...... 92 5-5. SWR Test on Open-Wire Transmission Line ...... 95 Checking Ssb Modulation ...... 96 g;: Checking IMD and Spurious Emission ...... 98 5-8. Checking Receiver Sensitivity and Squelch Threshold ...... 100 5-9. Checking Receiver Selectivity and Nonsymmetry ...... 101 5-10. Measurin,g Coaxial Transmission Line Loss ...... 105 5-11. Measuring SWR at the Antenna ...... 106 5-12. Measuring Open-Wire Line SWR ...... 107 5-13. Measuring Open-Wire Line Balance ...... 110 5-14. SWR Loss Test of Old Coaxial Cable ...... 112 7-l. Solid-State Receiver Interface Pad ...... 115

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CHAPTER 1. GENERAL INFORMATION AND REQUIREMENTS’

1. OBJECTIVE. * maintenanceprocedures to be iduded to AOS-200, National This handbook provides the necessaryguidance, to he Airway SystemsEngineering Division. . Y usedin conjunction with information available in instruction books and other handbooks,for the maintenanceof remote c. The BackupEmergency Communication (BUEC) Sys- communication facility (KY) equipment. tem andNationalRadio Communication System(NARACS) are not included in this handbook. These equipments are 2. SCOPE AND COVERAGE. coveredin .otherdirectives.

a. Remote communication facilities (RCF’s) are con- 3. AIRCRAETT ACCIDENT. solidated networks of radio communication equipment, in- * The NationalAkpace Systemeons is responsiilefor the c cluding antennas and transmission lines, that serve the evaluation and documentationof the technical performance combined needs of en route air traffic control, tennina air of facilities that were, or might have been, involved in an traffic control, and automated flight service stations. This aircraft accident.This requires that faciIity operational data handbookcovers radio transmittersand receivers,with their be obtainedand recordedin the maintenancelogs and perfor- associatedantennas and transmissionlines, operating in the mancerecord forms. These recorded data are official docu- vhf, uhf, and hf bands for agency air-to-ground (a-g) and mentsand may be usedby an aircraft accident investigation point-to-point (PTP) data and voice communications.Some board to determinethe facility operational status at the time systemconcepts are included, primarily for hf facilities. Sys- of the accident. To avoid any misinterpretation of the data, tem information for the vhf and uhf equipment is contained the entries shall be complete, clear, concise, and accurate. m iu Order 6480xX$ Maintenance of Terminal Air-to-Ground Order 8020.11,Aircraft Accidents and Incidents -- Notifica- (A-G) Communication Facilities, Order 6490.14 MXnte- tion, Investigation, and Reporting, should be consulted for name of FLigbt Service Station (FSS) Air-to-Ground Com- details. The following steps must be accomplished and the munication Facilities, and Order 6470.29A, Maintenanceof results recordedfor any RCF radio communication facilities En Route Air-to-Ground Communications Facilities. To involved in an aircraft accident. avoid repetition of standardsand tolerances,periodic maintenance, and maintenanceprocedures, the three systemband- a. No equipmentadjustments are to be madeuntil the as- lxx&s listed aboverefer to, but do not duplicate, equipment found readingsare recordedand after the flight check, if re- c datacontained in chapters3,4, and 5 of this order. Chapter1, quired, is accomplished. paragraph8 of Orders6470.29A and 648O.m containsguid- ance concerning use of inadvertent ConfIicting or redundant b. Check the operating equipment record to ascertain handbook information or ins&u&ions. The maintenance whether there has been a changeover in equipment. If a requirementsof this order do not apply to USAF radioslocated changeover has occurred, both sets of equipment must be at joint use (FAA/USAF) facilities. Air Force technical checked. orders, directives, and procedurescontain requirementsfor USAF receivers. t c. Recordall meterreadings as found, but makeno adjustments until after required flight inspection actions are com- b. Approaching obsolescencemakes it necessaryLO omit pleted. certain older equipment items from discussion in this order. Programmedreplacement items are either alreadycovered by d. Check voice modulation level. this order or will be accommodatedby revision at a future time. For the interim period, field organizations are en- e. Certify the meterreadings and the log entry. Also have * couragedto issue supplementsin accordancewith the latest another technician or the supervisor certify the log enmy. edition of Order 1320.1,FAA Directives System,for any ad- * ditional coveragedeemed essential for the older equipment f. Note any abnormalconditions, such as snow or ice on items. On the other hand, if the regional Airway Facilities antennasor insulators. (AF) divisions believe national guidancethrough this order is required, they should submit their recommendationsfor cov- g. If a check of thk engine generatorelapsed-time mclcr a-ageof standardsand tolerances,periodic maintenance,and indicates Ihat the generatorhas operatedsince lhe last visit,

Chap. 1 Page 1 Par. 1 6580.5 CHG 6

determinethat the engine generatorwill start and run on a no- 5. CERTIFICATION REQUIREMENTS. load test run. As soon as practicable,a full-load test shah be Refer to Order 6000.15A for general guidance- on the madeand all meter readingsrecorded. tification of systems,subsystems, and equipment. Antennas and transmissionlines are certified as an integral part of the 4. RECEIVER SENSITIVITY AND TRANSMITTER communication facility with which they are associated. POWER OUTPUT ADJUSTMENT POLICY. * The basic policy of Operational Support advocates 5: 6. PRECAUTIONS WHEN USING TEST TONES. standardization in system adjustment and performance. When making checks on any receiving channel, extreme However, operationaI requirements and environmental care shall be taken to avoid applying test tones or other sig- factors can impose constraints that demanddeviation from nals in excessof thoseprescribed by the procedures of this system equipment staudards. This paragraph contains directive. Not only will an excessive test level causecrosstalk policy guidance relating to the operational setting of very in adjacent teIco or RCL channels, but it wiII ako annoy high frequency/ultra high tiecluency (vhfkhf) receiver operating personnel if the interfering signal is delivered to radio frequency Q gain controls and to the authorized rf controller positions or is intercepted by maintenanceperson- power output levels of vhf/uhf transmitters.Since operation- nel at other points in the system. al situations that necessitate changes in these system parametersmay develop after facility commissioning, the 7. NONSTANDARD FACILITIES. responsibleAF fieId office implementing the change must The instructions, descriptions, standards and tolerances, coordinate with the concerned Air Traffic (AT) and Flight and procedures contained in this directive represent the Standards(FS) field office and fully documentthe details of agency’sbaseline, or standardcriteria concerning PTP and a- the changes. g radio communicationequipment. Some facilities under the purview of this directive may have been commissioned using a. Squelch Threshold and RF Gain Control Setting. equipment that was procured without benefit of agency-ap- Ideally the rf gain control of all vhf and uhf receiversshould proved specifications. Regiomd procurement of equipment be set for maximum usablegain, or slightly below the point and devicesto be usedfor air traffic control or navigation for wherenoise signals operate the squelchcircuit. However,un- which specificationshave not received prior agency approv favorable noise or interference may exist at commissioning Fiel is prohibited by Order 1100.5B, FAA Organization - a, or may ariseafter commissioning that requiresa reducedset- paragraph222j(2). The inclusion of such nonstandardequip- ting of the rf gain control for satisfactoryreceiver quieting. mentsin this directive is for maintenancepurposes only and Operationat a reducedsetting is authorized,provided that the as such will not be usedas justification for procurement, in- receptionrange and coverageneeded to meetoperational re- stallation, or commissioning of additional or simiIar equip- quirementshave beenverified by aircraft reportsand mathe- ment. matical analysis, and that appropriate initiaI and operating tolerancesare developed, approved, and published by the 8. AUTHORIZED EMISSIONS, regional Airway Facilities division. The authorizedemission types in the aeronautical mobile and fixed servicesare as follows. b. Transmitter Power Output. Ordinarily, transmitters usedin PTPand a-g communicationservice shall be adjusted a. Telephony--Amplitude Modulation. to emit authorized rf power output, except as required by Order 6610.3,Power Output Limitation: FSS,Terminal and (1) DoubIe-sideband(used by FAA) . . . A3 Low AltitudeEnrouteVHFandUHFTransmitters. However, interferencemay arise that requires operation at reducedrf (2) Single-sideband,reduced carrier . . A3A power output. Reducedpower output may also be required for equipmentrelated reasons.(See standards and tolerances (3) Single-sideband,full carrier . . . . . A3H for transmitter power output in chapter 3.) Operation with (usedby FAA) reducedpower output is authorized, provided that the transmission rangeand coverage meet operational requirements as (4) Single-sideband,suppressed . . _ . _ . A3J verified by aircraft reports and mathematicalanalysis, and carrier (usedby FAA) that appropriate tolerances are developed, approved, and published by the regional Airway Facilities division. (5) Two independentsidebands ...... A3B

Page 2 Chap. I Par. 3 lo/16189 6580.5

b, Telegraphy (Including Automatic Data Transmis- c. Facsimile. With modulation of the main . . . . A4 sions). carrier either directly or by a frequency-modulated snbcarrier (used by FAA) (1) Amplitude Modulation. d. Aeronautical Mobile Service. Appendix 26 to the ITURadio Regulationsprovides the frequency allotment plan (a) Telegraphy without the use of a ...... Al and related information for the aeronautical mobile service. modulating audio frequency (by on-off keying) Included in the related information is a subsection,Classes of Emission and Power. Although intended for the aeronautical (b) Telegraphy by the on-off keying ...... A2 mobile service, the emission types listed asbeing permissible of an amplitude-modulating audio frequency or for the aeronauticalmobile service are also the types that may . audio frequencies,or by the on-keying of the modulated be found in the aeronautical fixed service. The emission types emission usedfor hf a-g communicationsare generally restricted to A3, A3H, and A3J. Emission type ASHis also commonly referred (c) Multichannel voice-frequency ...... A7A to asame, or am equivalent, becausethe full carrier operation telegraphy, single-sideband,reduced carrier provides for reception by conventional receivers, and the operation is thereforecompatible with A3. In bi-mode a-g cir- (d) Multichaunel voice-frequency ...... A7J cuits, which are becoming widespread, the two modes are telegraphy, single-sideband,full carrier A3H and A3J with either emission type selectable by the operator as required by the operating procedures. (e) Multichannel voice-frequency ...... A7J telegraphy, single-sideband,suppressed e. Aeronautical Fixed Service. The most commonly carrier (used by FAA) used emission types in the aeronautical fixed service are A3, A3A, A3B, A3H, A3J, and Fl. The Al emission remains in (2) Frequency Modulation. limited use in someparts of the world; it is being replacedby more modem types of emission as time and economical con- (a) Telegraphy by frequency-shift ...... Fl siderations permit. Independent-sideband(ISB) operation is keying without the use of a modulating audio used to provide one or more voice channels and/or more signal, one of two frequencies being emitted at any instant teletypewriter channels. l (usedby FAA) f. Reference. The Spectrum Management Regulations and ProceduresManual, Order 6050.32, provides informa- (b) Telegraphy by the on-off keying ...... F2 tion on frequency protection, radio coverage, and antenna of a frequency-modulating audio frequency or lobing. by the on-off keying of a frequency-modulatedemission 9.-19. RESERVED.

Chap.1 Page 3 (and 4) Par. 8 lo/16189 6580.5

CHAPTER 2. TECHNICAL. CHARACTERISTICS

20. PURPOSEORFUNCTION. The remote communication facility (RCF) consists of service operations. The facilities were formerly known as transmitters, receivers, transceivers, coaxial transmission remote center air/ground communication facility (RCAG), lines, antennas,and associatedancillary equipment.It may be remote communication outlet (RCO), and remote transmit- collocated with air traffic control or flight service facilities, ters/receivers (RTR). Control facilities in each of the three with navigational aids (navaids) or radars, or it may be a operationsare connected to the RCF. The location of the RCF stand-aloneRCF installation, Figure 2-1, Basic Functions of is dependent upon the air space coverage assigned to par- the RemoteCommunication Facility, delineatesmany of the ticular frequencies and upon overall air spacecoverage as- general functions of the RCF. The RCF communication sys- signed to the control facilities. The RCF a-g communication tem provides a medium for analog voice communicationsbe- system is depicted in figure 2-2. It is characterizedby a com- tween air traffic controllers/specialists and both civil and munication network, solid-state equipment, remote main- military aircraft pilots operating under instrument flight rules tenance monitoring, and radio control equipment. The RCF (IFR) or visual flight rules (VFR) in domestic airspace.The and its tributary facilities are depicted in figure 2-3. Addition- system also provides recorded voice weather broadcaststo ally, the equipment described in this chapter supports data, pilots over selected frequencies and antenna facility loca- radio teletypewriter (rtty), and voice communication in the tions. The RCF system provides communication services to fixed and mobile aeronautical services.The official modesof civil aircraft primarily via very high frequency (vhf) and to operation used are listed in paragraph 8. Antennas and their military aircraft via ultra high frequency (uhf). The RCF sys- coaxial feed lines provide an efficient meansfor the radiation tem encompassesen route, terminal, and flight serviceopera- and reception of radio frequency (rf) energy with a minimum tions. A-g radio communication facilities originahy were loss of power. establishedaccording to regional requirementsfor eachof the three air traffic functions, i.e., en route, terminal, and flight 2L23. RESERVED.

Chap. 2 Page 5 Par. 20 6580.5 1 O/l 6189

CONTROL OR SERVICE FACILITY RCF

-_----_-WEATHER REQUESTS------_---_- ____ REMOTE COMMUNICATIONS -_------_---_-_------WEATHER RECUESTTRANSMISSION FACILITY (RCF) NONCONTROL INFORMATION REQUEST ------TRANSMSSION ------___-_---PIREP REWESTS + __~_~-_~_-_------______ASSISTANCE REQUESTTRANSMISSION CON,,ERSATlONAL VOICE f -c%-!!t!% %oVEsT?XS!!~~l- - - _- COMMUNICATIONS RADIO _ ------_--_--___------WIND-SHEARALERTTRANSMISSION

------_-______PIREPS TRANSMISSION g VOlCE COMMUNICATIONS + ~EE’!~L’~~3?Y’EN’EL~~- --_ -_ _ __------_-______PIREP REQUESTS $ + RADIO LINK. PIREP REOUESTTRANSMISSION ------_-__--_----EMERGENCY ASSISTANCE __-_-____-_-----_-______2 IN-FLIGHT WEATHER BRIEFINGS ------_--_-_--__-----AWOS BROADCAST

------IN-FLIGHT WEATHER BRIEFING TRANSMISSIO

------_--_-__-__-----TRAFFIC CONTROL TRANSMISSION ------_-_---______ATIS BROADCAST ------__-___-______EMERGENCY ASSISTANCE REQUESTS ------_-__------_____ ------__-_-_-______NONCONTROL INFORMATiON REQUESTS ----~~- NONCONTROL--_--_-_ INFORMATION -__----_-TRANSMSSION -_----_-__-_---_-_-______WEATHER REQUESTS ------_-_----_____EMERGENCY ASSISTANCE TRANSEHSSION -_----_-----_-_--_--____WlND SHEAR ALERTS ___-__~_-__-_--~----____NONCONTROL INFORMATION -_------_--_-__-____----TRAFFIC CONTROL ------_-_-_--__-____PIAEP REOUESTS ATCT __~-~_-__-__------______~____~______-____EMERGENCY INFORMATION

------_-_--__-----CLEARANCE REQUESTS P NONCONTROL INFORMATION REQUESTS L -_---_--_-_-__-_----____

LEGEND ----.- VOICE

- DATA

FROM: NATIONAL AIRSPACE SYSTEM-LEVEL 1 DESIGN, NAS-00-10001

Figure 2-1. Basic Functions of the Remote Communication Facility

Page 6 Chap. 2 Par. 20 10/16/89 6580.5

-AC/RCF

ASRIRCF ARSFVRCF

Figure 2-2. RCF A-G Radio Communication System

Chap.2 Page 7 Par. 20 6580.5 1O/l 6189

ARTCC

Figure 2-3. The RCF and Its Tributary Facilities

8 Page 8 Chap. 2 Par. 20 1 O/l 6189 6580.5

Section 1. RCF DESCRIPTION

Subsection 1. HIGH-FREQUENCY (HF) RCF

24. HF POINT-TO-POINT (PTP) AND AIR-TO- accommodatedin the 3kHz voice band that occupies the GROUND (A-G). upper sideband (usb) of the ssb radiated signal. The lower sideband(lsb) has been filtered out in the transmitters. Some a. Ground-basedFTP RCF’s carry dataand rtty traffic for ssb circuits use independent sideband (isb) with suppressed the Aeronautical Fixed Telecommunications Network carrier, where both usb and Isb 3kHz voice-frequency bands (AFTN) and the interregional administrative network. Inter- can be operating independently of each other over the same national flight service stations (IFSS) have message-switch- circuit. In systemplanning, the choice of ssbover am is based ing capabilities for handling AFTN air movement and on spectrumeconomy. It is possible to carry the sameamount meteorological traffic from and to a large number of addres- of traffic in the ssb mode in approximately half the frequen- ses. The hf a-g RCF handles two-way telephony between cy spectrum neededfor the am mode. Also, in the am mode, aircraft and ground stations.Radio transmittersand receivers half the transmissionpower is “wasted” in the carrier required operating asremote facilities of the IFSS, using hf equipment to enable demodulation by the am receiver. and antennas, are linked to the distant ground stations to which the switched traffic is addressed.The transmitters for c. Maintaining communication over an hf PTP RCF or a- PTP and a-g RCF’s are the international flight service trans- g RCF usually requires the assignmentof more than one fre- mitters (IFST). The receiver facilities for the samea-g com- quency in the spacebetween 3MHz and 3OMHz. The family munication services are the internal flight service receivers of frequenciesallocated is carefully chosenat the time the cir- (IFSR). The modeoftransmission and reception usedin these cuit is engineered, taking into consideration such factors as RCF’s typically is single-sidebandsuppressed carrier (ssbsc) distance, east-west or north-south orientation of the path, for data orrtty, or amplitude-modulated equivalent (ame)for hours and days of operation, antenna gains and transmitter the selective calling system (SELCAL). For analog voice powers, propagation, noise, and multiplexing requirements. broadcastwhich is ground-to-air (g-a) only communication, Predictions basedon reliability expectations for frequencies full-carrier amplitude modulation (am) is still used, pending or frequency bands are published by the National Bureau of full transition of airborne communication equipment from am Standards(NBS) and are usedby IFST, IFSR, and operations to ssb. The VOLTMET (meteorological information for personnel to maintain around-the-clock communication con- aircraft in flight) circuits that are usedfor en route or terminal tinuity. This is done by scheduling and correlating frequency weather advisory service are hf g-a circuits using the am changesbased on NBS predictions for the path. mode.A typical IFSS communication hfPTP anda-g network is depicted in figure 2-4 with the various antennas used for 25. HF VOICE BROADCAST. different services.The figure intentionally doesnot show all One-way broadcasttelephony is used to advise aircraft in commissionedcircuits. Some circuits back up subseacable flight of en route and terminal weather conditions and airport channelsleased by FAA. Note that uhf links are usedto carry runway and traffic conditions. VOLMET is international g-a data, voice, or rtty handled by the transmitters and receivers hf voice broadcastservice providing meteorological data to between the IFSS and IFSR. A typical antenna farm for an in-flight aircraft. Vhf and uhf channels are also used for IFSR RCF is depicted in figure 2-5. broadcast;however, hf propagation is used for long distance advisory services, usually to assist aircraft in transoceanic b. The data or rtty ssb transmitters and receivers are in- flight. terconnected with frequency-division multiplex (fdm) terminals so that up to 24 channels of data may be 26.-29. RESERVED.

Chap.2 Page9 Par. 24 TRANSMITTING

LOCAL AND EMERGENCY TRANSMITTERS AND RECEIVERS A-G

VHF ~N%4NAS 1 1 1 1 1 1 UHF “,,FENNAS

I\Luv LOG-PERIODIC--- -. tW= FAX

LANDLINES

TELEPHONY STEERABLE YAG I

REMOTE HF RECEIVERS \ 1 INTERREGIONAL-....- .HF . . \nc3 I tU DESIGN) \irc\ , CENTER (RCC) * EMERGENCY NET PTP RTTY (TELEPHONY) c

Figure 2-4. Typical IFSS Communication HF PTP A-G Network 1 O/l 6189 6580.5 I

0 Chap. 2 Par. 25 Page 11 6580.5 CHG 2 S/29/92 Subsection 2. VHF AND UHF RCF

30. AIR TRAFFIC CONTROL/SERVICE. limited transmitting range of the low-power aircraft Ground-based uhf and vhf transmitting and receiving transmitters. RCF’s engage in two-way telephony with aircraft both on the ground and in flight. Terminal service for * 32. REMOTE TRANSMI’lTER/RECEIVER CLASS 0 commercial aircraft includes clearance delivery, ground (RTR-0) AND REMOTE COMMUNICATIONS control, local control, departure control, and other OUTLET CLASS 0 (RCO-0) COMMUNICATION functions, some of which are exclusively handled by FACILITIES. airlines. En route control is of either low altitude or high a. The RTR-0 and RCO-0 facility designations altitude two-way communication from air route traffic were established to eliminate the older single-frequency control centers (ARTCC) via RCF’s. Vhf radio outlet (SFO) designation. This change was necessaryto frequencies are normally used for communication with avoid overlapping definitions in the standard codes commercial aircraft, while uhf frequencies are used with handbook, Air Traffic documents, and the Facilities military aircraft. Figure 2-6 illustrates a typical a-g radio Master File (FMF). An RTR-0 is controlled by a communication system. Typical transmitters in these terminal facility such as an ATCT, and an RCO-0 is facilities operate with 10 or 50 watts for vhf, and 10, 50, controlled by an FSS or AFSS. or 90 watts for uhf. Powers are determined by the operational range required and certain noninterference b. These facilities provide ground-to-ground criteria. For power output policy, refer to Order 6610.3, communications between air traffic control and pilots Power Output Limitation: Flight Service Station, located at satellite airports. This communication link is Terminal, and Low Altitude En Route VHF and UHF for delivering en route clearances, issuing departure Transmitters. System description and maintenance authorizations, and acknowledging instrument flight requirements for en route, terminal, and flight service rules cancellations or departure/landing times. In station communications facilities are covered by the addition, the facility may be utilized for advisory Order 64780.29A, Maintenance of En Route Air-to- purposes whenever the aircraft is below the coverage of Ground Communications Facilities, Order 6480.6B, the primary air-to-ground frequencies. Maintenance of Terminal Air-to-Ground (A-G) communications Facilities, and Order 649O.lA, c. The RTR-0 or RCO-0 facility consists of an Maintenance of Flight Service Station (FSS) Air-to- equipment shelter, that houses a single transmitter and Ground Communication Facilities. receiver, and an antenna. The equipment shelter may be pole mounted or attached to an interior/exterior 31. EXTENDED REMOTE CENTER AIR-TO-GROUND wall of a building, with the antenna being roof or pole (ERACG) COMMUNICATION FACILITIES. mounted. In addition, the radio gear may be removed The ERACG transmitter and receiver site provides vhf from the shelter and mounted in a rack within a communication between the center and air craft at building when such location is available. A voice grade extended distances from land. The original concept of line with in-band signaling provides the point-to-point ERCAG facilities was to provide high-power, land-based voice and push-to-talk control features. Voice- equipment to communicate with the standard complement frequency signaling equipment may also be utilized for of commercial vhf radio equipment. A later refinement control of the facility. Commercial power is used for of the facility design was to use the standard AN/CRT-21 powering the radio and/or signaling gear and the and AN/GRR-23, 50-watt equipment with an antenna telephone company equipment. Standby power and mounted on a 200-foot to 300-foot tower. This provided alternate telephone circuits are not required. * similar a-g radio communication capability becauseof the 33.35. RESERVED. I

Chap. 2 Page 12 par. 30 ALTERNATE Q=UHF CHANNELS BUEC SITE RCAG (VOR/VORTAC) a --VHF CHANNELS

LRR/BUEC

Figure 2-6. A-G Radio Communication System 6580.5 1 O/l 6189

Section 2. HF EQUIPMENT DESCRIPTION 36. GENERAL. 37. MODES OF OPERATION. This sectioncontains brief descriptionsof typical hf trans- The A3 am function is referred to as the am mode; the mimers,receivers, transceivers, coaxial transmission lines, A3A, A3H, and A3J ssb functions are referred to as the ssb antennas,associated ancillary equipment,and wave propaga- mode.See paragraph 8 for the modesof operation authorized tion. For a fuller description and all equipment theory, con- for aeronautical and fixed service. sult the applicable equipment instruction books and manuals. 38.-39. RESERVED.

Subsection 1. RF EQUIPMENT 40. HF TRANSMITTERS. sideband(Isb) signal at 1.75MHz. Its audio input comesfrom either a local dynamic microphone or a 500-ohm or 600-ohm a. Aerocom Model 1330 5kW Transmitter. Figure 2- impedancetelephone line. It has 2OdB of compressionand a 7 is a block diagram of a typical ssb hf transmitter, capable harmonic distortion limit of 3 percent.The crystal filter limits of high-power multimode operation with full, reduced, or the passbandof the lsb to 3OOHzto 3000Hz. A balanced suppressedcarrier. In the figure, the principal low-power modulator is the basic exciter element, and the carrier may be stagesare the sidebandexciter and the frequency converter. removed or reinserted depending on the desired operational An intermediate radio frequency (rf) amplifier provides . mode.Refer to figure 2-8 for a diagram showing lsb genem- amplification of one of six assigned frequencies. Further tion. amplification occurs in the final linear amplifier where peak envelope powers (PEP) up to 5000 watts are developed.The d. Aerocom Converter-Driver Type 127-1. The con- audio input, which may be voice or frequency-division-mul- verter-driver is a six-channel intermediate amplifier. It con- tiplexed (fdm) tones,first goesto a balancedmixer where the verts the 1.75MHz ssb signal from sideband generator type 1.75MHz carrier is inserted. The carrier and two audio 125-1to the desiredchannel operating frequency at sufficient sidebands go to a sideband filter that removes the upper rf power to drive either a 1kW PEP or 5kW PEP linear sidebandfrom the carrier allowing the lower sidebandto be amplifier. The rf drive voltage to the following linear fed through another mixer and finally to a third mixer in an amplifier stage is nominally 1OV across a 50-ohm load, or up and down conversion arrangementdesigned to minimize 2W. A crystal oscillator, called the vhf oscillator, feeds the frequency instability. The lower sidebandis inverted to be- final mixer of the converter driver to produce the channel fre- come the upper sidebandand is amplified to a high rf output quency.An oven-controlled hf crystal oscillator provides car- level. The usual method of generating an ssb signal is the rier frequency 1.75MHz and mixes this frequency with the balancedmodulator-filter arrangementof figure 2-8. Figure signal from the exciter. Channel frequency stability is 2-9 illustrates various undistorted ssbmodulation waveforms governed by the hf oscillator and the accuracy of the for different audio input signals. Part E of the figure is the 1.75MII.z ssb input signal. typical two-tone, suppressedcarrier modulation waveform. Part F is the extreme caseof modulation with a square-wave e. Miscellaneous Fixed-Tune Transmitters. signal, which results in infinitely-high excursions at the beginning and end of eachpulse and placesgreat demandson (1) Technical Material Corporation Model GPT- the transmitting system. 1OkW Transmitters. The GPT-1OK transmitter is an older but serviceable unit that is capable of 1OkWPEP operation b. Aerocom Model 13lllkW Transmitter. This trans- on all authorized modesof operation. It may be used on am, mitter is similar to the model 1330,except that a type 131-1, ssb, and continuous-wave (cw) circuits handling facsimile, 1kW linear amplifier is the final amplifier element. The ex- rtty, or broadcast traffic. The 1kW intermediate power citer and converter-driver elementsare the sameas those used amplifier (ipa) may be usedas a transmitter if the final power with the model 1330 5kW transmitter. amplifier (pa) fails or if the radiated power need not be a full 1OkW.The transmitter is bandswitchedfor frequency chang- c. Aerocom SSB Generator Type 125-l. The ssbgen- ing from 2MHz to 28MHz. The final amplifier will drive an erator is the basic exciter unit of the model 1330 and 1311 unbalancedor a balancedantenna feeder: the former can be transmitters. It drives a converter-driver stagewith a lower 50-ohm or 70-ohm, and the latter, 600-ohm impedance.

Page 14 Chap. 2 Par. 36 BALANCED SSB IF BAND PASS BUFFER TUNED FINAL TUNED MIXER FILTER AMPLIFIER MIXER FILTER MIXER AMPLIFIER CIRCUIT AMPLIFIER CIRCUIT

SIDEBAND \ /- UPPER SIDEBAND ‘-,

AUDIO INPUT -DU!hT

Fc + 64 MHz

NOTES:

I. Fc = CARRIER REFERENCE FREQUENCY (2-22YHz)

NOTE I Fc + 1.75 MHz

/ \ / TEMPERATURE CONTROLLED CRYSTAL ’ STABLE CRYSTAL OSCILLATORS OSCILLATOR

Figure 2-7. Block Diagram of an HF SSB Transmitter 6580.5 10/16/89

w UPPER SIDEBAND (USB)

m LOWER SIDEBAND (LSB)

USB PLUS LSB LSB

BALANCED I SIDEBAND TO AUDIO . . SIGNAL MODULATOR FILTER CONVERTER b t

Figure 2-8. Single Sideband Generation (2) Collins Radio Company Model 2055 10kW the same receiver, refer to the instruction manual for the Transmitter. The Collins 2055has been usedon FAA long- Aerocom 2210 hf am/ssbreceiver. As shown in the figure, haul PTP rtty circuits. It is bandswitchedover a range similar the incoming rf signal is converted to 64MHz in the first to that of the GPT-1OK.It will accommodateall authorized mixer. The 64MHz intermediate frequency (if) is the first if operating modesfor datacommunication, voice broadcast,or frequency. A crystal bandpass filter centered at 64MHz facsimile. It may be usedwith either an unbalanced(50-ohm) removesspurious mixer products. After the filter, the second or balanced(600-ohm) antennafeeder. mixer convertsthe 64MHz if to 1.75MHz, which is the second if frequency. The double-conversion processprovides good (3) THV-1 and THV-2 3kW Transmitters. The rf selectivity without a preselectorstage. Crystal lattice filters THV series provides a cw, rtty, and am 3kW multichannel provide both am/ameand ssb mode selectivity at the second transmitter. Frequenciesam pretuned in up to five identical if frequency. The detector is a phased-lockedloop common rf bays from 2MHz to 2OMHz. The associatedpower supply to both am and ssb modes. The second if signal is injected is in a larger, separatebay. An audio modulator bay can be with a highly stable 1.75MRz oscillator signal for carrier addedfor broadcastapplication by dropping one rf bay. reinsertion for ssb demodulation. A fast attack, slow decay automatic gain control (age) circuit allows smooth reception 41. HF RECEIVERS. at a speech-syllabic rate. Solid-state components are used throughout. The rf input circuit is a double-balancedSchot- a. Aerocom Model 2210 SSB-AM Receiver. Figure 2- tky diode mixer having excellent low intermodtdation charac- 10 is a block diagram of a typical hf ssb ground station teristics. The secondif crystal lattice filters are of eight-pole receiver capableof multimode operations: ssb, am, and ame configuration. The output audio amplifier connectsto either (am equivalent). The frequency range is nominally 2MHz to speechor rtty multiplex (mux) demodulator equipment. 22hNz. The receiver is intended primarily for a-g and broadcast communication. For a more detailed block diagram of

Page 16 Chap. 2 Par. 40 1 O/l 6189 6580.5

A. SINGLE TONE BALANCED B. SIGNAL A AFTER FILTERING MODULATOR OUTPUT OUT ONE SIDEBAND

C. SINGLE TONE SSB SIGNAL D. SINGLE TONE SSB SIGNAL WITH EQUAL AMPLITUDE WITH CARRIER IODB DOWN CARRIER

E. TWO EQUAL AMPLITUDE TONES, F. SSB SIGNAL WITH SQUARE- SUPPRESSED CARRIER SSB WAVE MODULATION

Figure 2-9. Single Sideband Modulation Patterns

Chap.2 Page 17 Par. 41 6580.5 1 O/l 6189

Page 18 1CJII 6189 6580.5

b. Miscellaneous Fixed-Tuned Receivers. A number tennas; for example, a pair of rhombic antennasoriented to of other ssb and am receivers have been used in PTP hf ser- the same azimuth but spaced up to several thousand feet vice. Prominent among these is the Radio Corporation of (meters)from eachother to combat the effects of fading. The America (RCA) model SSB-R3dual-diversity receiving sys- receiver will handle facsimile reception as well as voice. The tem. The type SSB-R3 covers 2.8MHz to 28MHz in four most common FAA use has been on lOO-words-per-minute bands. The receiver system is contained in two relay racks. (wpm) rtty circuits in the aeronautical fixed service. Its frequency-shift tone output will accommodate20 fdm channels in one sideband from 595Hz to 3825EIz. It is designed to operate from two space-diversity receiving an- 42~43. RESERVED.

Chap,2 Page 19 Par. 41 6580.5 10/16/89

Subsection 2. TRANSMISSION LINES 44. GENERAL. l Several types of transmissioin lines are used in communications. Someof theseare illustrated in figure 2-11. The two-wire, or open-wire, type is wideIy used for frequencies below 3OMHz.This type consistsof two wires mountedequal SINGLE-WIRE LINE -Q distancesabove the earth with constant spacing between the wires. TWISTED PAIR 45RESERVED.

WAVEGUIDE

COAXIAL LINE

Figure 2-11. Typical Forms of Transmission Lines

Subsection 3. ANTENNAS 46. GENERAL are highly directive with large front-to-back gain ratios to Below 3OMH2, antennasare usually large structures oc- minimize interference,and high forward gain with respectto cupying a relatively large amount of land. As transmitting an- an isotropic antennato overcome the large transmissionloss tennas,they must be capableof handling large amountsof rf of the hf circuit. The antenna of greatest importance in hf power, be directive, and have relatively high forward gain. communication for many years has been the rhombic anten- With such antennas,it is important that their front-to-back na. This antennaoperates on a fixed azimuth, may havea mul- signal discrimination be large to minimize atmospheric and tiwire curtain in its Iegs for obtaining a broadband - man-madenoise and to suppressinterfering signals. Fixed characteristic and lower impedance, is usually many point-to-point (PTP) antennasare oriented to place their max- wavelengths in length on each leg, and, consequently, re- imum radiation on a precise great-circle azimuth. High-fre- quires a large plot of ground for installation. Figure 2-16 is a . quency (hf) broadcast (ground-to-air) antennas are simplified drawing of a rhombic antennaequipped with a dis- omnidirectional. Loop and lens-type antennaswith selectable sipation line as terminating impedance.The dissipation line directivity provide moderategain on air-to-ground (a-g) and provides the antennawith uniazimuth directivity; otherwise, ship-to-shore(STS) circuits. Figures 2-12 through 2-15 show it would radiate at the feed end as well as at the terminated various types of antennas,operating in various government end. The characteristic impedanceof the rhombic antennaat bands from 3MHz to 3OMHz. its balanced feed point is approximately 600 to 800 ohms. When unbalanced feed is required, a balance-to-unbalance transformer (balun) is connected to the input of the antenna 47. HF POINT-TO-POINT AND BROADCAST AN- with its high-impedance terminals. The low-impedance, un- TENNAS. balancedside of the balun is connected to coaxial transmission line for further connection to the associatedtransmitter a. Antennas used for fixed station, point-to-point trans- or receiver. The directivity of the rhombic antennais depicted mission are large and have a broadbandcharacteristic. They by figure 2-17, which illustrates the horizontal and vertica * Page 20 Chap. 2 Par. 44 1 O/l 6/89 6580.5

plane patterns of the antenna.In forming the resultant radia- angle, a characteristicof value for long-distancepaths. Figure 0 tion pattern, each leg of the rhombic antennaacts like one or 2-18 shows a terminated sloping V antenna. more long-wire antennas.The terminating resistor (a dissipation line for high-power transmitters) permits the radiation c. Doublet antennasare used on hf circuits having short- that would normally be emitted to the rear of the antenna to haul groundwave or one-hop communication requirements. be dissipated in the terminating resistance.This producesan They have moderatedirectivity and unity gain (relative to a essentially unidirectional pattern with one major forward lobe ,dipole) and can be operated only over a relatively restricted for orientation on the great-circle azimuth. There are a num- range of frequencies.They exhibit broadbandcharacteristics ber of minor lobes,but no radiation 180” (back-azimuth)from only when multiplied in double-doublet or triple-doublet ar- the major forward lobe. The vertical radiation angle depends rangements. They can be fed with a low impedance (ap- - primarily on the length of each leg: the longer the leg, the proximately 70 to 100 ohms) twisted or open transmission lower the radiation angle (figure2-17). Consequently,the an- line. For unbalanced coaxial line feed, a balun is required. tenna can be usedover greaterdistances with fewer hops and The Granger Associates Model 1765-22 broadband dipole less total refraction loss. antennais a multiwire doublet as shown in figure 2-19. It can be usedfor either transmitting or receiving and has a frequen- b. Related to the rhombic antenna,the V antenna (some- cy range of 3.4MHz to 3OMHz. Its swr is a nominal 2:l in times erectedas a sloping V) has the open end pointed in the that range.The length of the antennabetween mounting poles desired direction of radiation. The apex terminal of the V is is 185 feet (56.4 meters).The height is 68 feet (20.7 meters), balanced and connectedvia open wire (or, with a bahm, via and the width is 134 feet (40.8 meters).The radiation pattern coaxial cable) to the transmitter or receiver. The V antenna is omnidirectional at the lower frequencies. In transmitting lacks the sharp directivity and high gain of the rhombic an- usage,its power-handling capability is 1 to 2 kW. tenna. In its sloping V form it provides a very low radiation

Chap.2 Page 21 Par. 47 f 1200

1200

1200 / e I L1 1 v! 7 7 BACK-GUYS BACK- GUYS

492 (N -0.05) $ MATCHING SECTION LFEET = FREQUENCY IN MHz

WHERE N = NUMBER OF HALF- WAVES IN ANTENNA

- NON-RESONANT TWO-WIRE LINE

Figure 2-12. Long-Wire Antenna

0 r ‘ 1O/l 6189 6580.5

NO. 12 AWG STRANDED

OR STAKE OR STAKE

Figure 2-13. Vertical V Antenna

OPTIMUM DIRECTION _

TO RECEIVER THROUGH RG-213/U COAXIAL

CWIRE COUNTERPOISE

I NOTE D CROWFOOT COUNTERPOISES ARE SOMETlMES USED AT POINTS A AND B INSTEAD OF THE WIRE SHOWN CONNECTING THESE POINTS.

Figure 2-14. Vertical Half-Rhombic Antenna

Chap.2 Page 23 Par. 47 L LOW FREO. ?d

GACK- GUYS

R------e \ FEEDPOINT STRANDED INSIJLATOR- COPPERWELD

/ L 466 / FEET- FREQUENCY IN MHz

TWO-WIRE OPEN WIRE OR RG-IIA/U FEEDER

Figure 2-15. Multiwire Doublet Antenna

I 1O/l 6/89 6580.5 REAR END POLE 7

SIDE CORNER POLE -

,ND ISSION

FRONT END POLE TILT ANGLE

SIDE CORNER POLE DISSIPATION LINE ROUND LINE

Figure 2-16. Transmitting Rhombic Antenna with Three-Wire Curtain and Dissipation Line

d. The Tanner wire-grid lens antenna is a highly spccial- e. The logarithmically periodic array (the log-periodic an- ized broadbandmultiazimuth antennalocated at the Molokai, tenna) is a highly directional, high-gain antenna. It can be Hawaii, FAAreceiving station. Originally erectedwith seven erectedin fixed azimuth configurations, or it can be compact- feedpoints, the Molokai wire-grid lens hasbeen used not only ly constructed to be rotated on a mast. It has many desirable on FAA radio teletypewriter (rtty) circuits to Australia, characteristicsfor hf communication service. Seefigure2-21. American Samoa,New Zealand,Japan, Canton Island, Wake, Granger Associates Model 273 l-3K rotatable log-periodic and Guam, but also for ship-to-shore communication for the antennas(not illustrated) have been procured for hf applica- Pacific Missile Range. The wire-grid lens has the unique tions by the FAA. These antennascover the band 4MHz to ability to permit rapid azimuth changes, during circuit re- -3OMHz and can handle 2.5kW of power. The tower height is quirement changes,by relocating the coupling horns around 100 feet (30.48 meters),and 360” rotation is accommodated. . the outer circumference of the grid. The lens can readily substitute for a number of rhombic antennas on different f. The familiar Yagi antenna is often used in hf com- azimuths, resulting in a great saving in land requirementsfor munication. While it is not normally constructed as a broad- , the antenna farm. The antenna is illustrated in figure 2-20. band antenna the elements of the Yagi can be modified for The wire-grid lens consistsof a pair of circular grids, 600 feet limited band harmonic operation. It is small enough to be (182.9m) in diameter, suspendedone above the other. Sur- rotated and provides good gain and directivity on a narrow rounding the lens proper is the horn, which increases the band of frequencies.One multiband model is shown in figure diameter of the array to 850 feet (259.1m). The horn is 2-22. analogous to the old-fashioned ear trumpet. It intercepts the wave-front power, concentratesit in the vertical direction, g. Another rotatable antennais the quad (short for cubicle and channelsit into the lens, that is, the vertical spacebetween quad). A commercial model quad is shown in figure 2-23. It the upper and lower grids. As the wave travels through, a is basically two square-loop antennas spaced 0.15 to 0.2 focusing effect takesplace; and the enhancedwave energy is wavelengthsapart, with a leg dimension of0.25 wavelength. coupled out and connected to coaxial line feedersof the hf One of the loops is driven by the transmitter, while the other receiver.

Chap.2 Page 25 Par. 47 1O/l 6/89

T STILT ANGLE TERMINATING n RESISTOR

B. RESULTANT RADIATION PATTERN

A. INDIVIDUAL RADIATION PATTERNS

LENGTH Of LEG 2 WAVELENGTHS 3 WAVELENGTHS 4 WAVELENGTHS

PATTERNS IN VERTICAL PLANE

Figure 2-17. Typical Rhombic Antenna Horizontal and Vertical Plane Radiation Patterns

Page 26 Chap. 2 Par. 47 -BALANCED FEEDER

TERMINATION

NOTE : THE AZIMUTH BISECTS VERTEX ANGLE A’. SLOPE ANGLE So DETERMINES SKYWAVE TAKEOFF ANGLE. Figure 2-18. Terminated Sloping V Antenna acts as a parasitic reflector. The gain of the quad is roughly a. Base-Station Antennas. Base-stationantennas are of equivalent to a three-elementYagi. several kinds. The most common are vertical masts and whips. The quarter-wave ground plane antenna is useful for h. The vertical monoconeantenna is omnidirectional and short-haul hf groundmobile operation. Figures 2-26 and 2-27 broadband and has little or no gain relative to a dipole. Its illustrate several types of hf base-station antennas. In the principal application is ground-to-air (g-a) voice broadcast. lower frequencybands, vertical polarization is mandatory,for The broadbandcharacteristic is derived from its conical cross it provides protection from horizontally polarized electrical section. Granger Associates Series 1794-5K monocone an- noise that otherwise would render communication impos- tennashave been procured for FAA hf circuits, for hf broad- sible. cast applications. The frequency band covered is 2.8MHz to 32MHz, and the power-handling capability is 5kW. The over- b. Vehicular-Mounted Antennas. The most common all height is 61 feet (18.7 meters); the diameter at the largest type of vehicular-mounted antennas in the hf bands is the cross-section is 90 feet (27.6 meters). See figure 2-24 for whip antenna, illustrated in figure 2-28, part A. The whip is details. a thin, flexible radiator usually operated and tuned as a grounded vertical antenna.The antennasmay range in length i. A loop antennaof special design by ‘TechnicalCom- from about 1 foot (0.3m) to over 20 feet (6m). They are con- munications International (TCI) is in use on the island of structed of steel, aluminum, or Monel metal tubing, usually Guam asan a-g receiving communication antenna.See figure 2-25. in telescopingsections. The basemay be spring-loadedto permit tiedown of the whip while the vehicle is in motion. The whip antennahas an omnidirectional pattern. The pattern will 48. GROUND-MOBILE ANTENNAS. be somewhatdistorted becauseof the proximity of the body Base-stationand vehicular-mounted antennasare used in ,of the vehicle. It is seldom practical for a vehicular antenna the 1.SMHz to 30MHz hf bandswhen necessaryto communi- to be directional in characteristic.Part B of the figure is aroof- cateover relatively long distancesbetween a fixed station and mounted stub, usually used at frequencies above lOOMlIz. vehicles. The lower high frequenciesare useful when terrain is rugged and line-of-sight is not possible. 49.30. RESERVED. 0

Chap. 2 Page 27 Par. 47 1 O/i 6189

Transmission Line to Transmitter

DIMENSIONS I Model Number Frequency Range Feet Meters Length (A) Height I!31 Width (Cl Length (Al Height (6) Width (Cl

1765.20.‘K 2.0 to 30 MHz 185 68 134 56.4 20.7 40.8

1765.21.‘K 2.4 to 30 MHz 160 59 116 48.8 18 35.4

1765.22.“K 3.4 to 30 MHZ 115 41 81 35 12.5 24.7

1765.23.‘K 4.3 to 30 MHz 90 32 62 27.4 9.8 18.9

Figure 2-19. Multimire BroacTbandAntenna

Page 28 Chap. 2 Par. 47 1O/l 6189 6580.5

INCOMIMGWAVE r- LENS POINT ENERGY

Figure 2-20. Tanner Wire-Grid Lens Antenna

Figure 2-21. Rotatable Log-Periodic Antenna

Chap.2 Par. 48 Page29 6580.5 1 O/l 6189

REFLECTOR (VHF)

DIRECTOR (HF)

DIRECTOR NO. I (VH

Figure 2-22. Rotatable Yagi Antenna

Page 30 Chap. 2 Par. 48 6580.5

Figure 2-B. Rotatable Cubical Quad Antenna

Chap.2 Par. 48

page31 6580.5 1 O/l 6189

STRUCTURAL

STABILIZERS

INSULATORS

Figure 2-24. Vertical Monocone Antenna

Figure 2-25. HF Loop Antenna Array

Chap. 2 Page 32 Par. 48 -I O/l 6189 6580.5

PLANE $ .a A4 SECTION

AIlL

FOLDED GROUND-PLANE ANY LENGTH FEEDER

TURNSTILE r-1 I I FIBERGLASS RADOME ---I I

FRANKLIN SKIRTED COAX

Figure 2-26. Omnidirectional Base-Station Antennas

Chap. 2 Page 33 Par. 48 6580.5 1O/l 6189

= I T CORNER REFLECTOR

PHASED YAGI’S

Figure 2-27. Directional Base-Station Antennas

ALTERNATE LOCATION

PREFERRED LOCATION

/ /

A. WHIP ANTENNAS B. STUB ANTENNA

Figure 2-28. Vehicular-Mounted Whip and Stub Antennas Chap. 2 Page 34 Par. 48 1O/l 6189 6580.5

Subsection 4. WAVE PROPAGATION 53. STRUCTURE OF THE IONOSPHERE. A brief discussionof radio wave propagationat hf frequen- There are four distinct ionic layers of the ionosphere as cies is included in this section. The geometry of propagation shown in figure 2-30. in the hf frequency band used by the FAA is discussed,including certain propagational disturbances having the a. D Layer. This layer is not always present,but when it greatest effect on the reliability of FAA radio communica- doesexist, it exists only in the daytime and is between3 1 and tion. 56 miles (50 and 90 kilometers) above the earth, being the lowest of the four layers. This region is so highly ionized that 52. BASIC. little or no skywave reflection is obtained from it; the wave Point-to-point and broadcast hf communication circuits is usually totally absorbed. use 3 to 30 MHz frequencies that are able to be propagated over many thousandsof miles by reflections from the earth’s - ionosphere.Such reflections (actually refractions) take place b. E Layer. This layer exists only during daylight hours a number of times on the long-haul circuits, following a great- between 56 and 87 miles (90 and 140 kilometers) above the circle path. Ionization of the ionosphere,usually by the sun’s earth. This layer depends solely upon ultraviolet radiation ultraviolet radiation, provides varying degreesof penetration from the sun. Since the E layer dependsdirectly upon the sun, and absorption. For each frequency incident on a layer as a it is most dense directly under the sun. Seasonalvariations skywave there is a critical frequency above which the energy occur in this layer because the sun’s zenith angle varies penetratesand doesnot return to earth. The critical frequen- seasonally.Shortly after sunsetthe layer disappears.Because cy is important for predicting the behavior of the ionosphere E layer density follows the sun, points of equal latitude have and, consequently, the efficiency of multihop radio transmis- the sameE layer conditions at the samelocal time. sion. The orientation of the transmitting antenna that places its main lobe of radiation on the great-circle azimuth of the c. The F Region. The F region includes the Fl and F2 distant station is obtained by trigonometric calculations. Ex- layers, which have differing altitudes, durations, and respon- amples are given in appendix 2. Figure 2-29 depicts three sesto solar radiation. The F2 layer is of greatestimportance 0 typical great-circle paths and the spherical triangles used for to long-haul multihop radio links. calculations.

Figure 2-29. Typical Great-Circle Spherical Triangles for Paths Above, Across, and Below the Equator

Chap. 2 Page 35 Par. 51 COMBINED F-LAYER -.-.-.-.-.-.-.-.>>...... -... .*.*. . -.*.*t.- ..‘...... -...... (. . .*.(...... (...... i. . . . .,f:‘...... ‘...*=-*-* -. .A=:.!+.. . - . . . - - * *. - - - ...... I. I.*..: +: 2’:ty:+> ._... 1 O/l 6189 *-*.f> *...(....- * * . * *.-.>y:\.>:.>.. .*...... ;...... *...... I.- .I...... q:y .. . . .*.

MULTIPLE SINGLE HOP HOP

C. IONOSPHERIC HOPS Figure 2-30. The Four Principle Layers of the Ionosphere

(1) Fl Layer. The Fl layer exists between87 and 155 ists during the night as well as during the day. This layer is miles (140 and 250 kilometers) above the earth during between 93 and 155 miles (150 and 250 kilometers) above daylight hours. This layer behaves like the E layer during the earth during the night for all seasonsof the year. During daylight; that is, it follows the sun. When the sun sets,the Fl the day in the summer it is between 155 and 177 miles (250 layer rises to merge with the next higher ionic layer, the F2 and 285 kilometers) high, and during the day in the winter it layer. is between 93 and 177 miles (150 and 285 kilometers) high. This variation in height is accountedfor by the effect of solar heat on the layer, which increasesits height and decreasesits (2) F2 Layer. Of all the ionized layers, the F2 layer is the most important for long-rangePTPand a-g communica- ion density during the summer.The reduction of solar heat in the late afternoon causesthe layer to descend.No complete tion. It is the most predictable layer, and for the purpose of explanation has been made for the existence of the F2 layer, maintaining 24-hour hf circuit continuity, the National but it is known that it is considerably affected by particle Bureau of Standards(NBS) issues short- and long-term hf radiation from the sun, evidencedby the strong influence that prediction bulletins basedon the F2 layer. Thesebulletins are the earth’s magnetic field has on the distribution of the F2 issued through the institute for Telecommunications Scien- layer. ces and Aeronomy (ITSA) to subscribersaround the world, including the FAA. (b) The effect of the earth’s magnetic field results in the greatestion density, and the highest critical frequency, (a) The F2 layer is the most useful ionic layer for in a region about 20” from the magnetic poles, rather than skywave transmissionbecause of its height and becauseit ex- directly under the sun as in the case of the D and E lavr A

Page 36 L Pai 10/16/89 6580.5

Since the earth’s magneticfield is not evenly distributed, lon- particular skywave path at a particular hour of the day. The gitudinal variations exist in the F2 layer for points of equal geographic location of reflection points, the time of day, latitude at the samelocal time. For this reason, the earth is season,and sunspot number all affect the muf. The muf for divided into three zones that represent different degreesof path lengths less than 2,480 miles (4000 kilometers) is dctcr- magnetic intensity to facilitate plotting Fl layer distribution. mined by the ionospheric conditions at the midpoint of the Thesezones are called the east,west, and intermediatezones. path. It is taken as the highest of the three maximum frequen- Monthly predictions of F2 layer distribution are then made cies, which will be reflected from the E layer, sporadic E by NBS for each of the three zones. layer, or F2 layer. The charts of median zero muf and median 4000 muf predicted for the proper month, from the NBS, are 54. SMYWAVE TRANSMISSION GEOMETRY. used to determine the muf for a given communication link. Skywave propagation essentially follows optical laws of phases.If there were no disturbance (paragraph56) affecting (2) The muf representsthe median maximum usablefre- the stability of the layers of the ionosphere,the incident wave quency. That is, 50 percent of the days the actual muf will be and the reflected wave of propagation would always have the less than the median muf, and 50 percent of the days the ac- same propagation angle of reception and transmission. A tual muf will be greater than the median muf. For this communication circuit establishedon such a path would have high reliability. The basics of skywave geometry are sum- marized in the following subparagraphsand are illustrated in the figures referenced.

a. Refraction Process. When skywave propagation is used for communication, the electromagneticwave from the antenna is transmitted toward an ionic layer at an oblique angle, The incident wave then appearsto be reflected, at the same oblique angle, from the ionic layer back toward the receiving antenna. Actually, the wave is not reflected, it is bent back toward the earth by refraction, just as a prism refracts light. The bending processis a function of the refractive index of the ionic layer and behavesin accordancewith optical geometry. Roughly stated in terms of ionospheric refraction of a radio wave, this law is as follows: For a wave incident upon a densely ionized layer to be bent back toward the earth, the wave must pass from a medium with a high refractive index to a medium of low refractive index.

h. Critical Frequency. A vertically transmitted frequency greater than the critical frequency will penetratethe ionosphere, while a frequency less than this value will be GROUND PLANE reflected. When the critical frequency (fO),for the ionosphere over a certain point is known, the frequency (f), which will AI RADIATION ANGLE ONE HOP E LAYER MODE just be reflected by the ionosphereover that point, can be cal- AZ RADIATION ANOLE ONE HOP F LAYER MODE culated by: f=fO csc A. This is the maximum usable frequen- A3 RADIATION ANGLE TWO HOP F LAYER MOOE cy (muf) for the vertical radiation angle A. Frequenciesabove the muf will penetratethe ionosphere; frequenciesbelow the muf will be reflected and become hops, as shown in figure 2-31. The muf can be determinedfor any distance,geographic location, sunspot number, or time of day.

c. Maximum Usable Frequency (MUF).

(1) The muf is the upper limiting frequency at which a communication circuit may be operated.The muf, as determined from available ionospheric predictions, is actually a Figure 2-31. Geometry of Ionospheric Propagation monthly median of the highest usabledaily frequenciesfor a

Chap. 2 Page 37 Par. 53 6580.5 10/16/89

reason,it is desirable to operatea circuit at a frequency that ing from the direct wave, depending upon the transmission is slightly less than the median muf to increasecommunica- path length. tion reliability. Where F2 propagation is used,this frequency of optimum operation (fot) (sometimes owf for optimum b. Forward Scatter. Within the past 30 years, success- working frequency) is taken as 85 percent of the muf. Where ful and highly reliable forward-scatter propagation has been E and Fl propagation is used, the fot is taken as the muf for used for multichannel rtty and voice communication. Tech- E propagation, becausethe muf variation from day to day is niques were developed for detecting extremely small rf sig- too small. nals in the presenceof cosmic noise. Circuits have beentested in both ionospheric scatter (20 to 60 MHz) and tropospheric d. Lowest Usable High Frequency (LUHF). The luhf scatter (60 to 1000 MHz) modes for ground-to-ground and (sometimes luf for lowest usable frequency) is the lower air-to-ground communication. Forward-scatter antennasare limiting frequency that will provide satisfactorycommunica- tion for a given link. The luhf is the frequency at which the not included in this order. received field intensity just equalsthe required field intensity 56. IONOSPHERIC VARIATIONS. for reception. The received field intensity dependson the an- Refer to tables2- 1 and 2-2 for regular and irregular varia- tennas,path length and absorption; and it generally increases with frequency. The required field intensity for reception tions of the ionosphere. dependson noise limitations, and it decreaseswith frequen- a. Sunspots. The sun is the major source of energy that cy. Therefore,by comparing the received median field inten- producesionization of the earth’s atmosphere.Therefore, any sity at various frequencieswith the required field intensity for solar disturbance produces variations in the ionic layers. the samefrequencies, the luhf is determined. Sunspotsare evidence of such solar disturbances that affect the ionic layers. These sunspotsappear as dark patchessur- 5.5. GROUNDWAVE AND SCATTER PROPAGA- rounded by a hazy gray edgeand are presumably vortexes of TION. enormous gas clouds. These gaseous clouds produce vast amountsof ultraviolet energy that affect the ionization of the a. Groundwave Paths. earth’s atmosphere.Therefore, the greater the number of sunspots,the greater the ultraviolet radiation and the greater (1) Groundwavepropagation is propagationof rf encr- the ionization. For this reason,the number of sunspotsis in- gy along the curved surface of the earth, without using the dicative of ion density, which, in turn, is a measureof the earth’s ionosphere. Where a groundwave is transmitted probability of skywave communication. Sunspot activity is beyond the line of sight, the conductivity of the earth’s sur- measuredby the Wolf sunspot number method, which con- face acts as a waveguide and bends the wave around the siders not only the number of actual sunspots but also the curved surface.Since fading is due primarily to ionospheric number of sunspotgroups. Observations of solar activity over fluctuations, there is no fading associatedwith groundwave the past 100 years have confirmed that sunspot activity is propagation. However, the extremely high lossesassociated cyclic, the cycle repeating every 11.1 years. There are varia- with groundwave dependsupon the type of terrain over the tions within this cycle and variations from cycle to cycle that transmissionpath, the transmitting and receiving antennas, make it necessaryto know the predicted sunspotnumber for the power output, frequency, and antennaheights. a given time in order to determine the probability of skywave communication. (2) Only vertical polarization, suchas is obtainedfrom vertical and whip antennas, is practical for groundwave b. Sudden Ionospheric Disturbances (SID’s). Oc- propagation. Horizontal polarization results in extremely casionally daytime communication by high-frequency high lossesdue to a short-circuiting effect of the earth. Even skywave propagation is lost by abnormally great absorption. with vertical polarization, the received field intensity of a The onset of this condition is usually very sudden with groundwave is far below that of the direct, free-spacefield. recovery being moregradual, and the condition may last from The antennaheight also affects groundwave propagation. a few minutes to several hours. This condition is known as solar flare disturbance, Delligner fade, or most commonly, (3) For line-of-sight transmissions,the received field sid. The result of an sid is a sudden increase in the ion den- intensity is composedof a direct wave and a ground-reflected sity of the highly absorptive D region, as well as an increase wave. If the two received wavesare about 180“ out of phase, in the ion density of the moderately absorptive E layer. the received signal level will be very low. Conversely, if the two received waves are in phase,the received signal will be c. Magnetic Storms. Magnetic storms are not the sameas almost twice as strong as the signal resulting from the direct sid’s, although they both have the same effect in that they wave. Therefore,for line-of-sight transmissions,the received reduce the probability of communication by skywave signal level varies from near zero to twice the signal result- propagation.The magnetic storm is associatedwith solar ac- 0 Page 38 Chap. 2 Par. 54 1 O/l 6/89 6580.5 Table 2-1. REGULAR VARIATIONS OF IONOSPHERE

Type of Variation Effect on Ionosphere Ejffect on Cummunicntion

1-YEAR FI and F2 layers particularly in- Higher critical frequencies during Use higher operating frequen- UNSPOT crease in density and height in years of maximum sunspot ac- ties for long-distance communi- :YCLE direct accordance with sunspot tivity. Higher maximum unusable cation during periods of sunspot activity (maximum activity, frequencies during high sunspot maximum, say 19 to 35MHz. minimum activity.) activity.

Use lower frequencies during minimnm, say 5 to ZOhlHz. Co11 suit predictions to determine maximum usable frequencies.

!7-DAY Recurrence of sudden ionospheric See effects of sid’s and iono- See compensation for sid’s and ‘UNSPOT disturbances and storms at 27-day spheric storms in Table 23, Irre- ionospheric storms in T~ll)lr 3-3, I intervals. Disturbed condition btiar Variations of Ionosphere. regular Variations of Ionosphere. frequently identified with very active sunspots whose radiations are directed from the sun every 27 davs as the sun rotates.

WRNAL Flayer: Density and height de- Skip distance varies below 30MHz. IJse higher medium frequencies variation wiith time of day) crease at night, increase after Absorption increases during day. during day, lower medium frc- dawn. During day layer splits quencies at night. into: (1) FLlayer whose density follows vertical angle of sun, (2) h layer whose density increases until later in the day and whose height increases until noon.

E layer: Density follows vertical angel of sun, height approximately constant. Practically disappears at night.

D layer: Appears after dawn, density follows vertical angle of sun, disappears at night.

iEASONA1 FZ layer height increases greatly Wider range of critical fre- Use @eater difference in night in summer, decreases in winter. quencies in winter. Maximum time and daytime operating ionization density rises earlier in usable frequencies are higher at frequencies in w

Chap. 2 Par. 56 6580.5 1 O/l 6189 TABLE 2-2. IRREGULAR VARIATIONS OF IONOSPHERE

-i-- Type of Variation Effect of lonospher~

SPORADIC E “Clouds” of abnormal ionization Excellent transmission with nor- LAYER occurring in the E layer or slightly mal skip distance. Occnsiondly. above for a large portion of long-distance commmlicatioll ou Lime each month result in ab- freqwncies of 60SlH.z and above. normally high critical frequencies. Usually spotty in geogmphic extent and time.

SUDDEN Unusually high radiation from Normal frequencies above I or 2 Raise working frr~lueucy drove IONOSPHERIC solar flare produces abnorndl~ 51Hz are mutle udess because of normal for short-distance tr;ms- DISTURBANCE high ionization in all layers. In- high absorption in liea\dv ionized mission autl lower frequew~ crease in ionization occurs very (SW D layer. Coraiclerably higher frr- below nonnd for hug-tlistanc~e sudclenly throughout daylight quencies may nol be absorbed transmission. portion of earth. for short-distance colllmunicatioll. Low frequencies may not peue- hate the D layer, hence thev ma\ be transmitted for bug clist~mcr~.

IONOSPHERIC Accompanies magnetic distur- Limits mmil~er of usable high frr- LTse frecyncies lower than STORMS bances occurring about 18 hours quencies. normal, especially in high luti- after SD’s, L’pper iouosphere tutk expands and diffuses; critical frequencies are below normal; virtual heights are above normal. Severe effects near poles. decreasing toward equator. Duration from few minutes Lo several hours: effects tlis- appear grduall~ iu a few davs.

SCATTERED Irregularities in density of layers Fading of signal5 the to arrival None. Usually fatling is of short REFLECTIONS but heights normal. of signals from slightly different duration. directions with varying phase relations.

Page 40 Chap. 2 Par. 56 1O/l 6189 6580.5 tivity, being more likely to occur during maximum sunspot communication below 3OMHz.) Although mdom noise is ir- conditions, and reoccurring in 27-day cycles, the rotation regular, its averagelevel can bc measured,and it exhibits a period of the sun. Magnetic storms are apparently causedby characteristicaverage power distribution that is constantover particle radiation from the sun, with the radiated particles the frequency spectrum.Impulse noise may be generatedby being deflectedby the earth’s magnetic field. For this reason, vehicular ignition systemsand local thunderstorms,and it is the effects of a magnetic storm are most severe in the two characterizedby discrete,well-separated noise pulses having geomagneticpole regions. The origin of a magnetic storm certain phaserelationships. may be the samesolar eruption that producesan sid; but since particle radiation is much slower than ultraviolet radiation, (2) Atmospheric noise is atuibutcd to world-wide ef- the effect of the magnetic storm is not noticed until 18 to 36 fects of thunderstorm activity. Atmospheric noise is highest hours after an sid. A magnetic storm has two phases.The first in the equatorial regions, where thunderstorms are most fre- phase expands the F2 layer, which reduces ion density. quent, and varies seasonally at the higher latitudes, being During this phase,the F2 layer’s critical frequency becomes highest in the summer months. Atmospheric noise is also lower than normal from reduced ion density. The second higher over land than over sea, because thunderstorms arc phaseis markedby a greaterconcentration of electronsin the more frequent over land. Thunderstorm activity occurs with highly absorptive D and E regions, especially in the geomag- hourly and daily variations, being more frequent between netic polar regions. The increasedabsorption that results may 1200and 1700 local time, which produces diurnal (daily) at- prevent communication by skywavepropagation.A magnetic mospheric noise conditions. Storms distant from the receiv- storm may last for several days, with its appearancebeing ing station produce random noise, while local stormsproduce very suddenand recovery to normal very slow. impulse noise. Prediction of the impulse noise from local d. Sporadic E Layer. A sporadic E layer, abbreviated stormsis not feasible,but prediction of the random noise from Es, cannot be accountedfor by the processesthat explain the distant storms is feasible. The ITSA publishes world noisc- normal E layer, which exists at approximately the sameheight distribution chartsfrom which canbe obtained the noise grade above the earth. It may be causedby particle radiation, or it for any receiving site. Minimum required incident field inten- may be a result of meteorsentering the earth’s atmosphere. sity curves for overcoming atmospheric noise are also The Es layer can exist during both day and night, but its provided. By using the curve for the proper noise grade, presenceduring the day is difficult to detect becauseof the proper season,and proper local time, the field intensity re- presenceof the normal E layer. The distribution of this layer quired to overcome atmospheric noise can be determined. cannot be predicted, but it is known to vary on thickness and ion density and is frequently patchy. It is also known that the f. Fading. likelihood of the existenceof a sporadicE layer increaseswith distancefrom the equator. The layer’s occurrenceis frequent enough in the middle latitudes to render Es sky-wave (1) Another disturbance impairing transmission over propagation from 25 to 50 percent of the time at frequencies hf ionospheric paths is fading. The received signal appearsto up to 15MHz. It is notorious for causing strong interference lose or gain signal strength at times slowly and at times so betweenupper hf and lowervhf at greatdistances, beyond the fast the effect is named flutter. Fading is a phenomenonthat normal service range at thesefrequencies. can be classified into two basic types: single-path fading and multipath fading. The causesare quite different. In single- e. Noise. ,pathfading, the geometry of the ionospheric path is altcrcd so that the skywave that was once aimed directly at the receiv- (1) A satisfactory communication system exists only ing location now skips over. This kind of fading alters only when the received signal level is sufficient to override the the signal strength, not the relative phaseof the signal com- noise level at the output of the receiving system.This implies ponents, so that there is no distortion. Multipath fading that there is a minimum required field intensity for satisfac- presentsa greater problem. This type of fading is causedby tory communication. This minimum required field intensity the skywave taking more than one path to reach the receiving dependsupon the receiving antenna,the receiver bandwidth, location. One path may propagateas a one-hop path; simul- the quality of the servicerequired, the type of modulation, the taneously, or nearly so, another path may develop as a multi- noise produced within the receiver, and the level of noise at hop path, adding relative time delay to the signal. This results the receiving location. The noise that must be overcome by in partial and sometimesfull cancellation of the signal. Be- the field intensity is random noise and impulse noise, and causesignal elements(bits) can be affected in relative phase, comesfrom the atmosphereand the receiver. Random noise considerablesignal distortion can result. In data or rtty trans- may be generatedfrom distant thunderstorms,resistive commission, such distortion will often cause errors in message ponents and tubes in the receiver, and cosmic noise of inter- traffic. In voice transmissions,areduced speechintelligibility stellar space. (Cosmic noise is seldom a problem for results.

Chap. 2 Page 41 Par. 56 6580.5 1 O/l 6189

(2) Fading is combattedby the useof one or more tech- error-detecting equipment must also be equipped to count niques, the most common being the spacing of two or more characterrepeats over time. Even so, a high error count may receiving antennasa number of wavelengthsapart. Each an- not necessarilyindicate equipment trouble. A number of vari- tenna is connected to a separate, identical receiver. The ablesaffect hf propagation efficiency-over a short interval or detected receiver outputs in a system are combined, or over severaldays. A perfectly well-designed circuit with nor- “selected” in another system, and the resultant steadyoutput mally operating equipment may exhibit a higher than normal is demodulatedby the usual terminal or mux equipment as- error rate. Becauseerror-rate criteria are more a matter of sociatedwith the circuit. Some diversity systemsuse signal basic design and engineering than channel deterioration or polarization diversity; however, polarization diversity is maintenance,this order does not include specific test for, or usually limited to the over-300MHz spectrumwhere antenna theory of, digital error-rate probabilities. The hf equipment sizesare much smaller. Error detecting and correcting equip- periodic maintenanceand equipment performanceparameters ment, such as ARQ (automatic repcat request), helps over- included in this and other orders are sufficient to preclude loss come the distortion effect on data or rtty traffic. of servicedue to deterioration of transmitters,receivers, or antenna systems. 57. RELIABILITY OF HF CIRCUITS. . b. Within the limit of the radio horizon, hf broadcast a. High-frequency PTP circuits are not rated in coverage. reliability is similar to that of vhf and uhf a-g circuits. Beyond The hf circuits arc designedto produce a minimum error rate that limit, the line-of-sight ionospheric and tropospheric in a model mux channel for a specified signal-plus-noise to propagation factors enter, and reliability is more like that of noise ratio at the receiver demodulator or combiner output. PTP circuits. However, no information is provided in this Theserequirements are not easy to evaluate in the field, un- order for such calculations. less special test equipment is available or unless the circuit usesdigital error-detecting and -correcting equipment. The 58.49. RESERVED.

Section 3. VHF AND UHF EQUIPMENT DESCRIPTION 60. GENERAL. theory, consult the applicable equipment instruction books This section contains brief descriptions of typical vhf/uhf and manuals. transmitters, receivers, transceivers, coaxial transmission lines, antennas, associatedancillary equipment, and wave 61.-62. RESERVED. propagation.For a fulleer description and all equipment

Subsection 1. RF EQUIPMENT 63. ITTMODELS AN/GRT-21 (VHF) AND AN/GRT-22 b. Oscillator-Synthesizer, AS(S). The optional oscil- (UHF) TRANSMITTERS. lator-synthesizer module can replace the crystal-controlled The vhf and uhf transmittersare intended for a-g am voice oscillator module to generate a selectable stable frequency telephoney (A3). The vhf transmitter operates in the when the desired frequency crystal is not available or is in- 116.00MI-Lto-149.975MHz spectrumutilizing one of 1,360 operable. This module provides for direct dialing of the channelsspaced 25kHz apart.The uhf transmitter operatesin doubler or quadrupler input frequency. Thumb-wheel the 225.00MHz-to-399.975MHz spectrum utilizing one of switches, accessiblebehind the front accesspanel, are used 7,000 channelsspaced 25kHz apart. The transmitter (the ex- to select the desired channel frequency. citer) contains circuitry that provides a 1OWminimum, 90- c. Doubler or Quadrupler, A9. In the doubler or quad- percent modulated signal output. When not in the dc power rupler circuit the crystal oscillator or oscillator-synthesizer mode of operation, the exciter power supply furnishes a output is frequency doubled or quadrupled to the output charging current to external batteries.Figure 2-32 is the func- operating frequency and is voltage-level controlled before tional block diagram of the transmitters.Described below are amplification by the driver and/or power amplifier. the major subassembliesof thesetransmitters. a. Oscillator-Multiplier, AS(M). A new oscillator-mul- d. Driver, AlOA.1. The driver in the driver-power stage tiplier, part number (pn) 8009546Gl hasreplaced the original is a three-stage(for uhf) amplifier with the first stage(for vhf) temperature-controlledcrystal oscillator, pn 8004290Gl/G2. or first two stages(for uhf) amplitude-modulated. The last With the oscillator-multiplier module, the operating frequen- two of three stagesare linear amplifiers. The input of the vhf cy can be maintained to a much tighter tolerance. Also, ad- driver is from the doubler, and its output is a signal to the justments can be made for crystal aging. tunable filter. The uhf driver’s input is from the quadrupler;

Page 42 Chap. 2 Par. 56 a OR PLER

I) J-

LOCAL TRANSFORYER RELAY CONTROL

i)TO PWR AYPL

1 TRANSFER g :[LMlfJ- :i::~fE~ TO REWOTE CONTROL T/R RELAY KEYER OR KI --I A2 Id-- I CONTROL/ 1. THESE MODULES DIFFER +V PWR BETWEEN VHF AND UHF KEYING 7 THERMAL % MOD AMPL wi rsENsoR * DETECTOR A7 IN EARLIER MODELS. SYSTEMS MANUFACTURED PSIAI AFTER AUGUST 1983 WILL +20 WC BATTERY REG BE PROVIDED WITH A CHARGE BROADBAND AMPLIFIER r POWER w REGULATOR I + 20 --VDC MODULE AND WILL BE TO SUPPLY - PSIA2 PWR AYPL IDENTICAL IN VHF AND UHF PSI13 SYSTEMS.(REF. ECP643) f, -1 ? +24VOC UNREG 2. WHEN POWER AMPLIFIER NOT USED, CONNECT Kl AS SHOWN IN FIGURE 12OV k 10% L, 22-30 voc 9.5 OF TI 6610.10A 240V t IO% FROM EATTERY 3. MODULE USED AT REMOTE MAINTE- 47- 420H2 AND CHARGE CURRENT TO BATTERY NANCE MONITORING SITES ONLY

Figure 2-32. Block Diagram of the AN/GRT-21 (VHF) and AN/GRT-22 (UHF) Transmitters, lo-watt 6580.5 1 O/l 6189

its output signal goesto the power amplifier. The tunable fil- supplies the dc voltage required to operate the carbon ter is placed between the last two stagesof the driver. microphone and the dynamic microphone preamplifier.

e. Tunable Filter, FL2. The tunable filter reduceshar- 1. Amplifier Filter Detector, A4. The amplifier filter monics and noise generatedin the driver. detectorperforms two functions. The first is to passfrequen- cies in the 3OOHzto 6kHz range with little attenuation and to f. Power Amplifier, AlOA2, -A3, -A4, -A5, -A6 The attenuatesignals outside of this range for application to the vhf power amplifier linearity amplifies the signal from the buffer modulator. The second function is to amplify the tunable filter to a minimum level of 1OW.The uhf power microphone inputs, local orremote, to provide the front panel amplificrconsistsof threepowerampliliers (A102A, A103A, meter with audio signal levels. AlOrlA), a hybrid (A106A), and a hybrid detector (A105A). The combination forms a linear amplifier that increasesthe m. Buffer Modulator, A5 The buffer modulator has modulatedsignal from the driver to a minimum level of IOW. two circuits. The first provides amplification for the meter modulation signal; the secondprovides wide-band datainput, g. Low-Pass Filter, FLl. The low-pass filter following a clipping level control, and limits to prevent overmodulation. the power amplifier suppressesharmonics generatedin the final stagesof the power amplifier. n. RF Control Modulator, A6. The rf control modulatorassembly contains the circuitry required to provide h. Power Detector, DCl. The power detector detects modulation to the driver. It also limits the power level when forward and reverse power and delivers this information to high standing waves exist, maintains a constant power level, the rf control and modulator board (A6). and logically determinesif the power amplifier is operational or not: it then furnishes this information to the A7 control unit 1. NOTE: Hardware delivered from the factory after August 1983contains redesigneddriver-power amplifiers that are broadbandand may be used interchangeably be- o. Control Unit, A7. This module contains circuitry to inhibit keying when excessive temperatures exist in the tween vhf and uhf exciters. The new driver power 0 amplifier consists of four push-pull broadbandamplifier power supply and connectsthe exciter to the antenna when- stageswith a minimum output of 10 watts. ever the power amplifier shuts down. It also contains the circuitry required to furnish percent modulation information to the meter. i. Antenna Transfer Relay Kl. The antenna transfer relay’s function is to switch the rf power from the power detector to either the antenna or the power amplifier. When p. Power Supply, PSl. The power supply module con- connected to the power amplifier, the relay connects the verts the 120V ac (or 140V ac) input power to both 28V dc power amplifier to the antenna.It can alsobe usedas the trans- unregulatedand 20V dc regulated. It also suppliesthe battery, mit-receive (tr) delay when the power amplifier is not used. if connected,a charging current of 300mA at approximately s Normally, there is a dedicatedantenna element for the trans- 38V. mitter output. q. System Metering. The system metering function ac- j. Line Amplifier or Audio Amplifier Compressor, ceptsthe various test signals generatedthroughout the exciter (Al(L). The audio amplifier compressoraccepts the local or as listed below. remote microphone input, amplifies it, and furnishes a constant voltage level to the amplifier filter detector. For those (1) Relay voltage installations where compressionis accomplishedahead of the transmitter input, a line amplifier Al@,) module is used in (2) Forward power place of the compressionamplifiers. (3) Reflected power k. Transfer Control Keyer, A2. The transfer control keyer contains the circuitry necessaryfor keying various as- (4) Automatic power control (ARC) scmblies in the exciter and furnishes an inverted signal that may be used for keying the power amplifier rf output. It also (5) Transmit-receiver relay

Page 44 Chap. 2 Par. 66 10116189 6580.5

(6) Voltage-standing wave ratio (vswr) strument multiplier. After passing through the power detector, the signal goes to the antenna via the antenna transfer (7) Rf output of power amplifier delay.

(8) Filter tune (2) Connector/Filter Assembly, A6. The connector filter assembly provides connections and filtering for the (9) Output of doubler or quadmpler various connections madeto the tuned cavity (A7).

(10) Oven heater current (3) Buffer Amplifier/Electrical Instrument Multi- plier, A5. The buffer amplifier electrical instrument multi- (11) Oscillator stageoutput plier contains circuits for a buffer amplifier between the detectorsfrom the power sensorand the rf control in the ex- (12) Unregulated power supply voltage citer. It also contains the system metering function, which monitors the following signals. (13) Battery voltage with power switch OFF (a) Exciter on (14) +2OV bus (b) Exciter keyed (15) +2OV bus current (c) Forward power (16) Keyed +2OV (d) Reflected power (17) Modulation index (e) Plate supply voltage (18) Modulation output from rf control modulator (I) Plate current (19) Output of amplifier filter (g) Screensupply voltage (20) Output of audio frequency (af) compressor (h) Control grid voltage (21) Remote audio power level (-15 to +8dBm) (i) Heater voltage (22) Remote audio power level (-18 to -2.5dBm) (j) High-voltage condition at power amplifier (23) Overtemperaturesensing circuit (k) Fan voltage s. Power Amplifier. Figure 2-33, a functional block diagram of the power amplifier, includes the major subas- (1) Overtemperature semblies describedbelow. The 50-watt power amplifier is a linear vacuum-tubeamplifier, which raisesthe exciter’s 1OW (4) Control Grid Power Supply/Control Circuitry, . output to a minimum level of 50W. When the ac power is in- A3. This module (A3) provides filament voltage, control terrupted,the exciter is automatically connectedto the anten- grid voltage, and turn-off of amplifier if excessive tempera- na and to an external dc power input, which provides a 1OW tures exist in the tuned cavity or if the blower fails. It also output. The power amplifier is normally not authorized for contains the interlock circuitry for the cavity and high-volt- use except for extreme coverageproblems. age power supply.

(1) Tuned Cavity, A7. The tuned cavity stage con- (5) Plate and Screen Grid Power Supply, A4. A4 tains various subassemblies.The vacuum-tube amplifier, contains the circuitry to provide the screengrid with 390V dc with input and output tuning, acceptsthe signal from the an- and the plate with 24kV dc. tenna transfer relay, and amplifies it to 50W level. The low- passfilter @‘L2)suppresses harmonics generated in the power (6) AC-to-AC Converter, A2. The ac-to-ac con- amplifier. The signal then passesthrough the power detector verter converts the 6OHz input power to a 400Hz 11OVsig- (DCl), which detectsforward and reversepower and delivers nal to run the blower. corresponding dc levels to the buffer amplifier/electrical in-

Chap.2 Page45 Par. 63 r I TUNED CAVITY A7 I

RF INPUT FROM EXCITER

CONNECTOR/FILTER ASSEMBLY A6 1

CONTROL GRID POWER SUPPLY/ :ONTROL CIRCUITRY A3

FILAMENT _ a SUPPLY w w- l P, AMPLIFIED SUFFER b PR AMPLIFIED GRID SYSTEM METERING - AMPLIFIER . SUFFER AMPLIFIER/ ELECTRICAL INSTRUMENT 3LOWER FAIL L

12ov +- 10% - 240V +_ 10% 47 -420 HZ - CONVERTER,

TUNE RF LEVEL TO EXCITER

+ 20V DC FROM EXCITER

POWER AMPLIFIER + RELAY CONTROL VOLTAGE TO EXCITER I: TO EXCITER

NOTE: THESE MODULES DIFFER BETWEEN VHF AND UHF SYSTEMS

Figure 2-33. Block Diagram of the AN/CRT-21 (VHF) and AN-CRT (UHF) Linear Amplifier, 50-Watt

0 10/16/89 6580.5

64. WULFSBERG MODEL WT-100 (VHF) TRANS- MITTERS. The transmitter is a compact transmitter utilizing 6A3 b. Audio Card, A2. The audio card (A2) contains the voice and 13A9 data modulation meanson any frequency in transmit audio speechprocessing circuitry. The transmitter the band of 118.00MHz to 135975MHz. The transmitter is a audio input is amplified, filtered, and limited beforebeing ap- fixed, single-channel type, with the frequency determinedby plied to the modulator circuitry. A transmit timer and relay a plug-in crystal elementoperating at one-sixth the output fre- on this board supply +15V dc to the transmitter module and quency. High frequency stability is achieved by the use of a also limit transmitter ON time if a key-down fault should crystal oven. The transmitter is particularly useful where dam occur. is to be transmitted over the usual voice bandwidth. An electronic transmit timer is incorporated to limit transmitter c. Line Interface Card, A3. The line interface card (A3) ON time should a key-down fault occur in the keying line. provides the audio input/output signal paths necessaryfor (This transmitter timeout may be defeatedby incorporation remote or local operation of the transmitter. This board con- of contractor’s engineering order 1026 to allow operation in tains a hybrid transformer which allows both transmit audio applications such as ATIS.) The transmitter consists of three input and receiver audio output (when the WY’-100 is collo- basic modules. These three modules are: transmitter module cated with a WR-100 receiver) to be passedalong a single (Al), audio card (A2), and line interface card (A3). These twisted pair telephone line. Also, keying of the transmitter is modulesplug into the chassisassembly (A4), which contains controlled by this module. The presenceof a tone or a dc cur- all the necessaryinterconnect wiring and cables,as well as a rent on various input lines will be detectedby circuitry on this voltage regulator that supplies +15V dc for the transmitter. board and will causethe transmitter to key. Remotetransmit- Figure 2-34 is the functional block diagram of the transmitter audio and keying can be configured in one of four ways ter. Described below are the major subassembliesof this through switching and interfacing on this card. Isolation transmitter. power for the keying lines is supplied by A3T2 and its as- sociatedrectifier/filter. Keying line isolation is maintainedby a. Transmitter Module, A-l. The transmitter module using optoisolator A3Ul to detect a key-down current. (Al) generatesand amplifies the rf signal up to the output level, not to exceed 20 watts. The frequency multipliers and filters following the crystal oscillator amplify the signal up to d. Loopback Audio. When LOOPBACK KEY line is a level suitable for driving the pa board (A6). Modulation and grounded, A3Ql turns off, which closes field-effect transis- final amplification takesplace on the pa board. The transmit- tor @ET) switch A3U4. In this mode,the telephoneline trans- ter module also contains a six-section elliptical low-pass fil- mit audio at A4Pl is connectedto the LOOPBACK AUDIO ter for harmonic energy rejection and an antenna relay to lines at A4Jl through LOOPBACK AUDIO LEVEL poten- switch the antennafrom the receiver to the transmitter when tiometer A3R2. This control acts as an adjustableattenuator. in transmit mode.

Chap.2 Page47 Par.64 1O/l 6189 6580.5 0 f

- --- cn -I ;i n P Ia

l- ---- g 4 b-P I A I t

i I I I I I / I I I I I I I I I I I

> k!ie ;;I-=I8 w. k- L Chap. 2 Page 48 Par. 64 1 O/l 6109 6580.5

65. ITT MODELS AN/GRR-23 (VHF) AND AN/GRR- h. Preamplifier, AF/AGC Squelch, A3. The detectedii 24 (UHF) RECEIVERS. (audio) signal is amplified by the preamplifier, and the audio The vhf and uhf receivers are identical except for their fre- output terminates at two audio volume controls. The age is quency determining elements.The vhf and uhf receivers are obtained by sampling the detected carrier level voltage, single-conversion, crystal-controlled, superheterodyne amplifying it, and applying this voltage to the mixer-multi- receivers for am (A3) service. They are identical in physical plier and if amplifiers. The age voltage is also fed to the configuration but differ electrically in the antenna coupler, squelchstage to quite the receiver in the absenceof a received the tunable filter, and the mixer-multiplier modules. In addi- signal. tion to thesemodules, the receivers have in common a local oscillator, buffer amplifier, crystal filter, if amplifier and i. Audio Amplifier, A4. The audio amplifier has two detector, preamplifier with automatic gain control (age) and channels, each having 9OmWoutput, one to the phone jack squelch circuits, audio amplifier, and power supply. Figure and the other for remote speakeroperations. 2-35 is a simplified block diagram of the vhf and uhf receivers. j. Power Supply, PSl. The receiver power supply converts the 47Hz to 42OHzac primary power into regulated and unregulated dc voltage to operatethe receiver circuits. When a. Antenna Coupler, A7. The antennainput is fed to the the ac primary input is interrupted, automatic switchover is antenna coupler, which provides the capability of operating accomplished to dc input from an external 24V storagebat- two receivers from a single antenna.It is an impedancetrans- tery, if such a battery is used. (These batteries are not sup- forming device that allows two receivers to operatefrom the plied at FM sites, except low-activity ATCT’s that use sameantenna with a maximum 2.5dB reduction in sensitivity, batteries as primary power.) when receivers are separatedby l.OMHz (vhf) and 3.OMHz (uhf) in operating frequencies. k. Oscillator-Synthesizer. The oscillator-synthesizer is a substitute for any version of the crystal-controlled oscillator b. Tunable Filter, FL2. The tunable filter provides two or the oscillator-multiplier, when a channel frequency crys- tuned cavity sections for preselection of the operating tal is not available or is not operable. Thumb-wheel switches frequency. accessiblebehind the front accesspanel are used to selectthe desired channel frequency.

c. Crystal Oscillator, Al. The 8009546 unit usesa fun- 66. WULFSBERG MODEL WR-100 (VHF) damental frequency crystal operating in an oscillator-multi- RECEIVER. plier circuit; temperaturecontrol is not necessaryto achieve The receiver can monitor am (A3) service on any single, the required frequency stability. fixed frequency in the band of 118.000MHz to 135.975h4Hz. The unit is a superheterodynedual-conversion receiver, with d. Mixer-Multiplier, A2. The mixer-multiplier stages the frequency determined by a plug-in crystal element run- double (vhf) or quadruple (uhf) the oscillator frequency and ning at one-ninth the first local oscillator frequency. High fre- heterodynes the resultant signal with the received signal to quency stability is achieved by use of a crystal oven. The produce a 20.6MHz intermediate frequency. receiver has exceptional selectivity provided by a four-pole helical resonator preselector. As a result, the receiver may e. Buffer Amplifier (or Noise Silencer), A5 The buff- operatein close proximity to rf transmitters. Audio output is er amplifier isolates the crystal filter from the mixer-multi- via either a 600-ohm balanced telephone line or a local plier. The center frequency is 20.6MHz, bandwidth 4MH2, speaker.Figure 2-36 is the functional block diagram of the or unity gain. Some systems use an interchangeable noise receiver. The receiver consists of three basic modules: if and limiter for the buffer amplifier. audio board (Al), receiver module-rf section (A2), and preselector (A3). These modules plug into the chassis as- f. Crystal Filter, FLl. The signal from the buffer sembly (A4), which contains all the necessaryinterconnect amplifier is fed to a20.6hB-Iz crystal filter, which establishes wiring and cables,as well as a voltage regulator that supplies the receiver selectivity at 5OkHzor 25kHz. +15V dc for the receiver. Described below are the major subassembliesof the receiver. g. IF Amplifier and Detector, A6. The if amplifier a. IF and Audio Board, Al. The ifand audio board (Al) provides a minimum of 94dB of amplification. This signal is contains the detection and audio processing circuitry. The then modulated to provide an audio output. post-detectionaudio is filtered and noise-limited beforepass-

Chap.2 Page 49 Par. 65 6580.5 CHG 3 9128193

SYNTHESIZER

OSCILLATOR

ANTENNA INPUT

\ ANTENNA TUNABLE MIXER CRYSTAL INTERFACE FILTER MULTIPLIER BUFFER AMP 6 FILTER FL1 (Nt ;E) (N:?E) (N:E)

AUDIO PRE-AMPLIFIER IF AMP AMPLIFIER AGOSQUELCH AND DETECTOR A4 A3 A6

, I

AC VOLTAGES (60Hz) AUDIO OUT 105*10?4. INTERFACE 120flo% 210*10% 240+10% NOTE: THESE MODULES EXCHANGED WHEN DC VOLTAGES CONVERTING FROM VHF TO UHF 22V TO 30V 24V

* Figure 235. Block Diagram of the AN/GRR-23 (VHF) and AN/GRR-24 (UHF) Receivers

Page 50 Chap. 2 Par. 66 1 O/l 6189 6580.5

------..-..--. -w-v------, l- -1 _I= I i 5: r& E i 83 0,2 IP I I I ! I I I

Chap,2 Par. 66 Page 51 4

6580.5 CHG 3 9128193

ing to the final audio amplifiers. Noise above the normal * determining elements. The vhf and uhf transmitters use a audio frequency range is filtered off, rectified, and use to microprocessor to control and display all tuning and ddrive the signal-to-noise squelch circuitry. This board also monitored functions. The technician interfaces with the contains an age amplifier which controls the gain of the microprocessor via four push-button menu con- various if stagesand drives the carrier level squelchcircuitry. trol/programming switches and a liquid crystal display b. Receiver Module-RF Section, A2. The receiver (LCD). The push-button switches and LCD display may module-rf section (AZ) contains the circuitry which converts be used to select the operating frequency and make the rf signal down to the if frequenciesand amplifies it to a level suitable for detection.The receiver is a dual-conversion operational parameter adjustments to the transmitter. superheterodynetype utilizing intermediate frequencies of Various transmitter functions such as relative transmitted 10.7MHz and 455kl&. The receiver frequency is controlled signal strength and internal power supply voltage levels by a plug-in crystal module (A5) which setsthe frequency of may also be monitored via the LCD display. Figure Z-36.1 the first local oscillator. Multipliers, filters, and buffers depicts a simplified block level diagram of the vhf and uhf amplify the local oscillator output up to a level suitable for transmitters. injection into the first mixer. The 10.7MHz output of the mixer is amplified, filtered, and mixed with a secondlocal oscillator to produce a pre-detectorif signal at 455kHz. a. Front Panel Controls and Indicators. The front panel controls and indicators consist of ac and dc power c. Preselector, A3. The preselector bandpassfilters the circuit breakers and light emitting diodes (LED), four incoming rf signal. The preselector is a four-pole helical push-button menu control/programming switches, vswr resonator type that provides a high level rejection of image and transmit LED’s, an LCD, and a microphone push-to- and spurious signals with a minimum of insertion loss. talk (PTT) jack. The filter consistsof four helical coils resonated by tuning capacitors. Once tuned properly, the preselector can b. Microprocessor. In normal operation, the micro- achieve skirt rejection in excess of 100dB at the image processor continuously runs an operational program to frequency, with less than 5dB passbandattenuation. digitally control and monitor all parameters of the transmitter. Selected values for critical performance d. Signal-to-Noise Squelch. The signal-to-noise parameters may be input to the microprocessor via the squelch circuit operates on the principle that the noise front panel adjustments and push-button switches. component of the audio output from the am detector decreases,or quiets, as the rf signal input is increased. c. RFSyuthesizer. Theradiofrequency (rf) synthesizer This reduction in noise (i.e., increase in the signal-to-noise maintains the transmitter output frequency via a voltage ratio) can be detected and used to operate the squelch gate controlled oscillator (vco), a phase lock loop (PLL), and circuitry. An 8kHz high-passfilter whosegain is controlled control signals from the.microprocessor. The frequency by s/n squelch adjust potentiometer strips off any voice- output range is 117.975 MHz to 136.975 MHz for vhf band audio and passesonly those frequency components transmitters and 225 MHz to 399.975MHz for uhf trans- (presumably noise) which lie above the normal voice mitters adjustable in 25 kHz steps. passband. The noise output is rectified and filtered, producing a voltage which is proportional to the noise d. Voltage Controlledm Attenuator/Amplifier. The signal. voltage controlled attenuator/amplifier utilizes a PIN diode attenuator and a voltage controlled amplifier to * 67. MOTOROLA MODELS CM-ZOOVT (VHF) AND regulate the signal level driving the rf power amplifier and CM-200UT (UHF) TRANSMITIkS. to provide audio frequency amplitude modulation. The The very high frequency (vhf) and ultra high frequency voltage controlling the attenuator/amplifier is supplied (uhf) transmitters are identical except for their frequency e from the automatic level control (ale) section. 8

Page 52 Chap. 2 Par. 66 9128193 6580.5 CHG 3

FSCENER

ANTENNA

110 24V VAC DC

* Figure 236.1. Block Diagram of CM-200VT and CM2004JT

* e. RF Power Amplifier. The power amplifier (pa) is a * h. RF Power Sensor. The rf power sensor two stage, fixed gain, rf amplifier, which is designed to utilizes an rf coupler and diodes to produce two dc deliver ten watts of continuous rf power. By means of the voltages that are representative of the transmitter internal microprocessor and circuitry, the transmitter pa forward and reverse power. These voltages are temperature and vswr are constantly monitored. If the utilized by the automatic level control and vswr microprocessordetects an abnormally high pa temperature protection circuitry of the transmitter. or vswr, it will instantly reduce the pa output power to protect it from the over-temperatureor high vswr condition. i. Automatic Level Control (ALC). The ale section receives representative voltages of forward and reverse f. RF Filter. The rf filter is a seven-pole bandpass power, control voltages from the microprocessor (for filter, which passes output signals within the intended setting the modulation level and rf output power), and bandwidth of the particular transmitter. Signals outside of a audio signal level from the audio section. The the passbandof the rf filter are rejected. The bandwidth output voltage from the ale establishes the rf power of the transmitters are: 117.975MHz to 136.975MHz for output of the transmitter and maintains a constant vhf transmitters, and 225 MHz to 399.975 MHz for uhf amplitude modulation for varying levels of audio transmitters. input.

g. RF Transmit/Receive Switch. The r-f transmit/rec- j. Audio Frequency (AF) Section. The af section eive (t/r) switch consistsof diodes which passsignals from of the transmitter amplifies the audio signal from the the antenna to the receiver when the transmitter is idle. microphone input and/or the remote input. The Signals are blocked from the transmitter to the receiver audio section contains an automatic gain circuit and when the transmitter is active. This configuration allows a audio bandpass filter with a frequency range of 300 to transmitter/receiver pair to operate in a transceiver mode. * 3400 hertz. *

Chap. 2 Par. 67 Page 52-1 6580.5 CHG 3 9128193 rk k. PowerSupply. The transmitter power supply utilizes * crystal filters that provide off-channel rejection and switching circuitry to convert primary power (120 Vat or selectivity. The overall gain of this stage is controlled by 20 to 30 Vdc) to the operating voltages used internally to the age voltage and the frequency conversion takes place the transmitter. These voltages are: + 5 Vdc, + 12 Vdc, -12 by mixing the first if(45 Mhz) and the output of the second Vdc, and +80 Vdc. lo synthesizer,which is faed at 44.545MHz. The 455 kHz output is applied to the second if stage. 68. MOTOROLA MODELS CM3OOVR (VHF) AND CM-2OOUR(UHF) RECEIVERS. c. Second IF Stage. The second if stage also provides The very high frequency (vhf) and ultra high frequency age controlled amplification. A 455 kHz ceramic filter (uhf) receivers are identical except for their frequency provides additional selectivity. The output of &is stageis determining elements. The vhf and uhf receivers use a applied to the detector. microprocessor to control and display all tuning and monitor functions. The technician interfaces with the d. Detector. The detector stagehas two basic functions; receiver’s microprocessor via four push-button switches to strip the am modulation from the if signal and apply it and a liquid crystal display (Icd). The push-button switches to the audio circuits, and to detect the amplitude of the and led display may be used to select the operating fre- incoming signal to develop the age voltage. This age quency and make operational parameter adjustments to voltage is then used to control the gain through the rf, if, the receiver. Various receiver functions such as relative and audio stages. received signal strength and internal power supply voltage levels may also be monitored via the led display. Figure e. Audio. The audio circuit provides a constant 2-36.2 dipicts a simplified block diagram of the vhf and uhf output level amplifier stage controlled by the age voltage. receivers. The output level is a function of modulation percentage. This stage also provides post-detection filtering to limit a. Pre-selector. Signals from the antenna are applied the audio output to a bandwidth of 300 Hz to 3.5 kHz. to the pre-selector section which provides tuned bandpass Two separate audio amplifiers drive the two balanced filtering to select the desired frequency and reject all outputs, remote audio out at connector 52 on the back others. The tunable range of the filters is 117.975MHz to panel, and headset audio out on the front panel. 136.975MHz for the vhf receiver and 225 MHz to 399.975 Separate volume controls are provided for each output. MHz for the &receiver. The received signal is amplified The squelch circuit consists of a comparator amplifier by a low noise amplifier (LNA) and converted to the 45 that compares the age voltage to a voltage set by a MHzintermediate frequency (if) by mixing it with the local squelch potentiometer on the front panel. If the age oscillator (lo) frequency supplied by the synthesizer. The voltage is lower than the squelch voltage, the audio synthesizer frequency has been set by the processor to the output is muted. operating frequency (Fo) + 45 MHz. A variable attenuator at the input of the pre-selector reduces the f. Synthesizer. The synthesizer is phase lock loop amplitude of large input signals. The amount of attenua- (pII) controlled with a frequency range of 162.975MHz tion is a function of the input signal strength and is to 181.975 MHz for the vhf receiver and 270 MHz to controlled by the automatic gain control (age) voltage. 444.975 MHz for the uhf receiver, 45 MHz higher than This allows the receiver to receive signals as high as 200 the operating frequency range. Data to select the proper mV rms without overdriving the receiver. frequency is supplied by the processor based on operator inputs. The frequency can be adjusted in 25 kHz steps. b. First IF Stage. The first if stage receives 45 MHz from the pre-selector. This stage provides filtering, g. Second LO Synthesizer. The second lo synthesizer amplification, and converts the frequency to the second if is a fned tuned pll synthesizer that operates at 55.545 frequency of 455 kHz. Filtering is accomplished by two Q MHZ. *

Chap. 2 Page 52-2 Par. 67 6580.5 CHG 5

hntenna

Automatic Gain Control

1lOirAC 24;DC -1 -I

Figure 2-36.2. Receiver Block Diagram

h. Front Panel Components. The front panel x amplifies or bypassesthe signal. In the BYPASS switch components consist of the liquid crystal display (LCD), position, the LPA is in a mode where it does not amplify four control push buttons, and the volume and squelch the rf signal regardless of input level. Finally the TEST controls. position forces the LPA into a mode where it always amplifies the input signal. The BYPASS and TEST . 1. Microprocessor. In normal operation the switch positions are intended to be used only for bench microprocessor continuously runs an operational program testing of the LPA’s. to digitally control and monitor all parameters of the receiver. Selected values for critical performance The LPA is a solid-state rf amplifier that has several parameters may be input to the microprocessor via the built-in safety and convenience features. The LPA may be front panel adjustmentsand push-button switches. Powered by 120 V ac, +24 V dc, or both. In the case where both ac and dc Power is supplied, the LPA is j. Power Supply. The receiver power supply utilizes designedto draw its operating Power from the ac line. For switching circuitry to convert primary Power (120 V ac or the CM-50 VHF LPA, the operating cm-rents range from 20 to 30 V dc) to the operating voltages used internal to less than 1 amp in the receive mode to 3.5 amps from the the radio. These voltages are: +24 V dc, +12 V dc, -12 V ac line or 10 amps from the dc line in the transmit mode. dc, +5 V dc, and -5 V dc. For the CM-51 UHF LPA, the operating currents range from less than 1 amp in the receive mode to 5 amps from * 69. MOTOROLA MODELS CM-SO (VEW)/CM-51 the AC line or 16 amps from the dc line in the transmit (UHJ?) LJNEARPOWERAMPLlFlERS (I-PA). mode. The very high frequency (VHF) and ultra high frequency (UHP) LPA’s are virtually identical. Where The normal transmit mode is entered when the diEerencesexist, they will be explained in the text and the LPA automatically detects the presence of a transmit model number of the applicable unit will be identified. All signal (8 to 12 watts) at the rf input connector. The equipment controls are located on the front panel. They LPA switches from the receive mode into the are the ac power switch, the dc power switch, the three- transmit mode, amplifies the signal to a 50-watt rf position operating mode switch, and the rf power adjust level and indicates the mode by lighting the 50W TX control. In the operational configuration, the three- indicator on the front panel. For the receive mode position operating mode switch should always be in the the LPA connects the signal coming in the antenna NORMAL position. In this mode, the LPA monitors input (rf output connector) to the rf input connector and and output rf levels, and based on these levels, either * the RX indicator is illuminated. x:

Chap. 2 Par. 68 Page 52-3 6580.5 CHG 5 4 O/23/95

Subsection 2. TRANSMISSION LINES

70. GENERAL. employ one or more cavities tuned to the associated For frequencies over 30MHz, the common type transmitter frequency,and as such provide isolation between of transmission line is the concentric line called units and suppressionof spurious and harmonic emissions. coaxial cable. This cable is available in a wide Additionally, the passivedesign of these units make them variety. Figure 2-37 illustrates two types of coaxial virtually fail proof. A disadvantageis they introduce a cable transmission lines, the air dielectric and the signal loss. solid dielectric coacial cable. The inner conducto; may be either solid or standard wire. Insulating b. Multicouplers may be either passive or active. material between the inner and outer conductors Passive multicouplers consist of tuned cavities. They may be air (shown in part A) or some material provide isolation between receivers and rejection to off- such as polyethylene or foam (shown in part B). frequency signals. They are virtually fail proof; however, The outer conductor is either braid or tubing. The they have an insertion loss causing a decrease in signal coaxial line is used in the agency for feeding level. Active multicouplers, used only with receivers, antennas used at vhf and uhf frequencies. provide signal ampliicaiton that can more than offset 71. COMBhERS AND MULTICOUPLERS. insertion loss. Although they can combine a large number The terms combiners and multicouplers are sometimes or receivers, up to twelve, in normal practice they are used interchangeably. However, combiners are normally limited to four receivers to minimize the impact of loss of associatedtransmitters and multicouplers with receivers. antenna, coaxial cable, or multicoupler. The broadband They are both devicesdesigned to allow the connection of nature of the input circuits required for full band coverage several transmitters or receivers to one antenna. is a distinct disadvantage. Also,strong signals may cause nonlinear operation and result in intermodulation distor- a. Combiners are tuned-cavity deviceswhich allow more tion. The active elements are subject to failure, which may than one transmitter to share a single antenna. They result in loss of service.

Chip. 2 Page 524 Par. 70 1O/i 6189 6580.5

INNER CONDUCTOR \ /- OUTER CONDUCTOR

L BEAD OR SPIRAL SUPPORT

A. AIR DIELECTRIC

OUTER CONDUCTOR INNER CONDUCTOR (BRAID) (SOLID OR STRANDED)

DIELECTRIC

L PROTECTIVE SHEATH

B. SOLID DIELECTRIC

Figure 2-37. Coaxial Cable Transmission Lines

Chap. 2 Page 53 Par. 71 6580.5 1O/l 6189

Subsection 3. ANTENNAS 72. GENERAL. 73. VHF SINGLE INPUT ANTENNAS. The generaltype of ground-basedvhf/uhf air-ground radio a. The TACO model D-2276 is a single-element,vertical- communication antennais the collinear, vertically polarized, ly polarized omnidirectional antenna, specifically designed omnidirectional dipole antenna. The simplest antenna is a to provide optimum performance throughout the frequency single input antenna that has no gain over a referencedipole band of 118 to 136 MHz. The radiating element is enclosed antenna.There are multiple input antennaswith no gain, and in a completely sealed1.50-inch (3.8 lcm) diameterfiberglass single input antennaswith gain. The radiation patternsin the radome. Figure 2-38, part A, is a general illustration of the horizontal plain are usually circular with a minimum of dis- antenna.Part B of the figure is a detail of the mounting clamp tortion. Additionally, thereis limited application of direction- supplied with each antenna. An optional clamping arrange- al gain antenna, such as a Yagi array and a log periodic. A ment permits mounting on either a 1.25-inch (3.175cm) or a brief description of the types most often used at agency 2.50-inch (6.35cm) mast. The clamp provides in-line mount- facilities is contained in the following paragraphs. ing with the mast, which allows feeding the antennawithout

I I- RADOME RADOME - f-7 PIPE CLAMP

CLAMP MOUNT HALF

- CLAMP MOUNT 3 ADAPTER GROUND HALF i I - MAST I I LUG

A. ANTENNA ASSEMBLY B. MOUNTING CLAMP DETAIL

Figure 2-38. General View of TACO Antenna

Page 54 Chap. 2 Par. 72 5/22/90 6580.5 SO SUP 1

72-SOI. EXTERNAL VHF AND UHF RF FILTERS FOR INTERFERENCESUPPRESSION a. General. If frequency interference occurs which cannot be eliminated by equipment, repair or adjustment, reassignment or relocation of antennas or frequency changes, it may be necessary to install an RF filter in the antenna transmission line. Since an RF filter increases the antenna system power loss, care must be taken to assure that the coverage requirements are met with the filter installed. Therefore, installation must be closely coordinated with the control facility and with the Systems Maintenance Engineering Branch. Written authorization is required for use of any external RF filter. Before an external filter is placed in service, SO Form 6630-2, VHF and UHF Filters (Transmitter), or SO Form 6630-3, VHF and UHF RF Filters (Receiver), shall be completed. The completed form shall become a part of the Facility Reference Data File (FRDF) and a copy shall be forwarded to the Systems Maintenance Engineering Branch, ASO-460, for inclusion in the facility file. The requirement for the filter shall be reevaluated each time an equipment or frequency change is made at the facility. If the filter is no longer required, it shall be removed and the control facility and the System Maintenance Engineering Branch notified in writing. b. Filter Types. The following types of RF filters are currently used in the Southern Region:

(1) VHF Triple Tuned Cavity Filters. Triple tuned cavity filters are used to eliminate transmitter spurious emissions, to prevent frequency mixing in the transmitter power amplifier stage (and subsequent retransmission of product frequencies) and, temporarily, to eliminate undesired signals from receiver inputs prior to purchasing crystal filters. They will not eliminate odd multiple harmonics of the channel frequency. Models currently in use are the FA-8769 (Microwave Applied Research Model 788-l), Decibel Products Model DB-4015, and Wacom Products Model WP-420-3. Although somewhat different physically, these three types have given essentially identical results. Each filter consists of three identical quarter wave resonant coaxial cavities connected with either rigid coaxial "U bends" or precut coaxial cables of critical length. One, two, or three cavities may be used and the center frequency and bandwidth of each cavity can be adjusted. Decreasing the bandwidth of a cavity or adding an additional cavity to increase the rejection of an unwanted signal also increases the insertion loss at the desired frequency and may derogate coverage. The minimum number of cavities and the minimum insertion loss necessary to eliminate the interference should be used. Detailed descriptions and adjustment procedures are provided in the manufacturers instruction books. Cavity filters should always be pretuned with a signal generator before being connected to a transmitter. If possible, a spectrum analyzer should be used as a detector so that the bandpass characteristics can easily be observed and optimized. This is especially important when using more than one cavity since accidental stagger tuning can cause inband ripple.

Chap 2 Par 72-SO1 Page 54-SO1 6580.5 SO SUP /1

(2) UHF Triple Tuned Cavity Filters. Except for physical size and frequency range, the UHF triple tuned cavity filters are identical to the VHF triple tuned cavity filters. However, due to the greater flexibility in UHF frequency selection, there has been little requirement for UHF filters. Models currently available are the FA-8945 (Microwave Applied Research Model 788-2) and the Decibel Products Model DB-4018.

(3) VHF Crvstal Filters. VHF crystal filters have a maximum input power of approximately 10 milliwatts and can only be used on receivers. They are very compact and usually have a narrower bandpass than the cavity filters. Crystal filters are also more stable than cavity filters under varying temperature and humidity conditions. Internal lightning protection is provided on recently purchased filters. Various models of crystal filters manufactured by Piezo Technology, Inc., are in use. The type of interference, coaxial connector . requirements, and the coverage and bandpass requirements must be considered when selecting a filter.

(4) Low Pass Filters. Various external low pass filters have been used in the past. Most of these have now been removed. They may prove useful in eliminating harmonic interference.

(5) Single Tuned Cavities. Older single tuned cavity filters such as the 4KYSA2 are generally much bulkier and less effective than the triple tuned cavity filters. There are currently no plans for use of these filters.

Chap 2 Page 54-SO2 Par 72-SO1 1 O/l 6189 6580.5

exposing the transmissionline. The antennaand clamp com- the band. Through broadbandsuppression of extraneouscur- bination meetswinciload requirementsof 85 knots with l/2- rents upon the transmission line, the undesirable clover leaf e inch (1.27cm) radial ice coating. pattern is avoided. The outer conductors oPboth halves of the dipole are at dc ground potential. A grounding lug is provided b. The design employed in the antenna results in broad- at: the base of each antenna for supplemental grounding band half-wave dipole characteristicsover 118 to 136 MHz. capability. Figure 2-39 showsvswr and radiation characteris- The desired figure-eight radiation pattern is generally con- tics of the antenna. stant throughout the band. Through broadband suppression of extraneous currents upon the transmission line, the un- c. AntennaProductsCotp model DPV-37 is an equivalent desirableclover leaf pattern is avoided. The outer conductors of the TACO D-2277. of both halves of the dipole are at dc ground potential. A grounding lug is provided at the baseof eachantenna for sup- 75. VHF DUAL INPUT ANTENNAS. plemental grounding capability. Figure 2-39 shows the voltage standing-wave ratio (vswr) and radiation characteristics a. The TACO model D-2272 is a dual-element, vertical- . of the antenna. ly polarized omnidirectional antenna, specifically designed to provide optimum performance throughout the frequency c. AntennaProductsCorp model DPV-35 is an equivalent band of 118 to 136 MHz. The two independently operating of the TACO D-2276. elements are enclosed in a sealed 2.250-inch (5.72cm) diameter fiberglass radome (see figure 2-38). An optional 74. UHF SINGLE INPUT ANTENNAS. clamping arrangementpermits mounting to either a 1.25-inch (3.175cm) or a 2.50-inch (6.35cm) mast.The clamp provides a. The TACO model D-2277 is a single-element,vertical- in-line mounting with the mast, which allows feeding the an- ly polarized omnidirectional antenna, specifically designed tenna without exposing the transmission line. to provide optimum performance throughout the frequency band of 225 to 400 MHz. The radiating element is enclosed b. The design of the antenna results in broadband half- in a sealed 1.50-inch (3.81cm) diameter fiberglass radome wave dipole characteristics over the 118MHz-to-136MHz (seefigure 2-38). An optional clamping arrangementpermits band. The desired figure-eight radiation pattern is generally mounting on a 1.25-inch (3.175cm) or a 2.50-inch (6.35cm) constant throughout the band. Through broadband suppres- mast. The clamp provides in-line mounting with the mast, sion of extraneous currents in the transmission line, the un- which allows feeding the antennawithout exposing the trans- desirablecloverleaf pattern is avoided. The outer conductors mission line. The antenna and clamp combination meets of both halves of each dipole are at dc ground potential. A windload requirements of 85 knots with l/2-inch (1.27cm) grounding lug is provided at the baseof eachantenna for sup- radial ice coatings. plemental grounding capability. Figure 2-39 shows vswr and radiation characteristicsof the antenna. b. The design of the antenna results in broadband half- wave dipole characteristicsover 225 to 400 MHz. The desired c. AntennaProducts Corp model DPV-36 is an equivalent figure-eightradiationpattem is generally constantthroughout of the TACO D-2272.

Chap. 2 Page 55 Par. 73 6580.5 1 O/l 6189

TACO MODELS D-2272, D-2276 AND APC: MODELS DPV-35, DPV-36 RI ZONTAL

VERTICA

FREQUENCY IN MHz A. VSWR VERSUS FREQUENCY 8. RADIATION PATTERNS

TACO MODELS D-2274, D-2277 AND MODELS DPV-37, HORIZONTAL

VERTICAL > 1.2 ,

1.0 6 225 400 FREQUENCY IN MHz

A. VSWR VERSUS FREQUENCY B. RADIATION PATTERNS

TACO MODEL D-2273 6 AND APC MODEL DPV-39 1RlZONTAL UHF - 2 I .a

g VHF--- I .6 0 P u 1.4 3 m > 1.2 VERTICAL -

0 FREQUENCY LN MHz

A. VSWR VERSUS FREQUENCY B. RADIATION PATTERNS

Figure 239 VSWR and Radiation Patterns, VHF and UHF Dipole Antennas Chap. 2 Page 56 Par. 75 1O/l 6189 6580.5

76. UHF DUAL INPUT ANTENNAS. 78. VHF OMNIDIRECTIONAL GAIN ANTENNAS.

a. The TACO model D-2274 is a dual-element, vertical- a. The TACO model D-2261A is a multielement, verti- ly polarized omnidirectional antenna, specifically designed cally polarized, omnidirectional gain antenna designed to to provide optimum performance throughout the frequency operate across the frequency band of 118 to 136 MI-L It band of 225 to 400 MHz. The two independently operating weighs 14 pounds (6.36kg) and is 142 inches (3.6m) long. elements are enclosed in a sealed 2.250-inch (5.72cm) The antenna elements are sealed inside a 1.5~inch(3.81cm) diameter fiberglass radome (see figure Z-38). An optional diameter, filament-wound fiberglass enclosure, which has a clamping arrangement permits mounting on a 1.25-inch molded fiberglass clamp at the baseof the antennafor install- (3.17Scm)or a 2.50-inch (6.35cm) mast.The clamp provides ing the antennaon a 3-inch (7.62cm) diameter support mast. L in-line mounting with the mast,which allows “feeding” to the The vertical radiation pattern at 127MHz has a vertical beam antennawithout exposing the transmission line. width of 40° with an upward tilt. The horizontal radiation pattern has a 1.5dB variation in its omnidirectional pattern. The b. The design of the antenna results in broadband half- gain of the antenna is 1.5dB over the standard gain dipole. . wave dipole characteristics over the 225 to 400 MHz. The The gain of the antenna is 4dB over an isotropic antenna, desired figure-eight radiation pattern is generally constant throughout the band. Through broadbandsuppression of ex- b. AntennaProducts Corp model DPV-40 is an equivalent traneous currents in the transmission line, the undesirable of the TACO D-226 1A. cloverleaf pattern is avoided. The outer conductors of both halves of each dipole are at dc ground potential A grounding 79. VHF DIRECTIONAL GAIN ANTENNAS. lug is provided at the baseof each antenna for supplemental grounding capability. Figure 2-39 shows vswr and radiation a. The TACO model Y102-B-130V vhf lo-element, characteristicsof the antenna. stackedYagi array antennais a vertically polarized, directional antenna designed to operate acrossthe frequency band of c. AntennaProductsCorp model DPV-38 is an equivalent 118 to 136 MHz. It weighs 12 pounds (5.4kg) and is 103 (2.6m) inches long and 50 inches (1.3m) high. The antennas of the TACO D-2274. are vertically stacked10 feet (3.04m) apart and are connected togetherwith a stacking harnessto permit increasedgain. The 77. VHF/UHF DUAL INPUT ANTENNAS. 0 single-antenna, vertical radiation pattern at 136MHz has a vertical beam width of 50”. The single antenna horizontal a. The TACO model D-2273 is a dual-element, vertical- radiation pattern has a horizontal beamwidth of 62O. The ly polarized omnidirectional antenna, specifically designed horizonral radiation pattern for two antennasvertically stack- to provide optimum performance throughout the frequency ed and skewed0” reducesthe horizontal beamwidth from 62’ bands of 118 to 136 MHz and 225 to 400 MHz. The two in- to 54”. The gain of the single Yagi antenna is 12dB over a dependently operating elements are enclosed in a sealed standarddipole at 136MHz. The antenna gain increases3dB 2.250&h (5.72cm) diameter fiberglass radome (see figure when stackedand skewedO”, and decreases3dB when stack- 2-38). An optional clamping arrangementpermits mounting ed and skewed 180”. Seefigure 2-40. on a 1.25~inch(3.175cm) or a 2.50~inch(6.35cm) mast. The , clamp provides in-line mounting with the mast,which allows b. There are similar antennasby other manufacturersin feeding the antennawithout exposing the transmissionline. the presentpopulation of FAA antennas. b. The design of the antenna results in broadband half- 80.431. RESERVED. wave dipole characteristicsover the 118 to 136 MHz and 225 to 400 MEL The desired figure-eight radiation pattern is 82. GROUND-MOBILE AND BASE-STATION AN- generally constant throughout the band. Through broadband TENNAS. suppressionof extraneous currents in the transmission line, Some effective base-station antennas serving ground- the undesirable cloverleaf pattern is avoided. The outer conductors of both halves of each dipole are at dc ground poten- mobile operations are shown in figures 2-26 and 2-27. Figure tial. A grounding lug is provided at the baseof each antenna 2-26 shows four omnidirectional types: the ground-plane or for supplementalgrounding capability. Figure 2-40 showsthe folded ground-plane (a modified quarter-wave whip); the vswr and radiation characteristicsof the antenna. turnstile, a type much more effective than the whip; the Franklin, a type permitting gain over a skirted coaxial anten- c. AntennaProductsCorp model DPV-39 is an equivalent na; and the skirted coaxial type, which behavesas a half-wave of the TACO D-2273. dipole in free space.Omnidirectional characteristicsmay not

Chap. 2 Page 57 Par. 76 1 O/l 6189

Figure 240. TACO Model Y102B-130V VHF Yagi Antenna

83. RADIO LINK ANTENNAS. always be desirable in base station facilities (as they are on The antennas used for radio link service are almost ex- vehicular antennas).Certain directional antennassuch as the clusively operatedover 3OMHz and are of high directional comer reflector or Yagi are usedto focusradiation in selected gain. Both parasitic arrays (Yagi) (figure 2-27) and corner- corridors or areas.Figure 2-27 showsthe two frequently used reflector antennas are common types, depending on path base-stationantennas, the comer reflector and the Yagi in characteristicsand reliability requirements. Figure 2-41 is a stackedform. The vehicular mount can appearas a whip or comer-reflector antennawith a dipole as a radiating element. quarter-wave stub mounted on trunk or roof. The metal sur- These directive link antennas must be oriented precisely face of the trunk or roof makesan effective, although some- horizontal polarization in one antenna and vertical polariza- what distorted in effect, ground plane. Figure 2-28 shows tion in the other. Connectedto different receivers,and the two three whips and two stubs. receiver outputs combined, the fade margin of the link circuit is improved.

Page 58 Chap. 2 Par. 82 1 O/i 6189 6580.5

REFLECTOR

Figure 2-41. Corner-Reflector Antenna for Radio Link

84.-89. RESERVED.

Subsection 4. WAVE PROPAGATION

90. GENERAL. communication reliability can be direct-wave cancellation by 0 A brief discussion of radio wave propagation at vhf and multipath propagation, co-channel interference, adjacent- uhf frequenciesis included in this subsection.The geometry channel interference, and atmospheric or man-madenoise. of propagation in the vhf and uhf frequency bands, including certain propagation disturbanceshaving the greatesteffect on 92. WAVE GEOMETRY. the reliability of air-ground radio communication, is in- The total energy radiated from the transmitting antennaa cluded. few wavelengths above the earth’s surface to a receiver more than a few wavelengths from the transmitting antenna, con- 91. BASIC. sists of three parts: the direct wave, the earth-reflected wave, Propagation of vhf and uhf waves differs from that of hf and the ground wave. The sum of the direct and earth- wavesprincipally becausethe layers of the ionosphereare not reflected waves is called the spacewave. These components required for propagating the signals of higher frequency (over are shown in figure 2-43 and are discussedbriefly below. 3OMHIz).At times, the D and E regions may have an effect on the propagational efficiency of the higher frequency waves.For the most part, the propagation is line of sight and a. Direct Wave. The direct wave travels along a direct little bending or wave refraction occurs. The line-of-sight path from transmitter to receiver and doesnot require the par- mode of propagation can be represented by an imaginary ticipation of the troposphere or earth for transmission. The cylinder called the service volume. Examples of the service path of the direct wave may be curved slightly by refraction volume for various air traffic control’ zones are shown in in the earth’s atmosphere.Between isotropic (point source) figure 2-42. The main transmission factors to provide re- antennas,the direct wave attenuatesin accordancewith the quired coveragein the service volume are effective radiated general equation for free-spaceor transmission loss: power, antenna pattern or directivity, and transmission loss (attenuation of the signal through theatmosphere).The trans- LOSSdB = 1olOglO + mission loss is modified over and above the basic free-space loss by obstructions, absorption of higher frequencies, and Where Pt = Power inrwatts at transmitting antenna ducting. Obstructions may be mountains, hills, trees, tall Pr = Power in watts at receiving antenna * buildings, and the like, Other derogating factors decreasing

Chap.2 Page 59 Par. 83 6580.5 1 O/l 6189

A. SERVICE VOLUME CYLINOER B. SERVICE VOLUME CYLINDER c. SERVICE VOLUYE CYLINDER FOR HIGH ALTITUDE EN ROUTE FOR TERMINAL APPROACH FOR TERMINAL LOCAL TRAFFIC CONTROL AN0 ATIS TRAFFIC CONTROL AND VFR RADAR ADVISORY SERVICE TRAFFIC

NOTE: NOT TO SCALE

Figure 2-42. Typical Air-Ground Communication Service Volume

Figure 2-43. Components of VHF and UHF Wave Propagation

Page 60 Chap. 2 Par. 92 10/16/89‘ 6580.5

The direct wave is the wave on which the service volumes are wave, the two signals (at the receiver) are in phaseand con- based. sequently are of greatestsignal strength. If an odd number of wavelengths are traveled by the reflected wave farther than b. Earth-Reflected Wave. The reflected wave travels the direct wave, they will be in a 180’ out-of-phase relation- to a point on the earth’s surface (land or water). After being ship and thus producea minimum of received signal strength. reflected at an angle equal to the incident angle, the wave As an aircraft travels toward a transmitting antenna on the travels along another direct path to the receiving antenna. ground, it will passthrough a seriesof lobe maxima and min- This is called multipath interference, which may possibly ima and therefore experience changing received signal causethe receiver to experiencea signal loss or cancellation, strength. Seefigure 2-45, part A, for an example of the lobe dependingon the comparatorlengths of the two paths and the structure over a flat, reflective earth. Antenna pattern con- + phaseof the signals. The speechsignal at the receiver may be tribution to a loss of communication reliability can often be phasedistorted, or there may be fast fading (flutter) affecting minimized by changing the antenna, providing polarization intelligibility of speech. diversity, or making antenna elevation adjustments- Con- sideration of aircraft flight paths and the engineering factors c. Ground Wave. The ground (or surface) wave travels along or near the earth’s surfaceand dependson the presence necessaryto provide an acceptableservice volume should be a part of overall system design. of the earth for propagation. The ground wave plays almost no part in vhf or uhf a-g communications. b. Absorption. Radiated energy can be absorbed by vegetation and ground objects as well as by the atmosphere. d. Tropospheric Wave. The tropospheric wave is bent Although normally not a big problem below XKMHz, ab- in the ionized troposphere(the upper altitude limit of which sorption will affect the vhf and uhf transmissionif the ground- is about 36,000 feet (10,975 meters))and is sent back to earth basedantenna is located too close to dense,humid vegetation. at an angle equal to the angle of incidence. Usually the Heavy rainfall and squall lines are capableof temporarily at- returned wave suffers a great loss of field strength and will tenuating vhf and uhf waves. Figure 2-44, part B, illustrates not normally cause interference if returned by a normally obstruction and absorption effects. ionized troposphere.When this wave is returned by the E c. Ducting. Ductingresults when thenormal atmosphere region, which may sporadically becomehighly ionized, it will is altered so that the refractive index decreasesrapidly with interfere with receivers at or beyond the radio horizon. The an increasein altitude. This causesa strong downward bend- sporadic E mode of propagation is discussed in paragraph 56d. ing of nearly horizontal waves traveling in the layer. The two types of ducts are the ground-based and the elevated duct. Temperatureinversions often produce the ground-basedduct. 93. FACTORS AFFECTING COVERAGE. The elevated duct is the result of meteorological subsidence, The service volume is usually not a perfect cylinder, be- a slow, downward settling of a large massof air such asa stag- causea number of factors affect coverageand the direct wave nant high-pressurearea, coupled with the horizontal spread- suffers additional attenuation,or there is blocking from radio- ing of the air above the lower layers of the atmosphere.The opaque structures. Siting of antennas and antenna lobing different effects on vhf and uhf propagation depend on problems, atmospheric absorption, and ducting are factors whether the transmitting and receiving antennasare located . causing greatestdegradation in the received field strength at within, above, or below the duct. Two aircraft communicat- either the ground or the airborne antenna. ing with eachother, if both are within the duct, would probab- a. Antenna Patterns. Only the theoretical isotropic an- ly experience enhanced signal strength. But if one aircraft tenna, a point source,provides a truly omnidirectional radia- above the duct is in communication with a ground station or tion pattern. Dipoles and other simple arrays yield some with another aircraft below the duct, there would probably be directivity with the result that the receiving antenna will a decreasein signal strength. The effect on a-g communica- respond less to the wave when oriented in certain directions tion should be greatestat or near the extreme limit of the ser- relative to the orientation of the transmitting antenna. A vice volume or when communicating with a distant aircraft characteristic of an antennaradiation pattern of significance just above the radio horizon. in a-g propagation is lobing. Lobing can be calculatedby considering the antenna to be at various elevations above the 94. COVERAGE AND RELIABILITY ANALYSIS. reflective earth. Antenna elevation changesto the phasedifference between the direct and reflected wave at the distant a. Flight Checks. A flight check using an aircraft flying point ofreception. The production of lobes in the antennapat- a circular orbit around a transmitting or receiving facility is a terns, which representmaximum and minimum field strength very effective method of determining the range of com- zones,derives from the fact that if the reflected wave travels munication. Either the aircraft or receiving station should be an integral number of wavelengths further than the direct equipped with a strip-chart recorder previously calibrated in 0 Chap.2 Page61 Par. 92 6580.5

I ,s NULL

/ANTENNA I \

A. LOBING EFFECTS

B. OBSTRUCTIONS AND ABSORPTION

Figure 2-44. Lobing, Obstructions, and Absorption Effects

Page 62 Chap. 2 Par. 94 1O/l 6189 6580.5 termsof signal strength. It will show effects of additional path Path LOSSdB = 38 + 20 log10 fMHz + 20 log10 d loss from obstructions (radio opaque) and multipath problems, including the effects of antenna lobing. An where d is line-of-sight distance in nautical miles operatoron the ground at a ground-basedtransmitter, using a f is in MHz (for vhf, the midband frequency transit or theodolite, may interrupt the transmitted signal to 127.5MHz is used) causebearing-related markers to appear on the trace on the airborne recorder.Nominally, thesewill be at 5” or lO^ inter- The constant 38 for the loss between isotropic (point source) vals. The effect of airborne antennaattitude and responseto antennascannot be used directly without considering factors ground signal will appear in such checks and must be such as receiver sensitivity, transmitter power, antenna loss evaluated. A trailing-wire antenna will eliminate most at- or gain, and total coaxial transmission line loss on eachpath, titude effects. ground-to-air and air-to-ground. A sample calculation (sub- paragraphs (1) and (2) below) for each path shows the b. Mathematical Analysis. A computer may be methodsto be used to apply corrected attenuation. Then, the programmed with geological survey data to show radio range is interpreted for expected, or desired, probability of shadow from land elevations versus antenna location. Be- causeof the transhorizon tropospheric and diffraction effects communication. The latter computation determines that modify low-angle line-of-sight propagation, such com- reliability of actual radio contactsusing the channel. For these samplecalculations,an aircraft transmitter power of 16Wand puter information may be limited in applicability. An effec- a ground transmitter power of 1OWare assumed.The ground tive mathematicalevaluation computespath loss and contact reliability to obtain maximum line-of-sightrange betweenthe receiver sensitivity is assumedto be -99.0dBm. An assump- aircraft transmitter (or receiver) and the ground-basedtrans- tion i.\ 11ladethat 130 feet of coaxial cable typeRG-218/U, in- mitter (or receiver). Such computation is similar to the en- cludi~~p other elements such as 10 connectors, one gineering of radio link circuits, where fade margin is the basis changeover relay, and one rf body (directional wattmeter) on which to determine the statistical reliability of the circuit. collectively introduce a loss of 4.5dB. Aircraft coaxial cable This margin is simply the amount of excessrf signal avail- and connector loss is estimatedat 5.5dB. able at the receiver antenna to compensate for the other derogating factors on the system. The fade margin in a-g (1) Airborne VHF Receiver and Ground VHF Trans- channels determines the probability of successful (intel- mitters. Assume the following data: ligible) contact between the ground and airborne stations. A reliability nomogramis given in figure4, appendix 8. The fol- Ground transmitter 1OWpower ...... +4OdBm lowing datais usedin the wave attenuation and reliability cal- output culations of this paragraph. Ground antenna (dipole antenna) ...... -O.OdB loss over isotropic antenna Subtract from Isotropic Aircraft Contact Probability Free-SDaceLoss Ground coaxial cable, connector, ...... -4.5dB directional wattmeter body, coaxial cavity or 50 percent of contactsare O.OdB other isolation device losses intelligible Aircraft l/4-wave whip loss over ...... O.OdB 90 percent of contactsare 1odB isotropic antenna intelligible Aircraft coaxial cable and ...... -5.5dB connector loss 99 percent of contactsare 2odB intelligible Aircraft receiver sensitivity ...... +93dBm

99.99 percent of contacts 3odB NOTE: The total net gains (+) and losses(-) of the above arc intelligible factors yield a range spaceloss of 123.0dB.

NOTE: Data is basedon a 30-nautical-mile range. Inter- (a) Substituting the range spaceloss (123.0dB) in polation can be obtained from the nomogram of figure 4, the isotropic antenna formula and solving for distance d: appendix 8. 20loglod = 123.OdB- 38 - 20 loglo 127.5MHz c. Attemiation and Reliability Calculations. The following is a standardformula for computing the attenuation of a d = 139.47 nautical miles maximum line-of-sight radio path between isotropic (point source) antennas: range. Chap.2 Page 63 Par. 94 6580.5 1 O/l 6189

This range is theoretically the maximum that will allow a Aircraft transmitter 16W power ...... +42dBm communication reliability of 50 percent. output l (b) A reliability of 90 percent modifies by 1OdBthe Aircraft l/4-wave whip antenna loss ...... OdB range loss, or 123.OdB- 10 = 113.0dB. over an isotropic antenna Aircraft coaxial cable and ...... -3.7dB NOTE: Standing-waveratio (swr) must be added to the connector loss cumulative losses for cable, connector, and rf wattmeter body. Obtain the swr loss to be addedfrom figure 13, ap- Ground receiving antenna ...... +O.OdB pendix 8. (broadbandcoaxial dipole) gain over an isotropic antenna * Substituting in the formula and solving for distance d: Ground receiver coaxial cable, ...... -4.5dB 20 loglo d = 113.OdB- 38 - 20 loglo 127.5MHz connector, cavity or other isolation device loss Ground (AN/GRR-23)) ...... +98.0dBm d = 44.2 nautical miles maximum line-of-sight receiver sensitivity (3.OuV = -98.OdBm) range. For this, the total gains (+) and losses(-) of the above factors (c) To compute the maximum range to be expected yield a range spaceloss of 131.8dB. Correcting range space for 99 percent reliability, modify the range loss of 123.OdB loss for 99 percentreliability by 131.8dB - 20dB = 111.8dB. by 123.OdB- 20dB = 103.0dB. Substituting the correctedrange spaceloss in the isotropic antenna spaceattenuation formula and solving for distanced: Substituting in the formula and solving for distance d: 20 loglo d = 111.8dB- 38 - 20 loglo 127SMHz 20 loglo d = 103.OdB- 38 - 20 loglo 127.5M-H~ d = 38.4 nautical miles maximum line-of-sight d = 14.0 nautical miles maximum line-of-sight range range. (3) UHF Calculations. Calculations for UHF links should be made at the midband frequency of 337MHz. The (2) Airborne VHF Transmitter and Ground method used is the sameas that of (1) and (2) provided that VHF Receiver. The gain and loss factors of subparagraph appropriatefree-space loss corrections are used. (1) are replacedby: 95-99. RESERVED.

Page 64 Chap. 2 Par. 94 CHAPTER 3. STANDARDS AND TOLERANCES 100. GENERAL. measuredby an insulation tester(megger) connected between This chapter prescribes the standardsand tolerancesfor center conductor and shield and the line disconnected from the remote communication facilities equipment, as defined the rf body at the sending end of the line. and described in Order 6000.15A. All key performance 5 parametersand/or key inspection elementsare identified by e. The standing-wave ratio (swr) is measuredat the an- an arrow (+) placed to the left of the applicable item. tenna end of the line with the antenna left connectedas load. The directional wattmeter rf body is inserted in the line at or , 101. NOTES AND CONDITIONS. very close to the antennainput connector. A dummy load ter- The following information and suggestionsare given to minating the line in its characteristic impedance shall NOT promote uniformity and consistency in making various BE USED for the measurement.The antennamanufacturer’s measurements.They should be referred to when referenced specifications in swr for the particular model of the antenna in Section 3, Antennas and Transmission Lines. is the reFerenceinitial value at time of commissioning. Ac- tual commissioning value of swr for each antenna and line a. Where transmitting and receiving equipment are con- should be enteredin station records for future comparison to nected to their control point by means of leased or FAA- determine deterioration. owned lines, the standards and tolerances and periodic maintenance tests for evaluating the lines are contained in f. This measurementrequires use of an rf or dummy load Order 6000.22, Maintenance of Two-Point Private Lines. and directional wattmeterat the antennalocation, which may be on top of a tower or tower platform. To enableaccomplish- b. Excessive modulation and frequency modulation (fm) ment of this check with minimum inconvenience and shut- deviation and off-tiequency transmission are potential down of the channel, the check should be scheduled to be dangersin the operation of transceiving equipment.The port- accomplishedwith the check of swr at the antennaend of the I) able or mobile transceivers are usually operated near line. electronic air navigation or communication faciIities that could be adversely affected. Therefore, it is essential that all g. FAA forti 198 records are no longer required. transceivers be inspected for over modulation and off-fre- However, commissioning records should be madeof coaxial quency crystals in accordancewith the standardsand toleran- transmissionline loss per antennaand all station spares.This ces and the maintenanceschedules of chapter 4. will permit comparison at a later date if deterioration is suspected. c. Insulation resistance cannot be measuredin shorted- stub, balun-input, or the TACO 2200 series very-high fre- h. Unless otherwise indicated, standardsand tolerances . quency (vhf) and ultra-high frequency (uhf) antennas.These apply equally to transmitting and receiving antennas and types of antennasare exempt from the standardsand toleran- transmission lines, whether the equipment is ground-based, ces for insulation resistanceapplicable to other types of an- mobile, air-ground, ground-air, or radio link. tennas.See paragraph 293 for alternate checks. i. DCseries resistance cannot be measuredin TACO 2200 d. The transmission line alone is measured.It is discon- seriesand APC vhf and uhf antennas.These antennasare ex- nectedfrom the normal load and an open circuit left between empt from the standardsand tolerances for dc series resis- center conductor and shield. The insulation resistance is tance applicable to other types of antennas.

Chap. 3 Page 65 Par. 100 6580.5 1 O/l 6189

102. REFERENCES. tion books that do not have TI numbers. An example of these Some references in this chapter are to equipment instruc- is Aerocom IB, par. 5.2.2. References listing only paragraph tion books that have FAA technical issuance (TI) numbers. numbers are found in this handbook. An example is TI 6620.2A, Receiver, Radio An/GRR-23 and AN/GRR-24. Others are to various manufacturers’ instruc- 103.-109. RESERVED.

Section 1. HIGH FREQUENCY EQUIPMENT

Subsection 1. TRANSMITTERS

Reference Toleran Limit Parameter Paragraph Standard Initial Operating

110. MODEL 13305KWA;MAKD SSB . . . , . . . ippendixes TRAXSNTTER...... 2and3

-+ a. Rated Output Power (M311), Modulation, SWR, and Channel Frequency.

(1) Am and amemodes (carrier plus single . . 240 2025w 2025w 280 percent tone) on meter on meter of initial (5000W PEP) (5000W PEP)

(2) SELCAL mode (carrier plus two tones) . . 240 1500w 1500w ~80 percent on meter on meter of initial (5OOOWPEP) (5000W PEP)

(3) Ssb or isb mode (carrier suppressedplus . 240 2025w 2025w 280 percent two tones) on meter on meter of initial (5000W PEP) (5000WPEP)

(4) Modulation on complex signal (two tone . 241 No distortion Same as Same as test) acrated PEP on oscilloscope standard standard

(5) Swr (M312) ...... 240 l.o:l 1.5:1 max 1.8:1 max

(6) Channel frequency ...... _ . 243 Assigned +o.ool% &0.001% frequency

-3 b. Intermodulation Distortion, ...... 242 ?29dB below Same as 225dB below Third and Fifth Order on 5KW PEP Output. 2-tone ref- standard 2-tone reference level erence level

111. MODEL 13lllKW AYvlAND SSB . . . . , . . Appendixes TRAA’SMITTER. 2and3

a. Rated Output Power (M403), Modulation, SWR, Channel Frequency.

(1) Amandamemodes ...... 240 1.O on meter 1.O on meter X30 percent (carrier plus single tone) (IOOOWPEP) (1OOOWPEP) of initial

Page 66 Chap. 3 Par. 102 1 O/l 6189 6580.5

Subsection 1. TRANSMITTERS (Continued)

Reference Tolerant Limit Parameter Paragraph - Standard Initial Operating

(2) SELCAL mode ...... 240 0.5 on meter 0.5 on meter X30 percent (carrier plus two tones) (300W PEP) (300W PEP) of initial

(3) Ssb or isb modes (carrier suppressed plus . 240 1 .O on meter 1 .O on meter 280 percent two tones) (1OOOWPEP) (IOOOW PEP) of initial

(4) Modulation on complex signal (two-tone . 241 No distortion Same as Same as test) at rated PEP on oscilloscope standard standard

(5) Swr (M403) ...... , 240 l.O:l 1.2:l max 1.2 to 1.5:l

(6) Channel frequency ...... 243 Assigned +0.001 +0.001 frequency percent percent

-9 b. Intermodulation Distortion ...... 242 229dB below Same as 2.25dB below Third and Fifth Order on 2-tone ref- standard 2-tone ref- 1KW PEP Output. erence level erence level

112. MODEL 127-1 CONVERTER- ...... l Appendixes DRIVER. 2and3

a. +28V DC Supply ...... 28.OV dc 28.OV dc +1.ov

b. RF Output Voltage ...... 1OV ac flV ac f2V ac

c. VHF Oscillator Frequency Stability . . . . . 243 Transmit fre- kO.005 f0.005 quency +64MHz percent percent

-+ d. HF Oscillator Frequency Stability . . . . . 243 Transmit fre- flOHz +lOHz quency +175OkHz

113. MODEL 125-1 SB AND 125-3 ...... I ippendixes ISB GENERATOR. 2and3

a. RF Output Voltage (TP-C) . . . .~...... 240 1.OV ac 1.OV ac *o.o1v

b. Carrier Reinsert Level ...... 240 Max Max Max

c. 1750kHz Oscillator Output (TP-A) . . . . . 243 0.55V ac 0.55V ac +o.o1v

+ d. 17SOkHzOscillator Frequecy Stability _ . 243 175okHz +lOHz +lOHz

114. MODEL GPT-1OKW AM AND SSB ...... I ippendixes TRANSMITTER. 2and3

Page 67 6580.5 1 O/l 6189

Subsection 1. TRANSMITTERS (Continued) _. Reference Toleraru Limit Parameter Paragraph Standard Initial Operating

+ a. Rated Output Power Modulation, SWR (MlOOS), and Channel Frequency.

(1) Am and amemode (carrier plus ...... 240 10,OOOWPEP 10,OOOWPEP 280 percent single tone) (5kW avg) (5kW avg) of initial

(2) SELCAL mode (carrier plus two tones) . . 240 10,OOOWPEP 10,OOOWPEP 280 percent (5kW avg) (5kW avg) of initial

(3) Ssb or isb mode (carrier suppressed . . . . 240 10,OOOWPEP 10,OOOWPEP 280 percent plus two tones) (5kW avg) (5kW avg) of initial

(4) Modulation on complex signals (two- . . . 241 No distortion Same as Same as tone test) at rated PEP on oscilloscope standard standard

(5) Swr (M312) ...... 240 l.O:l 1.2: 1 max 1.2 to 1.5:l

(6) Channel frequency ...... 243 Assigned fO.OO1 fO.OO1 frequency percent percent

b. PA Section, 1OkW AX-509, ...... 240 See test data See test See test Balanced Operation. data date Antenna I (No. 1 and No.2).

+ c. Intermodulation Distortion’Third and . . . 242 ?35dB down >35dB down >35dB down Fifth Order on 1OkWor 1kW PEP Output. on spectrum on spectrum on spectrum analyzer analyzer analyzer

d. Oven-Controlled Crystal Oscillator . . . . . 243 Assigned +lOHz +lOHz Frequency Stabibility. frequency

115.-117. RESERVED. -

Page 68 Chap. 3 Par. 114

. .

. 10/16/89 6580.5

Subsection 2. RECEIVERS

Reference Tolerant Zimit Parameter Paragraph Znitial Operating

118. MODEL 2210 AM AND SSB ...... I Lppendix 2 RECEIVER.

-+ a. Sensitivity ...... 250 2uv Sameas 5uV (-93dBm) (-1OldBm) standard max, 1OmW max, 1OmW in 600 ohms in6OOohms

+ b. Squelch ...... 251

(l)Open ...... 2uv SStlELVi 5uV (-93dBm) (-lOldJ3m) standard max to open maxtoopen

(2) Close ...... Approx two- Same as Sameas thirds opening standard standard value

+ c. Frequency Stability ...... 253

(1) 175OKHzoscillator, clarifier ...... 1750Hz *4Hz +lOHz a midrange. (2) Vhf oscillator ...... carrier plus 10.001 fO.001 64Mhz percent percent

(3) Hf oscillator ...... carrier plus ZkO.001 f0.001 1750kHz percent percent

+ d. AM Selectivity ...... 252

(1) 6dBpoints ...... 6kHz min 6kHz min 5.8kHz min

(2) 60dBpoints ...... 14kHzmax 14kHzmax 15kHz max

(3) Nonsymmetry 60dB points ...... 15 percent 15 percent 20 percent max max max

+ e. Ssb Selectivity ...... 252

(1) 6dBpoints ...... Zfc + Ssmeas Sameas 27OOHz standard standard sfc + Sameas Samess 3CIOHz standard standard

(2)3OdBpints ...... If= Sameas Sameas standard standard

Chap.3 Page69 Par.’ 118 6560.5 CHG 5

Subsection 2. RECEIVERS (Continued)

Reference TolerancelLim’t Paragraph Standard Initial ) Operating ,, Parameter I lfct 34OOHz Same as Same as standard standard 2 f,-450Hz Same as Sameas standard standard

119.~123.RESERVED. I I

Section 2. VHF AND UHF EQUIPMENT Subsection 1. TRANSMITTERS

Reference Tokram ;imit Parameter Paragraph Standard Initial Operating

124. VHF AND UHF TRANSMITlXRS, TYPES AN/GRT-21, AN/GRT-22, CM-2OOW, CM-2OOUT, AND WI’-100.

a. Output Power ...... 240

(1) Low power ...... low I-1w

(2) High power.

(a) AM-6154/GRT-21 and ...... 5ow k2W 35w to 55w AM-6155/GRT-22 (including linear amplifier).

(b) WT-100 ...... Commissioned ClW k2W Value x: (c) CM-5O/GRT-21 or CM-2OOvT . . ..__.. 48W *2w 46 +4W and CM-5 l/GRT-22 or CM-2OOVT. * -+ b. Frequency Stability ...... _.__._...... 243,236c(9) (1) AN/GRT-21/22.

(a) Oscillator-Multiplier Module . . Assigned f 0.001 percen +O.OOl percent frequency

(b) Synthesizer Module ...... Assigned + o.ooo5 +O.OOOS frequency percent percent

(2) WT-loo ...... * ...... Assigned r0.0003 + o.ooo3 frequency percent percent

(3) CM-2OOVT/UT ...... Assigned + o.oom ~0.ooo5 frequency percent

Page 70 Chap. 3 Par. 118 s/22/ 90 6580.5 SO SUF' 1 .

SO SUPPLEMENTALPAGE

131-SOI. VHF AND UHF SOLID-STATE RECEIVERS TYPES AR/GRR-23 AND AN/GRR-24.-

. All AN/GRR-23 and AN/GRR-24 receivers equipped with 25 kHz'IF crystal filte& (NSN 5915-01-073-0231, P/N 1790) shall be maintained to the "25 kHz separation" tolerances for frequency stability, selectivity, and nonsymmetry. All UHF and VHF receivers operating on 121.5 MHz or 243.0 MHz shall use a 50 kHz IF crystal filter. The Air Force shall determine which crystal filter will he used in military-operated frequencies at Joint Surveillance System (JSS) sites. Other AN/GRR-24 receivers may contain either 25 kHz or 50 kHz IF crystal filters, depending on the date of manufacture. In addition, some AN/GRR-24 receivers have been retrofitted with 25 kHz IF crystal filters to eliminate interference.

b. When an antenna multicoupler. tuned cavity. or crystal filter is on a receiver, it shall be treated as part of the receiver when performing periodic maintenance. All receiver standards and tolerances must be met with the external multicoupler, tuned cavity, or crystal filter treated as part of the receiver. DO NOT EXCEED 10 MW into a crystal filter. Reference Tolerance/Limit C. Parameter Paragraph Standard Initial Operating

(1) Audio/AGC Par. 254-SO1 1 dB max, 1 dB max, Action 30 to 95% 30 to 95% modulation. modulation. Continuously Continuously Continuously decreasing decreasing decreasing below 30% below 30% below 30% modulation. modulation. modulation.

(2) Squelch Par. 251-SO1 +3 dB from 50 mv +6 dB from Threshold the deter- maximum. the deter- With a Test mined mined Antenna nominal nominal value. value. 50 mV max.

Page 70-SO2 Par 131-SO1 1 O/l 6189 6580.5

Subsection 1. TRANSMITTERS (Continued)

Reference - ToleranceILimit Parameter Paragraph Standard lnnltial Operating

125. MISCELLANEOUS PARAMETERS.

+ a. Modulation Level at _ ...... 241 95 percent 85 to 95 60 to 95 Transmitter Output, on 1OOOHzTone percent percent . or Voice Peaks.

+ b. VSWR on Transmitter Output ...... 240 1.011 1.8/l max 2.8/l max

126. HIGH POWER VHF TRANS- MITTER, AEROCOM, TYPE 7023.

a. Output power ...... 240 Commissioned +lO percent f20 percent value

b. Channel Frequency ...... 243 Assigned M.002 M.002 frequency percent percent

c. VSWR ...... 240 l.O:l 1.5:1 max 1.5:1 max

d. Modulation ...... 241 95 percent 85 to 95 60 to 95 percent percent

127.-130. RESERVED.

Subsection 2. RECEIVERS

Reference TolerancelLimit Parameter Paragraph Standard Initial 1 Operating

131. VHF AND UHF RECEIVERS, t TYPES ANIGRR-23 AND AN/GRR-24. * + a. Sensitivity ...... Tl6620.2A 3.ouv 3.ouv 5uV (-93dBm) (-98dBm) (--98dBm) max, 90mW max, 9OmW max, 9OmW in 600 ohms in 600 ohms in 600 ohms

-+ b. Squelch ...... y ...... TI 6620.2A

(1) Open ...... 1.5uv 1.5 to 5.ouv (-103dBm) 4.ouv (-93dBm) (-103dBm to max -95dBm)

* Chap. 3 Page 71 ~ Par.325 6580.5 1 O/l 6189

Subsection 2. RECEIVERS (Continued)

Reference Toleran -z Limit Parameter Paragraph Standard Initial Operating

(2) Close ...... Approx two- Same as Same as thirds open standard standard value

+ c. Frequency Stability ...... TI 6620.2A

(1) Synthesizer Module ...... Assigned +_0.0005 +_0.0005 frequency percent percent

(2) Oscillator-Multiplier Module ...... Assigned +0.001 frequency percent

-3 d. VHF Selectivity and ...... TI 6620.2A Nonsymmetry. and Appendix 2

(1) 5OkH.z Separation.

(a) 6dB points ...... 32kHz min 3lkHz min 30kHz min

(b) 6OdBpoints ...... 8OkHz max 80kHz max 80kHz max

(2) 25kHz Separation.

(a) 6dB points ...... 20kHz min 16kHz min 14kHz min

(b) 6OdBpoints ...... 5OkHz max 5OkHz max 5OkHz max

-+ e. UHF Selectivity and ...... TI 6620.2A Nonsymmetry. and Appendix 2

(1) 50kHz Separation.

(a) 6dB points ...... 36kHz min 31kHzmin 30kHz min

(b) 6OdBpoints ...... 80kHz max 80kHz 80kHz

Page 72 Chap. 3 Par. 132 6580.5

Subsection 2. RECEIVERS (Continued) - Reference Toleran Limit Parameter Paragraph _ Standard Initial Operating

(2) 25kHz Separation.

(a) 6dBpoints ...... 20kHzmin 16kHz min 14kHz min

(b) 6OdBpoiIlts ...... 5OkHz max 5OkHz max 5OkHz max

f. AVCorAGCAction ...... 254

(1) Threshold (all vhf ...... 5.ouv 6.OuV 8uV and uhf) (-93dBm) (-9ldBm) (-89dBm) max max max

(2) Level control ...... 3dB from 3dB from 4dB from 3.ouv to 3.ouv to 3 .ouv to 50,000uv 50,000uv 50,000uv (-97.5dBm (-97.5dBm (-97.5dBm to -13dBm) to -13dBm) to -13dBm)

132. VHF REKEIVERWulfsberg TYPE WR-100. installation operation manual

-3 a. Sensitivity ...... 4uv 4uv 5uv (-96dBm) (-96dBm) (-93dBm) max 9OrnW max 9OmW max 9OmW in 600 ohms in 600 ohms in 600 ohms

4 b. Squelch. S+N (1) Open ...... 15dE! T 15dB y f5dB N .

(2) Closed ...... Approx two- Same as Same as thirds open standard standard value

+ c. Frequency Stability.

(1) 25kHz separation ...... Assigned +1).0003 *0.0003 frequency percent percent

(2) 5OkHz separation ...... Assigned Z!Io.o003 f0.0003 frequency percent percent

Chap. 3 Page 73 Par. 737 6580.5 1 O/l 6189

Subsection 2. RECEIVERS (Continued)

Reference Tolerant Limit Parameter Paragraph Standard Initial Operating

+ d. Selectivity.

(1) 25kHz Separation.

(a) 6dB points . . . . . k9.8kHz min k9.8kHz mm B.8kHz min

(b)8OdBpoints . . . . f2lkHz max k2lkHz max e1kI-I~ max

(2) 5OkHz Separation.

(a) 6dB points . . . . . H4.8kHz mm +I 4.8kHz min

(b)8OdBpoints . . . . +28kHz max +28kHz max +28kHz max

e. AGC Action.

(1) Threshold ...... 5.ouv 6.OuV 8.OuV (-93dBm) (-9ldBm) (-89dBm) max max max

(2) Level control ...... 3dB born 3dB from 3dBm from 3.ouv to 3.ouv to 3 .ouv to 0 300,000uv 300,000uv 300,000uv (-97.5dBm (-97.5dBm (-97.5dBm to +2.55dBm) to +2.55dBm) to +2.55dBm)

133. HIGH-GAIN VHF RECEIVER, AEROCOM, TYPE 8080.

-3 a. Sensitivity ...... _ Areocom IB, 0.5uv 1.ouv par 5.2.2 *

4 b. Squelch ...... Aerocom IB, par 5.2.3 A

(1) Open ...... <0.5uv

Approx 3uV Same as Same as standard standard

-3 c. Frequency ...... Aerocom Exact +o.OOl +o.OOl II33 p= frequency percent percent 5.4.3.1

-3 d. Selectivity ...... Aerocom IB, par 5.4

.:m ’ Page 74 ChaD. 3 Par. i 32 9128193 6580.5 CHG 3

Subsection 2. RECEIVERS (Continued) Reference Tolerant Limit Paragraph Standard Initial Operating

(1) 6dB ...... 15kHz + 1kHz + 1kHz

(2) 60dB ...... 30kHz 30kHz max 30kHz max

e. AGC Action ...... Aerocom IB, par 5.2.4

(1) Threshold ...... 1uv 1uV max

(2) Level control ...... 3dB, 1uV to Same as Same as 500,ooouv standard standard

* 134. VHF AND UHF RECEIVERS, TYPES CM-200UR AND CM-200VR.

a. Sensitivity ...... TI 6620.6, 3.ouv Same as 5uv TI 6620.7 (-98dBm) max, standard (-93dBm) max, 90mW in 600 9OmW in 600 OhILlS ohms

+ b. Squelch ...... I’1 663a.6, r16620.7

(1) Open ...... 1suv 1.5 to 4.ouv 5.ouv (-103dBm) (-103dBm to (-93dBm) max -95dBm)

(2) Close ...... Approx 1SdB Same as Same as less than open standard standard value

3 c. Frequency Stability ...... rI 6620.6, 16.8 MHz ~0.0001 +-0.0005 r1662:0.7 percent percent *

Chap. 3 Par. 133 Page 75

,r-- . 1 4 - 6580.5 CHG 3 g/28/93

Subsection 2. RECEIVERS (Continued)

Reference Tolerance .imit Parameter Paragraph Standard Initial Operating

* + d. VHF IF Selectivity ...... TI 6620.6, -6dB, +9kHz sameas Sameas n 6620.7, min. -6OdB, ;tandard standard ippendii 2 + 25kHz max.

+ e. UHF IF Selectivity ...... TI 6620.6, -6dB, + 9kHz &me as Same as I?16620.7, min. -6OdB, standard standard Yppendii 2 f 25kHz max.

f. AVC or AGC Action ...... L54

(1) Threshold (all vhf and uhf) ...... 5.ouv 6.OuV 8uV (-89dBm) (-93dBm) max (-9ldBm) max max

(2) Level control ...... 3dB from Same as 4dB from 3.ouv to standard 3.ouv to 50,000uv 50,000uv (-97.5dBm to (-97.5dBm to -13dBm) -13dBm)

135-139. RESERVED.

Chap. 3 Page 76 Par. 134

I .

, 10123195 6580.5 CHG 5

Section3. ANTENNAS AND TRANSMISSION LINES

-I- Reference Tokrancm Limit Paragraph Standard Initial Operating Parameter - 140. INSULATION RESISTANCE, , ...... lOld, i; 290 Infinite > 50 megohms > 3 megohms ANTENNAS.

141. INSULATION RESISTANCE, ...... lOle, i; 291 hfiite > 50 megohms > 3 megohms TRANSMISSION LINES.

+ 142. SYSTEM INSULATION ...... lOld, i; 291 Infinite > 50 megohms 2 3 megohms RESISTANCE.

+ 143. SWR MEASURED AT ANTENNA ...... lOlf, i; 261; l.O:l Manufac- 3.&l max 262 turer’s specification; if not specified, 2.0:1 max.

A IF Motorola LT!A CM-5O/CM-51 ...... 2.0:1 max *

- +144. DC SERIES RESISTANCE ..,.....*...... ,..... lOli, j; 292 Zero Commission- a ohms ing value

+145. TRANSlMISSION LINE LOSS ...... lOlg, h, i; Manufacturer’s SManufac- IManufac- 260 specification turer’s speci- turer’s speci- ficaton plus ficaton plus 0.5 dE3 1.0 dB 146.-159. RESERVED.

0 Chap. 3 Par. 140 Page 76-I (and 76-2)

*U.S. GOVERNMENTPRINTING OFFICE:1996-769-016/20083 3/29/90 6580.5 CHG 1

CHAPTER 4. PERIODIC MAINTENANCE

160. GENERAL. controls and functions, which are necessary to determine This chapter establishesall the maintenanceactivities that whether operation is within establishedtolerances/limits. The are required for point-to-point (PTP) and air-to-ground (a-g) second section identifies other tasks that are necessary to communications transmitters,receivers, antennas,and trans- prevent deterioration and/or ensurereliable operation. Refer mission lines on a periodic, recurring basis,and the schedules to Order 6000.15A for additional general guidance on peri- for their accomplishment.The chapteris divided into two sec- odic maintenance. tions. The first section identifies the performancechecks (i.e., tests, measurements,and observations) of normal operating ltd.-i64. RESERVED.

Section 1. PERFORMANCE CHECKS

Subsection 1. HF TRANSMITTERS

Reference Parag graph Performance Check Standards & Maintenance Tolerance Procedures

* 165. QUARTERLY.l

a. PowerOutput. Measureand record results on FAA ...... 110a; Illa; 240; W form 6610-l. 114a Appendixes 2 and 3 b. Modulation Percentage. Measure with oscilloscope ...... 1 lOa(4); 11 la(4); 241; I and modulation monitor or voice peaks. 114a(4) Appendixes 2 and 3 Recordresults on FAA form 6610-l. ~.

c. Standing-Ware Ratio (SWR). Measure and record ...... llOa(5); 11 la(5); 240 results on FAA form 6610-l. 114a(5)

* 166. SEMIANNUALLY.

a. Measure oven-controlled crystal oscillator frequencies, ...... 112d; 113d; 243; and record results on FAA form 6610-l. 114d Appendix 2

b. Measure miscellaneous crystal oscillator frequencies, ...... 112c 243; and record results on FAA form 6000-K Appendix 2

* 167. ANNUALLY.

a. Measure swr on open wire transmission lines ...... 1 lOa(5); llla(5); 23W3), (4); 114a(5) 240e(3)

b. Measure intermodulation distortion (imd), using spectrum ...... IlOb; lllb; 242; analyzer and two tone-test. 114c Appendix 2 . . . . _. Certain transmitter parametersmay he checkedremotely via the Rh4MS if so equipped, but must be checked semmmuall~ {a t the transmitter sites. *

Chap. 4 Page 77 Par,200 6580.5 CHG 1 3129190

Subsection 2. HF RECEIVERS . Reference Paragraph Performance Check Standards & Maintenance Tolerance I Procedures

168.-169. RESERVED.

* 170. QUARTERLY.1 *

a. Sensitivity or Noise Figure (NF). Measure and record ...... 118a; 250; results on FAA form 6620-l. Instruction Appendix 2 book

b. Squelch Threshold. Measure open and close levels, ...... 118b; 251 and record results on FAA form 6620-l. Instruction book

c. Frequency Stability. Measure oven-controlled ...... 118c; 253; crystal oscillator frequencies, and record Instruction Appendix 2 results on FAA form 6620-l. book

d. Diversity Balance. Where applicable, observe diversity ...... - 236 balance on space-diversity receiving systems, and record results on FAA form 6620-l.

* 171. SEMIANNUALLY.

a. Measure miscellaneous crystal frequencies, and ...... 118~ 253; record results on FAA form 6000-8. Appendix 2

b. Reserved.

172. ANNUALLY.

a. Measure intermediate frequency (if) amplifier 6dB ...... 118d, e 252; and 60dB selectivity and 60dB nonsymmetry. Record Appendix 2 results on FAA form 6000-8.

b. Reserved.

173~174. RESERVED.

’ Certain receiver parametersmay be checkedremotely via the RMMS, if so equipped,but must be checkedseminannually at the receiver sites.

Page 78 Chap. 4 Par. 200 . ’ J

212195 6580.5 CHG 4

* Subsection 3. VHF AND UHF TRANSMITTElRS

Reference PoraPrank Per;formance Check -T Standards & Maintenance Tolerance Procedures

* 175. WITHDRAWN-CHG 4 * 176. SEMIANNUALLY.

a. Measure the gequency of crystal-controlled oscillators ,...... -...... 124b; 126b 243; Appendix 2 or measure the transmit frequency at the transmitter output, and record results on FAA form 66006.

b. Measure the synthesizer frequency in types ANIGRT-2 I,...... 124b; 126b I,gstruction book AN/GRT-22, CM-200UR, CM-2OOVR, and WT-100 transmitters so equipped.

* c. RF’ Power Output at Transmitter. Measure and record . . . ..__.._._____.___, 124a 240; resuh on FAA form 66006. Appendixes 2 and 3

d. Modulation Percentage. Observe voi& peaks with an . . ..__. . . . ,.____..__._.._ 125a 241; oscilloscope and modulation monitor, and record results Appendixes 2 and 3 on FAA form 66006.

e. Standing-Wave Ratio (SWR). Measure the SW at ._.____..______t____.._.._..__ 125b 240 the transmitter output (input to the transmission line). Record results on FAA form 6600-6.

177.-179. RESERVED. -

Chap. 4 Page 79 Par. 175 6580.5 CHG 6

Subsection 4. VHF AND UHF RECEIVERS

Reference PCvagraph Performance Check Stanahds C? Maintenance Tolerance’ 1 Procedures 180. WITHDRAWN-CHG 4

181. SEMJANNUATJLY.

a. Measure crystal oscillator Gequencies, and record ...... _..__. . .._.. 131c, 132~ 253; Appendix 2; results on FAA form 6530-l or FAA form 66006. TI 6620.2A, Par 6.4; Aerocom 8080 lB, Par 5.4;. 1

b. Measure synthesizer kequency in those ANIGRR-23, . ..m...... _+...... m 131c, 134c TI 6620.2A; ANIGRR-24, CM-200 VR and CM-200 UR Appendix 2 receivers so equipped. TI 6620.6, TI 6620.7

* c Performfie fouow-ing&e&s on receivers...... --. _. 131, 132, 133, 134 Appendis 2 -. _.

(1) Sensitivity or Noise Figure (NF). Measure, and . . . ..______._. _.__... 250 record results on FAA form’6600-6.

(2) SquelchThreshold. Measure squelch threshold ...... _.__..... _ 251 level, and record results on FAA form 6600-6.

(3) AVC Action Measure the level controls, and ...... __..___.__.__..__._..__, 254 record results on FAA form 66006.

Page 80 Chap. 4 Par. 180 9/28/93 6580.5 CHG 3

Subsection 4. VHF AND UHF RECEIVERS (Continued)

Reference Paragraph Performance Check Standards & Maintenmce Tolerance Procedures

182. ANNUALLY.

a. Measure if 6dB and 60dB selectivity and 60dB nonsymmetry, ...... 1314 e 252; and record results on FAA form 6600-6. 132d, e TI 6620.2A ry 134d,e T16620.6 , T16620.7 Jr b. Reserved.

183~184. RESERVED. I I

Subsection 5. ANTENNAS AND TRANSMISSION LINES

Reference Paragraph Performance Check Standards & Maintenance Tolerance Procedures

185. ANNUALLY.

a. Measure transmission line loss ...... 145 260

b. Measureswrattheantenna ...... 143 261,262

186~189. RESERVED.

Section 2. OTHER MAINTENANCE TASKS

Subsection 1. TRANSMITTERS

Reference Paragraph Other Maintenance Tasks Standards & Maintenance Tolerances Procedures

190. QUARTERLY:

a. HF Transmitter Tuning and Neutralization.

(1) Adjust all stages for proper tuning and, if ...... Instruction appropriate, neutralization of Class C amplifiers. Books

(2) Verify frequency change...... llOa(6), llla(6) 243 114a(6)

’ Certain transmitter parametersmay be checkedremotely from the RMMS if so equipped,but must be checked semianndally at the transmitter sites.

Chap. 4 Page 81 Par. 182 6580.5 CHG 2

Section 2. OTHER MAINTENANCE TASKS

Subsection 1. TRANSMITTERS (Continued)

Reference Para, v-4 Other Maintenance Tasks Standards & Maantenance Tolerances Procedures

b. HF Transmitter Automatic Load Control ...... Instruction Adjust ssb automatic load control (ALC). Books c. Withdrawn .. . CHG 2 d. Withdrawn . .. CHG 2 Instruction 191. SEMIANNUALLY...... Books a. Inspect, clean, and, if necessary, replace air filters b. Check aiid adjust air switches for proper operation

c. Lubricate blower motors of types TV-36, TU-9, FA-7480, * and FA-7841 transmitters.

192.-194. RESERVED.

Subsection 2. RECEIVERS I Reference Paragraph Other Maintenance Tasks Standards & Maintenance Tolerances I Procedures

* 195. SEMIANNUALLY.

Inspect, clean, and, if necessary, replace air filters...... - Instruction Lubricate blowers that are not self-lubricated Books

196.-199. RESERVED.

Subsection 3. ANTENNAS AND TRANSMISSION LINES

graph Other Maintenance Tasks Isfnndnrds& Maintenance Tolerances Procedures

200. ANNUALLY.

a. Measure system insulation resistance ...... 142 291; 293

b. Measure dc series resistance ...... 144 292; Order 6950.22l

Page 82 Chap. 4 Par. 190

l U.S. GOVERNMENT PRINTING OFFICE 1993-O-568-016/80066 Y

5/22/90 6580.5 SO SUP 1 .

SO SUPPLEMENTALPAGE I 200-SOI. PERFORMANCECHECKS, ANNUALLY. ~. a. Transmitter External VHF and UHF RF Filters. If external RF filters are used to suppress transmitter spurious outputs, measure the input and output VSWR and insertion loss. If the VSWRexceeds 1.5/l or the insertion loss has increased more than 1 dB over the loss at the time the installation data sheets were prepared, filters must be returned and new data sheets prepared. Review the data sheets to verify that the condition requiring installation still exists.

b. Receiver External VHF or UHF RF Filters. If external RF filters are. installed to eliminate interference in receivers, verify that they are still required and that they do not derogate receiver performance. Review the installation data sheet to verify that the condition requiring installation has not changed. The crystal filters should be treated as part of the receiver.

C. Antenna Multicouplers. Since only two solid-state receivers can be directly connected to a single antenna, antenna multicouplers have been installed at some locations in order to connect more than two receivers to one antenna. These multicouplers provide approximately 3 dB of gain to the received signal. The antenna multicouplers should be treated as part of the receiver.

d. Performance Checks, Annually. Check the TACO and DHV type antenna i- fiberglass radome for deterioration. If the,antenna paint appears to be &z-deteriorating, it may be leaking water into the elements. The operational rl)‘ g symptoms are loss of coverage although the VSWRmay be normal. ;=~ The insulation -- resistance may also measure low. If the paint on the antennas appear to be deteriorated, they should be painted using the following recommended paint: Primer - DuPont 1986s Gray Paint - DuPont Special IMRON White #817 (applied per DuPont Specifications) Hardener - IMRON Polyurethane Enamel #192S (mix one part #192S activator to three parts IMRON i/817 paint hardening)

Chap 4 Par 200-SO1 Page 82-SO1 - 5/22/90 6580.5 SO SUP 1 L .I --- SO SUPPLEMENTALPAGE -c;:~- 227-501. TEST EQUIPMENT. Module extender cables for the AN/GRR:23/24 receivers and extender boards for the AN/GRT-21/22 transmitters are available from the FAA Depot, AACLIOO. These extender boards and cables are to facilitate maintenance and troubleshooting of these transmitters and receivers. The National Stock Numbers are : , Transmitter - 6625-00-253-9204 Receiver - 5995-00-253-3994

THE FRONT OF THIS PAGE IS INTENTIONALLY LEFT BLANK

Chap 5 Page 83(and 84)-SO2 Par 227-SO1 1 O/l 6189 6580.5

Subsection 3. ANTENNAS AND TRANSMISSION LINES

Reference Paragraph Other Maintenance Tasks Standards & Maintenance Tolerances Procedures

c. Clean all antenna insulators, replace cracked or ...... broken insulators or other defective parts.

d. Check operation of antenna heaters, where ...... installed.

201.-224. RESERVED. r

1 Order 6950.22. Maintenance of Electrical Power and Control Cables.

Chap. 4 Page 83 (and 84) Par,200 1 O/l 6189 6580.5

CHAPTER 5. MAINTENANCE PROCEDURES

225. GENERAL. 227. TEST EQUIPMENT. This chapterestablishes the proceduresfor accomplishing Refer to the applicable test equipment instruction manuals the various essential maintenanceactivities that are required for conventional usage.Procedures in this chapter do not infor point-to-point (PTP) and air-to-ground (a-g) communica- clude step-by-steptest equipment adjustments.For built-in or tion transmittersand receivers on either a periodic or inciden- special testequipment, the applicable maintenanceprocedures tal basis. The chapter is divided into three sections.The first include instructions for setting up or adjusting such test equip- section describesor referencesthe proceduresto be used in ment. Table 5-l lists all test equipment necessaryto perform making the performancechecks listed in chapter4, section 1. the procedures prescribed by this chapter. Refer to Order The secondsection describesor referencesthe proceduresfor 6200.4C, Test Equipment Management Handbook, for addi- doing the tasks listed in chapter 4, section 2. The third sectional descriptions of test equipment, model numbers,and ap- tion describesthe proceduresfor doing special tasks,usually plication information. nonscheduled and not listed in chapter 4. Refer to Order 6000.15A for additional general guidance. 228. PHYSICAL REPAIR AND MAINTENANCE OF CABLES. Order 6950.22, Maintenance of Electrical Power and Con- 226. INSTRUCTION BOOK REFERENCES. trol Cables, contains instructions for installing, testing, and Referencesare made to certain instruction book proce- physically maintaining and repairing above-ground wire lines dures or instructions to avoid unnecessaryduplication. These and cablesowned by the agency.The instructions cover splic- referencesare primarily contained in chapter 3 and 4 tabula- ing and weatherproofing of coaxial cables, solid and foam tions. Instruction book material may be referencedwithin the dielectric, of the types used in communication antenna sys- proceduresor paragraphsof this chapter when necessaryto tems.When it becomesnecessary to replace,splice, or evaluate provide additional information. the condition of new or old cable, refer to Order 6950.22.

Table 5-l. TEST EQUIPMENT

Generic Name Preferred Item Substitute Item

Audio power level meter General Radio model CA-3432 (receiver test set) GR-1840; FA-5515

Audio signal Hewlett Packard generator model 65 1A

Audio distortion Hewlett Packard analyzer model 339A

AC voltmeter Triplett model 801, type 2

DCregulated supply Trygon model HR40-7C

DC voltmeter Triplett model 80 1, type 2

Digital multimeter Fluke model 8100A Fluke model 8000

Chap. 5 Page 85 Par. 225 6580.5 1 O/l 6189

Table 5-1. TEST EQUIPMENT (Continued)

Generic Name PreferredItem Substitute Item Directional wattmeter Bird model 440 or Transmitter built-in equal, including rf bodies and elements Aerocom transmitter built-ins

Dummy load, 50-ohm, 25W SeeOrder 6200.4C SeeOrder 6200.4C and lOOW,for vhf and for details for details uhf transmitters . Electronic frequency Systron-Donnermodel counter 6153-50

Frequency counter Fluke model 1952A Hewlett Packard5383A

Function generator Clarke-Hessmodel 748 Hewlett Packard (audio oscillator) model 200CD 600-ohm load Value: &lo%, l/2 watt Microphone Shure 414B Modulation meter Marconi Instruments model TF 2304

Oscilloscope Tektronix model 465 Oscilloscope,general Ballantine model 1066 purpose, dc to SOkHz, single trace Rf power meter Coaxial Dynamics Bird Electronics model 85 model 43 Rf signal generator Hewlett Packard8640B Wavetek model 300 Rf isolation pad Wulfsberg PN 300-2069-000 (WBI DB-1)

Signal generator Hewlett Packard Hewlett Packard HP608D/E HP-864OB Spectrumanalyzer Hewlett Packard PanoramicPanalyzer model model H26-8553B SB-12; Transmitter built-in Trolley meter FAA type CA-543A, None (swr meter) per drawing CD-C- 33-l-2

Two-tone test set Panoramicmodel TTG- 1 None

Page 86 Chap. 5 Par. 228 1 O/l 6189 6580.5

Tabl- 5-1. TEST EQUIPMENT (Continu-d

I Substitute HewlettPackard model 4OOD; Simpson model 330

Volt-ohm millimeter Triplett model 60NA Simpson model 260, (vom> Triplett model 630NA I

229.-234. RESERVED.

Chap. 5 Page 87 Par. 228 6580.5 10/16/89

Section 1. PERFORMANCE CHECK PROCEDURES 235. TECHNICAL PERFORMANCE RECORDS. into the transmissionline by the formula Pt = It%. Trans- 0 The following FAA forms 6000-00, technical perfor- mission line current balance is also obtained by comparing mance records (formerly called the FAA form 418 series), the individual readings of the two ammetersif the transmis- shall be used for recording hf, vhf, and uhf transmitter and sion line is unbalanced, for example, if it is zO= 50-ohm receiver performancefor PTP and a-g communication equip- coaxial transmissionline, enter the forward power direction- ment. The forms are illustrated in figures 5-l through 5-4. al wattmeterreadings under Ant II and reflected power direc- Order 6000.15A provides generalinstruction on the useof the tional wattmeterreading under Ant 12. forms. When necessaryto depart from Order 6000.15A instructions, such as for specific equipmentapplication, follow (4) SWR. Enter the standing-wave ratioas indicated the instructions in paragraph236. by the transmitter swr meter or taken from the charts of forward power andreflectedpower in the transmitter instruction a. FAA Form 6610-l (HF Transmitters). Refer to books (or directional wattmeterinstruction manual). Forward figure 5-l for a sampleof this form. and reflected power are metered individually in sometrans- mitters. Swr of balanced transmission lines is obtained by b. FAA Form 6620-l (HF Receivers). Refer to figure using very-low-power channel frequency excitation of open- 5-2 for a sampleof this form. wire line with a trolley meter.

c. FAA Form 6600-6 (VHF/UHF Transmitters and Receivers) Refer to figure 5-3 for a sampleof this form. (5) Ant Type Indent. Enter the type of antenna: rhombic, V, sloping V, Yagi, log-periodic, doublet, vertical d. FAA Form 6000-8 (Continuation or Temporary monopole.Therespective abbreviations should be: R, V, S/V, Record/Report). Refer to figure 5-4 for a sample of this Y, LP, D, VM. form. This form shall be used to record miscellaneousdata required by chapter 4. It may also be used,at the discretion (6) PA PEP. Enter the final amplifier peak envelope of the local maintenancesupervisor, to record other necessary power obtained from the metered ssb transmitter, based on information, such as special test data.The columnar arrange- the chapter 3 standardsand tolerances. ment of the form may be altered locally to accommodatecer- tain situations, at the discrerion of the local maintenance (7) IPA PEP. Enter the intermediate power supervisor. amplifier peak envelope power meteredat the driver output.

236. ENTRIES IN TECHNICAL PERFORMANCE (8) PA Pl I. Enter the meteredfinal amplifier plate RECORDS. current in milliamperes. Numerical entries are required for quantitative nominal- line entries. Use checkmarksto denotequalitative conditions (9) PA Pl V. Enter the meteredfinal amplifier plate and observationsthat meet observedperformance limits. Do voltage in volts. not usecheckmarks to denoterepetitive in-tolerance readings that correspond to a quantitative nominal-line entry or a (10) PA Scr I. Enter the metered final amplifier numerical standard. screencurrent in milliamperes.

a. FAA Form 6610-l. (11) SB Gen RF V. Enter the sidebandexciter or generator rf drive to the converter-driver stagein volts. (1) Circuit. Enter the call sign or communication circuit designator. (12) Conv-Drvr RF V. Enter the converter-driver rf drive to the intermediate power amplifier stagein volts. (2) Mode. Enter the operating mode for the equipment and circuit. Refer to paragraph10 of this order for desig- (13) Carr Ox Stability. Enter the measuredoven- nations of the authorized modes. controlled carrier oscillator frequency at the sidebandgener- ator. (3) Ant 11 and Ant 12. Enter the series rf ammeter readingsin amperesin eachside of the balancedtransmission (14) HF OSC Stability. Enter the measured oven- line. Thesevalues, when addedtogether and divided by two, controlled high-frequency crystal oscillator in the converter- yield the averagerf current for calculating total output power driver stage.

Page 88 Chap. 5 Par. 235 TECHNICALPERFORMlEE RECORD SSB-AMTRANSMITTER, NIGH-FREQUENCY POINT-TO-POINT/BROADCAST FAClLlTl l.OCATlDN ,CU”. SYL& l hwrl. atha?, DATES (From--L*)

EcJUlrMEnT SEIIIAI. NO. ClRC”,l MODE WCERVISOR Wnuhr,)

I NOMINAL

FAAform 61610-1(5-n)

Figure 5-1. Sample FAA Form 6610-l 6580.5 1 O/l 6189

------

- - - -

- -

------

- - - -

- - - - E - - - - - &

- - - - J W E - - - - ; - - - -

Chap. 5 Page 90 Par. 236 , 0 l

TECHMlCALPERFORMME RECORD VHF/UHF AIR/GROUND RECEIVERS/TRANSMlTTERS

FACILITY LOCATION (Citv, State, airport, other) DATE (From-to) - TYPE RECEIVER SERIAL NO. FREQUENCY TYPE TRANSMllTER SERIAL NO. FREQUENCY SUPERVISOR (Signotwe) - RECEIVER TRANSMllTER SELECTIVITY 3 TIME NC NON. $“I& 4% SW. POWER REMARKS 2 DATE (GMT) \y;: FREQUENCY 6dB 6OdB vswll- FREQUENCY Md”. NV z& BAND. BAND. “W?l% * 5 5Ea”s TdRiL WIDTH WIDTH “FiYY %%: - NOMINAL - - -

- - -

- -

FplAForm6600-6 (3-n) Formerly FM Form 6630-l (S-76) which will br used “4. wvER”HmPmml~G GfFa z 1m--oz91-835 8 Ei Figure 5-3. Sample FAA Form 6600-6 in TECHNICAL PERFORMANCE RECORD CONTINUATION OR TEMPORARY RECORD/REPORT FORN

FACILITY DATES SUPERVISOR’S SIGNATURE (ArCI, FSS, ARTCC, VOR, LOC, ETC.) FROM TO LOCATION EQUIPMENT FREQ .

(CITY, STATE, AIRPORT, OTHER) (A/G, OF, COMPONENTi, ETC.) I REMARKS

w 3 3 E s 5 z NOMINAL I

hA Form 6000-8 (S-76) FORMERLY FAA FORM 4lb24 ” u. 5. GWERNUENT PRlnTlnC OFIXCC ‘916 -6676-,,6/42

Figure 5-4. Sample FAA Form 6000-S 1 O/l 6189 6580.5

(15) Station Freq Stability. Enter the transmitter c. FAA Form 6600-6. output carrier or channel frequency, measuredfrom a test point of the transmitter final amplifier or from an attenuator (1) Sensitivity uV. Enter the measuredreceiver sen- probe in the directional wattmeter. sitivity in microvolts. (2) Squelch Threshold pV. Enter the measured rf (16) Percent Modulation. Enter the value of A3 signal in microvolts required to deactivate the squelch. mode modulation in percent. In the ssb modes, observe modulation with an oscilloscope, and enter a checkmark if (3) AVC Level Control DB. Enter this value in dB. satisfactory. (4) Frequency. Enter in MHz the measuredfirst oscillator frequency of the receiver. (17) JMD. Enter a checkmark if intermodulation distortion products meet the third- and fifth-order product limits (5) Selectivity. Enter the measured 6dB and 60dB in chapter 3 for the ssb modesof operation. selectivity of the ITT receiver (6dB and 80dB for the WR- 100 receiver). b. FAA Form 6620-l. (6) Nonsymmetry. Enter the measured if nonsymmetry of the receiver in percent. (1) Circuit. Enter the call sign or communication circuit designator. (7) Power Output Watts. Enter the measuredpower output in watts of the transmitter, into the normal transmis- (2) Mode. Enter the operating mode for the equip- sion line/antenna load of the channel. ment and circuit. Refer to paragraph10 of this order for designations of the authorized models. (8) VSWR. Enter the swr measuredat the transmitter output with the thru-line wattmeter. (3) Diversity. Enter yes or no. (9) Frequency. Enter the measured station (on-the- air) frequency of the transmitter, measuredat a directional (4) Sens 1 through Sens 4. Enter the measured coupler inserted at the transmitter output, when connectedto receiver sensitivity at the antenna terminals of four diversity the normal transmission line/antenna load. receivers (two pairs). The value is to be in microvolts. (10) 5% Modulation Voice. Enter the peak voice (5) Ant l/Ant 2; Ant 3/Ant 4. Enter the antennatype: modulation on an active channel, measuredwith the modula- rhombic, nested rhombic, V, sloping V, Yagi, log-periodic, tion monitor and oscilloscope. doublet, wire-grid lens. The respective abbreviations should be: R, N/R, V, S/V, Y, LP, D, WL. The blanks can accom- 237. AURAL MONITORING. modatetwo diversity pairs. Aura monitoring of speechtransmission on an a-g than- nel provides a means to determine the usability of the ch‘an- (6) Div Bal. Enter a checkmark if observation of the nel. Off-the-air monitoring, using a vhf or uhf receiver, can diversity combiner-selector metering indicates that each provide, from a remote point, an indication of the quality of diversity receiver is connected to the system approximately the entire a-g channel from microphone to transmitter. The 50 percent of the time. preferred method for aural monitoring at the remote outlet is to connect a headsetreceiver via a bridging amplifier across (7) SSB/BFO OSC Stab 1 through SSB/BFO OSC the circuit and listen to the controller’s or pilot’s transmis- Stab 4. Enter the measured frequency of the oven-con- sions.It is important that only bridging (high impedance)controlled ssbbeat-frequency oscillator (bfo) crystal oscillator. nections be made and under no circumstances, on an operational channel, should the headsetbe patched into line (8) SSB/LO OSC Stab 1 through SSB/LO OSC or equipment jacks that will open the channel. Stab 4. Enter the measured frequency of the oven-controlled ssb/local oscillator. 238.-239. RESERVED.

Chap. 5 Page 93 Par. 236 6580.5 CHG 2 S/29/92

Subsection 1. TRANSMITTER CHECKS 240. TRANSMITTER OUTPUT POWER AND (d) With a directional wattmeter chart plotted STANDING-WAVE RATIO (SWR). directly from reflected and forward power readings,enter the chart on the horizontal and vertical axes and read the swr a. Object. To measurethe transmitter output power into curve intercepted. the transmissionline feeding the antenna. (e) In the absenceof charts, the swr can be com- b. Discussion. Output power is measuredwith direction- puted from readings of forward and reflect power by the for- al wattmeters in an unbalanced transmission line, such as mula: coaxial cable, or with series rf ammeters in each side of a balancedtransmission line, such asopen-wire line. The directional wattmetersam either direct reading, or the power is in- terpretedwith a chart from which swr can also be determined. (f) For transmitters having individual meters for The series ammetersare read individually, and the readings forward and reflected power, the procedure is the sameas in are added together and divided by two. The averagecurrent steps(a) through (e) for obtaining power and swr, except that obtained from this is then used in a simple calculation to ob- no meter switching is involved. Some transmitters have tain total power developed in the nominal impedance2% of direct-reading swr metersthat may be used. the transmissionline. (g) For transmitters having both a final output c. Test Equipment Required. Usually none; the direc- amplifier swr meter and an antenna output swr meter, record tional wattmeter is, typically, built-in equipment. For swr both meter indications on FM form 6610-l. The applicable checks of open-wire transmission lines, a trolley meter is tolerance shall apply to both readings. used. (2) Using Series RF Ammeters in Open-Wire Line d. Conditions. For most power determination, no shut- (Figure 1, Appendix 2). down is required. If shutdown is required, coordinate it with the air traffic watch supervisor before proceeding. (a) Read the antenna current in rf amperesin each line, and enter the reading on FAA form 6610-l. e. Detailed procedures. (b) Calculate the transmitter total average output (1) Using the Directional Wattmeter (Figure 1, Ap- power, basedon the averageantenna current, with the follow- pendix 2). ing formula:

(a) In equipment using a single meter for forward power and reflected power, note the reading when the selector switch is in the forward power position. Record the read- (c) Computepower asPEP from averagepower ob- ing in watts on FM form 6610-l. tained in step (b):

fb) Select the reflected power position of the meter PEP=Pt X 2 switch and record the reading in watts. Enter the results in the PEP column of FAA form 6610-l. (c) With the directional wattmeter chart plotted in percent reflected power versus swr (refer to page 25 of the EXAMPLE: 11 = 3.1 amperes model 1330 5kW ssb transmitter instruction manual for an example), enter the chart with percentageof reflected power I2 = 2.8 amperes calculated with the formula: Pr Z0 = 600-ohm nominal for rhombic Percentageof Pr = pf X 100 transmission lines. where Pf and Pr are forward and reflected power values from step (a) and (b) above. Read swr from the horizontal axis as interceptedon the curve in the chart. = 5221.5 watts, average

Page 94 Chap. 5 Par. 240 101-l6189 6580.5

PEP = Pt X 2 Meter minimum = 5221.5 X 2 scale deflection = 25 = 10,443-Owatts, PEP (3) Using the Trolley Meter for SWR on Open- Substituting: swr Wire Line (Figure S-5). To determine swr on open-wire transmissionline, suchas the 600-ohm feedersused forrhom- = 29125 bit and other PTP antennas,a trolley meter is required. The swr cheek is usually made between the location of the stub = l/.16 nearest the transmitter building and the feed-through insulators in the side of the building. This ensuresthat the trans- = 1.08 mitter is loaded with the correct impedance and low-swr conditions. Figure 5-5 showsa typical trolley meter in useon (b) A non-square-lawtrolley meter is accompanied the stubbedtransmission line. by a chart for the relation of meter deflection to electric field. For thesetrolley meters, the actual meter deflection must be (a) The power fed to the line under test must be low converted to the chart value for use in the above formula. and just enough to deflect the meter in the trolley meter to about two-thirds of full scale.An rf signal generatormay have 241. TRANSMITTER AUDIO MODULATION enough output for thejob. The generatoris loop-coupled into LEVEL AND PERCENTAGE. the output tuner of the transmitter, which must be shut down, and the high voltage must be removed from all stages.The a. Object. To check the maximum undistorted audio trolley meter is drawn up and down along one side of the line modulation of the transmitter. outside the building to obtain a peak reading. As the trolley meter is moved, the meter maximum reading and minimum b. Discussion. reading corresponding to the standing-wave peaks and troughs are recorded. The meter deflections cannot be used directly if a square-law detector is involved. The swr is ob- (1) Modulation checks for ssb and am transmittersarc tamed from the formula: accomplishedby using different techniques.Refer to appendix 2 for a discussionof ssbmodulation. Appendix 3 contains l swr = maximum meter deflectiion testarrangements and nomographsfor measuringmodulation minimum meter deflection for am transmitters of vhf and uhf a-g channels. Modulation EXAMPLE: Meter maximum in ssb transmitters is determined by using an oscilloscope. scale deflection = 29 Figure 2-9 ( and figure 3 of appendix 2) illustrates normal and abnormal ssbmodulation patterns. ,

COUPLING \ LOOP AN::NNA

0f Y r-DRAW o CORD

Figure 5-5. SWR Test on Open-Wire Transmission Line

Chap. 5 Page 95 Par. 240 6580.5 10/16/89

(2) To check modulation on active channel without (1) Checking Ssb Modulation (Figure 5-6). shutdown, an oscilloscope and modulation monitor can be connectedwithout the use of a dummy load. When adjusting (a) Connect the test equipment as shown in figure lOOOHstest-tone modulation sensitivity, shut down the trans- 5-6. At certain installations, this arrangementmay be built in mitter, and replace the antenna with a dummy load of the with the transmitting equipment. proper power dissipation. (b) Apply a low-level audio signal, 1OOOHzat -3OdBm or less, to the input of the ssb generatoror exciter, c. Test Equipment Required. and gradually increasethis level while observing the oscilloscope.Continue to increaselevel just until flat-topping is ob- (1) Oscilloscope. served on the oscilloscope waveform, with full transmitter PEP. (2) Audio oscillator, function generator, or two-tone test set. (c) Record the level at which flat-topping occurs. (3) Modulation monitor. (d) Back off the audio input level just until flat-top- (4) Dummy load. ping disappears.This is the maximum modulation audio input level. If this level agrees with the level commissioned for (5) Directional wattmeterand elements. audio input, enter a checkmarkon FAA form 6610-l.

(6) Audio power level meter. (2) Checking AM Percentage (Figures 2 through 5, appendix 3). d. Conditions. When shutdown is required, coordinate it in advancewith the air traffic watch supervisor. (a) From appendix 3, select the test setup required.

e. Detailed Procedures. (b) Apply a 1OOOHzaudio sine wave test tone to the transmitter modulator input at the level required for the appropriate interface level.

AUDIO

AUDI 0 I POWER LEVEL I

Figure 5-6. Checking Ssb Modulation

Page 96 Chap. 5 Par. 241 1 O/l 6189 6580.5

(c) Observe the modulation monitor-oscilloscope (2) Ensure that the transmitter is operating at rated PEP pattern and determine the modulation percentage. Adjust and that meteredstages are performing satisfactorily. Reduce modulator gain as required to meet the limits of chapter 3. sidebandexciter or converter-driver output to zero. (d) Record results on FAA form 6610-l or FAA form 6600-6. (3) Remove the normal audio input and apply, at the sameaudio level, the output of the two-tone test generator to f. Detailed Procedure for WT-100 Transmitter. See the audio modulation input of the sidebandexciter. section 4.4.5 of the manufacturer’s instruction book for detailed procedures. (4) Increase the sideband exciter output to return the lransmitter to full PEP. 242. SPURIOUS EMISSIONS AND INTERMODULA- TION DISTORTION @MD). (5) Set the spectrum analyzer input gain so that the peaksof the two tonesare at 0 dB on the display vertical scale. . a. Object. To ensure that the transmission adequately The displays of figure 3, part A, in appendix 2 should be ob- supressesunwanted radiation and that intermodulation distor- mined. tion (imd) products are within prescribed limits. (6) Check for the presence of imd signals along the b. Discussion. baseline and observe the relative amplitudes of the carrier, and third- and fifth-order products. If within tolerance, enter (1) Spurious emission is usually emitted by a transmit- a check mark on FAA form 6610-l. These products should ter outside the message signal band of the transmitter. be equal to or less than the limit established in paragraphs Parasitics, harmonics, harmonics of imd products, and imd 1lob, 11lb, and 114~ of chapter 3. Abnormalities such as products are some causes of spurious emission. The most shown in parts B and C of figure 3, appendix 2, should be cor- troublesomeimd are the third- and fifth-order products.Refer rected. to appendix 2 for a discussion of imd. 243. FREQUENCY STABILITY. (2) Some transmitters are equipped with the spectrum 0 analyzer, the basic test equipment item for detecting spurious a. Object. To ensurethat the transmitter crystal oscillator emission. Where these are not permanently installed, they frequenciesare within tolerance. may be obtained as portable test equipment. The procedure given below applies to most ssb applications and available b. Discussion. Particularly in the ssb transmitter, the models of spectrum analyzers. The portable spectrum crystal-controlled oscillators that determine the carrier fre- analyzer should be connectedto a sampling loop probe in the quencies must be held very closely within tolerances transmitter output directional wattmeter body. specified in chapter 3. This permits exact reinsertion of the suppressedcarrier at the receiver and prevents signal distor- c. Test Equipment Required. tion. (1) Spectrumanalyzer, or Panalyzer. c. Test Equipment Required. (2) Two-tone test set. . (1) Electronic frequency counter. (3) Vom and/or vtvm. (2) Insulated screwdriver. d. Conditions. Transmitter shutdown will be required when a two-tone audio test signal is applied to the sideband d. Conditions. If frequency adjustments are required, exciter. Coordinate the shutdown with the air traffic watch the transmitter will be shut down. Coordinate shutdown with supervisor before proceeding. the air traffic watch supervisor. e. Detailed Procedure for Measuring IhlD (Figure 5- 7). e. Detailed Procedure, Ssb Transmitter Models 1330 and 1311. (1) Warm up the spectrum analyzer and obtain a trace on its cathode-ray tube (crt). Set for a logarithmic presenta- (1) Warm up the electronic frequency counter for at 0 tion. least 15 minutes. Chap. 5 Page 97 Par. 241 POWER LEVEL

I J I 1

A. CHECKING IMD PRODUCT LEVELS

4 I 4 I

B. CHECKING MISCELLANEOUS SPURIOUS EMISSION

Figure 5-7. Checking IMD and Spurious Emission 1 O/l 6189 6580.5

(2) Adjust the frequency range of the counter to the fre- mit frequency + 64MHz. After completion, disconnect the uency of measurement,and make the testsusing the follow- counter. a ing test points of the transmitter: (d) 1750kHz Oscillator. Connect the counter to test CAUTION: To avoid damaging a counter, ensurethat a point A at the output of the buffer amplifier in the type 125 proper dc blocking capacitor is used at the counter input. 1 (ssb) or type 125-3 isb generator.Adjust, if necessary,C8 1 for exactly 1750kHz. After completion, disconnect the (a) Channel Frequency. Connect the counter input counter. to a sampling loop in the directional wattmeterbody. Reinsert f. Procedure for Miscellaneous Transmitters. The re- the carrier if operating with a suppressed carrier. After quired frequency stability for am hf, vhf, and uhf transmitters measurement,disconnect the counter and resuppressthe car- may be checked for channel frequency (transmit frequency) rier. asin-step (a) of paragraphe above. Substagecrystal oscillator (b) Transmitter HF Oscillator, Transmit Fre- frequency checksrequire locating the output of the oscillator quency + 1.750MHz. Connect the counter to the hf oscillator that is driving the mixer circuit and coupling into this circuit output terminal. Adjust, if necessary, capacitor F of the with a dc blocking capacitor to prevent possible damage to selectedchannel for exactly the transmit frequency of step(a) the counter input circuit. To obtain the best test point for such i- 1.750MHz. After completion, disconnect the counter. measurements,refer to the individual schematicdiagrams of the transmitters,located in the equipment instruction books. (c) VHF Oscillator, Transmit Frequency + 64MHz. Connect the counter to the vhf oscillator OUT ter- 244.-249. RESERVED. minal. Adjust, if necessary,L8 1and C82 exactly for the trans-

Subsection 2. RECEIVER CHECKS 250. SENSITIVITY. (2) Turn the receiver squelch control to OFF and the audio gain control to maximum (fully clockwise). a. Object. To ensure that the receiver will respond to a specifiedinput level in microvolts for a specified audio power (3) Adjust the signal generator or CSM for 1OOOHz 0 output level, or for a specified signal-plus-noise to noise ratio modulation at 30 percent. at the audio output. (4) Adjust the generator to the exact channel frequen- b. Discussion. A receiver may deteriorate in perfor- CY- mancefrom defective components,changes in tuned circuits, (5) Adjust the generator output until the receiver out- or changesin operating voltage. This deterioration is reflected put causedby the rf signal voltage exceedsthe noise level by in lowered sensitivity or gain. at least 50mW. Peak the receiver’s antenna trimmer. (6) Set the generator output for the level in dBm from c. Test Equipment Required. the applicable initial or operating tolerancespecified in chapter 3. (1) Signal generator or communications service monitor (CSM). (7) Set the receiver’s audio gain control to obtain the audio power level specified in chapter 3. (2) Audio power level meter or receiver test set. (8) Shut off the tone modulation of the generator. d. Conditions. Receiver sensitivity is the microvolt level required to produce a signal-plus-noise (signal gencr- (9) Without changing the receiver’s audio gain con- ator modulation on at lOOOHz,30percent) to noise-alone(sig- trol, vary the generator rf output level while observing the nal generator modulation off) ratio of 1OdB.This is a power audio power output on the power level meter. At the same ratio of 10:1 and a voltage ratio of 3.16: 1. time, turn the tone modulation on and off. When a ratio of 10:1 (modulation on:modulation off) is obtained, record the e. Detailed procedure for AM Receivers. generator output attenuator setting. This will be the value in dBm ormicrovolts representingthe required sensitivity stated (1) Connect the test equipment__ as shown in figure 5-8, in the applicable paragraph of chapter 3. If not within the and allow a warmup of at least 15 minutes. stated tolerance/limit, troubleshooting of the receiver is re- 0 quired. Chap. 5 Page 99 Par. 243 6580.5 10/16/89 ‘,

(10) If tolerance/limit is met, the test for receiver e. Detailed Procedure for WR-100 Receivers. squelch threshold can be performed, as test equipmentarran- paragraphs4.3.8 and 4.3.9 of the manufacturer’s instruction gementis the same. book.

251. SQUELCH THRESHOLD. 252. SELECTIVITY AND NONSYMMETRY MEASUREMENTS. a. Object. To determine receiver quieting in the absence of a received signal. a. Object. To determine the if amplifier and crystal filter minimum selectivity at the 6dB points and the maximum b. Discussion. The test arrangement for sensitivity, selectivity at the 60dB (80dB for WR-100) points. This pro- shown in figure 5-8, is also used for squelch-actionchecks. cedurealsomeasures thepercentof nonsymmetryat the 60dB points. c. Test Equipment Required. b. Discussion. . (1) Signal generatoror CSM. (1) Selectivity is a measureof the receiver’s ability to (2) Audio power level meter or receiver test set. reject unwanted signals. Nonsymmetry checks ensure that faulty circuits do not distort the selectivity responseto cause d. Detailed Procedure. loss of fidelity in the desired signal or loss of contact.

(1) Connect the test equipment as shown in figure 5-8, (2) Selectivity and nonsymmetry checksof amreceivers and allow a warmup of at least 15 minutes unlessa sensitivity are different from those applied to ssb receivers in that fre- check hasjust been accomplished. quency offsetsin the mixer to if amplifier chains must be considered. (2) Turn the receiver squelch control to ON. c. Test Equipment Required. (3) Adjust the signal generatoror CSM rf output to zero. Observe the receiver noise output on the audio power level (1) Rf signal generatoror CSM. 0 meter. The receiver noise should be quieted. (2) Vtvm, vom, or digital multimeter. (4) Gradually increase the generator output until the squelch deactivates(opens). This level in dB or microvolts is (3) Electronic frequency counter if CSM is unavailable. the squelch threshold. d. Detailed Procedures. (5) If tolerances/limits are met, and no other checksare to be performed, disconnect the test equipment and restore (1) Procedure for AM Receivers (Figure 5-9). the receiver to service. Peak the receiver’s antenna trimmer . for maximum age using an on-the-air signal. 6

Figure 5-S. Checking Receiver Sensitivity and Squelch Threshold

Page 100 Chap. 5 Par. 250 l 5/22/90 6580.5 SO SUP1

SO SUPPLEMENTALPAGE

251-SOI. SQUELCHTHRESHOLD.

a. Purpose. This paragraph describes requirements and procedures for checking the squelch threshold on UHF and VHF receivers with a test antenna. b. Affected Receivers. All UHF and VHF air/ground receivers. Background. Gradual deterioration of a receiver antenna system may not be deE:cted until it results in missed aircraft calis. This is particularly true of receivers on emergency and other seldom used frequencies.

d. Detailed Procedures. (1) Connect an RF signal generator to a permanently installed test antenna. The test antenna need not be a standard antenna, but should be mounted outside the building if possible and in a location that will NOT require more than 50 mV to break the receiver squelch. (2) Adjust the signal generator to the channel frequency. DO NOT modulate the signal generator output. (3) Starting with minimum RF output on the signal generator, increase the output until the receiver squelch circuit operates. Record the signal generator attenuator setting, in dBm, on the FAA Form 6600-6 in an unused column. 0 The value shall not exceed the tolerance specified in Chapter 3, paragraph 131- SOlc(2) and will be the reference value for all future checks. (4) Connect an RF signal generator to the test antenna as noted in steps (1) and (2). Starting with minimum RF output, increase the output until the receiver squelch threshold is reached. The squelch threshold shall be recorded on the FAA Form 6600-6 in an unused column and shall not exceed the tolerance in paragraph 131-SOlc(2). (5) CAUTION: This procedure causes radiation of a signal on an operational channel. Do not exceed 50 mV RF output on the signal generator. To prevent interference problems, coordinate in advance with Air Traffic Control personnel and keep periods of radiation to a minimum. (6) These operational tests will supplement but not replace the periodic maintenance schedules described elsewhere in this handbook.

Chap 5 Par 251-SO1 Page IOO-SO? 1 O/l 6189 6580.5

Figure 5-9. Checking Receiver Selectivity and Nonsymmetry

_ (a) Turn the receiver and the signal generator or (i) Increase the output of the signal generator or communicationsservice monitor (CSM) power on, and allow CSM over the value of step (e) by 60dB (80dB for the WR- a warmup of at least 15 minutes. Turn the receiver squelch 100 receiver). off. (k) Repeat steps (g) and (h) in turn, recording the (b) Connect the 50-ohm signal generator or CSM generatoroutput frequencies for each. cable to the antennaconnector. Set the generatormodulation to off and the rf output attenuator for zero output. (1) Compute the bandwidth at the 60dB points by subtracting the lower of the two recorded frequencies (steps (c) Connect the volt-ohm milliammeter or digital (g) and (h)) from the higher frequency. multimeter test leads between the age voltage and ground. (m) Compute nonsymmetry in percent as follows: (d) Adjust the signal generatoror CSM to the exact channel frequency. Use an electronic frequency counter to Percent nonsymmetry = (Afl/Afz) - 1 X 100 0 monitor all frequency adjustmentsif the CSM is not available. Where Afl = difference between channel frequency and the frequency below channel fre- (e) Slowly increasethe signal generatoror CSM rf quency at which 60dB attenuation occurs. output from zero until the vom indicates age action hasjust begun. Record this voltage as the age reference voltage. DO Af2 = difference between channel frequency NOT OVERDRIVE TI%EAGC CIRCUIT DURING THIS and the frequency above channel frequency at STEP.Note the level of rf output in dBm on the generatoror which 60dB attenuation occurs. CSM output attenuator dial. A If Af2 is larger than Afl: (f) Increasethe generatoror CSM rf output by 6dB on the output attenuator dial. Percent nonsymmetry = (Afz/Afl) - 1 X 100

l (g) Carefully increasethe signal generatoror CSM (n) Refer to chapter 3 for limits for selectivity and output frequency (above the channel frequency) until the age nonsymmetry. reference voltage of step (e) is again obtained on the vom. Record the generatoror CSM output frequency. EXAMPLE (perfect symmetry):

(h) Carefully reduce the signal generator or CSM Afl = 4OkHzat the 60dB point higher than chan- output frequency (below the channel frequency) until the age nel center frequency reference voltage of step (e) is again obtained. Record the generatoror CSM output frequency. Afz = 4OkHzat the 60dB point lower than channel center frequency (i) Compute the bandwidth at the 6dB points by subtracting the lower of the two recorded frequencies (steps e (g) and (h)) from the higher frequency. Chap. 5 Page 101 Par. 252 6580.5 1 O/l 6189

Substituting: (d) Lower the generatoroutput frequency to obtain the age referenceof step (b) and record the frequency of the Percentnonsymmetry = [(Afl/Afz) - 11X 100

=( 40/40 )-1X100 (e) Increasethe generatoroutput frequency through the peak of the if responseuntil the sameage reference of step =1-1x100=0% (b) is again obtained. Record the higher frequency.

EXAMPLE (symmetry in tolerance): NOTE: The higher frequency should be greater than the carrier frequency +27OOHz.The lower frequency (step Afl = 43kHz at the 60dB point higher than chan- (d)) should be less than the carrier frequency +3OOHz. - nel center frequency. (f) Increase the generator rf output to 30dB above Af2 = 40kHz at the 60dB point lower than channel the referencelevel. center frequency. (g) Lower the generator frequency output to again Substituting: obtain the age reference level. Record this frequency. It should be less than or equal to carrier frequency. Percentnonsymmetry = (Afl/Df$ - 1 X 100

=( 43/40 )-1X100 (h) Increase the generator rf output to 50dB above the referencelevel. = 1.075- 1 x 100 = 7.5% (i) Lower the generator frequency output to again EXAMPLE (symmetry out of tolerance): obtain the age referencelevel. Record the frequency.

Afr = 47kHz at the 60dB point higher than chan- (i) Increase the generator output frequency to ob- nel center frequency. tain the agereference level. Record the frequency. The higher and lower frequenciesshould be asstated in the standardsand 0 Af2 = 38kHz at the 60dB point lower than channel tolerancestable. center frequency. 253. FREQUIINCY STABILITY. Substituting: a. Object. To ensure that the output of the first crystal oscillator, or all oven-controlled oscillators in ssb receivers, Percent nonsymmetry = [Afr/Af$ - 11X 100 is within required tolerancesor limits.

= ( 47/38 ) 28M- 1 X 100 b. Test Equipment Required. = 1.2368- 1 X 100 = 24% (1) Electronic frequency counter or CSM. (2) Procedure for Aerocom Ssb Type 2210 (2) Digital multimeter (for ssbreceiver). Receiver. Selectivity measurementsin type 2210 receiver . am mode are performed the same as for vhf and uhf am receivers (subparagraph 1)). For this measurement,the age c. Discussion. Frequency accuracy of the first or local referencevoltage is obtainedat the ageoutput of the 175OkHz oscillator of vhf and uhf receivers is important for operation- if amplifier card. al performanceof the receivers in a 5OkHzor 25kHz channel spacing.For ssbreceivers, frequency accuracy is of extreme (a) Adjust the signal generatoror CSM for an out- importance in suppressed-carrier modes to enable the put frequency of carrier frequency + 1OOOHz. receiver to properly demodulatethe received signal.

(b) Adjust the generator rf output to obtain ap- d. Detailed Procedure for Type AN/GRR-23 and proximately +6V at the age output. Record this level as the AN/GRR-24 Receivers. A complete oscillator test proce- agereference voltage. dure is located in paragraph 64 of Instruction Book TI 6620.2A, Receiver,-Radio,-ANIGRR-23 and ANIGRR-24, (c) Increasethe generatorrf output 6dB. Volume 1. 0

Page 102 Chap. 5 Par. 252 c s/22/90 6580.5 so SUP 1 l

254-SOI. AUDIO/AGC CHECKSON AN/GRR-23/24 RECEIVERS. a. Purpose. This paragraph describes requirements and procedures for checking the audio/AGC circuits in the AN/GRR-23/24 receivers. :’

b. Affected Receivers. VHF and UHF fixed tuned receivers, AN/GRR-23/24.

C. Background. If the audio/AGC circuit in the AN/GRR-23/24 receiver is not properly adjusted, the audio output will increase as the percent of modulation of the input signal is increased. A UHF receiver was tested with the AGC voltage maladjusted to 50 mV. When the percent of modulation was increased from 30% to 95%, the receiver audio output increased 9 dB. The AGC was then properly adjusted to 125 mV and the modulation percentage increased from 30% to 95%. The receiver audio output increased 0.75 dB. If the AGC voltage is adjusted above the 125 mV level, the receiver noise output will increase and, therefore, decrease the receiver signal to noise ratio.

d. Detailed Procedures.

(1) Turn the receiver squelch off.

(2) Adjust the signal generator or CSM for 1,000 Hz modulation at 30% and adjust the generator to the channel frequency.

(3) Connect the generator to the receiver to be tested and adjust the generator output for 50 uV. e (4) Varv the percent of modulation on the generator from 30% to 95%. The receiver audio output should not vary more than 1.5 dB.

(5) Vary the percent of modulation control on the generator from 30% to 15%. The receiver audio output should continuously decrease.

(6) If adjustment of the audio/AGC is required during these checks, refer to the Instruction Book, TI 6620.2A, Section 9, paragraph 9.5.

Chap 5 Page 102-SO2 Par 254-SO1 S/29/92 6580.5 CZIG 2

e. Detailed Procedure for Type WR-100 Receivers. A gesof rf signal input that the receiver may be subjectto, there- complete oscillator test procedure is located in paragraph4- by eliminating the need for constantly readjusting the manual 4.2.3 of the Wulfsberg installation-operation manual. volume control.

f. Detailed Procedure for Aerocom Type 2210 Ssb/AM Receiver. c. Test Equipment Required.

(1) Connect the counter to the 1750kHz oscillator out- (1) Rf signal generator or CSM. put, 54, at the rear of the receiver. (2) Audio power level meter or receiver test set. (2) Measure the frequency. If it is not exactly * 175O.OOOkHz,adjust capacitor Cl on the 175O.OOOkHzoscil- d. Conditions. Adjacent receivers must be protected lator, with the clarifier control at midposition, for exactly from high-level rf signals. Do not allow rf test signals to 175O.OOOkHz. radiate longer than necessary to make the test. Limit rf generator output to 50,OOOpV(-13dBm). * (3) Connect the counter to the hf oscillator output, 56, 1 at the rear of the receiver. e. Procedure, AVC Threshold.

(4) Measure the frequency of the crystal. If the crystal (1) Increase the signal generator or CSM output while frequency is out of initial tolerance,adjust Cl on the hf oscil- observing the audio output level for the point at which avc lator for the exact crystal frequency. throttling action starts. This is the point where the output ceasesto increasein direct proportion to the input. (5) Connect the counter to vhf oscillator output, J5, at the rear of the receiver. Connect a digital multimeter to TP- (2) AVC threshold is the rf test voltage input at which A on the vhf oscillator board. avc threshold occurs.

(6) Measure the frequency. If it is not within the initial f. Procedure, AVC Level Control. tolerance given in chapter 3, adjust C204 and C206 for maximum output and exact frequency. (1) Increasethe signal generator or CSM output for an 0 rf test voltage input to the receiver of 5Ou.V. (7) Enter the required crystal oscillator measurements * on FAA form 6620- 1. (2) Adjust the af gain control for a receiver output of 50mW. (8) Disconnect the test equipment, and restore the receiver to service. (3) For solid-state recievers, sweep the receiver input with rf test voltages from 3l.tV to 50,OOOpV. Note 254. AUTOMATIC VOLUME CONTROL (AVC) AC- the corresponding receiver maximum and minimum power TION. output levels for each step. a. Object. To determine the automatic volume control (4) Determine the difference of maximum to 8 (avc) threshold and the effectiveness of the avc circuit in minimum receiver power output expressed in dB. maintaining a constantreceiveroutput level under wide variations of rf signal input. g. Detailed Procedure for Type WR-100 Receivers. A complete test procedure is located in paragraph 4.3.3 of the Wulfsberg installation-operation manual. b. Discussion. The avc feature is required to maintain a nearly constant audio output from the receiver for wide ran- 255259. RESERVED.

o-Chap. 5 Page 103 Par. 253 6580.5 10116/89

Subsection 3. ANTENNAS AND TRANSMISSION LINES 260. MEASURING TRANSMISSION LINE LOSS. shutdown coordination shall be accomplished with the air traffic (AT) watch supervisor in advance. a. Object. To measurethe loss of a coaxial transmission line between transmitter output and antennainput. e. Detailed Procedure. See figure 5-10.

b. Discussion. (1) Coordinate the channel shutdown with the AT watch supervisor. (1) Loss in a coaxial cable transmissionline is a function of the physical construction of the cable and the radio (2) Deenergizethe transmitter keying circuit, and dis- frequency in use. The presenceof standing waves on a line connect the coaxial transmission line from the antennainput connector. add to the basic cable loss. Figure 13 in appendix 8 provides swr losses that may be used to derive total cable loss. The values on the horizontal axis represent the flat line lossesof (3) Connect an in-line rf body of a directional watt- the particular cable from figure 14 in appendix 8. From this meter set in seriesin the line, and connect a dummy load of figure, determine the loss of the cable under consideration, the proper impedanceand power rating at the output of the rf and locate the value on the horizontal axis of the graph of body to act as a termination. figure 13, appendix 8. The swr loss that must be addedto this value may be determined by following the vertical line that (4) Insert a directional element of the proper power connects this point with the insertion of the appropriate swr rating in the forward power position in the rf body. curve (load end). Then read horizontally to the left edge of the graph where the additional lossesare indicated in dB. Line (5) Energize the transmitter, and read and record for- lossesfor a discrete frequency can be estimatedby consider- ward power at the antennaend of the transmissionline. Read ing that the attenuation varies (approximately) as the square forward power at the sending end of the line, using the same root of the frequency ratio and is directly proportional to the rf body and wattmeterat the transmitter facility that was used length of the line. at the antennaend.

EXAMPLE: (6) Deenergize the transmitter. Compute the line loss as follows. For RG-213/U at lOOMHz, attenuation is 2.0dB per hundred feet. Therefore, attenuation at 125MHz is: do (loss) = IO Loglo P (transmitter end) P (Antenna end) = 2.24dB per hundred feet

(2) With an in-line directional wattmeter connectedat NOTE: This test arrangement cannot be used for swr the sending end of the line that is terminated in a 50-ohm measurementat the antenna. The antenna must be recon- dummy load and rf power applied, a check of forward and nected as a load for the swr check. However, the swr and reflected power may indicate an unsatisfactory line im- line loss checks can be accomplished at the sametime to pedanceif the reflected power is 5 percent or more of the for- avoid the need to schedule an additional shutdown of the ward power. Under these conditions, the transmission line channel. may have deterioratedand should be replaced. (7) If line loss is within tolerance, remove the rf body and dummy load, and reconnect the antenna. Proceed to c. Test Equipment Required. check other lines terminating on the sameantenna tower that are scheduledfor the check. (1) Directional wattmeter set. 261. MEASURING SWR ON COAXIAL TRANSMIS- (2) Dummy load. SION LINES.

d. Conditions. Transmission line loss measurementre- a. Object. To measurethe swr on coaxial transmission quires disconnecting the line from the antenna. Therefore, lines at the load (antennainput).

Page 104 Chap. 5 Par. 252 FACILITY TOWER PATCH JUNCTION FIELO BOX

FACILITY TEY PORARY ANTELNA RULINE r-l r-l THRULINE DISCONNE CTED : BODY

=-I

r-l DIRECTIONAL - DIRECTIONAL WATTMETER WATTMETER I (MEASURE) ,1 (NOTE 2) (NOTE 11

A. MEASURE POWER DELIVERED TO LOAD

TDWE R FACILITY JUNCTION PATCH BOX

FACILITY

CHANNEL TRANSMITTER

L DIRECTIONAL NOTES : 4 WATTYETER I. USE SANE WATTYETER FOR BEST RESULTS.

(MEASURE) 2. CONTROL WATTMETER FOR INITIAL POWER ADJUSTMENT I(NOTE I 1

a. MEASURE FORWARD POWER AT TRANSMITTER

Figure 5-10. Measuring Coaxial Transmission Line Loss L 6580.5 1 O/l 6189

b. Discussion. The swr is not constantalong a transmis- (2) Disconnect the transmission line from the antenna sion line, but is greatestat the load (antenna) end. For this connector and insert the directional wattmeter rf body be- reason,it is necessaryto make the principal swr check of the tween the line and antenna. antennasystem at the antennaterminal of the line. The term “at the antenna” as used herein meansat the antennaconnec- (3) Install a directional element in the forward power tor or at any transmissionline connectorthat is accessibleand position in the rf body. Ensure that the element with proper that lies within 30 feet (1Om)of the antenna.Swr readings at power rating is installed. the rf bodies of the directional wattmetersat the transmitter output are related readings only. Those readings do not indi- (4) Energize the transmitter, and read and record the cate swr unless the transmissionline from transmitter to load forward power indicated on the wattmeter. is 30 feet (10m) or less. Swr of communication transmission cables may be checked with a slotted line. However, unless CAUTION: Before the larger power element is it is necessary to adjust the swr with a coaxial stub, the removed,determine, by reversing the direction of this ele- precision afforded by the slotted line is not needed.Slotted ment to read reflected power, that the magnitude of line stubbing proceduresare not included in this order. reflected power does not exceed the power rating of the element used in step (5). If swr has become large, suffi- c. Test Equipment Required. Directional wattmeter cient reflectedpower may damagethe low-power element. with directional detectors. (5) Deenergizethe transmitter, and install a direction- d. Conditions. When necessaryto shut down the chan- al elementwith lower power rating in the reverseor reflected nel for the required check, prior coordination with the AT power position in the directional wattmeter. watch supervisor is mandatory. (6) Energize the transmitter, and read and record the e. Detailed Procedure. Refer to the test arrangementof reflected power indicated on the wattmeter. If insufficient figure 5-11. deflection of the meter is obtained, deenergizethe transmitter, and insert an element with lower power rating, after first (1) Coordinate with the AT watch supervisor, and determining (see the CAUTION above) that the lower- remove the channel transmitter from service. powered element will not be damaged. 0

Figure 5-11. Measuring SWR at the Antenna

Page 106 Chap. 5 Par. 261 10/16/89 6580.5

(7) Compute the swr from the recorded values of for- transmitting equipment.Just enough power should be used to ward and reflected power by useof the applicable formula in ‘obtain a maximum trolley meter deflection of about two- appendix 8. The swr versus power curves in the directional thirds the full-scale meter reading. wattmeter instruction book can also be used, as can figure 3, appendix 8. e. Detailed Procedure.

(8) If the swr is within the tolerance allowed in chap- (1) Refer to figure 5- 12 for a sketch showing a trolley ter 3, reconnect the line to the antenna, and continue swr meter in use on an open-wire feeder. checkson other transmissionlines on the tower. (2) With the draw cord and sufficient low power ap- 262. MEASURING SWR ON OPEN-WIRE TRANS- plied to the line, slow-draw the trolley meter (after peaking MISSION LINES. its meter coupling circuit to maximum) from a position near the correcting stub toward the transmitter building. a. Object. To measureswr on open-wire feeders. (3) When the meterpointer reachesa maximum value, b. Discussion. Directional couplers are generally im- goes through it, and then reaches a minimum, record these practicable for open-wire lines of pole-line construction. It is maximum and minimum values. Repeatprocedure by towing necessaryto move a standing-wavedetector over the line and the meter backward toward the stub, reconfirming the maxi- observemeter maxima and minima, which are then converted mum and minimum readings on the meter. by a simple computation to standing-wave ratio. A movable meter known as a trolley meter is used for this purpose.The (4) If the trolley meter is a square-law type, compute portion of the line on which the meter is used is normally a the swr by using the applicable formula of appendix 8 and the horizontal section between the matching stub closest to the readings of step (3). transmitter building and the transmitter output. (5) If the trolley meter is of the non-square-law type, c. Test Equipment Required. Trolley meter, type CA- there will be a chart on the meter box or in the trolley meter 543A or equal. instruction manual by which the meter deflections are converted for use in the sameformula. d. Condition. High transmitter power cannot be used when this check is made. The transmitter is shut down fol- (6) An excessive swr indicates matching is incorrect. lowing prior coordination with the AT watch supervisor. A The correcting stub may have to be repositioned and/or low-power oscillator or low-power stageof the transmitter is lengthened or shortened to obtain a sufficiently low swr on loosely coupled at the coupling of the transmissionline to the the line.

Ll \ * e 0/’ ” CORRECTING -DRAW o CORD

Figure 5-12. Measuring Open-Wire Line SWR

Chap.5 Page 107 Par. 261 6580.5 1 O/7 6189

NOTE: Before moving or otherwisechanging the dimen- mitting. Therefore, performance tests and other maintenance sions of the stub, check the condition of the transmission tasksapplicable to the transmitting line are equally applicable line, and rechecktrolley meterreadings. A standing-wave to the receiving line. When receiving facilities are separate ratio that suddenlychanges is a likely indication of damage from transmitting facilities, use a movable low-power trans- to the line or improper techniquein useof the trolley meter. mitter or portable transceiverto energize the receiving line for tests.In so doing, observethe necessaryprecaution to prevent (7) Following all required proceduresteps, remove the interfering with receiving equipment. Prior coordination with low-power line excitation, and restorethe equipment and an- AT operations in mandatory. tenna systemto service.

263. RECEIVING ANTENNA AND TRANSMISSION 264.-269. RESERVED. LINE TESTS. At most a-g vhf and uhf facilities, the sametransmission line type or types are usedfor receiving as are usedfor trans-

Section 2. OTHER MAINTENANCE TASKS PROCEDURES

Subsection 1. Transmitters 270. GENERAL. 271.-279. RESERVED. Refinements in tuning and neutralization are to be accomplished periodically in asccordance with chapter 4 schedules.

Subsection 2. RECEIVERS 280.-289. RESERVED.

Subsection 3. ANTENNAS AND TRANSMISSION LINES 290. MEASURING INSULATION RESISTANCE OF 291. MEASURING INSULATION RESISTANCE OF ANTENNAS. TRANSMISSION LINES. With a 500-volt insulation tester, measurethe insulation Using a 500-volt insulation tester, measurethe insulation resistance of the antenna from the accessible connector resistance of the transmission line (at the transmitter or nearestthe antenna(minimum length of cablebetween the in- receive end) with the line connected to its associatedanten- sulation tester and the antenna). Antennas with internal na. If the measuredvalue of insulation resistanceis less than shorted stubs or capacitive coupling are exemptedfrom this 3 megohms,investigative action is needed. Disconnect the procedure. If the insulation resistance has fallen below the transmission line from the antenna, and check the insulation tolerance specified in chapter 3, the causeof the low resis- resistance of the transmission line alone. If the measured tancereading should be determined and corrected.the cable resistanceis less than 3 megohms, corrective action is re- and connectorsshould not be overlooked during investigation quired. The cause for low values of insulation resistance of the antenna even though the cable length may be only a should be tracedand corrected.Rf cable connectorsare usual- few feet. The usual causeof low antennainsulation resistance ly a source of leakage (due to presenceof moisture) unless is moisture absorption by the insulators and input receptacles well protected from the weather. If moisture is present, or a coating of dirt, ice, and/or moisture on the surfaceof the remove the connectorsfrom the cable, and thoroughly dry or insulators. Cleaning of the insulators is a required steptoward replacethem with new connectors.If the insulation resistance restoring the insulating resistanceto within tolerance.For in- still readsless than 3 megohmsafter removal of the connec- formation purposes, a check of swr should be conducted tors, the trouble may be due to cold-flow migration of the cen- before and after cleaning the insulators. ter conductor to the shield or contamination of the cable

Page 108 Chap. 5 Par. 262 1 O/l 6189 6580.5

dielectric causedby migration of the vinyl jacket through the The construction of certain vertical antennas,particularly shield. Since the latter condition is usually not apparentfrom the shorted-stub types, balun-input types, TACO, and DHV a visual inspection, check the line characteristic impedance. high-performance, vertical, single-dipole, and multielement Seealso paragraphs53 and 54, Order 6950.22, Maintenance types makes impossible routine insulation resistance of Electrical Power and Control Cables. measurementof the lines only in accordancewith paragraph 101e.The condition of the antennasshould be ascertainedby 292. MEASURING DC SERIES RESISTANCE. applying the swr check of paragraph261 at the antenna input Using a shorted connector or clip lead to short the anten- at the frequency of operation assignedto the particular antenna, measurethe center conductor to outer shield loop resis- na. For the TACO and DHV antennas,the swr versusfrequen- tance with a volt-ohm milliammeter (vom) at the equipment cy curves of figure 2-40 can be used to compare the swr as end of the line. For TACO 2200 seriesantenna systems,dis- measured. For other antennas for which curves are not connect the line at the antenna,and measurethe resistanceof published, swr versus frequency curves can be measuredlo- the line only. This can be accomplished by using a shorted cally and plotted for retention in station files. Prior to all connector or clip lead to short the line and measuringthe cen- measurements,antennainsulating elementsand hardware,inter conductor to outer shield loop resistance with a vom. cluding connectors, should be cleaned and free of accumu- Record the value in ohms for comparisons with facility lated grime and grease. records. Seealso paragraph54 of Order 6950.22.

293. ALTERNATIVE CHECKS FOR SHORTED- 294.-299. RESERVED. STUB, BALUN-INPUT, TACO, OR DHV ANTENNAS.

Section 3. SPECIAL MAINTENANCE PROCEDURES

300. TIME-DOMAIN REFLECTOMETER TESTS ON 97077. Included in the manual are illustrations showing typi- TRANSMISSION LINES. cal crc displays for the most common cable faults.

a. The time-domain reflectometer (TDR) is a portable, battery-powered oscilloscope instrument for the evaluation ;Ollp;ll:Sl’ING FOR STRAY COAXIAL LINE RADIA- of d&continuities in 50-ohm transmissionlines. It transmitsa . fast-rise pulse of 140 picoseconds (ps) or less and displays Coaxial cable, when properly installed, energized, and the reflection component. Anomalies in the reflection dis- loaded, should have no rf radiation along its length. The played on the cathode-ray tube (crt) of the instrument or presenceof stray radiation is an indication of some kind of recorded on the thermal paper tape indicates discontinuities fault. Stray radiation will interfere with nearby services and such as crimps, breaks,shorts, cold-flow, and other problems causeinefficient operation of the antenna system associated in the transmission line. The calibrated time base of the crt with the cable. Detection of radiation is accomplished with a permits locating a fault with resolution depending on the wavemeter or grid-dip meter, the probe of which is passed range time base used. The model 1502 has a range of up to along the length of the cable (within the facility) and observed 2000 feet (500 meters).(A metric range model 1502is an op- for a meter deflection. A broadly responsive instrument may tion.) A short-range model is under current procurement for require shutting off all other equipment except that energiz- evaluation of the relatively short-run cable round at vhf and ing the line under test. Somedefects that result in stray radia- uhf communication transmitter and receiver sites, and at tion are: corroded and tarnished braid, defective coaxial a. navigational and landing aids facilities. Connectorsand connections,mismatched lines and loads,and excessivepower for the cable type in use. b. A valuable feature of the recording option is the cable signature run that should be conducted at the time new cable is installed or when cable that is known to be good is check- 302. OPEN-WIRE TRANSMISSION LINE BALANCE. ed. Kept on file, the recorded pattern is useful for future signature comparisons as the cable ages or a fault, such as a. Object. To check the balance of rf current in open- cold-flow, is suspectedto have developed. wire balanced feeders.

c. Completeoperating instructions are contained in the in- b. Discussion. When rf ammetersare insert at identical struction manual, Tektronix 1502 Time Domain Reflec- points in each side of a balanced transmission line, the tometer, Tektronix, Inc., P.O. Box 500, Beaverton, Oregon relationship between the two readings indicates the state of balance in the line. When a transmission line is

Chap.5 Page 709 Par. 291 6580.5 10116i89

TRANSMITTER

FINAL AMPL n c GALUN TO TRANSMITTING ANTENNA OR 4

TUNING UNIT

PERCENT UNBALANCE= ($=$- - I) X 100

Figure. 5-13. Measuring Open-Wire Line Balance perfectly balanced,there is a minimum of radiation from the put terminals or in eachside of the line near the balun output. line itself. Therefore, if the meter readings show more than a Seefigure 5-13. 10 percentdifference, the line should be readjustedfor proper balance.When balancedlines are usedin unsymmetrical an- (3) Energize the transmitter, and adjust for normal tenna systems,such as an end-fed half-wave antenna,a dif- ferencein the readings of the two sides of the line indicates operation. that the antennais of improper length. (4) Record the readingsof the ammeters.The readings should differ by no more than 10 percent. c. Test Equipment Required. Two rf ammeters,range or scalecalibration adequatefor current expectedin the trans- (5) If in tolerance, shut down the transmitter, remove mission line (each side). the ammeters,reconnect the transmission line, and restore normal transmitter operation. d. Conditions. If the rf ammeters are permanently NOTE: Open-wire balance can be determined with a mounted in the transmission line, usually no shutdown will trolley meter. However, series-connectedrf ammetersare be needed.If a shutdown is neededto insert the ammetersin much more convenient to use. series with the sides of the line, prior coordination with the AT watch supervisor is mandatory. 303. RADIATION PATTERN GROUND CHECK. A ground check of a-g communication antennasis not nor- e. Detailed Procedure. mally an effective procedure. The angle of radiation (skywave) is above the terrain and not ordinarily measurable on the ground. However, the use of vehicular-mounted (1) Shut down the transmitter, and ensurethat all high transceivers capable of receiving discrete a-g frequencies voltage is removedby testing with a shorting stick after opening the main high-voltage contactor on the transmitter final may provide reference data to determine system deteriora- amplifier power supply. tion. The ground check is madewith a procedurevery much like that in Order 6530.3D, Maintenance of Direction Finder (DF) Equipment. Checkpoints are established at places (2) Connect eachrf ammeterin serieswith one side of marked on maps of the communication facility area where the transmissionline as close to the transmitter output aspos- transmitters and receivers are installed. If reliable two-way sible. If a balun is used to convert an unbalancedtransmitter contact can be madefrom 10 to 40 miles (16m to 64m) from output to balanced,connect the ammetersat the balancedout-

Page 110 Chap. 5 Par. 302 1 O/l 6189 6580.5

the facility and can be repeated, the facility can be said to be cable) substituted. A short shutdown of the channel may be operating satisfactorily. The best check is reliable two-way required; the AT watch supervisor should be contacted for aircraft contact which is madevia routine AT operation many permission to exchange antennas and lines. times aday. It would be under exceptional circumstancesthat a ground check would be required or be of any great benefit. e. Detailed Procedure.

304. SWR LOSS CHECK OF OLD COAXIAL TRANS- (1) Remove from service the cable to be tested. Sub- MISSION LINES. stitute either a spare cable for the assigned antenna or a complete antenna and transmission line system on the channel a. Object. To evaluate swr loss on old coaxial transmis- affected. sion lines. (2) Disconnect the cable at the antenna end from the b. Discussion. Coaxial lines that have been in use for antennainput connector. Short-circuit the cable at the anten- severalyears may have deterioratedso much that their losses na end by substituting a shorted receptacle connector of the have increased above the unit-length values published for the type used at the antenna input. type of cable. Such cable will decrease effective radiated power, especially for low-power (10 watts or less) transmitters. It is essentialthat theseolder cablesbe checkedbetween (3) With the directional wattmeter connected at the the third and fifth year of use. They should be replaced if the driven end, as in figure 5-14, part A, supply low power to the test results are poor. No test equipment is required at anten- line at the frequency of use and measure the forward and na end of the line. reflected power.

c. Test Equipment Required. (4) Compute the swr on the line (seeappendix 8) and, using the chart of figure 5-14, part B, determine the total loss (1) Directional wattmeter set. of the transmissionline when perfectly terminated.If this loss exceedsby 5 percent the published loss of that type of cable (2) Short-circuit connector termination. per unit length, replace the entire length of transmission line.

d. Conditions. The coaxial cable must be temporarily removed from service and a spare cable (or antenna with 305.-314. RESERVED.

Chap,5 Page111 Par. 303 DIRECTIONAL COUPLER ANTENNA END LOW POWER TRANSMITTER SHORT CIRCUIT ( IOW OR LESS) 0 \id-n-$) I I TRANSMITTER OR RECEIVER END

0/ WATTMETER

A. -MEASURING SWR OF SHORTED LINE

LINE ATTENUATION dB

8. SHORTED-LINE SWR LOSS CHART

Figure 5-14. SWR Loss Test of Old Coaxial Cable

, . . 1 O/l 6189 6580.5

CHAPTER 6. FLIGHT INSPECTION

315. GENERAL. b. Changein transmitter rf output level for the purposeof Plight inspections are made to verify the overall perfor- increasing or decreasingservice area. manceof an air-ground (a-g) communication facility. The instructions for flight inspection are contained in OA P 8200.1, c. Frequency changes. United StatesStandard Flight Inspection Manual. Flight inspections are required as specified in the flight inspection I manual and when requestedby regional authority. Ground- d. Replacement,relocation, or reorientation of antennas. to-air (g-a) communications, such as VOLMET and other voice broadcastcommunications, are flight checkedby nor- 317. ACTIVITIES NOT REQUIRING A CONFIRM- mal aircraft contact. Pilot reports (pirep’s) concerning ING FLIGHT INSPECTION. deficiencies in coverage and intelligibility are filed and The following may be accomplished by electronic main- responded to by Airway Facilities divisions. Point-to-point tenancetechnicians without recourse to flight inspection: (PTP) circuits operating as fixed stations are not flight checked. a. Replaceor repair transmitter components.

316. ACTIVITIES THAT MAY REQUIRE A CON- b. Retune all stagesof the transmitter. FIRMING FLIGHT INSPECTION. Flight inspections of commissioned communication c. Measure and adjust voice modulation percentagesto facilities are normally accomplished in conjunction with values establishedduring flight inspection. other primary navigational aids. The expenseof a special trip or priority flight inspection is not warrantedin most situations if sufficient targets of opportunity are available on which to d. Accomplish other maintenance procedures, provided makea decision. (Detailed policy is outlined in OA P 8200.1.) the conditions are restored to those that existed at the time of The following activities should be considered as candidates the last flight inspection asreflected in the current FAA forms for requesting a confirming flight inspection: 6600-6,6610-l, or6620-1.

a. Major changesin location obstructionsor buildings that 318.-324. RESERVED. may affect the signal strength or coverage.

Chap.6 Page 173 [AND 7 14) Par.315 CHAPTER 7. MISCELLANEOUS

325. GENERAL. 66 type cable is not subject to expansion, contraction, orcold- This chapter contains miscellaneous information and flow problems. guidance concerning communication antennas and transmission lines. 327. INTERFACING AN/GRR-23 AND AN/GRR-24 TYPE RECEIVERS TO TELCO EQUIPMENT. 326. EXPANSION AND CONTRACTION. a. The audio output impedance of the AN/GRR-23 and The coefficient of expansion of the center conductor of a - AN/GRR-24 receivers is approximately 150 ohms. A mis- coaxial cable is greater than that of the dielectric. With long matchwill occur where receiversinterface to telco equipment transmission lines and wide temperature variations, this dif- whosecharacteristic impedance is 600 ohms. Ample receiver ference in expansion results in a considerabledegree of slip- gain is available to overcomesignal loss; however, poor audio page of the center contact pin of the coaxial connectors. quality and high signal-to-noise ratios will result. During cold weather conditions, the technician should be alert for open transmission line connections. To ensure electrical b. The impedance looking back into the receiver output continuity as coaxial cable expands and contracts with should be measured.If the impedance is significantly less temperaturechanges, UG-495A and WHC-321-1 connectors than 600 ohms (such as 450 ohms), a balanced H-pad should with telescoping pin contacts should be provided or should be installed between the receiver output and the telco line. be replaced with captivated connectors.Foamflex or Styro- Figure 7-l shows such a pad with resistor values and national stock numbers (NSN).

Note: Resistor NSN’s are: 51-ohm 5905-00-l 14-5438 200-ohm 55MX-00-141-0727 looo-ohm 5905-00-110-0198

Figure 7-1. Solid-State Receiver Interface Pad

Chap.7 Page 115 (and 116) Par. 235 1O/l 6189 6580.5

APPENDIXES

Paragraph Page

APPENDIX 1. GLOSSARY ...... 1

APPENDIX 2. BASIC TESTS FOR TRANSMITTERS AND RECEIVERS ...... 1 General ...... 1 :- Transmitter Output Power ...... 1 3: Transmitter Modulation ...... 3 4. Spurious Emission ...... 6 5. RF Signal Generators and the Communication Service ...... 6 Monitor (CSM) 6. Receiver Sensitivity ...... 7 Receiver Selectivity and IF Bandpass Symmetry ...... 7 ;: Frequency Stability ...... 7 9. MiscellaneousTests ...... 7 Figure 1. Three Methods for Metering Output Power in ...... 2 an Ssb Transmitter Figure 2. Correlation of Peak Envelope and Average Power .... 3 in the Ssb Transmitter Figure 3. Spectrum Analyzer and Oscilloscope Patterns ...... 4 of Two-Tone Ssb Tests Figure 4. Relationship of Two-Tone Amplitudes to Carrier ...... 5 and Intermodulation Distortion in an Ssb Signal Figure 5. Typical Receiver IF Selectivity Response ...... 8

APPENDIX 3. TRANSMITTER AMPLITUDE MODULATION (AM) ...... 1 MEASUREMENTS 1. General ...... 1 2. The Trapezoidal Pattern ...... 1 3. The Envelope Pattern ...... 1 4. Modulation Adjustment Techniques ...... 1 Figure 1. Modulation Measurement by the Trapezoidal Pattern . . 2 Figure 2. Modulation Measurement by the Envelope Pattern .... 2 Figure 3. Production of Trapezoidal Pattern ...... 3 Figure 4. Various Trapezoidal Patterns ...... 4 Figure 5. Various Envelope Patterns ...... 4 Figure 6. Nomograph for Percentage of Modulation, ...... 5 50 to 95 Percent Figure 7. Nomograph for Percentage of Modulation, ...... 6 0 to 60 Percent

APPENDIX 4. REFERENCE DATA FOR AUDIO FREQUENCY ...... 1 MEASUREMENTS 1. General ...... 1 2.\ DB-VU-DBM Unit Conversion ...... 1 3. RMS Volts to Power Level Conversion ...... 1

Page i 6580.5

Paragraph

4. Meter Correction Graph ...... 1 5. Decibels Above and Below a l-Milliwatt Reference Level ...... 1 6. Conversion of Noise Units ...... 2 Table 1. Decibels Above and Below a Reference Level ...... 2 of 1 mW into 600 Ohms Figure 1. DB-VU-DBM Unit Conversion Chart ...... 3 Figure 2. RMS Voltage to Power Level Conversion Chart ...... 4 Figure 3. Meter Correction Graph ...... 5 Figure 4. Nomograph for Conversion of Noise Units, ...... 6 0 dBm to -40dBm Figure 5. Nomograph for Conversion of Noise Units, ...... 7 -4OdBm to -90dBm

APPENDIX 5. PRINCIPLES OF RF TRANSMISSION LINES ...... 1 1. General ...... 1 Electrical Types of Lines ...... 1 :: Standing-Wave Ratio ...... 1 4. TunedLines ...... 2 5. Open-Wire Line Spacing ...... 2 Characteristic Impedance of Matched Lines ...... 3 F’ Harmonic Suppression ...... 3 8: Open-Wire Line Requirements ...... 3 9. Sagging of Open-Wire Spans ...... 4 IO. Rigid, Air-Dielectric Coaxial Lines ...... 4 11. Flexible, Solid-Dielectric Coaxial Lines ...... 4 12. Twisted-Pair Transmission Lines ...... 5 13. Transmission Lines at VHF and UHF Frequencies ...... 5 14. Coupling and Matching ...... 5 15. Transmitter Coupling ...... 5 16. Inductive Coupling ...... 8 17. Direct Coupling ...... 8 18. Pi-Network Coupling ...... 8 19. LinkCoupling ...... 8 20. ReceiverCoupling ...... 8 21. Matching Antenna to Line ...... 8 22. Antenna-Coupling Transformers ...... 8 23. Matching Line Sections ...... 9 24. Half-WaveLines ...... 9 25. Matching Stubs ...... 10 26. Balanced-to-Unbalanced Matching Systems ...... 10 27. Interference Suppression ...... IO Figure 1. Standing Waves on Open-Circuited and Short- ...... 1 Circuited Lines Figure 2. Relation of Mismatch to SWR ...... 2 Figure 3. Sectional View of Air-Insulated Coaxial Cable ...... 4 Figure 4. Sectional View of Solid-Dielectric Coaxial Cable ...... 5 Figure 5. CompleteTransmitter-and-Receiver-to-Antenna ...... 6 Transmission System Figure 6. Transmitter Coupling Arrangements ...... 7 Figure 7. Open-Wire Impedance-Matching Transformers ...... 9 Figure 8. Coaxial Impedance-Matching Transformers ...... 9

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Figure 9. Stub-Line Impedance-Matching ...... IO Figure IO. Graph for Quarter-Wave Stub Length and Positioning . 11 Figure 11. Quarter-Wave and Half-Wave Balun Arrangements . . 11

APPENDIX 6. PRINCIPLES OF ANTENNAS ...... 1 1. General ...... 1 2. Electrical Characteristics ...... 1 3. Radiation Pattern ...... 1 4. Effect of Radiation Pattern on Signal Intelligibility ...... 2 5. General Directional Requirements ...... 3 6. Strength of Field ...... 4 7. Antenna Resistance ...... 4 Input Impedance - Radiation Resistance ...... 4 i: Antenna Gain AntennaBandwidth:::::::::::::::::::::::::::::::::::::: z ::: Reciprocity...... 6 12. Power Absorbed by Receiving Antennas ...... 6 Figure 1. Basic Forms of Conductor Antennas ...... 1 Figure 2. Radiated Field from a Short, Straight Conductor ...... 2 in Free Space Figure 3. Three-Dimensional Nature of Radiation Pattern ...... 2

APPENDIX 7. ORIENTATION OF HIGH-FREQUENCY (HF) ...... 1 DIRECTIVE ANTENNA 1. General ...... 1 2. Preliminary Procedure ...... 1 3. Basic Formulas and Symbols for Calculations ...... 2 4. Surveying the Antenna ...... 2 Figure 1. Plan View of Rhombic Antenna ...... 2

APPENDIX 8. WORKING AND SUPPLEMENTARY DATA ...... 1 1. General ...... 1 2. Formulas for Antenna and Transmission Line Calculations ...... 1 3. Charts and Nomographs ...... 6 Table 1. RF Cable Data ...... 19 Figure 1. Metric Conversion Factors ...... 2 Figure 2. Two-Wire Line Characteristics ...... 4 Figure 3. SWR Chart of Forward Versus Reflected Power ...... 5 Figure 4. Reliability Nomograph ...... 7 Figure 5. Open-Wire Line Characteristic Impedance ...... 8 Figure 6. Quarter-Wave Matching Section ...... 9 Characteristic Impedance Figure 7. Radio and Optical Line-of-Sight Distances ...... IO Figure 8. Line-of-Sight Distances for Elevated Antennas ...... 11 to 5,000 Feet Figure 9. Line-of-Sight Distances for Elevated Antennas ...... 12 to 50,000 Feet Figure 10. Path Attenuation at 150MHz ...... 13 Figure Il. Path Attenuation at 300MHz ...... 14 Figure 12. Obstruction Loss Relative to Smooth Earth ...... 15

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Figure 13. Graph of Additional Losses Caused by ...... 16 Standing Waves Figure 14. Attenuation Characteristics for Coaxial Cable ...... 17 Types RG-142/U, RG-214/U, RG-217/U, RG-223/U, RG-331 /U, and RG-333/U Figure 15. System Losses in Air-Ground Communication ...... 18

APPENDIX 9. FABRICATING EMERGENCY ANTENNAS AND . . , ...... 1 . FEED LINES 1. General ...... *...... 1

Section 1. EMERGENCY SUPPORTS AND GUYING

2. SupportPoles ...... 1 3. Other Kinds of Supports ...... 9 4.-9. Reserved.

Section 2. EMERGENCY ANTENNA AND FEEDER FABRICATION

IO. General ...... 9 11. HFAntennas ...... 9 12. VHF and UHF Antennas ...... IO 13. ImprovisedFeeders ...... 15 14. Improvised Matching Transformers ...... 15 Table 1. Pole-Setting Depths ...... 1 Figure 1. Methods of Raising and Setting Poles ...... 2 Figure 2. Guy Anchors ...... 3 Figure 3. Guy Attachment ...... 4 Figure 4. Serving Antenna Wire ...... 5 Figure 5. Tying Strain and Spreader Insulators ...... 6 Figure 6. Typical Emergency Half-Wave Dipole and Feeder ..... 7 Figure 7. Folding Mast Antenna Support ...... 8 Figure 8. Example of Butt Splice for Poles ...... 9 Figure 9. Multiwire Doublet Antenna ...... 11 Figure IO. Vertical V and Half-Rhombic Antennas ...... 12 Figure 11. Long-Wire Antennas ...... 13 Figure 12. Whip Antenna ...... 14 Figure 13. Vertical Half-Wave Dipole Antenna...... 14 Figure 14. Vertical J Antenna ...... 14 Figure 15. Open-Wire Line Construction ...... 14

APPENDIX 10. CONNECTING ADDITIONAL RECEIVERS TO A ...... 1 SINGLE ANTENNA 1. General ...... 1 2. Multipling of HF Receivers on One Antenna...... 1 3. Methods of Coupling Balanced-Input Receivers on One Antenna . . 1 4. Multipling VHF Unbalanced-Input Receivers on One Antenna. .... 2

Page iv . 1 O/l 6189 6580.5 Appendix 1

APPENDIX 1. GLOSSARY

Absorption Loss. That part of the transmission loss Bandwidth (of a wave). The least frequency inter- due to the dissipation or conversion of electrical energy val outside of which the power spectrum of a time- into other forms of energy (e.g., heat), either within the varying quantity is everywhere less than some speci- medium or attendant upon a reflection. fied fraction of its value at a reference frequency. Un- less otherwise stated, the reference frequency is that at Air filobile. Communication between a fixed base which the spectrum has its maximum value. station located on the ground, and aircraft, or between an aircraft and other aircraft. Boknneter. A specially constructed resistor which has a positive temperature coefficient and which is Antenna. A means of radiating or receiving radio used for power measurements. waves. Carrier Wave. A wave generated at a point in the Antenna Array. A system of antennas coupled to- transmitting system and modulated by the signal. gether for the purpose of obtaining directional gain effects. Characteristic Impedance (2%). The ratio of the voltage to the current at every point along a transmis- Antenna Resistance. The quotient of the power sion line on which there are no standing waves. supplied to the entire antenna circuit by the square of the effective antenna current referred to a specified Coefficient of Reflection. The square root of the point. Antenna resistance consists of such components ratio of the reflected power leaving a reflecting surface as radiation resistance, ground resistance, radio-fre- to the power incident to the same surface. quency resistance of conductors in the antenna circuit, and equivalent resistance due to corona, eddy currents, Conduction Current. The power flow parallel to the insulator leakage, and dielectric power loss. direction of propagation expressed in watts per square meter. 0 Aperture (of a unidirectional antenna). That portion of a plane surface near the antenna, perpendicular to Conductivity. A measure of the ability of a material the direction of maximum radiation, through which the to act as a path for electron flow. It is the reciprocal of major part of the radiation passes. resistivity and is expressed in mhos/meter.

Atmospheric Duct. An almost horizontal layer in Critical Frequency. The limiting frequency below the troposphere, extending from the level of a local which a magnetoionic wave component is reflected by, minimum of the modified refractive index as a func- and above which it penetrates through, an ionospheric tion of height, down to a level where the minimum layer at vertical incidence. value is again encountered, or down to the earth’s surface if the minimum value is not again encountered. Cross Modulation. Modulation of a desired signal by an undesired signal. Attenuation. Of a quantity associated with a traveling wave in a homogeneous medium, the decrease with Dewpoint. The temperature at which the water distance in the direction of propagation. vapor in the air begins to condense.

Attenuation Constant. For a traveling plane wave LXffraction. The bending of a wave into the region at a given frequency, the rate of exponential decrease behind an obstacle. of the amplitude of a field component (or of the voltage or current) in the direction of the propagation, in Dipole Antenna. A straight radiator, usually fed in nepers or decibels per unit length. the center, and producing a maximum of radiation in the plane normal to its axis. The length specified is the overall length. Bandwidth (of a device). The range of frequencies within which performance, with respect to some char- Direct Wave. A wave that is propagated directly -- acteristic, falls within specific limits. through space. e Page 1 6580.5 1O/l 6189 Appendix 1 Direction of Propagation. At any point in a homo- Fading. The variation of radio field strength caused geneous, isotropic medium, the direction of time aver- by changes in the transmission medium with time. age energy flow. Fraunhofer Region. That region of the field in Directional Antenna. An antenna having the prop- which the energy flow from an antenna proceeds es- erty of radiating or receiving radio waves more effec- sentially as though coming from a point source located tively in some directions than others. near the antenna. If the antenna has a well-defined aperture D in a given aspect, the Fraunhofer region in Directive Gain. In a given direction, 45~ times the that aspect is commonly taken to exist at distances ratio of the radiation intensity in that direction to the greater than 2D2/h from the aperture, h being the total power radiated by the antenna. wavelength.

Dire&Sty (of an antenna). The ratio of maximum Fresnel Region. The region between the antenna radiation intensity to the average radiation intensity. and the Fraunhofer region. If the antenna has a well- (In a theoretical antenna that is 100 percent efficient defined aperture D in a given aspect, the Fresnel re- and with no losses, directivity and gain are the same.) gion in that aspect is commonly taken to extend a distance 2D”/X in that aspect, h being the wavelength. Displacement Current. The current at right angles to the direction of propagation determined by the rate Fresnel Zones. Zones of wave reinforcement and at which the field energy changes. destructive interference caused by interaction of direct waves and those waves reflected from the earth. Distortion. An undesired change in wave form. Gain (of an antenna). The ratio of the maximum ra- Effective Area. The square of the wavelength mul- diation intensity in a given direction to the maximum tiplied by the power gain (or directive gain) in that di- radiation intensity produced in the same direction rection, and divided by 477. from a reference antenna with the same power input. (In communication and television, the reference an- NOTE: When power gain is used, the effective area tenna is usually the half-wave dipole; whereas, in mi- is that for power reception; when directive crowave applications, an isotropic source is usually the gain is used, the effective area is that for di- reference antenna.) rectivity. Ground Mobile. Communication between a fixed Effective Radius of the Earth. An effective value base station located on the ground and ground vehi- for the radius of the earth, which is used in place of the cles, or between a ground vehicle and other ground ve- geometrical radius to correct for atmospheric refrac- hicles. tion when the index of refraction in the atmosphere changes linearly with height. Under conditions of Groundwave. A radio wave that is propagated over standard refraction the effective radius of the earth is the earth and is ordinarily affected by the presence of 8.5 x lo6 meters, or 4/3 the geometrical radius. the ground and the troposphere. The groundwave includes all components of a radio wave over the earth Electric Field Strength. The magnitude of the elec- except ionospheric and tropospheric waves. tric field vector. NOTE: The groundwave is refracted because of Electric Field Vector. At a point in an electric field, variations in the dielectric constant of the the force on a stationary positive charge per unit troposphere including the condition known charge. This may be measured either in newtons per as surface duct. coulomb or in volts per meter. This term is sometimes called the electric field intensity but such use of the Group Velocity. Of a traveling plane wave, the ve- word intensity is deprecated in favor of field strength locity of propagation of the envelope of a wave oc- since intensity connotes power in optics and radiation. cupying a frequency band over which the envelope delay is approximately constant. It is equal to the re- Elliptically Polarized Wave. An electromagnetic ciprocal of the rate of change of phase constant with wave for which the electric and/or the magnetic field angular frequency. Group velocity differs from phase vector at a point describes an ellipse. This term is usu- velocity in a medium in which the phase velocity varies ally applied to transverse waves. with frequency.

Page 2 1 O/l 6189 6580.5 Appendix 1 Half-Power Width of a Radiation Lobe. In a plane Lowest Useful High Frequency. Tile lowest high containing the direction of the maximum of the lobe, frequency effective at a specified time for ionospheric the full angle between the two directions in that plane propagation of radio waves between two specified about the maximum in which the radiation intensity is points. one-half the maximum value of the lobe. NOTE: This is determined by factors such as ab- Harmonic. A sinusoidal component of a periodic sorption, transmitter power, antenna gain, wave or quantity having a frequency that is an integral receiver characteristics, type of service, and multiple of the fundamental frequency. For example, a noise conditions, component the frequency of which is twice the fundamental frequency is called the second harmonic. Magnetic Field. A state of the medium in which moving electrified bodies are subject to forces by vir- Heterodyne. To beat or mix two frequencies in a tue of both their electrifications and motion. nonlinear component so as to produce different frequencies from those introduced. Magnetoionic Wave Component. Either of the two elliptically polarized wave components into which a HorizontaZly Polarized Wave. A linearly polarized linearly polarized wave incident on the ionosphere is wave whose electric field vector is horizontal. separated because of the earth’s magnetic field.

Incident Wave. In a medium of certain propagation Maximum Usable Frequency. Tile upper limit of characteristics, a wave that impinges on a discontinuity the frequencies that can be used at a specified time for or medium of different propagation characteristics. radio transmission between two points and involving propagation by reflection from the regular ionized lay- Interference. In a signal transmission System either ers of the ionosphere. extraneous power, which tends to interfere with the reception of the desired signals, or the disturbance of sig- NOTE: Higher frequencies may be transmitted by nals that results. sporadic and scattered reflections.

Ionosphere. The part of the earth’s outer atmos- Modif;ed Index of Refraction. In the troposphere, phere where ions and electrons are present in quanti- the index of refraction at any height increased by h/a, ties sufficient to affect the propagation of radio waves. where h is the height above sea level and a is the mean geometrical radius of the earth. When the index of Isotropic Antenna (unipole). A hypothetical an- refraction in the troposphere is horizontally stratified, tenna radiating or receiving equally in all directions. A propagation over hypothetical flat earth through an at- pulsating sphere is a unipole for sound waves. In the mosphere with the modified index of refraction is sub- case of electromagnetic waves, unipoles do not exist stantially equivalent to propagation over a curved physically but represent convenient reference anten- earth through the real atmosphere. nas for expressing directive properties of actual antennas. Multipath Transmission. The propagation phenomenon that results in signals reaching the radio re- Kelvin Scale (absolute scale). A temperature scale ceiving antenna by two or more paths, usually having using the same~divisions as the centrigrade scale, but both amplitude and phase differences between each with the zero point established at absolute zero path. (z - 273”C), th eoretically the lowest possible temperature. Noise. Any extraneous electrical disturbance tend- ing to interfere with the nonnal reception of a trans- Leakage Radiation (stray radiation). In a transmit- mitted signal. ting system, radiation from anything other than the intended radiating system. Optical Horizon. The locus of points at which a straight line from the given point becomes tangential to the earth’s surface. Linearly Polarized Wave. At a point in a homogeneous, isotropic medium, a transverse electromagnetic Optimum Working Frequency. The most effective wave whose electric field vector at all times lies along a frequency at a specified time for ionospheric propaga- fixed line. tion of radio waves between two specified points.

Page 3 6580.5 1 O/l 6189 Appendix 1 NOTE: In predictions of useful frequencies the Radio Horizon. The locus of points at which direct optimum working frequency is commonly rays from the transmitter become tangential to the taken as 15 percent below the monthly me- earth’s surface. dian value of the maximum usable frequency, for the specified time and path. NOTE: On a spherical surface the horizon is a circle. The distance to the horizon is affected Path Attenuation. The power loss between trans- by atmospheric refraction. mitter and receiver due to all causes. It is equal to 10 loglo Pt/Pr where Pt is the power radiated from the Reflection. The phenomenon that causes a wave transmitting antenna and Pr is the power available at which strikes a medium of different characteristics to the output terminals of the receiving antenna. It is ex- be returned into the original medium with the angles pressed in decibels. of incidence and of reflection equal and lying in the same plane. Permeability. A measure of the ability of a material to act as a path for magnetic lines of force. Refkaction. The phenomenon that causes a wave which enters another medium obliquely to undergo an Phase Constant. For a traveling phase wave at a abrupt change in direction if the velocity of the wave given frequency, the rate of linear increase of phase lag in the second medium is different from that in the of a field component (for the voltage or current) in the first. direction of propagation, in radians per unit length. Refracted Wave. The part of an incident wave that Plane Velocity. Of a traveling plane wave at a travels from one medium into a second medium. single frequency, the velocity of an equiphase surface along the wave normal. Refractive Index. Of a wave transmission medium, the ratio of the phase velocity in free space to that in Plane Wave. A wave whose equiphase surfaces the medium. form a family of parallel planes. Scattering. When radio waves encounter matter, a Polar Diagrams. A system of coordinates in which a disordered change in the direction of propagation of point is determined by the length and the angle of a the waves. line connecting the center of the diagram and the point. Selective Fading. Fading in which the variation of radio field intensity is not the same at all frequencies in Power Gain. In a given direction, HIT times the ratio the frequency band of the received wave. of the radiation intensity in that direction to the total power delivered to the antenna. Signa&To-Noise Ratio. The ratio in decibels of the value of the signal to that of the noise. This ratio is USU- Propagation Constant. For a traveling plane wave ally in terms of peak values in the case of impulse noise at a given frequency, the complex quantity whose real and in terms of the root-mean-square values in the case part is the attenuation constant in nepers per unit of the random noise. Where there is a possibility of am- length and whose imaginary part is the phase constant biguity, suitable definitions of the signal and noise in radians per unit length. should be associated with the term; for example, peak- signal to peak-noise ratio, root-mean-square signal to Radiation Efficiency. The ratio of the power radi- root-mean-square noise ratio, and peak-to-peak signal ated to the total power supplied to the antenna at a to peak-to-peak noise ratio. given frequency. Smith Chart. An impedance chart consisting of or- Radiation Intensity. In a given direction, the power thogonal families of circles. One family consists of con- radiated from an antenna per unit solid angle in that stant resistance circles. The second family consists of direction. constant reactance circles. Circles of constant vswr are concentric with the center of the chart. The point of Radiation Resistance. The quotient of the power zero reflection coefficient (vswr = 1) is at the center radiated by an antenna divided by the square of the of the chart. The locus of unity reflection coefficient antenna current referred to a specific point. (vswr = infinity) is the limiting circle of the chart.

Page 4 -IO/l 6189 6580.5 Appendix 1 Spherical Wave. A wave whose equiphase surfaces Troposphere. That part of the earth’s atmosphere in form a family of concentric spheres. which temperature generally decreases with altitude, clouds form, and convection is active. The troposphere Standard Refraction. The refraction that would occupies the space above the earth’s surface to a height occur in an idealized atmosphere in which the index of of about 10 kilometers. refraction decreases uniformly with height at a rate of 39 x 10W6per kilometer. Tropospheric Wave. A radio wave that is propagated by reflection from a place of abrupt change in NOTE: Standard refraction may be included in the dielectric constant or its gradient in the tropo- groundwave calculations by use of an effec- sphere. tive earth radius of 8.5 x lo6 meters, or 4/3 the geometrical radius of the earth.

Standing Wave. A wave in which, for any compo- NOTE: In some cases the groundwave may be so nent of the field, the ratio of its instantaneous value at altered that new components appear to one point to that at any other point does not vary with arise from reflections in regions of rapidly time. changing dielectric constants. When those components are distinguishable from the Surface Duct. An atmospheric duct for which the other components, they are called tropos- lower boundary is the surface of the earth. pheric waves.

Tenth-Power Width. In a plane containing the di- Vector. A quantity that has both magnitude and direction of the maximum of a lobe, the full angle be- rection or an arrow drawn in the direction of, and tween the two directions in that plane about the maxi- whose length is proportional to, the magnitude of the mum in which the radiation intensity is one-tenth the quantity. maximum value of the lobe. Vertically Polarized Wave. A linearly polarized Thermistor. A specially constructed resistor that has wave whose magnetic field vector is horizontal. a negative temperature coefficient; it is used for power measurements. Voltage Standing-Wave Ratio (VSWR) The voltage ratio expressing standing-wave ratio (rf on a transmis- Transverse Electric Wave (TE Wave). In a homo- sion line). For example: genous isotropic medium, an electromagnetic wave in swRdB = 20 log10 VSWR =20 log10 e which the electric field vector is everywhere perpendicular to the direction of propagation. Waveguide. A system of material boundaries capable of guiding waves. Transverse Electromagnetic Wave (TEM Wave). In a homogenous isotropic medium, an electromagnetic Wave Interfwence. The variation of wave ampli- wave in which both the electric and magnetic field tude with distance or time, caused by the superposition vectors are everywhere perpendicular to the direction of two or more waves. of propagation.

Transverse Magnetic Wave (TM Wave). In a homogeneous isotropic medium, an electromagnetic wave in NOTE: As most commonly used, the term refers to which the magnetic field vector is everywhere perpen- the interference of waves of the same or dicular to the direction of propagation, nearly the same frequency.

Traveling Plane Wave. A plane wave each of whose Wavelength. In a periodic wave, the distance be- frequency components has an exponential variation of tween points of corresponding phase of two consecu- amplitude and a linear variation of phase in the directive cycles. The wavelength A is related to the phase tion of propagation. velocity, “, and the frequency, f, by X = ./f.

Page 5 10/16/89 6580.5 Appendix 2

APPENDIX 2. BASIC TESTS FOR TRANSMITTERS AND RECEIVERS

1. GENERAL. ship provides the measureof averagepower. The wattmeter is installed in the transmission line near the output of the a. This section discusses the basic tests to be used in transmitter. Of course, the coaxial line loss and swr at this checking the critical transmitting and receiving equipment point determine the actual forward power delivered to the an- performanceparameters. The parameters,and their standard ‘tennaby the transmission line. A high swr results in exces- values, tolerances, or limits, are listed in chapter 3 of this sive reflected power, which must be subtracted from the order. forward power and added to the line loss.

b. The transmitter tests are for rated power output, b. Ssb Transmitters. The technique of measuring trans- modulation percentage,spurious emissions,and crystal oscil- mitter output power in the ssb transmitter is identical to that lator frequency stability. In single-sideband (ssb) transmit- usedfor am transmitters.Power is expressed,however, in the ters, the internal sideband exciter and converter caseof thessb transmitter, in watts of two-tone peakenvelope crystal-frequency stability is of utmost importance.Receiver power (PEP) instead of single-tone averagepower in watts, tests include sensitivity in rf antenna voltage for a specified which is usual for the am transmitter. In addition to power audio output, crystal oscillator frequency stability, and inter- output measurement,the metering of plate current, screen mediate-frequency (if) amplifier selectivity and bandpass current, plate voltage, grid current and grid bias voltage symmetry. protects transmitters operating at high power. The directional wattmeter is a much more accurate determination of the 2. TRANSMITTER OUTPUT POWER. power output of the equipment, but is limited to unbalanced output. Certain transmitters used in FAA are operatedinto a a. AM Transmitters. The technique of measuring rated balanced transmission line, for example, a 600-ohm open- transmitterpower (for example,am transmitter output power) wire line to a rhombic antenna. In order to measurethe out- dependultimately upon the service employed and the federal put power in such a system, it is necessaryto use series rf regulations involving that type of service. For example, am ammetersin each side of the open-wire line. In this manner or continuous wave (cw) transmitters used in amateurradio antennacurrent and the impedanceof the line will give an ac- service are rated in plate input power for which the maximum curate indication of the power actually delivered to the line. allowed is stipulated by the Federal Communications Com- Directional wattmetersused with ssb transmittersand the as- mission (FCC). For a measurementof this kind, it is neces- sociated forward power and reflected power meters may be sary to measureonly the key-down plate current to the loaded installed as part of the transmitter or station design. Figure 1 final amplifier tube and the dc plate voltage, then multiply the shoesvarious ways a transmitter is meteredfor power output two to obtain the input power. For a preciseindication of final and swr. The 1330 hf transmitters are equipped with a for- amplifier output power, it is necessaryto measureeither the ward power meter and a vswr meter. The vswr meter read- average transmission line current in a known antenna input ings are valid only for single tone ssb output at the rated impedance, or to use a directional rf wattmeter in a coaxial 5OOOWlevel. transmission line. In FAA vhf and uhf applications, it is a universal practice to use the directional wattmeter in the c. Peak Envelope Power. coaxial line to determine both the standing-wave ratio (swr) and the transmitter output power. Most vhf and uhf transmit- (1) The term “peak envelope power” (PEP) has been ters usedin FAA are classC amplifiers having a relatively ef- adopted to replace the term “carrier power” becausethe lat- ficient (up to 70 percent) output stage. The linear am ter doesnot expressthe true power output of a transmitter. In transmitter amplifier, which sometimesfollows a high-level- particular in ssb, carrier power ceasesto have meaning be- modulated class C amplifier, will operatein a mode between causein one or more modesof sb operation the carrier may class A and class B, (ABl or AB2) and is of lesser efficien- be suppressed.The term PEP meansthe averagepower sup- cy than the class C amplifier. The linear amplifier power is plied to the antenna transmission line by a transmitter during best determined, for an unbalanced output, by the direction- one radio frequency cycle at the highest crest of the modula- al wattmeter. For a balancedoutput, by using rf ammetersin tion envelope, taken during normal operation. There hasbeen seriesin each side of the transmissionline, the 12Z0relation- a tendency due to the word “peak” to consider PEP mistaken-

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C 1

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ly as an instantaneouspeak power value at the peak of the output of the transmitter. Some ssb transmitting equipment radio frequency cycle. This approachwill yield a value twice contains a test unit to generatea two-tone audio signal aswell the correct value. The true averageof PEP value is the result as a spectrumanalyzer for analysis. A general procedurefor of considering the root mean square (rms) amplitude of the imd checksusing the two-tone test is in chapter5 of the hand- radio frequency voltage (0.707 of the peak voltage) rather book proper. Figures 3 and 4 illustrate a typical two-tone test than the peak value. For an am transmitter with 100 percent display of a spectrum analyzer, showing the two primary modulation, the PEP is four times the carrier power. The PEP modulating audio tones and their amplitudes on the y-axis. for a cw transmitter usedfor frequency-shift keying (fsk) rtty Their relation to intermodulation products and the carrier at is the sameas the carrier power. The most useful power test lower amplitudes is shown to the right and left of the tones of an ssb transmitter is the two-tone test. In this caseaudio along the x-axis of the display. In normal ssbcommunication, test tones of equal amplitude represent complex-signal ssb the carrier is not required asa carrier of intelligence. It is used modulation. Figure 2 is a summary of power relationships only for a reference frequency to make sure that the receiv- from two-tone ssb test signals showing the correlation of ing equipment is able to track precisely the transmitted sig- averagepower and the power in two equal tones.The analysis nal. Carrier power to PEP relationships may be expressedas: can be extended to more than two audio tones applied to the transmitter; for example, a three-equal-tone test signal in (a) Full carrier, which is carrier emitted at a power which the power in each tone is one-ninth of the PEP and the level 6dB or less below PEP. averagepower dissipated in the load is one-third the PEP. (b) Reduced carrier, which is carrier emitted at a power level between 6dB and 32dB below the PEP and preferably between 16dB and 26dB below PEP. This particular usage is to achieve automatic frequency and/or gain control at the receiver.

e2 en (c) Suppressedcarrier, which is carrier restricted to a t I e2 1 -e2 e2- power level of more than 32dB below the PEP and preferab- -et el - - el et e2 ly 40dB or more below PEP.The double-sidebandamplitude- t I modulatedemission consistsof a full carrier that has a power level exactly 6dB below PEP at 100 percent modulation.

3. TRANSMITTER MODULATION.

TWO TONE ssa a. AM Transmitters. SIGNAL (1) High-level plate modulation is measured in am transmitters with an oscilloscope and modulation monitor. Vrms q 8, te2 (inphase ) Pep = Vfms/Rload = 4e:/Ror 4e:/R The trapezoid display provides more information on system where et = er problems than the envelope display. In initially setting Paveroge = e:/Rte:/R= Ze:/R or 2e:/R modulation sensitivity, the envelope pattern is adequatefor Therefore : (I) Pep = Vfms/R determining when maximum allowable peak modulation on (2) Paveroge = + Pep tone is obtained. For amplitude modulation, 95 percent is (3) Ptone I or Ptone L =f Pep maximum, rather than 100percent, to provide a buffer against the possibility of strong speechovermodulating the transmitter and splattering adjacentchannels. When using a test tone Figure 2. Correlation of Peak Envelope and for lineup and setting the modulation sensitivity of an am sys- Average Power in the Ssb Transmitter tem, a 1OOOHztest tone is applied, at its equivalent system level, to the transmitter modulator. The audio gain of the (2) Power relationships discussedin paragraph (1) do modulator is then adjusted to indicate exactly 95 percent on not consider the effects of distortion; however, distortion is the oscilloscope. A further refinement of modulation is using usually so small that it can be neglected.The two-tone test of an averagetalker on the microphone at the operating position an ssbtransmitter is perfect for transmitter performancetests to provide a standard test count. During this process, trans- becauseit provides a stabledisplay on an oscilloscope.It also, mitter modulation is observed on the oscilloscope, and the c with a spectrumanalyzer, displays odd-order intermodulation modulator audio gain is adjustedfor 95 percent maximum on distortion (imd) products. These products must be held at a voice peaks.The typical am transmitter signal modulated 100 * low level with respectto transmitter PEP for the purity of the percent occupies about 6kHz of channel space.Speech com-

Par. 2 Page 3 0 0

-IO -IO -10 --

SPECTRUM ANALYZER -20 -20 DISPLAY -20 --

-30 -30 -30 --

-40 -40

OSCILLOSCOPED,SPLAY ~

A. PROPERLY ADJUSTED SSB 6. IMPROPER BIAS AND CARRIER LEAK C. OVERDRIVE WITH SPLATTER TRANSMITTER, LOW IMD HIGH THIRD AND FIFTH ORDER IMD

Figure 3. Spectrum Analyzer and of Two-Tone Ssb Tests I

0, 1 . 0 Figure 4. Relationship of Two-Tone Amplitudes to Carrier and Intermodulation Distortion in an Ssb Signal ponents over a band of approximately 1OOHzto 3OOOHzare In unsymmetrical audio modulation, it is possible to have combined with the am radio frequency carrier to yield two more than 100 percent upward modulation while having 100 sidebands occupying a frequency spectrum from about percent downward modulation, and no distortion, as long as 3OOOH.zbelow the carrier to 3OOOHzabove. Compared to ssb, the modulated waveform exactly reproducesthe modulating this is arelatively wasteful system,for the spectrumoccupan- waveform. cy with ssb transmission carrying equivalent intelligence is only about 3OOOHz. b. Transmitters. There is no needfor an elaboratemethod . of measuring modulation in the ssb system (or linear power (2) Modulation percentagemeasured on a symmetrical amplifier) because 100 percent modulation is achieved and input signal is basedon the fact that the modulation signal has can be observedon an oscilloscope when the audio input to equal peak positive and negative amplitudes. This is true of the ssb exciter is of the proper level to provide undistorted an audio sine wave, such as 1OOOHztest tone modulating a rated transmitter output. The ssbtransmitter usually employs transmitter. The formula for such modulation is: audio compressionin the exciter to prevent overdriving the rf amplifiers. This compression is similar to automatic gain Percent modulation = Emax- Emin x 100 control (age)in areceiver in that a large signal causesthe gain Emax + Emin to be reduced through the system and the rate of gain reduc- If the modulating signal is unsymmetrical, depth of modulation is that corresponding to the syllabic rate of speech.The tion can be both “upward” and “downward,” and percentage ssb system employs automatic level control (ALC), or of modulation is by two formulas: automatic load control, to ensure that the output linear amplifier is not driven beyond linearity. Various kinds of dis- Percent upward modulation = Emak-.Emin x 100 tortion on an ssbsignal are illustrated in figure 3. Among the mm most common faults that may occur on an ssbsignal are over- Eti - min envelope drive, which results in peak clipping, and insufficient loading Percentdownward = downpe* x 100 of the linear amplifier. Additional problems are incorrect modulation Emin amplifier bias and unwanted modulations causedby carrier leak-through. To reiterate the principal advantageof a two-

Par. 3 Page 5 6580.5 1 O/l 6189 Appendix 2 tone test for observing modulation of an ssb signal is that it spectrum analyzer) for checking imd and other spurious produces a stable oscilloscope display easy to examine for responses.In figure4, it should be noted that the spacingbc- defects.On the other hand, it is impossible to evaluatean ac- tween each tone of the pair and the adjacentintermodulation tive speechwaveform. Many ssb transmitters have a sniffer products, and the spacing between subsequentintermodula- circuit in the final rf stageto direct a small amount of rf ener- tion products is equal to the spacing fl betweenthe two basic gy to a front panel jack on the transmitter so that modulation tones. The imd signals adjacent to the desired tones are the or drive can be observedwhile the transmitter is in operation. third-order products.The next pair are the fifth-order, spaced Procedures for the use of the oscilloscope and spectrum equally outside the third order products; the next pair are the analyzer in ssbperformance checks are contained in chapter seventh, then the ninth, and so on. The order of a distortion 5 of the handbook proper or in referencedinstruction books. product is the sum of the coefficients in the frequencyexpres- sion. For example, the third-order products will be twice the 4. SPURIOUS EMISSION. frequency of one desiredtone minus the frequency of the op- Spurious emission is undesired transmitter radiation of posite tone. The fifth-order product is three times the frequen- two basic types: spuriousresponses outside the passband,and cy of one tone minus two times the frequency of the other. imd and other distortion in or near the passband.Harmonics The odd-order products falling in or near the desired trans- and parasitic oscillations are the principal kind that fall out- mission band are the most objectionable because, once side the passband;these may include emission of frequency generated,they cannot be eliminated by either the transmit- synthesizersand broadband noise arising in lower level stages tcr or the receiver. The signal-to-distortion ratio is the ratio of amplified by the final power amplifiers. The best instrument either of the two desired test tones to the largest undesired on which to observe any of these unwanted disturbancesis productsexpressed in decibels. A signal-to-distortion ratio of the spectrumanalyzer. A receiver tunable to the frequencyof at least 35dB to 40dB is considered acceptablefor an hf ssb interest is also useful if coupled to a suitable output indicator. communication system.Unless unusual cancellation exists in The most effective test of the output purity of an ssbtransmit- the power amplifier, the third-order imd product will be the ter output is the simultaneous application of two cqual- largest, and all higher order products will be progressively amplitude audio tones (the two-tone test). The two-tone test smaller. hasbecome a standardtest because:(a) one signal is insufficient to produce intermodulation for observation: (b) more 5. RF SIGNAL GENERATORS AND THE COM- than two signals result in so many intermodulation products MUNICATION SERVICE MONITOR (CSM). that analysis is impractical; (c) two or more sine-wave tones of equal amplitude place more demanding requirementson a. An essential test equipment for receiver tests is a gen- the ssb system than it is likely to encounter in normal use.In erator of rf microvolts ranging typically from O.lpV to effect, a two-tone test signal representsa very complex sys- lOO,OOOl.rV.The rf output is typically 50 ohms, controlled tem that provides a very clear meansfor observing a number with an adjustableoutput attenuator calibrated to read direct- of deficiencies in the system.The two-tone test that generates ly in terminatedmicrovolts. Therefore, when the generatoris a number of intermodulation products is shown in figure 4. connected lo 50-ohm receiver antenna input terminals, the In this illustration, the relationship of the carrier and the two generatoractually delivers to the receiver the level indicated testtones is shown on the x-axis of the coordinatesystem. The on its attenuatordial. Formerly, somegenerators were of uneven- and odd-order productsthat may result from both rf and terminated (open circuit) output and required a 6dB pad be- af intermodulation are plotted on the y-axis, as related to the tween the generatoroutput to match the external circuit being two desired modulating audio frequencies; the carrier, and tested,so that the output attenuator was properly calibrated. any other signals in the passband.Figure 4 is a simplified il- Use of the pad at the output of the older generatorsrequired lustration of the relationship of test tones,odd-orderproducts, twice the voltage from the unterminatedgenerator to produce and the carrier and shows the logarithmic relationship that is a terminated level at the device being tested. From this expectedin a normally operating system.The productsof the resulted the concept of standard test voltage (STV) in FAA most significance are thoseof odd order, especially the third- equipment specifications, standards and tolerances, and and fifth-order products,The even-orderproducts always fall maintenance procedures. Presently, it is unnecessary to so far outside the frequenciesof interest that they are not ob- specify or use STV levels, or a pad, where the circuit under served nor do they affect the passband.(They can interfere test matchesthe 50-ohm generatoroutput. with other service, however). The seventh- and ninth-order productsusually are so greatly attenuatedwith respectto PEP b. Acquisition of the cqmmunication service monitor that they can be neglected.The fifth-order product is general- (GM), equippedwith the stableand accuratefrequency syn- ly much lower than the third order and also may be neglected thesizer,has eliminated the electronic frequency counter as a in actual testing. However, the third-order intermodulation monitor of the test frequencyduring receiver tests.The direct- products must always be evaluated. Chapter 5 of the hand- reading CSM can be set exactly to the required frequency; book proper contains a generalized procedure (using a and suchtests as if bandwidth and if bandwidth nonsymmetry

Page 6 Par. 3 I 1O/i 6189 6580.5 Appendix 2 can be made with confidence that frequency drift and setup observed.) As the channel frequency is approachedby the error has not occurred. generatorfrom below in frequency, the curve is seento pass symmetrically from a level well below a point 60dB below c. An early model CSM was procured in a limited quan- age threshold, through a point 6dB below the age threshold. tity for FAA evaluation, and was allocated to only a few Then when the curve reachesits nose, or maximum excur- facilities. This was the Singer-Metrics FM- IOCS.The nation- sion, a flat-top region (with some ripple) will be observed al procurement was for a simpler version, the CSM-1. The before it falls away in mirror image on the higher frequency proceduresin this handbook are basedon the latter unit. side. Figure 5 illustrates a typical if selectivity curve of a receiver having a crystal filter. The 6dB and 60dB points that

” 6. RECEIVER SENSITIVITY. are the standard reference levels for selectivity are shown. The 6dEl levels are chosen as checkpoints as it is necessary a. Sensitivity testsof communication receiversare of two to have a given minimum bandwidth for undistorted, basic types. The first yields the lowest rf voltage (in received-signal, double-sideband reception.The 60dB levels microvolts) impressed at the antenna terminals that will are chosen similarly to ensure that the lower skirt slope produce a specified af power at the audio output loaded,in its characteristics do not exceed the maximum actually needed proper impedance. This is useful at the lower frequencies for the passband.The standardreference levels for WR-100 (e.g., below about 25MHz) where atmospheric noise is the receivers are the 6dB and 80dB points. dominant noise of the system.The secondprovides the lowest rf antennaterminal voltage (in microvolts) for a specified sig- b. Symmetry of the if passbandis essentialto prevent skirt nal-plus-noise to noise ratio, also measuredat the audio out- distortion of one sidebandor the other during reception. Sym- put of the receiver. The latter test is the better of the two for metry is dependenton the accuracyof the first oscillator crys- vhf and uhf receivers, where receiver noise dominates. tal and on troublefree if and crystal filter stages.Usually, an Another form of sensitivity test is the front-endfigmeof merit off frequency crystal or mistuning of if stages(or a defective of the receiver, or noise figure as it is usually called. This test, filter) will cause large out-of-tolerance symmetry measurements, which are measured in percent of nonsymmetry. normally useful with receivers of 3OMHz operating frequen- Figure 5 is an if passbandwith somenonsymmetry evidenced. cy and above, is basedon the ratio (expressedin dB) of noise power developed in the ideal (quiet) receiver to noise power 8. FREQUENCY STABILITY. developedin the actual (noisy) receiver. It is particularly useful for frequency-modulated (fm) receivers used in-corn- a. To provide reliable communication, a receiver must munication link systems. stay precisely tuned to the incoming rf signal. For this reason (in ssb precise timing is more important than in am), the b. Test equipment required for the rf voltage input for modem receiver uses oven-controlled, local oscillator crys- specified audio frequency (at) output power, or for signal- tals having tight stability specifications. As mentioned in plus-noise output, is (1) a stablerf signal generatortunable to paragraph7, an inaccurateor drifting crystal-controlled local the receiver’s frequency rangewith an accuraterf output level oscillator circuit will causethe if frequency generatedin the attenuator,and (2) an audio power level meter to measurethe mixer circuit to shift and thereby skew the useablepassband af power output or receiver noise &4&r. F%r noise figure to affect if symmetry, possibly to the point of great signal tests,anoise-figure test set with calibrated noi&&rce is re- degradationand loss of contact. quired. b. The frequency-synthesized communication service 7. RECEIVER SELECTIVITY AND IF BANDPASS monitor (CSM-1) is a precision substitute for the older, tunable rf signal generators and Gertsch frequency meters, SYMMETRY. which necessitateduse of an external electronic frequency counter to make most measurements.The Gertsch frequency a. The selectivity of a receiver is a measureof its ability meterstypes PM-3 and FM-6 should be avoided when apply- to reject unwanted signals. Selectivity is almost exclusively ing the proceduresof this order. determined by the intermediate-frequency (if) stages of a receiver. In modemreceivers equipped with crystal-filterele- 9. MISCELLANEOUS TESTS. mentsin the if stages,it is the crystal filter that determinesthe Sometimesit is useful to evaluate a receiver for other than bandpasscharacteristic. The typical measureof selectivity is the basic parametersdiscussed in paragraphs 5 through 8. basedon the curve formed by sweeping an rf signal, applied Such factors as intermodulation, spurious oscillation in at the antenna terminals, symmetrically above and below the amplifiers, excessive noise developed in the receiver, audio center, or channel, frequency of interest. The receiver age .frequency response, and age response can be measured. detector circuit dc voltage draws this curve when metered However, they are not included in this handbookbecause they with a dc voltmeter. (Most receiversare equippedwith an age are primarily used in design qualification tests or for test jack at which the changes in age voltage may be troubleshooting. 6580.5 Appendix 2

f CHANNEL 0

CHANNEL = fl+fe FREQUENCY 2 (AT 606 POINTS)

IF Afi IS LARGER,

PERCENT NONSYMMETRY =

\ IF At2 IS LARGER,

PERCENT NONSYMMETRY =

+ LOW-IF FREQUENCY - HIGH +

Figure 5. Typical Receiver IF Selectivity Response

Page 8 Par. 9 1 O/l 6189 6580.5 Appendix 3

APPENDIX 3. TRANSMITTER AMPLITUDE MODULATION (AM) MEASUREMENTS

1. GENERAL. normal 10%percent modulated signal with good linearity. To measureamplitude modulation on test tone or voice Convex or concave sloping sides indicate linearity problems peaks,connect the transmitter to a dummy load, a modulation in the final amplifier. Part B of figure 4 shows an overmodu- monitor, and an oscilloscope, as shown in figures 1 and 2. lated condition. Part C indicates an audio phase shift in the transmitter, commontosomedegree in most transmitters.Use 2. THE TRAPEZOIDAL PATTERN. a simple phase-shift network in the oscilloscope horizontal input line. This phase-shift network may bc made up of a a. The trapezoidal modulation pattern offers an excellent 0.OQ.F capacitor in series with the audio line and a 50,000- method of checking transmitter distortion and modulation ohm potentiometer in parallel with the audio line. Parts D percentage.Figure 3 illustrates how the rf and audio signals through F show various kinds of distortion. Part G is an over- combine to produce the trapezoidal pattern. modulated transmitter with excessive screen voltage on the class C modulated stage. WARNING: High voltage is present on external test leadswhen making this modulation check.Observe proper precautions. 3. THE ENVELOPE PATTERN.

(1) Do not apply the modulated rf carrier directly to the a. Figure 5 showsvarious modulation patternswith the os- vertical deflection plates. Obtain suitable output from the cilloscope adjusted and connected for the envelope pattern modulation monitor, which converts the modulatedtransmit- technique (test arrangementin figure 2). Part A of figure 5 is ter rf output signal to a 1OOkHzmodulated rf signal. Then a normal, loo-percent modulatedpattern. Part B showsa nor- apply this signal to the vertical input of the oscilloscope. mal overmodulated pattern. Part C is an overmodulated pattern showing the effects of regenerative feedback.Part D is (2) Only a small portion of the audio voltage is applied an overmodulated pattern showing the effects of excessive to the horizontal deflection plates of the oscilloscope. Ob- screen voltage in relation to the plate voltage in the modu- serve caution to avoid contacting the high voltage present at lated stage.Part E illustrates crossover distortion causedby the modulator test points. excessivegrid bias on the modulator tubes.Part F is a pattern causedby speechamplifier clipping. NOTE: Avoid using the audio output from the modulation monitor for horizontal drive to the oscilloscope. Use b. Figures 6 and 7 are nomographs for determining pcr- audio ahead of the modulated stage of the transmitter, cent of modulation (by either trapezoidal or envelopepattern) preferably the final output of the modulator, for the without calculations. horizontal drive source.

(3) Figure 1 showsa typical test setup for use with a uhf 4, MODULATION ADJUSTMENT TECHNIQUES. single-channel transmitter. A similar setup for vhf transmit- Set the transmitter voice modulation as close as possible ters will work equally well by bridging the oscilloscope to 95 percent without overmodulating the transmitter. The horizontal input acrossthe audio signal input of the transmit- technique is simple. Requesta controller to transmit a stand- ter modulator. ard voice test count, and increase the transmitter audio gain until a few points of overmodulation can be seenon an oscil- b. Many modulation problems can be identified by loscope.Then slightly decreasethe transmitter audio gain so analysis of the trapezoidal pattern. Figure 4, part A, shows a that the overmodulation peaksno longer occur.

Par. 1 Page 1 6580.5 1O/l 6189 Appendix 3

TRANSMITTER

AUDIO INPUT = !b

* * SYNC IN ,>-“1 3 OSCILLOSCOPE WARNING-HIGH VOLTAGE S--OX y-e-

Figure 1. Modulation Measurement by the Trapezoidal Pattern

RF PROBE MODULATION MONITOR

IF OUT SYNC OUT

NOTES 1 SUBSTITUTE RATED POWER DUMMY LOAD OSCILLOSCOPE FOR ANTENNA TO PREVENT CHANNEL INTERFERENCE.

2 TEST ARRANGEMENT IS FOR SINUSOIDAL DISPLAY

3 AT SOLID-STATE. COLLOCATED TRANSMITTER/RECEIVER SITES, THE INTERMEDIATE FREQUENCY (IF) OF THE MODULATED SIGNAL MAY BE OBTAINED FROM THE RECEIVER IF OUTPUT JACK. JlO. IF A MODULATION MONITOR IS NOT AVAILABLE. Figure 2. Modulation Measurement by the Envelope Pattern

Page 2 Par. 4 1O/l 6189 6580.5 Appendix 3

\ \ \ \ -"t----A--TT--- \ \

‘a \ T’r ,

L ------_- ~y.-i~~ ‘\ - --- \ 1 I- - -y- ;-tt’ \ t w ------I \

Figure 3. Production of Trapezoidal Pattern

Par. 4 Page 3 6580.5 10116/89 Appendix 3

Figure 4. Various Trapezoidal Patterns

Figure 5. Various Envelope Patterns 1 O/l 6189 6580.5 Appendix 3

Modulation s- Percent

Emax

6 ‘0

75-

20 -- .21 22 ------Y .23 “- 24 6 ,a To determine modulation percent, ------* 26 7 27 apply Emax to left scale; Emin to 28 center scale: read 70on right scale. B M = Emax-Emin x 1w 29 Emax*Emin 3c 9 .31 Example: 32 lo -33 Emax- squares on oscilloscope 34 .35 Emm;&squares on oscilloscope Y 37 36 -38 4c

Figure 6. Nomograph for Percentage of Modulation, 50 to 95 Percent

Par. 4 Page 5 6580.5 1 O/l 6189 Appendix 3 Mamtatii Emin lo Percent II 3 PEmax

13 Iw 6

22 13- -t 24 IS- 25 t--- 427 26 17-

ls- 2a 20 2l- 22 To determine modulation percent, 23- Emax-Emin 31 30apply Emaxto left scale; Emin to 24 M= 2% Emax+Emin ’ 100 32 center scale: read 70on fight scale. 26 33 27- Example: 20 34 29- Emax- squares on oscilloscope 30 35 3’- Emin= squares on oscilloscope 32 36 MOD-2010 3s 37 34 35- 38 36 37- 39 36 140 PO Figure 7. Nomograph for Percentage of Modulation, 0 to 60 Percent

Page 6 Par. 4 10116l89 6580.5 Appendix 4

APPENDIX 4. REFERENCE DATA FOR AUDIO FREQUENCY MEASUREMENTS

1. GENERAL. 3. RMS VOLTS TO POWER LEVEL This appendix provides graphs, charts, and a table CONVERSION. for assisting in the calculations that are a necessary Figure 2 is a graph of volts rms to power in dBrn part of measuring and evaluating audio frequency (af) across various load impedances. and noise parameters in the point-to-point (PTP) or air-ground (a-g) communication channel. 4. METER CORRECTION GRAPH. Figure 3 permits correction of meter readings made with the same meter across various resistive load impedances. 2. DB-VU-DBM UNIT CONVERSION. Figure 1 is a chart-that is useful in converting from 5. DECIBELS ABOVE AND BELOW A one audio unit of value to another. It provides both l- l-MILLIWATT REFERENCE LEVEL. milliwatt and B-milliwatt reference scales and a scale Table 1 is numerical data, accurate up to five signif- of volts root-mean-square (rms) across a 666ohm im- icant figures, relating dB, volts nns, and dBm referred pedance. to 1 milliwatt in 600 ohms.

Par. 1 Page 1 6580.5 IO/16189 Appendix 4

Table 1. DECIBELS ABOVE AND BELOW A REFERENCE LEVEL OF 1 MW INTO 600 OHMS

dB Down Level dB Up Volts Milliwatts dBm Volts Milliwatts 0.774 6 l.ooo -o+ 0.774 6 1.000 0.690 5 0.794 3 1 0.867 1 1.259 0.616 7 0.631 0 2 0.975 2 1.585 0.548 4 0.501 2 3 1.094 1.995 0.488 7 0.398 1 4 1.228 2.512 0.435 6 0.316 2 5 1.377 3.162 0.388 2 0.251 2 6 1.546 3.981 0.346 0 0.199 5 7 1,734 5.012 0.308 4 0.158 5 8 I.946 6.3 IO 0.274 8 0.125 9 9 2.183 7.943 0.244 9 0.100 0 10 2.449 10.000 0.218 3 0.079 43 11 1.748 12.59 0.194 6 0.063 10 12 3.084 15.85 0.173 4 0.050 12 13 3.460 19.95 0.154 6 0.039 81 14 3.882 25.12 0.137 7 0.031 62 15 4.356 3 1.62 0.122 8 0.025 12 16 4.887 39.81 0.109 4 0.019 95 17 5.484 50.12 0.097 52 0.015 85 18 6.153 63.10 0.086 91 0.012 59 19 6.905 79.43 0.077 46 0.010 00 20 7.746 100.00 0.043 56 0.003 16 25 13.77 316.2 0.024 49 0.001 00 30 24.49 I.OOOW 0.013 77 0.000 316 35 43.56 3.162W 0.007 746 o.ooo 100 40 77.46 1o.oow 0.004 356 3.16 x 1O-5 45 137.7 31.62W 0.002 449 1.00 x 10-S 50 244.9 1oow 0.001 377 3.16 x lO-6 55 435.6 3 16.2W 0.000 774 6 1.00 x 10-6 60 774.6 1ooow 0.000 435 6 3.16 x lo-’ 65 1 377 3 162W o.ooo 244 9 1.00 x IO-’ 70 2449 10 ooow o.ooo 137 7 3.16 x lO-8 75 4 356 31 620W 0.000 077 46 1.00 x 10-S 80 7 746 100 ooow

NOTE, The ~mwr hold> fir on? impdmrr. bur rhr w,,,ogr hokls rrd, ,,,r 60” oh ,I,. r

6. CONVERSION OF NOISE UNITS. other of a different noise-weighting characteristic. Conversions are possible between flat (3kHz) noise, Figures 4 and 5 are nomographs permitting the con- FIA-weighting, 144-weighting, and C-message weight- version of noise readings from one noise meter to an- ing in dBm, dBa, dBrn, and dBnc units.

Par. 5 Page 2 1 on 6189 6580.5 Appendix 4

.IAMPS V ‘OLTS

10 9 8

I I I I II I II I I I I I I m I I I I +5+6 ) +4 +3 - ) +2 E+1

.3 / / .5

.2 .1

.W ,- i -. 08 -25 -2c -15 -10 -5 0 +5 +10 +15 +20

DE- VU- DBM

Figure 1. DB-VU-DBM Unit Conversion Chart

Par. 6 Page 3 * 6580.5 1 O/l 6189 Appendix 4

.60

.OOl .Ol .l 1 10 100 AC VOLTS (RMSI

Figure 2. RMS Voltage to Power Level Conversion Chart

Page 4 Par. 6 1 O/l 6189 6580.5 Appendix 4

10 100 1000 10K 1OOK IMPEDANCE (OHMS1 5

Figure 3. Meter Correction Graph

Par. 6 Page 5 6580.5 10/16189 Appendix 4

A -40 -30 -J-A,-20 -10 0 DBM I I

I I I I I I I I t so + 60 + 70 + 80 DBA z;p+.>I II I LEG”TING

+ 50 + 60 t70 t 80 DBA I I

+ 90 DBRNC SCALE FOR IKHZ TONE

C MESSAGE WEIGHTING

SCALE FOR NOISE DBRNC

+50 ,I t 60 + 70 I t 60 + 90 DBRN SCALE FOR I I I I I IKHZ TONE

SCALE FOR NOISE

Figure 4. Nomograph for Conversion of Noise Units, 0 to -4OdBm

Page 6 Par. 6 1 O/l 6189 6580.5 Appendix 4

-40 DBM

0 + IO I.+ 20 + 30 +40 +50 DBRNC

C MESSAGE l-t WEIGHTING

0 l IO + 20 + 30 +40 DBRNC I

0 + IO + 20 + 30 + 40 DBRN

Figure 5. Nomograph for Conversion of Noise Units, -40 to -90dBm

Par. 6 Page 7 1 O/l 6189 6580.5 Appendix 5

APPENDIX 5. PRINCIPLES OF RF TRANSMISSION LINES

1. GENERAL. added to swr loss may make some low-power transmitting This section covers basic principles of rf transmission and some receiving systems unacceptable in reliability. lines. Consult commercial and military manuals devoted to Where it is necessaryto have relatively long runs of solid- transmissionline theory for additional details. dielectric coaxial cable, the need to keep swr low becomes paramount.Tables and nomographsare provided in appendix 2. ELECTRICAL TYPES OF LINES. 8 of this order to provide information relative to potential and Transmission lines (feeders) convey rf energy from a actual loss that can bc experienced with selection of certain transmitter to an antenna or from an antenna to a receiver. types of line, increaseof swr from inattention to maintenance From an electrical viewpoint, there are two general types of requirements,dielectric deterioration, moisture leakage,and lines. severeweather effects.

a. Tuned lines have standing waves and must be tuned or cut to resonanceat the operating frequency.

b. Matched lines have no standing waves; they are terminated by the antennaor receiver in a resistanceequal to the characteristic impedance(Z,) of the line.

3. STANDING-WAVE RATIO.

a. In any line, the ratio of the current maximum (loop) to the current minimum (node) is called the standing-waveratio (swr). This ratio is always identical to the ratio of the line im- A. OPEN-CIRCUIT LINE pedanceand the terminating impedance. Thus, if the transmission line has a 600-ohm impedanceand is terminated by either a 72- or a 5,000-ohm resistance,the mismatch and the swr are 8.3 to 1 in either case.A measurementof the standing waves along the line gives an indication of the degreeof mismatch present and can be used in the adjustment of matchedtransmission lines. Figure 1 shows, in part A, standing waves on an open-circuited line. In part B, the standing waves are shown on a short-circuited line. A high swr indicates that power which should be reaching the antenna or B. SHORT-Cl RCUITED LINE receiver is being radiated or dissipated by the transmission line. As an illustration of the effect of mismatch on swr, parts A and I3 of figure 2 both have a magnitude of 5 for the termination with relation to the Z,, of the line. If the standing- Figure 1. Standing Waves on Open-Circuited and wave current shown is measuredon one line at points B’ or Short-Circuited Lines C’ and on the other at points B and C, it will be found that the current at B’ and B is five times that measuredat C’ and C. c. A term frequently encountered in standing-wave Therefore, the swr is 5 to 1, exactly the relationship that ex- measurementsis the voltage standing-waveratio (vswr). This ists between the characteristic impedanceof the line and the term expressesvoltage maxima and minima on a transmis- load resistance. sion line. Swr can be expressedin decibels by use of the following relationship. b. The importance of keeping the swr low in designing and V maintaining communication antennasand transmission line SmdB = 20 lOglO vsm = 20 log10 $+ systemscannot be overemphasized.The normal lossesof line nun

Par. 1 Page 1 6580.5 1 O/l 6/89 Appendix 5 0

zo = 3009 R=6OQ

Y=SX . Y i; . X

zo=3oo!-l R = 15000

Y=SX

’ E t 1 B f a

Figure 2. Relation of Mismatch to SWR

The general term swr, for the most part, is used throughout whether a voltage or current loop appearsat the transmitter this order. Vswr is used when specifically addressing a end of the line. A parallel-tuned circuit should be used to measurementof voltage maxima and minima on a line. resonatethe system at a voltage loop and a series-tunedcir- cuit at a current loop. 3. TUNED LINES. c. It is not necessaryto have the line any exact length, in- a. Tuned lines generally are usedfor multiband operation asmuchas the tuned circuit can compensatefor a lot of devia- of an antenna.Obviously, if the line can be tuned to any fre- tion. However, it is best to have it as near aspossible to some . quency by a coupling device at the transmitter or receiver, multiple of a quarter wavelength, since there are a few criti- then power can be introduced into or taken from the system cal lengths that are difficult to resonateon particular frequen- antennaand transmissionline at any frequency. cies. If difficulty is experiencedin tuning the line, a few turns of wire addedto eachfeeder line usually add sufficient length b. Tuned lines generally are connected to the antenna at to permit tuning. the centeror at one end. However, in an antennathat is several halfwaves long, the tuned lines can be connectedat any point in the antenna that is a voltage or current loop. If the line is 5. OPEN-WIRE LINE SPACING. connectedat any voltage loop (or at the end of the antenna), the termination has a high impedance,and voltage loops ap- a. Between Feeders. The spacingbetween the two feeder pear every half wavelength along the line. Conversely, if the lines must be a small fractioriof the wavelength. A separation line is connectedat any current loop (or the center of a half- of 0.01 wavelength or less is desirable. At 2OMHz the lines wave antenna),the termination hasa low impedance,and cur- neednot be closer than 6 inches (15cm). As the frequency in- rent loops appear at the end of the line and every half creases,this spacing decreases,and other means should be wavelength along the line. From this can be determined used for transferring power to the antenna when this maxi-

Page 2 Par. 3 1 O/l 6189 6580.5 Appendix 5 mum spacingbecomes so small that open-line construction is coupled at the low-voltage point on the final amplifier tank - impractical. circuit coil. This low-voltage point appearswhere the tank coil is bypassedto ground or at the center of a balanced cir- b. Between Grouped Transmission Lines. If two or cuit. In somecases, it may be necessaryto ground the center more transmission lines run near each other, the minimum of the link coil to sufficiently decreasethe transfer of h,ar- spacingbetween the two lines should be at least 10 times the m80nicenergy. spacing between feeders.For example, with 8-inch (20cm) spacing between feed lines, transmission lines should be c. A Faraday shield can also be used to prevent excessive separatedno less than 80 inches (2OOcm).Criteria for fixed harmonic radiation from the antenna system.This shield is a , signal installations are set at 8 feet (2.44m) horizontal and 4 comb of metal between the coupling coils. No electrical cir- feet (1.2m) vertical separation as minimum for open-wire cuit, such as closed loops of wire, should be attachedto any transmissionlines. p&artof the shield, becausethe induced currents would cause heating of the shield and additional inductive losses. The 6. CHARACTERISTIC IMPEDANCE OF MATCHED shield is flat if it is usedbetween two coils, the ends of which LINES. are coupled; it must be concentric and between the two coils if it is used with concentrically coupled coils. In either case, a. Open Wire. With an air dielectric, the characteristic it can be madeby winding wire (spacedits own diameter) on impedanceof a parallel-wire transmissionline is given by the a flat or round form of heavy paper or other insulating formula: material. Wire of any size from No. 14 to No. 22 American Wire Gauge (AWG) can be used. The winding should be Zo = 276 log $ painted with several coatsof coil lacquer. When dry, the coil should be cut in a straight line parallel to its axis. One set of where& is the characteristicimpedance in ohms,b is the cen- cut ends are then soldered to a straight piece of wire. The ter-to-center spacing between the two feed lines, and a is the result is a comb-like formation of parallel wires, either flat or radius of the conductor. The quantities for b and a must be the round, insulated from each other but metallically coupled at sameunits of measure- inches,centimeters, etc. This formula one end. The shield is placed between the tank and output is applicable to any parallel-wire transmissionline having the coils and is grounded.TheFaraday shield preventscapacitive majority of its separationformed of air. coupling, but it hasno effect on the normal magneticcoupling between the two coils. b. Coaxial Lines. The characteristic impedanceof an air- dielectric coaxial line is given by the formula: 8. OPEN-WIRE LINE REQUIREMENTS.

zo= 138 log + a. The minimum spacingbecomes a factor where conductors may swing in the wind or become coated with ice. where Z,, is the impedancein ohms, b is the inside diameter Mechanical strength rather than current-carrying capacity of the outer conductor, and a is the outside diameter of the usually is the major factor to consider in selecting the gauge inner conductor.The quantities for b and a mustbe in the same of wire for open-wire rf lines. Wire having low tensile units of measure.This formula is correct for air dielectric and strength cannot be stretchedtightly enough without breaking bead-supportedcoaxial cables.The characteristic impedance under wind or icing conditions. Wire that is too large in . of solid insulated rf coaxial cablesdepends on the type of in- diameterrequiresexcessive sag, which makesit more suscep- sulation used. tible to swaying in the wind (paragraph 9). A three-strand conductor (each strand No. 12 AWG) or its single-strand rf 7. HARMONIC SUPPRESSION. equivalent (No. 6 AWG) generally is used.

a. Tuned transmissionlines generally permit a higher har- b, The lengths of the two electrical sidesof the lines should monic radiation than matchedline systems,except when they be kept identical. Sharp turns should be avoided wherever are used with a broadbandantenna. Pure inductive coupling possible.A necessarysharp turn should be madewith jumpers from the transmitter to the transmission line usually reduces that take a gradually curving path. The jumpers on opposite the harmonic radiation from the antenna system. sidesof the line must be identical in length and have the same spacing throughout their curve as does the transmission line. b. Harmonics usually are transferred to the antenna by Theselength and spacing requirements are most convenicnt- capacitive coupling. Thus, it is desirable to reduce or ly met by twisting the transmission line to a vertical position eliminate any capacitive coupling between the transmitter just aheadof the turn, and returning it to horizontal position and the transmission line. When using a link coupling to after the turn has been completed. The twists (or semi- eliminate the harmonic transfer, the link coil should be transpositions) in the line must be gradual. After twisting the

Par. 5 Page 3 6580.5 1 O/l 6189 Appendix 5 transmission line to a vertical position to make a bend, it is array. They lend themselveswell to corrective matching by advisable to twist the line again in the oppositedirection and the sleeve or stub method, and they have high rf power for the samedistance. This equalizesthe capacitiveunbalance capabilities. Fixed directional couplers or wattmeterscan be introduced by the first twist, which places one conductor built into theselines by using standardhardware supplied for closer to the ground than the other. the purpose,and they can be mademoisture-proof with an insert gas (e.g., nitrogen) line pressure system. Figure 3 is a c. The line spacing should be measuredaccurately and cutaway drawing of an air-insulated coaxial cable. kept uniform. Any slight variation of line spacing may cause a point of impedanceirregularity to be formed in the transmission line.

d. All wire connections should be well served and INNER soldered. All connections should be either pour or dip CONDUCTOR solderedto prevent the uneven solder lumps and points that . form when a soldering iron is used.

e. The supporting poles should be placed at varying dis- tancesfrom eachother, with no two adjacentpole spansalike. Each insulator adds to the conductor a definite massof conductive material in the form of tie wire and metal ends of the insulator. The variation of pole spans prevents the estab- lishment of resonantsections in the lines by reflections from Figure 3. Sectional View of Air-Insulated Coaxial Cable the various lumps of conductive material.

f. Special attention should be given to building entrance b. The rigid coaxial line is made of copper tubes that, for arrangements.Entrance to the building by the line must be all practical purposes, cannot be bent. Assembly of these spaced to maintain the correct impedance. Electrical con- tubes is essentially a pipe fitting job requiring the necessary tinuity must be maintained through the building wall. Light- couplings, junctions, and terminal fittings. ning protection should be designedand installed so that both wires of the line have identical circuits through the protective c. Some cables of 7/8-inch (2.2cm) outside diameter or device.Electrical conductorsmust be preventedfrom ground- less are called soft-temperedcables and can be bent. These ing through the building walls in wet weather. are essentially air-dielectric coaxial cables.

g. No connections to the line should be made that would d. It is necessarythat moisture be kept out of air-dielectric result in different impedancesto ground from each conduc- lines becauseany changesin the humidity of the air dielectric tor. Each connection or tie wire on one side of the line should would give a corresponding change in impedance.To keep be duplicated in an identical manner and at exactly the same the lines dry, they are usually filled with dry air or inert electrical point on the other side of the line. nitrogen gas under pressure. e. The larger sizes of air-dielectric lines are capable of 9. SAGGING OF OPEN-WIRE SPANS. . Sag is the maximum departureof a wire from the straight transmitting considerableamounts of power. line between the two supported ends of the wire. The common tendency is to pull small conductors too tightly and to 11. FLEXIBLE, SOLID-DIELECTRIC COAXIAL leaveexcessive sag in large conductors.When the small wires LINES. are too tight, they may break in cold weather, or stretch, and The most widely usedcoaxial line, or coax, is the flexible, thus reduce the cross-sectionsize of the wire. polyethelyne, solid-dielectric coaxial cable. This cable is available in many types, diameters, and characteristic im- 10. RIGID, AIR-DIELECTRIC COAXIAL LINES. pedance.Losses of rf energy are higher in solid-dielectric cable than in air-insulated cable or open-wire lines. The a. Rigid, air-dielectric lines have characteristicimpedan- dielectric is also subject to cold flow, a deteriorating process ces ranging between 50 and 75 ohms. They have relatively whereby the centerconductor losesperfect concentricity with low loss per unit length. Their unbalancedelectrical charac- the outer metallic sheath. Periodic testing of installed and teristic makes them low radiators of spurious energy and storedcoaxial cable is necessaryto ensurethat its lossesfrom therefore desirable when necessaryto run several cables in age, water, and deterioration are not greater than the proximity, as when feeding antennas in a multifrequency published loss for the particular cable in use. Foam-filled

Page 4 Par. 8 1 O/l 6189 6580.5 Appendix 5 flexible or semiflexible coaxial cable provides less loss per b. Connecting an antennato equipment generally involves unit length than the solid polyethelyne type. A trade nameof the useof a transmissionline that may be severalwavelengths one make of this cable is Foamflex. Figure 4 is a sectional il- long. Proper coupling at the antenna end and the equipment lustration of a solid-dielectric cable. end of the line is necessaryfor efficient operation.

c. At the antennaend, the characteristic impedanceof the line should be as nearly equal as possible to the input impedanceof the antennato avoid reflection of energy and con- sequent standing waves. Excessive reflections at this point can causehigh line losses,spot heating, flashover in the line when transmitting, and detrimental echo and intermodulation effects in multichannel communication circuits. The ade- qiuacyof the match is determined by a measurementof the swr along the line.

d. In the caseof a transmitter, the final amplifier general- Figure 4. Sectional View of Solid-Dielectric ly is tuned and coupled to the line so that amaximum of power Coaxial Cable is transferred, consistent with the power rating of the 12. TWISTED-PAIR TRANSMISSION LINES. amplifier. Ideally, the procedure consists of tuning out any The characteristic impedance of a pair of wires twisted amplifier output reactanceand in matching resistances.Ac- around each other is approximately the same as the im- tually, some reactance is usually developed in the line as a pedanceat the center of a half-wave antenna (72 ohms). This result of slight imperfections in the antenna match, in which provides a simple methodof connection to this particular type casethe transmitter tuning includes the introduction of reac- of antenna. The losses in such a line, however, are greater tance of opposite sign to cancel that appearing in the line. than the loss in a comparablelength of open-wire line. Since the line has an overall low impedance, the rf voltage in the e. Connecting transmitting and receiving equipment to an line itself is relatively low, and the line is easyto insulate. For antennausually involves interconnection via a number of dif- receivers, the twisted-pair line loss, up to several ferent antenna cable types and connectors. When main and wavelengths, is unimportant becausethe loss in the line at- standby transmitter switching and series receiver multipling tenuatesthe signal and any rf noise picked up in the antenna are requirements of the facility, a further complication is in- systemin the sameproportion. Thus, the signal-to-noise ratio troduced, by use of a transfer rf relay in the transmitter case remains essentially unchanged. For transmitters, however, and by a series coaxial arrangementor transfer relays in the special low-loss twisted-pair lines having sufficient insula- receiver case.Further requirements may include patching in tion to carry the rf power without breaking down should be the facility. An antenna junction box on a tower accom- used. modatesfinal connection to the transmitter and receiver antennas.Figure 5, part A, is a simplified diagram of main and 13. TRANSMISSION LINES AT VHF AND UHF FRE- standby transmitter connections showing cable and connec- QUENCIES. tor types. Part B of the figure shows receivers that are series At vhf and uhf frequencies, transmitters generally have connected. Main and standby relays are also used for low-power output, permitting the use of solid-dielectric receivers that are not seriesconnected. coaxial cablesfor transmissionlines. In the vhf and uhf bands, 50- to 70-ohm, solid-dielectric, flexible coaxial cable (or 15. TRANSMITTER COUPLING. foam-dielectric cable) ordinarily is used to feed elevated an- Several types of transmitter coupling (and tuning) circuits tennas.However, the useof closely spacedopen-wire lines is are shown in figure 6. They include inductive, direct, pi-sec- also possible. For high power in the lower vhfband, rigid air- tion, and link coupling. One of these circuits may be incor- dielectric coaxial lines may be installed. porated in a transmitter design according to the relative importance of such items as number of extra components, 14. COUPLING AND MATCHING. number of controls, easeof adjustment, and suppressionof harmonics. The signal bandwidth is ordinarily such a small a. Feedersare connected to antennasor receiving equip- percentageof the carrier frequency that, except for special ment by coupling and matching arrangements. These ar- systems,any type of coupling yields a sufficiently flat charac- rangements, or circuits, are considered as part of the t.eristicover the required band. Tuning methodsare described transmissionline system.Such elements are essentialto max- in the manual for the particular radio set incorporating the imum transfer of power between equipment and antenna. method of coupling. The coupling system usedin a transmit-

Par. 11 Page 5 6580.5 10116189 Appendix 5

TRANSMITTING 1 TRANSMITTER L( RG-214/U OR RG-331/U ANTENNA 1TR4K.Y1(I:TER (MAI l-\~~~,::T:, aRF BODY WALL- MOUNTED 1 COAX R PATCH FIELD JUNCTION BOX

-; : ’ -;j~~:,,U -8RG-214,” OR RG

A A

A.TRANSMITTER -TO- ANTENNA SYSTEM

RECEIVING ANTENNA

WALL- MOUNTED TOWER PATCH FIELD JUNCTION BOX

RG-214/U OR RI-331/U ; RG-214/U OR RG-333/U

SERIES LINK

B. ANTENNA -TO-RECEIVER SYSTEM

Figure 5. Complete Transmitter-and-Receiver-to-Antenna Transmission System

Page 6 Par. 15 10/16/89 6580.5 Appendix 5

BLOCKING CAPACITOR TO BALANCED LINE TO UNBALANCED TRANSMISSION LINE

A. DIRECT COUPLING B. DIRECT COUPLING (UNBALANCED) (BALANCED)

C. INDUCTIVE COUPLING D. LINK COUPLING

cb TRANS- TRANS- Be MISSION LINE 22 = =

T Tc” F. PI -NETWORK COUPLING ( BALANCED) E. PI-NETWORK COUPLING (UNBALANCED)

Figure 6. Transmitter Coupling Arrangements

Par. 15 Page 7 6580.5 1 O/l 6189 Appendix 5 ter should be determined before selecting the type of trans- 20. RECEIVER COUPLING. mission line for use with that transmitter. When matching an antennaand line to a receiver, the em- @ phasis is not only on transferring a maximum of power, as it 16. INDUCTIVE COUPLING. is at the transmitter, but is also on improving the signal-to- noise ratio and avoiding interference. Some communication a. Inductively coupled circuits (part C of figure 6) arebet- receivers have input-tuning adjustments to cancel the line ter than the direct coupled circuits if an unbalancedtank coil reactance.However, the objective is to improve responseat feedsa balancedtransmission line. Line unbalancecaused by the desired frequency and reject other frequencies more ef- the final tank circuit may be avoided in this manner. fectively, thus increasing the selectivity. With only reactive compensation,the resistancesof the line and the receiver are b. The transmissionline coil, generally called the antenna usually unmatched.The reflection loss causedby this mis- coil, should be coupled to the final tank coil so that the cen- matchis tolerable in most casessince a cable generally is used ter of the antennacoil is near the electrical center,orrf ground that has an impedanceapproximately the sameas the input point, of the final tank coil. impedanceof the receiver. The loss in efficiency is no disadvantage where external noise is the controlling factor since 17. DIRECT COUPLING. both signal and noise are attenuated equally. In many receiverswith transformerstep-up at the input, a mismatchis a. The direct-coupled transmission lines (parts A and B, deliberately designedinto the input circuit to improve the sig- figure 6) are most useful when the final amplifier plate supp- nal-to-noise ratio from equipment noise alone, provided the ly is series fed to the plate. The capacitorsare used to keep echoesreflected over a long connecting line are not exces- the final plate voltage off the antenna system.They should sive. Methods of coupling more than one receiver to a single have a voltage rating higher than the maximum plate voltage antennaare covered in appendix 10. used, and they should have a comparatively high capacity. The current rating should be higher than any current normal- 21. MATCHING ANTENNA TO LINE. ly encountered. When connecting an antenna to a transmission line, the line can often be selected to match the antenna input im- b. A single-wire transmissionline is tappedonto the coil pedance.For example, a 600-ohm open-wire line would be a (part A of figure 6) at different points on a trial and error basis fairly good match for a three-curtain rhombic antenna,or a until normal full-load plate current is drawn with the final 300-ohm line would suffice for a two-wire, half-wave, folded amplifier tuned to resonance. dipole. When direct matching is not practical, as with very low or very high impedance antennas,or where cables that c. A two-wire transmission line (part B of figure 6) is are manufacturedin a limited number of sizesare used,some tappedonto the final amplifier tank coil symmetrically about form of matching device is’necessary.Usually, impedance- the center of the rf ground point of the coil. The taps are ad- matching transformer systemsare connected in series with justed to makethe final amplifier draw normal, full-load plate the line, and auxiliary tuned systemsare connectedin paral- current when tuned to resonance. lel with the line.

18. PI-NETWORK COUPLING. 22. ANTENNA-COUPLING TRANSFORMERS. The pi-network types of coupling shown in parts E and F of figure 6 are low-pass filters. These networks are capable a. Antenna-coupling transformersare the common, coil- . of coupling two impedancesthat have a large difference of type rf transformer and may be used to couple an antennato reactance.The variable capacitorsin the transmissionline cir- an rf transmission line or a transmission line to a radio set. cuit may be from 1OOp.Eto 1,OOOpFeach, depending on the They permit impedance transformation for matching pur- operating frequency. The spacingbetween the plates of these posesandbalanced-to-unbalanced connections. Mostof these capacitors should generally be at least half that of the final units are made so that one side of the transformer must be tank capacitors. operatedbalanced.

b. Some standard antenna-coupling transformers were 19. LINK COUPLING. designedto give no more than a 2dB loss from 6 to 20 MHz. Variable link coils may be used at either end of the link. Later models of thesetransformers are designedfor a loss of Link coils consist of two or three turns of wire coupled to the no more than 2.5dB from 2 to 30 MHz. Thesestandard trans- amplifier tank coil at a low voltage point and to the antenna formers are intended for use with receiving installations, and coil at the electrical midpoint. Seefigure 6, part D. have low power-handling capabilities.

Page 8 Par. 15 1 O/l 6189 6580.5 Appendix 5 c. In general, antenna-coupling transformersare designed actly one-quarterwave long (or any odd multiple thereof) can for matching 200- or 600-ohm balanced antennasto 50- or transfer rf energy to another transmission line of any im- 70-ohm unbalanced coaxial cable. Optional connections pedancewith none of the detrimental effects of mismatching. usually are available on the high-impedanceside of the trans- The quarter-wave matching line is designedto have a charac- former for use with either ZOO-or 600-ohm antennas.Some teristic impedanceequal to the square root of the product of models have 250- and 700-ohm connections on the high-im- the impedancesat the ends. Thus, a 200-ohm load can be pedanceside of the transformer. matchedto a 50-ohm cable if, at the end of the cable, a quarter- wave length of line or cable having a characteristic im- d. There is usually a dc path across the transformer pedanceof 4 200 x 50, or’ 100 ohms, is inserted. Usually, it through rf chokes. This permits dc testing of the antennaand is necessary to tune out any antennareactance before includ- termination resistance. ing the quarter-wave transformer. Changing the antenna height may sufficiently alter the antenna input impedanceto 23. MATCHING LINE SECTIONS. aid in securing a good match. This method limits the use of Several types of matching line sections have been the systemto a single frequency. designed for construction in the field. The more common types are the delta match, the tapered line, and the quarter- d. Coupled sections and reentrants are open-wire match- wave matching line. ing methods frequently used when minor corrections are necdcdin impedancematch, or when multifrequency systems a. The delta match (part A of figure 7) generally is as- of feedersneed to be tuned independently to a common

e. Coaxial line matching sectionsor balanceconverters are DIPOLE ANTENNA shown in figure 8.

--- A. DELTA MATCH

TAPERED LINE / 600.OHM ANTENNA i 200-OHM A C CONVERTER LINE 7 8. TAPERED LINE 1

A 200 OHMS IOO- OHM LINE I C.QllARTER - WAVE MATCHING LINE

Figure 7. Open-Wire Impedance-Matching Trans- COAXIAL LINE b. A tapering transmission line with a progressively in- creasingcharacteristic impedancemay be used to feed an antenna at a moderately high impedancepoint. For example, a Figure 8. Coaxial Impedance-Matching Transformers taperedline (part B of figure 7) can be used to connect a 200- ohm transmission line to a 600-ohm antenna. The gradual 24. HALF-WAVE LINES. taper of the line changesthe characteristic impedanceslow- The half-wave line is based on the principle that the im- ly enough so that reflections are negligible. pedanceof a resonant line with low loss is the sameat suc- cessive half-wave intervals along the line. Thus, similar c. A quarter-wave matching line (part C of figure 7) can impedancescan be matched at a particular frequency at any be inserted between two segmentsof line. This matching one of thesehalf-wave points, regardlessof the characteris- device is based on the principle that a transmission line ex- tic impedance (&) of the transmission line. For example, to

Par. 22 Page 9 6580.5 10116/89 Appendix 5 connect a receiver with a 300-ohm input impedanceto a 300- dissymmetry causesextraneous currents along the outer sur- ohm antenna,it is possible to use a coaxial cable of any ZOif face of the cable or line. These currents are present, even the length of the cable is exactly one-half wave or a multiple though the impedances are apparently matched, and they thereof. Any length of 300-ohm line may be used from the causeradiation that may be undesirable. They can be mini- antenna to some point close to the receiver, and then con- mized by the useof specialbalanced-to-unbalanced networks nectedto a length of coaxial cable exactly one half-wave long called baluns. (or multiple thereof) for passagethrough building walls or interior ducts to the receiver. This system limits the antenna, a. A method of constructing a balun for coaxial cablesis transmissionline, and receiver to use on only one frequency. shown in part A, figure 11. A concentric cavity, a quarter Therefore, the use of half-wave lines for matching purposes wavelengthlong, is placed around the cable sheathat the feed , is limited by operational considerations. point. The lower end is short-circuited to the sheath so that the upper end presentsa high impedance.Any currents that 25. MATCHING STUBS. might flow along the outer surface are therefore minimized. Another method of matching impedancesis to use a tuned, quarter-wave,matching-section stub line (figure9). The exact b. Another commontype of balun that effectsthe balance- length of the matching sectionand the position of the line taps to-unbalancetransformation and also affords al-to-l step-up must be determined experimentally becausethey dependon in impedance,is shown in part B of figure 11. It includes a the impedanceof the transmission line, as well as the anten- half-wavelength line (usually coaxial) multipled to the output na impedance at the point of connection. The tuning stub of the feed line. The output voltage between the two inner usually can be used to match an antenna to any line im- conductors is balanced. However, because the voltage be- pedance. tween the inner conductor and sheath at the end of the half- wavelength line is equal and opposite to that at the input, a

CURRENT LOOP POINT VOLTAQE LOOP POINT 2-to-1 increasein voltage between respective inner conduc- OF ANTENNA OF ANTENNA tors is obtained at the output terminals. As in an ideal trans- 7 7 former, this voltage increaseresults in a fourfold increasein impedance.

27. INTERFERENCE SUPPRESSION.

TRANSMITTER a. Coaxial bandpasscavities may be inserted in transmis- LINE TO / TRANSMITTER sion lines for the purposeof suppressingor eliminating rf in- L OPEN terference.One of thesecavities placed between the antenna and receiver will improve receiver selectivity immensely. The cavity will reduce or minimize off-channel interference Figure 9. Stub-Line Impedance Matching that otherwise would passthrough to the receiver’s front end and cause desensitization, spurious responses, or inter- a. The approximate length of a quarter-wave matching modulation interference. When tuned to a transmit frequen- stub is calculated from: cy and installed betweena transmitter and associatedantenna the cavity will reduce spurious and harmonic radiation or transmitter sidebandnoise that could get into nearbyreceivers anddegrade performance. The bandstopcavity is the opposite This formula gives an approximatelength, and the stub should of the bandpasscavity. It is tuned to reject unwantedfrequen- be tuned after it has been installed. cies or a band of frequencies quite close to the wanted fre- b. Approximate valuesof distancesX and X plus Y (figure quency or, if necessary,several megahertz away. Notch filters 9) may be determined from the curves in figure 10. These can be added in series to obtain additional attenuation to an curves apply only to 600-ohm transmission lines. Trial and interfering frequency. Insertion loss of the cavities must be error adjustment for exact matching to the terminating addedto the other systemlosses in computing service volume impedanceis required after the matching stub is constructed coveragecapabilities. according to thesecurves. b. Ferrite isolators may be inserted in transmitter antenna 26. BALANCED-TO-UNBALANCED MATCHING lines for the purpose of suppressingor eliminating rf inter- SYSTEMS. ference.Within the rated bandwidth of the ferrite isolator up When unbalancedtransmission lines connect to balanced- to 30dB of isolation from other transmitterscan be provided type antennas,such as a coaxial line to a dipole antenna,the to reduce or eliminate intermodulation product generation.

Page 10 Par. 24 6580.5 1 O/l 6189 Appendix 5

I(10 \ I 140

0 gP:28 :: x 8 888: x 8 0” 8 8 :xX8 2 ” : : : :: - - LEGEND:- OPEN STUB E SI 8 D (B c-II0 9 gti 4 3 0d 0Ii ioooq d i 0 TERMINATING IMPEDANCE (OHMS) --- SHORTED STUB

Figure 10. Graph for Quarter-Wave Stub Length and Positioning

200 -OHM BALANCED BALF rNCED OUTPUT OUTPUT

HIGH IMPEDANCE

SO-OHM COAXIAL ‘COAXIAL CABLE CABLE(UNBALANCED)

A.QUARTER-WAVE BALUN B. HALF-WAVE BALUN

Figure 11. Quarter-Wave and Half-Wave Balun Arrangements

Par. 27 Page 11 1O/l 6/89 6580.5 Appendix 6

APPENDIX 6. PRINCIPLES OF ANTENNAS

1. GENERAL. a. General physical characteristics: size, construction This section covers basic principles of antennas. For requirements,and kind of site required. r theory of antennasin greater detail, consult available antenna handbooksand manuals,both military and commercial. b. Directional properties: suitability for the kind of radio path proposed,such asground wave or sky wave, and the dis- a. An efficient antennasmoothly transferspower from one tance involved. transmission medium such as a wire circuit to another medium such as surrounding space;and vice versa. On the c. Polarization: For groundwave use, antennas on the wire side of the circuit, the usual wire network conditions of samecircuit at both ends of a radio path shouId have similar impedancematch and low inherent loss must be satisfied.The polarization. antennamust launch the energy into spacewith little loss of power and usually with the added requirement of directing d. Mutual interference: approximate antenna patterns the energy in the proper directions. Essentially, the antenna and separation distances required to prevent mutual intcr- is a wire circuit termination of special size and shape, so ference and intermodulation. placed as to perform thesefunctions efficiently. e. Gain: need not be known separately in groundwave b. A short length of wire energizedwith a high-frequency computations if the overall efficiency of the radio set is voltage is a simple form of antenna. The current flowing known. For computations of skywave paths, the gain must bc along its length is the sourceof the radiation, with the moving known, becauseit is one of the limiting factors in the com- electronsproducing the radio wave, or field, that reachesout putations. to great distances.Conversely, the samekind of wire, when exposed to a radio wave, has a voltage induced into it and f. Matching: antenna impedance and balance to ground producesa potential acrossan associatedresistance. Thus the when matching the antennato the radio set or the rf transmis- wire delivers the energy collected from space to a conven- sion line. tional radio receiver. Figure 1 shows the basic forms of conductor antennas. g. Positioning: This dependson whether theantennamust be close to the radio set or whether it will work properly with a transmissionline. In general, antennasmuch shorter than a quarter wave must be close to the set or a coupling network.

h. Grounding: methodsof grounding at radio frequencies and protection against high voltage.

3. RADIATION PATTERN,

a. The distribution of the radiated field in spacedepends upon the current distribution in the antennaand the angle from A. LOOP ANTENNA a. OPEN-CONDUCTOR ANTENNA the antenna. A short, straight, energized conductor gives no evidence of current flow when viewed at its end. Therefore, the radiated field in either end direction is essentially zero. At Figure 1. Basic Forms of Conductor Anfennas progressively greaterangles from the axis of the conductor to a line perpendicular to the conductor, the current appearsin progressively greater perspective so that the intensity of the 2. ELECTRICAL CHARACTERISTICS. radiated field becomesincreasingly stronger. The maximum The following antennacharacteristics are important in the current and radiated field is reachedat right angles to the con- e design of a facility. ductor. This radiated field is illustrated in figure 2. The thick-

Par. 1 Page 1 6580.5 10116189 Appendix 6 nessof the lines in part A of this figure representsthe relative posite currents in the opposing sides of the loop result in a strength of the field. cancellation of the field. In the plane of the loop the fields 0 from opposite sides do not cancel becauseof the difference in phaseof the two fields. The field actually attains a maximum in this plane with the result that a doughnut shape is again obtained for the overall pattern.In the plane of the loop, the field is polarized in a direction tangential to a circle drawn from the center of the loop. The loop antennais used mainly in direction-finding and homing equipment.

Figure 2. Radiated Field from a Short, Straight Conductor in Free Space

b. Each antenna has its own unique pattern in free space. The arrows in part B of figure 2 are proportional in length to the radiated field strength. The line around the arrowheadsin this casedescribe a figure eight, which is the indicated radiation pattern of this particular antenna.This pattern represents only the radiation field not the ordinary inductive field. The inductive field around antenna is negligible beyond a large Figure 3. Three-Dimensional Nature of fraction of a wavelength from the conductor and does not Radiation Pattern enter into radio propagation. f. A narrow, elongated loop energized at the midpoint of c. The pattern in part B of figure 2 hasbeen represented in one long side has the appearanceof a dipole folded back on one plane only. Since the aspectof the short, straight wire is itself and is called a folded dipole. When the sidesare a half- the same in all other planes passing through its length, the wave long, the standing wavesof currents in the two sidesact samepattern is obtained in all such planes. Thus, the field in phase to develop a radiation pattern similar to that of the measuredat points on any circular path in a pIane perpen- simple half-wave dipole. dicular to the wire is constant in value. The complete radiation pattern, therefore, is a three-dimensional figure, g. From the preceding subparagraphsit can be seen that somewhatlike a doughnut (figure 3). The general method of the shapeof the antenna,the length of the individual sidesor illustrating a radiation pattern, however, is in a cross section conductors in the antenna, the position of the conductors in of the full pattern, showing only one particular plane. relation to the ground, and other less specific factors all af- feet the exact radiation pattern produced from any particular d. As the straight wire is shifted or rotated in space,the antenna. radiation pattern moves with it. For example, a vertical wire radiatesa uniform field in all directions in the horizontal plane 4. EFFECT OF RADIATION PATTERN ON SIGNAL and, therefore,is adaptableto mobile or broadcastingservice INTELLIGIBILITY. where broad areacoverage is required. This field is vertically polarized. Conversely, a horizontal conductor radiates a. Signal intelligibility at the receiver input terminals is af- mostly in the transversevertical plane and, therefore,is use- fected by the effects of the propagation path on the trans- ful for high-angle skywave transmission.The polarization in mitted signal and by the patterns of the transmitting and any direction is perpendicular to the radial line of radiation. receiving antennas.It is difficult to separatethe two effects; one hinges on the other. For example,a wave of constantfield e. The pattern for a square loop antenna can be deduced strength may vary in its angle of azimuthal arrival within th from the combined effects of me currents in the sides. In a limits of only a few degrees.If the receiving antenna has line perpendicular to the plane of the loop, the equal and op- pattern that is too sharp to respond uniformly over the angle

Page 2 Par. 3 1 O/l 6109 6580.5 Appendix 6 of azimuthal deviation, the receiving antenna thereby intro- ing the intelligibility of the signal by Lhis method. If multi- ducessignal variation. If the receiving antennahas a deepnull path delays cannot be eliminated, there is little advantageto in its pattern and the arriving wave swings, the receiver will increasing transmitter power to improve signal intelligibility. register a deepfade that may not have beenpresent in the arriving wave, but which must be assignedto the receiving an- e. The transmitting antennaradiation pattern also is impor- tennapattern. If azimuthal variation is a factor on a particular tant. If it were possible to radiate all the power at the one op- circuit, then the ideal receiving antenna azimuthal pattern timum vertical angle that gives the best transmission path, should be uniform over the r&ge of possible angles of signal there would be relatively little radiated at the angles that give arrival and have zero responsein all other directions. rise to multipath transmission. The angle of departure for a given wave path is roughly the sameas the angle of arrival at b. What is true in the azimuthal plane is true in the verti- the receiving end ofthepath. It will usually be of value, there- cal plane as well. There may be severalwave groups arriving fore, to transmit less power at the undesired angles if one is simultaneously at different vertical angles, although one trying to eliminate certain wave groups in order to improve group will dominate in intensity from movement to move- intelligibility at the receiver. When the transmitting and ment. Under theseconditions, the receiving antennawill pick receiving antennas are complementary, with maximum up, in effect, a single wave that is constantly changing its responsesat the most favorable wave angles and relatively angle of vertical arrival. If the field strength of the arriving low responsesat all other angles, it is possible to improve wave is constantbut changing in angle, the vertical pattern of operating margins by using greater transmitting power. the receiving antenna, if nonuniform in response over the rangeof arrival angles,introduces signal variations as the sig- f. Considering the above-mentionedfactors, it is apparent nal comesin on different portions of its pattern. If the range that antenna gain may be a secondary consideration in the includes a null in the antennapattern, the receiver input ter- design of an antenna.The primary objective is to produce the minals would register a very deep fade in the signal. These most favorable radiation pattern in both vertical and horizon- effects due to antennaresponse occur in many instances,and tal planes,so as to minimize multipath and lobing difficulties. the signal itself also varies over a considerable range of Too much directivity in the antennapattern may be as unsatis- values. When the horizontal and vertical anglesof arrival cor- factory as insufficient directivity. Using random patterns or respond to directions of minimum antenna responsesimul- patterns not expressly designed for the desired service can taneously with a minimum arriving signal strength, the signal give poor results. at the receiver input terminals may be far below the noise level and produce an interval of unintelligibility. These ef- 5. GENERAL DIRECTIONAL REQUIREMENTS, fects combine, and the signal at the receiver terminals under- goesa wide range of variation from moment to moment. a. Antennas for usein broadcastingor in mobile net operation should not be sharply directional. Antennas for transmis- c. Another problem arises wlien more than one wave sion between two fixed points should be as directional as group arrives in the vertical plane with different time delays possible. along eachof the arrival paths.The resulting phasedifference causessignal distortion even when the signals are strong. The b. In general, antennas for skywave transmission (or delay is characteristically greater as the angle of arrival be- reception) should differ in their vertical directional patterns comeshigher, since each wave traversesa longer path. Wave from those used for groundwave transmission. For interference betweenthe different wave groups at the receiv- groundwave transmission, antennasshould have good radia- ing antenna causesfading of the signals due to the delays. tion patterns along the ground. For short-distance skywave (200 miles (32Okm))or less, the greatestradiation should be d. On somepropagation paths there is sufficient angle be- almost vertical. For medium-distance skywave (200 to 500 tween the multipath wave arrivals so that the vertical pauem miles (320 to 800 km), somewhatlower angles are required. of the receiving antennacan selectone andreduce or suppress And for long-distance skywave (over 500 miles (8OOkm)), the others. The shorter the circuit, the more likely it is that still lower angles of radiation are necessary. substantial angular difference in wave’arrival will exist, including the effect of angular changesdue to changesof layer c. At high frequencies,antennas with satisfactorypatterns height, thus permitting selective reception of one dominant for groundwave transmissioninclude vertical whips, mastan- wave group. On long-haul circuits, however, two or three or- tennasand towers, T-antennasand other top-loadedverticals, ders of hops may arrive at so nearly the sameangle that an- wave antennas,and vertical half rhombics. gular selection is impractical. Angular selection would involve an extremely sharp antennapattern that would cause d. Antennas with good patterns for short-distance deep fading of the received signal when the wave-arrival skywave include half-wave horizontals at heights above angle varied. In such a case,there is no possibility of improv- ground that are not more than a quarter wavelength at the

Par. 4 Page 3 6580.5 1O/l 6189 Appendix 6 operating frequency. Sloping-wire, half-wave antennasare “end effect.” Each installation will have a different capacity also usablefor the short-distancesky wave, if the slope is not deviation. A good averagedeviation is 5 percentless than the too steep.The poorest type of antenna for this transmission length of a half wave in free space.The formula for finding method is a short vertical whip. the physical length of a half-wave antennais: L =- 468 e. Antennaswith good patternsfor long-distanceskywave f include suitably designed rhombics, half-wave horizontal dipoles at heights betweenone-half and one wavelength, and where f is in MHz, L is in feet. vertical mast or tower antennas. NOTE: This formula does not apply to antennaslonger f. Skywave distancesbetween 200 and 500 miles (320 and than a half wavelength. 800 km) are transitional. Half-wave horizontal dipoles a quarter wavelength above ground or up to a half wavelength 7. ANTENNA RESISTANCE. above ground, for 500 miles (SOOkm)are good. Energy supplied to an antenna is expended in two forms, radio waves and heat losses.The useful part is the radiated 6. STRENGTH OF FIELD. energy in the radio waves.The formula for dissipatedpower (F) is: a. The strength of the radiated field from an antenna is determinedby the current flowing in the antennawire and the P=12R length of the wire. When the circuit is resonant,that is, when the reactanceof the wire at the frequency of the rf current is where R is the resistance,I is the current. In computing the zero, the current flow in the wire is at a maximum. The power dissipatedby an antennain the form of radiation, R is shortest length of wire resonant at a particular frequency is an assumedresistance that would if it were actually present, the length that will just allow the rf current to travel from one dissipatethe amountof power that is radiated.The total power end to the other and back again in the time required for one is found, then, by combining this theoretical radiation resis- complete rf cycle. Radio energy travels at the speedof light, tancc with the actual resistancein the antennawire itself, the 300,000,000 meters per second.Thus, the distance covered insulators, guy wires, etc. Thus, the total power dissipatedby by the rf current in one complete rf cycle is: an antenna is expressedby:

h _ 300,000,000 P=12(Rr+R) f where f is the frequency in hertz, h is the wavelength in where R is the real, or ohmic, resistanceof the antenna and meters.Therefore, the shortest resonant wire is a half wave Rr is the radiation resistance. long, since the energy must traversethe wire twice. 8. INPUT IMPEDANCE - RADIATION b. A more useful formula that has been derived from the RESISTANCE. above formula to give the length of a half wave in spaceat any frequency is: a. Lengthening a straight conductor from very small dimensions up to slightly over a half wavelength does not L=492 alter the radiation paltem appreciably. However, it does af- f fect the input impedance,that is, the ratio of the input voltage where L is in feet, f is in MHz. and current. A short center-fedconductor has a large reactive componentand actsas a leaky capacitive element.The induc- For metric dimensions, the half-wave, free-spacelength can tive reactanceincreases as the wire length increasesand even- be calculated as follows. tually counteractsall the capacitance,so that only a resistance appears.This occurs when an isolated conductor is about a L- -- 150 half wave long. Such a resonant condition is obtained at ex- f actly one-half wavelength for an infinitely thin conductor,but where f is the frequency in MHz, L is the length of the half- occurs at lengths that are a few percent under a half wave dipole in meters. wavelength for conductors of practical thicknesses. Resonance also occurs at every odd multiple of a half c. Severalfactors affect the electrostaticcapacity of an an- wavelength. tennawire. This capacity is higher than normal becauseof the dielectric effect of insulators at the ends of the wire antenna b. At the half-wave resonant length, the input impedance supports,guy wires, and other nearby objects. This is called of a very thin, lossless,center-fed antenna, is a pure resistance

Page 4 Par. 5 1 O/i 6189 6580.5 Appendix 6 @! of about 73 ohms. This input resistanceusually becomesless dB) with respect to the isotropic radiator. The respective as the conductor thickness is increased.However, measure- values are shown in the following chart. ments generally do not show consistent results. In some instances, the resistance drops to as little as 60 ohms for a Gain length-to-diameter ratio of about 100; in other cases, the Numerical ratio dBi reduction is much less for the sameratio. The differencesap- bower) parently occur asa result of inequalities in the amountsof gap spacingat the center feed point and the type of feed-line con- Short conductor . . . . . 1.50 1.76 nection. Shorter, straight conductors have progressively Half-wave radiator . . . . 1.64 2.15 lower resistances,but they are always accompanied by a capacitive reactancethat must be tuned out for bestoperation. d. A half-wave dipole radiating a power of 1kW in free A half-wave folded dipole has an input resistancefour times spacedevelops a field intensity of 137.6 millivolts per meter that of a simple dipole, about 292 ohms when the conductors at 1 mile (1.6km) in the direction of maximum radiation. are thin. e. When an antenna has appreciable loss in its tuning ele- c. The radiation resistancevaries with the position of the ments or in the ground connection, the power radiated may feedpoint, wherever thereis a changein the current amplitude be only a fraction of that delivered by the transmitter. along the length of the conductor. This is always the casewith resonantantennas (such asdipoles) that have a standing wave 10. ANTENNA BANDWIDTH. and hencenonuniform distribution of current. a. A resonant antenna, such as a half-wave dipole, is d. The ordinary loop antennahas a radiation resistanceof generally adjustedin length so as to be tuned to a specific fre- less than 1 ohm, and an inductive reactanceis always present. quency. It therefore has a certain input resistanceat this fre- For efficient operation, a variable capacitor is placed across quency. At frequencies increasingly displaced from this the input to permit tuning to resonance.The loop current is reference frequency, the resistance changes somewhat and then large but fairly constant over the loop length. reactanceis introduced. Both of thesechanges affect the impedancematch to the connectedapparatus. The band of fre- 9. ANTENNA GAIN. quenciesover which thesedeviations remain within specified limits is called the bandwidth of the antenna. In general, an- a. Generally, the direction of maximum radiation from tennasmade of thick conductors (or several thin conductors any antennais the direction of principal interest in radio com- in multiple and usually fanned out) have smaller impedance munication. The power propagated in that direction is a variations for a given frequency displacementfrom midband measureof the beaming power of the antenna. The antenna and, therefore,have wider band characteristicsthan thin-con- is rated by a comparison of its radiation along this line with ductor antennas. that of a basic or reference antenna of equal total radiated power. The ratio of thesetwo values, expressedas the square b. With most practical antennas,the impedancematch is of the field intensities at agiven point, is called the directivity not greatly changedover a frequency band equal to a few per- gain of the antenna. cent of the carrier frequency. Most resonant-type antennas, therefore, inherently have sufficient bandwidth to accom- b. The reference antenna may be a short conductor, or it modatethe sidebandsintroduced by modulation of the carrier may be a theoretical point source,called an isotropic radiator, by the signal. For voice or data transmission in the hf band which is assumedto radiate uniformly in all directions and, and higher, the average dipole antenna has sufficient therefore, has a spherical radiation pattern. The isotropic bandwidth to handle several multiplexed channels without radiator has a gain of unity, and all other antennas have a noticeable discrimination. Multiple arrays tend to narrow the greatergain, since the slightest deviation in the spherical pat- bandwidth appreciably relative to a single element. tern signifies an increase of the field in some direction over that for the uniform field. This is always compensatedfor by c. For reliable skywave transmission in the hf range, it is a smaller field in someother direction, since the total radiated usually necessaryto change frequencies two or more times power is assumedto be constant. over a 24-hour period. This requires greater bandwidth than can be included in a resonant-typeantenna, so that when half- c. In more complicated antenna arrangements,it is com- wave horizontal dipoles are usedit is necessaryto changean- mon practice to use the half-wave dipole as a reference ele- tennas with a shift in frequency. The other alternative is to %ent. The gain of an antenna in terms of a half-wave dipole, use a nonresonant-typeradiator, such as a rhombic antenna, or in terms of a short conductor, can be converted to the which hasan inherently wider band characteristicand can ac- isotropic reference by adding the gain of either of these (in commodatea 2- or 3-to-1 change in frequency with relative-

I Par. 8 Page 5 6580.5 1 O/l 6/89 Appendix 6 ly moderateimpedance changes and minor changesin current is madeto widely separatedpoints of unbroken conductor, a distribution. tapered line is necessary for impedance matching, as ex- emplified by the delta-matchantenna. 11. RECIPROCITY. b. When a receiver has the sameinput resistanceas is seen a. An antenna may be used to transmit or to receive. The acrossthe antennaconnection, it is said to be matchedto the characteristicsof radiation pattern, gain, and radiation resis- antenna.In such a case,one-half of the induced voltage ap- tance apply equally well whether the antennais used for one pears across the receiver, the other half across the internal purposeor the other. As a consequence,a receiving antenna (radiation) resistanceof the antenna.The wave at the receiver can be beamedto be responsiveto an incident field over only can be assumedto be a plane wave. If the antenna is in line * a small angle,just asa transmitting antennais madeto radiate with the direction of polarization of the field, the total, in- a field over only a small angle. In this way, the receiving an- duced voltage is the product of the field strength @V/m) and tcnna absorbsmore power from the passing wave than if it the effective length. The actual length of a resonant-typean- were not beamed,a fact that is reflected, as in a transmitting tennacannot be usedin this product becausethe current is not antenna,in a higher directivity gain. uniform, but has a standing-wave distribution. The effective length is the length the antennawould have if the current were b. Over skywave transmissionpaths, the radio wavesmay uniform and the antennaabsorbed the sameamount of power. not take the samepath through the ionosphcrc in both direc- In the caseof a half-wave dipole and a quarter-wavewhip, it tions of transmission.Therefore, the above rule may not al- is 0.636 times the actual length. For shorter lengths of dipoles ways apply. An incoming wave at the receiver may not strike and whips, the effective length approachesone-half the ac- the antenna at the angle, in either the horizontal or vertical tual length. The absorbedpower is then the squareof the volt- plane, that gives the bestresults. Therefore, different parts of age acrossthe receiver input divided by its ac resistance.For the directive pattern may be usedby the incoming waves and example, suppose that a half-wave dipole with a physical some departure from complete reciprocity results. But this length of 1.5 metersis placed in a 1OOMHzfield that has an situation is rare. Any observeddeparture from reciprocity is intensity of lOl.tV/m parallel to the antenna,then the induced more likely to be causedby differencesin equipmentor noise voltage is the product of this field intensity and the effective--l level at the two locations. length, or 10 x (1.5 x 0.636), which equals 9.54pV. The volt- m age acrossthe matchedreceiver (assumea 73-ohm match) is 12. POWER ABSORBED BY RECEIVING one-half of 9.54p,V, or 4.77lt.V; and the absorbedpower is ANTENNAS. (4.77)2+ 73 = 0.3 12 picowatt (pw). With other receiving~an- tcnnas,the gain (in dB) relative to a half-wave dipole is added a. A passingwave induces a current in a conductor placed to obtain the absorbedpower. in the proper plane of polarization. By breaking the conductor somewherealong its length and placing a load resistance c. When using tuning units having internal losses,when in it (or connecting directly to widely separatedpoints on an grounding systemsof appreciable resistanceare present, or unbroken conductor), a localized voltage is produced. This when an antenna is operatedoff its resonant frequency, it is voltage can be amplified in a receiver bridged acrossthe con- necessaryto consider such conditions in determining the net ductor. As in the transmitting case,the break for a half-wave absorbedpower. They introduce additional lossesthat reduce dipole is usually made at the center in a quarter-wave whip the efficiency of the receiving system. This reduction in ef- or mast.The break is usually at the ground end. In either case, ficiency is not detrimental when external noise controls the a transmissionline is run from the break to the receiver,where received signal-to-noise ratio, since signal and noise are then the resistancemay take the form of an actual resistanceunit. reducedtogether. In transmitting antennas,or in receiving an- Or it may be a transformer network that steps up the im- tennas when equipment noise is controlling, it is always pedanceto that of a first rf stage.Where a shunt connection desirable that lossesbe reduced to a minimum.

Page 6 Par. 10 1 O/l 6189 6580.5 Appendix 7

APPENDIX 7. ORIENTATION OF HIGH-FREQUENCY DIRECTIVE ANTENNAS

1. GENERAL. b. The calculations involve the use of natural trigonometric functions. These functions may be obtained a. Because a high-frequency (hf) antenna for point- from published tables or, most conveniently, directly to-point (ptp) operation is highly directive, it naturally from any one of several “slide-rule” electronic calcula- must be pointed exactly in the proper direction. Radio tors. The latter instrument considerably eases the labor waves in the hf bands follow a great-circle route as and improves the accuracy of great-circle calculations. they are reflected by the ionosphere. Therefore, it is necessary to calculate the transmitting azimuth of the great-circle route to the receiving station. The same is c. The stations marked A and B in figure 2-40 corre- true for the reverse path: the distant station must point spond to the notation A and B in the formulas given in its transmitting antenna at the correct great-circle azi- the procedure below. muth to the distant (local) receiving station. Figure 2- 40, in chapter 2, illustrates the three great-circle models from which calculation are made: part A, when 2. PRELIMINARY PROCEDURE. both receiving and transmitting stations are north of To assist in obtaining a concept of the great-circle the equator; part C, when both receiving and transmit- arc to stretch between the transmitting and receiving ting stations are south of the equator; and part B, points on the earth, a moderate-sized library globe may when the great-circle path spans the equator. Azimuth be used initially to lay out the path. From this, a rough and distance calculations described in this appendix determination of latitude, longitude, and azimuth can will assist the reorienting of existing antennas if there be obtained. More precise latitude and longitude in is a need to relocate circuits or relocate transmitter or degrees and minutes are required for actual great- receiver stations. They are useful to initially orient or circle calculations. For these, a large-scale map or reorient rotatable log-periodic, quad, or yagi hf direc- charts of Mercator projection showing the individual tional antennas such as may be used in the interre- transmitting and receiving sites are suitable. If neces- gional emergency network or ship-to-shore circuits. sary, the data can be obtained through survey proce- Great-circle charts centered on large cities throughout dures. In preparing for the calculations, it is useful to the world are published and may be used for rough de- ascertain the mathematical signs (+ or -) to be used terminations of great-circle azimuth. with the various functions in paragraph 3.

One Point in East Longitude; Both Points in East Longitude Both Points in West Longitude One Point in West Longitude

If longitude of A is greater than If longitude of A is greater than If A is in east longitude, A is longitude of B, A is east of B; if longitude of B, A is west of B; if east of B unless arithmetic sum less,A is west of B. less,A is east of B. of the longitudes is greater than 180”. Then A is west of B. If A is west longitude, A is west of B unless arithmetic sum of the longitudes is greater than 180”.

Page 1 6580.5 1 O/l 6189 Appendix 7

3. BASIC FORMULAS AND SYMBOLS FOR (1) La = latitude of station A, positive for north CALCULATIONS. latitude, negative for south latitude.

a. There are three basic formulas for determining (2) Lb = latitude of station B, positive for north great-circle data. They are: latitude, negative for south latitude.

(1) (3) Lo = difference in longitude between A and B. CosD,-b = SitlL, sinLb + COSL, cosLb x COSL, (4) C, = direction of B from A (great circle). Cos Lb Sin Lo , (2) Sin C, = (5) Cb = direction of A from B (great circle). Sin Da _ b 4. SURVEYING THE ANTENNA. Cos s Sin Lo The following steps apply to a rhombic antenna. The (3) Sin Cb = Sin Da _ b end poles are aligned along the azimuthal axis of the array. The azimuthal angles are C, and Cb calculated in paragraph 3. The angle used depends on whether the local station is at point A or at point B. Refer to the b. Formula (1) computes the great-circle distance plan view illustration of the rhombic antenna, figure from A to B in minutes of arc or nautical miles (1 1, for construction elements of the antenna. minute of arc = 1 nautical mile = 1.853km = 1.152 statute miles). a. Place a transit at the design center of the antenna, with plumb line over the center stake. Adjust c. Formula (2) computes the azimuthal direction of the transit for 0” elevation angle on the vertical circle. B from A, in degrees east or west from north in the northern hemisphere and from south in the southern hemisphere. b. Adjust the horizontal circle and vernier for 0” at true north. d. Formula (3) computes the azimuthal direction of A from B. c. Swing the transit horizontally from 0” to the C, or Cb azimuth on the horizontal circle. e. Explanation of symbols.

SIDE POLE I -0

REAR POLE- PRONT POLE

I SIDE’POLE

Figure 1. Plan View of Rhombic 4ntenna

Page 2 Par. 3 0 1 O/I 6189 6580.5 Appendix 7 d. Stake out the location for the end pole to support g. Horizontally rotate the transit 180”. Stake out the the radiating apex of the antenna, at the correct dis- other side pole location at the same distance of step tance from the center stake of the array (one-half the f. This completes staking the two end poles and the total design length of the antenna), two side poles. Pole locations for a dissipation line e. Rotate the transit exactly 180”. This sights the (at the radiating end of the axis) and feed line (at back azimuth of the array. Stake out the end pole loca- antenna back azimuth) can be staked out from engi- tion at the driven end of the axis at the same distance neering drawings that show the other construction de- used for the radiating end pole. tails of the particular rhombic. The stake at the radiat- f. Horizontally rotate the transit + or - 90”. ing end of the antenna should be painted red or other- Stake out one side pole location at the distance re- wise clearly marked to prevent the wrong stake from quired by the antenna design. being used during later phases of construction.

Par. 4 Page 3 1O/l 6189 6580.5 Appendix 8

APPENDIX 8. WORKING AND SUPPLEMENTARY DATA

1. GENERAL. (3) Length L of an Inverted V Antenna. . This appendix contains formulas for computing dimensions of antenna elementsand transmission line parameters. 468 It also contains a number of charts and nomographsfor such Lfeet = Frequency in MHz parameters as transmission loss under various conditions, line-of-sight distances between antennas, shadow losses, dimensions of two-wire transmissionline, attenuation versus frequency of coaxial cable, and reliability of a communica- (4) Length L of a Long-Wire Antenna. tion system, With these data minimum reference to other documents will be neededduring performance checks, sys- 492 (N - 0.05) tem evaluation, and construction of emergencyantenna sys- Lfeet = Frequency in MHz tems.

2. FORMULAS FOR ANTENNA AND TRANSMIS- where N = number of half-waves in L SION LINE CALCULATIONS. These formulas are in three groups: formulas for calculat- (5) Length L of a Flexible Whip Antenna. ing the dimensions of antenna elements; formulas for calculating spacing and other dimensional criteria of Linches= 2800 transmissionlines; and formulas for laying out antennatrans- Frequency in MHz mission line structures.Formulas for great-circle calculations and certain performance tests and measurementsare located in the chaptersand sectionscontaining the applicable proce- (6) Length L of a Vertical J Antenna. dures. Results obtained in English units can be converted to metric units by using the data in figure 1 of this appendix. (a) Upper Radiator. a. Antenna Formulas. 5600 . (1) Length L of a Half-Wave Dipole in Space. Linches= Frequency in MHz

L&t = 492 . Frequency in MHz (b) J Section.

2950 (2) Length L of a Half-Wave Antenna. Linches= Frequency in MHz

Lfeet = 468 Frequency in MHz NOTE: Formulas are for rod or tubingelements.

Par. 1 Page 1 METRIC CONVERSIOW FACTORS

Approximate Conversions tm Metric Meesures Apprmximrtr Conversions from Metric Mersures

Wkra Yov Knmr MultiplY bv Te Find Svmbd

LEMGTH

LENGTH miltimeters 0.94 inches ceminwers 0.4 inches inches ‘2.5 ~k?,O 3.3 test tee, 30 meters 1.1 yards yards 0.9 krlcmeters 0.6 miles miles 1.6 AREA AREA square mtblleters 0.16 sqwzm inches 2 6.5 square inhss square cm,mle,e,* squar* m,er* 1.2 square yards ;* square fee, 0.09 *quar* ms,er* square kilmalers 0.4 square miles mi* square yards 0.6 *qua,* me,@?* hectrsr (lO.MIo m21 2.5 acres square miles 2.6 square kilometer* ac,e* 0.4 haclsres MASS (weight) MASS (weight)

0.036 07. ClLY”CSZS 28 grams gram* 2.2 tb wd* 0.45 kllogramr kilograms tmsss (1900 kg) 1.1 short ,on* 0.9 ,onne* (ZOM) lb) VOLUME VOLUME

teaspom* 5 m,lf,lnn* 0.03 fluid ounce* fl 07. tablespoons 15 lien 2.1 pintr pt fluid cu”c,!* 30 liters 1.06 qLUrt* qt CUPS 0.24 lit& 0.26 gallmr gll pints 0.47 cwsbic me,“* 35 cubic teat ft3 qua”* 0.95 cubic me,*r* 1.3 cubic yard* vd’ gallons 3.8 cubic fee, 0.03 C”blC yard* 0.76 TEMPERATURE (rxrct) TEMPERATURE (exact) Celsius 9/5 (then tmper*re add 32) 5.9 (after subtractmg 321

Figure 1. Metric Conversion Factors 0 , s/29/92 6580 .5 CHG 2 I Appendix 8

(7) Length L of a Vertical Dipole Antenna. c. Standing-Wave Ratio (SWR) Formulas.

5600 (1) Using Trolley Meter on Open-Wire Line. Linches = Frequency in MHz maximum meter deflection swR= minimum meter deflection

b. Transmission Line Formulas. (2) Using the Directional Wattmeter.

(1) Impedance of Two-Wire, Open-Wire Line. * SWR= l +gizzEz Z = 276 loglo 2 0 D

NOTE: Seefigure 3 of this appendix for a plot of this for- where D = diameter of the wire and mula.

S = center-to-centerspacing between conductors (3) Reflection Coefficient Related to SWR. SWR-1 k= SWR+l NOTE: Seefigure 2 of this appendix for a plot of this formula. (4) For Resistive Loads. z, (2) Impedance of Coaxial Cable. SWR = ZL or 2

(a) Air-Insulated. ZL = impedanceof load

Zo = 138 loglo I?d ZO = characteristic impedanceof the line NOTE: SWR is 2 1.0.

(5) Expressed in Decibels for Voltage Ratio (VSWR). whereD = inside diameter of outer conductor and

SWRdB = 20 log10 vsm = 20 log10 ;$- d = outside diameter of inner conductor (same units as D) d. Matching Section Formulas.

(b) Solid-Dielectric. (1) Impedance of Open-Wire, Quarter-Wave Sec- tion.

zo =$ log10 + z=Jzz Zr = antenna impedance

Z. = characteristic impedanceof connecting line where E = dielectric constant of the insulating material (e.g., E = 2.25 for NOTE: Construction data is located in figures 3,4, and polyethylene) 5 of this appendix.

Par. 2 Page 3 ;a 0 CD. sol a CHARACTERISTIC IMPEDANCE -OHMS x Q)

O- NO

a-- --Q,

TUBING DIAMETER -‘v’ WIRE SIZE BB S GAUGE 0 . c

STANDING WAVE RATIO (SWR)

1.9 1.8 1.7

1.6

1.5

1.4

1.3

1.2

FORWARD POWER (Watts)

Figure 3. SWR Chart of Forward Versus Reflected Power 6580.5 10116l89 Appendix 8 (2) Length L of Open-Wire, Quarter-Wave Section. (2) Free-SpaceLoss, Between Half-Wave Dipole An- tennas: 246V Lfeel = Frequency in MHz Lf = 32.3 + 20 loglo f + 20 loglo D

where Lf = free-spacepropagation loss in dB where V = velocity factor f = frequency in MHz (3) Delta-Match of Feeder to a Half-Wave Dipole. D = distancebetween antennas in nautical miles 468 Lfed = Frequency in MHz (3) Free-Space Loss Between Isotropic Antennas.

Lf = 38 + 20 loglo f + 20 logto D where L = length of the half-wave dipole to be matched (Seepar 94 for usage) 148 Efeet = (4) Transmission Over Obstructions. Frequencyin MHz Hfeet = Ho _ Hwh; HAd2 _ - dtd2 I 1.X 1 where E = clearancebetween the dipole and the beginning of MO-ohm tranmission line where HA = height of antenna above mean sea 118 Cfeet = level (msl), Frequency in MHz HB = height of aircraft abovemsl,

where C = spreadof feederat point of attachmentto Ho = height of obstruction above msl, the dipole dl = distanceof obstruction from antennain statute miles,

NOTE: For the above formulas, the frequency in MHz D = distance of aircraft from antennain statute will be the samevalue for a given delta-match construc- miles, tion. d2 = D - dl in statuemiles, e. Propagation Formulas. K = equivalent earth’s radius factor (nominally (1) Free-SpaceField Intensity. 1.33for frequenciesabove 1OOMHz)

3. CHARTS AND NOMOGRAPHS.

a. Figures 1 through 15 are charts and nomographsuse- E,, = free-spacefield strength in volts per meter ful for evaluating antenna performance and constructing emergencyantennas and lines. D = distancein meters

P = radiatedpower in watts b. Table 1 gives technical characteristics of flexible coaxial transmission line (common types used for com- G = power gain ratio of transmit in antenna munication).

Page 6 Par. 2 1O/l 6189 6580.5 Appendix 8 90 - - IO

99 - c 20

99.9 - 30

99.99 - 40

Figure 4. Reliability Nomograph

Par. 3 Page 7 6580.5 10116189 Appendix 8

50 - - 02 1000 * 40 7

F 20 -_ 7 .03 30 - 900

I818 -- -04.04

20 - 1 000 I616 .05

- .06 14 -_ 1 - .07

g . 12 .00 : 3i - .09 . IO -E-- .I0 i+ 5 In 6 0-- m 2 3 E 6 -- 2

!l 4 .20 5 8 -1) 2-r f 2 -.30 E 3- 0-z

-40

2- --do . -.60

-.70

-.80 -.90 I- - 1.0 9- Zoo276 LOGlO (2;p) OHMS 8---- D-AXIAL SPACING IN INCHES 7- (WIRE SEPARATIONS ON CENTERS) d=WIRE DIAMETERIN INCHES 6-

5- -20 Figure 5. Open-Wire Line Characteristic Impedance m Page 8 Par. 3 1O/l 6/89 6580.5 Appendix 8 20 =, J 1000 - 1000

(I) - 800 - 800

600 - 600 - 600

500 -- SOD - 500

400 - 4000 - 400

- 300

- 200

. . I------_ ------. ----.- y 100 .- y ID0 100 -. -. -- 80 - 80 -- - 80 N” ----- .- 70 - 70 d- + 70 60 s - 60 - 60 f 50 s - 50 - 50 0 - 40 - 40 0 t;; E - 30 - 30 F 2 a %3 - 20 - 20

- IO

-8 -7 -6

-5

-4

-3

-I Figure 6. Quarter-Wave Matching Section Characteristic Impedance

Par. 3 Page 9 6580.5 1Ol16l89 Appendix 8

2000 2000 1900 1900 0 q 1800 I800 _

1700 1700 -.

1600 1600

1500 1500

1400 1400 so -- 1300 I300 :- 100 1200

=-- 1100 II00 *

- IOOD 1000 1200 i L - 900 900 k! - tr z - 800 80 0001 k! a - f - 700 700 c” - s 5 - E - 600 600 P _ i F - f - 500 P 500 5 2 - ii 2 Y I- - a - 400 400 B _ i5 s t2 % ? - 300 P _ 300 !2 2 =I e f

- 200 200

- 100 100 - 80 80

- 60 60

- 40

7 20

T 10

Figure 7. Radio and Optical Line-of-Sight Distances

Page 10 Par. 3 1O/l 6189 6580.5 Appendix 8

5000 5000 4600 4600 4600 4600 4400 4400 4200 4200 4000 4000 3800 3800 3600 + 170 3600 3400 3400 3200 160 3200 - 3000 i 3000 t A. l- “w 2800-- 150 2600 2600 c & 2600-- ii 140 2400 & g 2400-- : + $ 2200-- --2200 g 1130 2 iii :_2000 a : :~~~~l Y ::I900 = 120 B 1800:: r 2 1700:~ 16OOy % II0 5 l500-- z a 2 14ooy I- v) g 13ooy 100 2 l200-- z I- I lOO-- s e lOOO-- -1W 90 -- 1000 2 l- G -- 900 = z 900-- IL 0 600-- 80 -- 600 2 I: 2”F 700 -- z --700 a i 70 600 ii k 1 5 z tl3 500 iz 2 60 :: s 400 0: I- 50

40 200 -t i I50 -L 30 100 -f -f 20 SO-- 50

i O- 0 10 Figure 8. Line-of-Sight Distances for Elevated Antennas to 5,000 Feet

Par. 3 Page 11 6580.5 1O/l 6189 Appendix 8

-650

- 50000 --48000

--46000 -- 600 --44000

--42000

--40000

-- 3lwOO

-- 36000

--34000

-- 32000 -- 800 --30000 -- 29000 -- 28000 --27000 --26000 -- 25000 -- 24000 --23000 b --22000 2 -- 21000 ii -- 400 --20000 ::

-‘- --1s000 0’ t .- -- In000 E -- 17000 III !! P -- 16000 0, s q- 16000 l 2 0 . . 14000 Qii I- __ 13000 c az :: -. 12000 m __ 1 300 s 11000 i E 7 -* a E -’ i _.

E i 10000960007000 000 f;83% B: -- 6000

-- 200 -- 6000

-- 4000 I

-- 3000

-- 2000 -- 1600 -- 100 -- I 200 -- 1000 -- 800 -- 600 -- 400

-- 200 -- 100 - 50 * IO -0 0 Figure 9. Line-of-Sight Distances for EIevated Antennas to 50,000 Feet

Page 12 Par. 3 6580.5 Appendix 8

I ktt-t-4 I I 1 1 ----OVER SEA WATER tVERT POL) 1 90 i &i i-1 I I I I LAND (EITHER POL) \I\ I I 8 SEA WATER (HORIZ POL) I I I I I I I I I I I 100

56 8 IO 15 20 30 40 50 60 80 100 150 HORIZONTAL DISTANCE BETWEEN ANTENNAS-MILES

Figure 10. Path Attenuation at 150MHz

Par. 3 Page 13 6580.5 10116/89 Appendix 8

ANTENNA 140 - HEIGHTS \ (BOTH muti~) \ \

\ I50

56 8 IO 15 20 30 40 50 60 80 100 150 HORIZONTAL DISTANCE BETWEEN ANTENNAS- MILES

Figure 11. Path Attenuation at 300MHz

Par. 3 dld2 H-H,, - --TX 1 H = IN FEET HA= HEIGHT OF ANTENNA AMSL, FEET HB= HEIGHT OF AIRCRAFT AMSL, FEET H, = HEIGHT OF OBSTRUCTION AMSL FEET

d, = DISTANCE OF OBSTRUCTION FROM ANTENNA, STATUTE MILES D - DISTANCE OF AIRCRAFT FROM ANTENNA, STATUTE MILES d 2 D-d,, STATUTE MILES K = EQUIVALENT EARTH RADIUS FACTOR (USUALLY 1.33)

/ H / / / - / / ’ . . / / - HA 1 d2 &I! D

Figure 12. Obstruction Loss Relative to Smooth Earth 6580.5 10116/89 Appendix 8

l/w I I IIII I I

0 ; Z 0.8 E 0.7 T !z 0.6

0.5

0.2 0.3 0.4 0.5 0.7 1 .o 2 3 4 5 6 7 0 10 LINE LOSS IN DB. WHEN MATCHED Figure 13. Graph of Additional LossesCaused by Standing Waves

Page 16 Par. 3 6580.5 Appendix 8

FREQUENCY IN MEGAHERTZ

Figure 14. Attenuation Characteristics for Coaxial Cable Types RG-142/U, RG-214/U, RG-217/U, RG223/U, RG-331iU and RG-333/U

Par. 3 Page 17 ) ~+&!%..;~~N;~~s y- ~~~y;~S;~ ” TRANSMITTER AUDIO IO WATTS 50n LOSSES son LOSSES 5Oi-l -2.2DB -3.0 DB

FREE SPACE LOSS w 114.8DB

RECEIVE ANTENNA ODBI GAIN :yLL;Ntzis ” RECE,VER ,A”D,O

5on LOSSES 5of-l LOSSES 5ol-l -3.ODB -2.2 DB

NOTES: I. 12DB MARGIN FOR SYSTEM BASED ON 3.0&V SQUELCH SETTING FOR RECEIVER. 2. UNITY GAIN IS ASSUMED FOR BOTH ANTENNAS.

Figure 15. SystemLosses in Air-Ground 1O/l 6189 6580.5 Appendix 8 Table 1. RF CABLE DATA’

(Cables Used with VHF and UHF Air-Ground Communication Antennas)

Cable Dimensions Type Jacket Braid2 Dielectric Center Conductor % RGIU O.D.-MAX OJ).-MAX OD.-MAX Stranding O.D.-NOM Ml Spec

142/U .195 .171D .116 Solid .037 50 MIL-C-17/60

214/U .432 .360D .292 71.0296 .089 50 MIL-C-17/75

217/u s45 .463D .370 Solid .106 50 MIL-C-17/78

223/u .212 .176D .116 Solid .035 50 MIL-C-17184

331/u .625 SOOT .450 Solid .162 :I MIL-C-23806/18

333/U / 1.052 1 .875T .801 Solid .288 1 1 MIL-C-23806128

’ This table is presented as convenient reference only. For detailed specifications, refer to the applicable Mil Spec.

2 D denotes double braid; T denotesaluminum tube, single covering

Par. 3 Page 19 (and 20) 10/16/89 6580.5 Appendix 9

APPENDIX 9. FABRICATING EMERGENCY ANTENNAS AND FEED LINES

1. GENERAL. rary antennas and their feed lines that operate In the Severe damage or destruction to a primary antenna high-frequency (hf) and very-high-frequency (vhf) and transmission line system requires ‘erecting a substi- and/or ultra-high-frequency (uhf) bands. Section 1 tute system to maintain critical communication. This concerns supports and guying; section 2 describes appendix contains instructions for improvising tempo- emergency antennas, lines, and matching sections.

Section 1. EMERGENCY SUPPORTS AND GUYING

2. SUPPORT POLES. hole can be obtained from the table for either firm soil or If the support for the antenna is damaged or destroyed or rock; however, rock emplacement should be avoided is unsafe for personnel to climb to repair or replace the because an explosive to blast a hole is dangerous to the antenna, it is necessary to construct a substitute support. facility and to personnel. Figure 1, part E, shows a pole The simplest support is a tall tree or pole, such as a using underbracing. This is a mandatory procedure if the telephone pole. If the local telephone company (telco) ground is swampy or unstable in any other way. approves, one of their utility poles near the facility may be used. A tree may be satisfactory; however, radio-frequency b. Setting the Pole. Figure 1 parts A through D show (rf) absorption may impair the tree-mounted antenna. various methods for raising and setting the pole in place. Obtaining and raising a pole may be the best substitute When there is no available machinery, the pole can be procedure. Poles may be obtained from sawmills, utility raised with pikes as shown in part A of the figure. A gin companies, lumber yards; or they may be found stored pole (figure 1 part B) may be used if a block and tackle is along utility rights-of-way and borrowed with permission of available. Utility company equipment such as derricks and the utility. The utility may provide emergency assistance power winches make pole-setting easier as shown in parts C for raising the pole at the site, or it may lend such and D of the figure. A back-brace may be necessary for the machinery as earth augers, winch trucks, and ladders. If pole to bear against during the raising operation. This can necessary for agency personnel to erect the pole, the be made of heavy gauge metal, heavy planking, or a short following general instructions should be observed. post. Before raising the pole, any hardware such as antenna-mounting bases, guy plates or collars, pole steps, a. Hole Excavation. The hole excavated for setting and eyebolts should be installed. the pole must be properly located. Things to consider include the length of run of the transmission line or lines, c. Guying the Pole. Figures 2 and 3 illustrate var- nearby obstructions, guying requirements, soil ious guying methods and attachment and clamping of characteristics, proximity of electrical powerlines or guy cables. Figure 2 part A shows an improvised plank transformers, and proximity of the permanent antenna anchor in a hole. The anchor is fabricated from a tower on which work must be done. The depth of the ground rod, threaded and with an eye. A log anchor is

Table 1. POLE-SETTING DEPTHS

Length of pole (ft) Hole depth in firm ground (ft) Hole depth in rock (ft)

16 (1.8m) 3½ (1.1m) 3 (0.9m) 20 (6.1m) 4 (1.2m) 3 (0.9m) 25 (7.6m) 5 (1.5m) 3 (0.9m) 35 (10.6m) 6 (1.8m) 4 (1.2m) 50 (15.2m) 7 (2.1m) 4½ (1.4m) 70 (21.2m) 9 (2.7m) 6 (1.8m) 90 (27.3m) 11 (3.3m) 7 (2.1m)

Par 1 Page 1 6580.5 10/16/89 Appendix 9 Figure 1. Methods of Raising and Setting Poles Setting and of Raising 1. Methods Figure

Page 2 Par 2 10/16/89 6580.5 Appendix 9

Figure 2. Guy Anchors shown in part B of the figure. It is simply a short section of near the top of the pole. Shorter poles are guyed at about tree trunk (a section of heavy timber will also suffice, size 4 two-thirds their height. by 4 inches and up) around which the guy cable is looped, clamped, and served. Creosote treatment of these anchors d. Stabilizing the Pole. Four technicians are required to may not be necessary in view of their short utilization time. set and guy a pole. A person is needed on each guy while the Figure 3 contains four guy tying methods. Part A is the fourth observes and advises on the vertical aspect of the pole. simplest, using an eyebolt through a hole drilled in the pole Guys should be “tensioned” and never made “taut.” Shunt or stub, held in place with a flat washer and nut. Part B dynamometers to measure tension are advisable when large uses a double eyebolt, when back-guying is necessary for masts or towers are guyed, so that equal tensioning can be additional strength. Part C shows methods of guying and applied to each guy cable. For the shorter structures, the back-guying a bracing stub, which is a short pole set near a “feel” of the guy should be that of some slack and not a larger pole or mast for additional guying strength. Part D violin-string tautness. An inch or so of play should remain illustrates the use of scrap metal to fabricate a guy collar; after the guy clamps are tightened at the anchor end. During this method is useful when the pole is relatively large in the guy-tightening operation, pikes should be set against the cross section. It will work for smaller poles, also. Part E of pole at three or more locations around the pole to provide the figure shows the best way to tie a guy to the eye rod of a stability during the refinement of guy tension. Loose earth guy anchor. A clamp is used and the guy cable is served at around the base of the pole should be tamped firmly, using the end. Serving methods are provided in figure 5. As tamping rods or sections of 4-by 4-inch or 2- by 4-inch shown in figure 2, the guy anchors are set in at an angle to timber. Any depression left after thorough tamping should be provide collinear strain on the guy and cable sections. The filled in with gravel and tamped. angle at which the guy hole is excavated is determined by the distance of the guy anchor from the pole and the height e. Attaching the Antenna. Once the pole is stabi- of the guy where it attaches to the hole. This angle can be lized and can be safely climbed, attach the antenna. If computed by the tangent formula for a right triangle. Tall the antenna is a whip, vertical ground plane, or other poles may have to be guyed at two levels, one at about simple structure such as a coaxial antenna, it is only a midway up the pole and the other matter of attaching it to its base with standard hard-

Par 2 Page 3 6580.5 10/16/89 Appendix 9 Figure 3. Guy Attachment 3. Guy Figure

Page 4 Par 2 10/16/89 6580.5 Appendix 9

Figure 4. Serving Antenna Wire

Par 2 Page 5 6580.5 10/16/89 Appendix 9 ware. High-frequency antennas such as half-wave di- verter and fed at the center. A short pole is set at the poles, vertical rhombics, or long-wire antennas require center of the antenna to serve as a stabilizing support for strain and spreader type insulators and the serving of the the matching converter made of coaxial cable. Strain wire used in the antenna itself. Figure 4 shows proper insulators are used to insulate the ends of the antenna (in serving of solid and stranded antenna wire. Figure 5 a half-wave dipole, the ends are high-voltage points) shows the tying of wire in the eyes of strain and spreader and, at the center, to break the antenna into two sections insulators. Figure 4 part A is a sketch showing the driven by the feeder arrangement at the output of the serving of a deadend loop, such as that installed at the converter. The inset of figure 6 provides an enlarged pole eyebolt support of an antenna or the eye of an view of the method of connecting coaxial cable center anchor rod. Figure 6 illustrates the installation of a conductor and outer shield to both sides of the antenna simple half-wave dipole, complete with matching con- feed point.

Figure 5. Tying Strain and Spreader Insulators

Page 6 Par 2 10/16/89 6580.5 Appendix 9 Figure 6. Typical Emergency Half-Wave Dipole and Feeder Emergency Figure 6. Typical

Par 2 Page 7 6580.5 10/16/89 Appendix 9

Figure 7. Folding Mast Antenna Support

Page 8 Par 2 10/16/89 6580.5 Appendix 9

Figure 8. Example of Butt Splice for Poles

3. OTHER KINDS OF SUPPORTS. b. Extended Mast. Extension of the height of an an- Other than trees, utility poles (already installed), and tenna call be obtained by butt-splicing lumber or poles. poles obtained from various sources, supports can be See figure 8. fabricated from finished lumber. Light-duty receiving television masts can be obtained from television supply c. Supporting a Number of Antennas. A four-corner outlets and used provided that the antenna to be sup- tower and platform can be approximately duplicated by ported is not too heavy. Some fabricated supports are setting four wooden poles at the same height and con- described below. structing a wooden platform and railings. Pipe masts can be clamped on the railings and the communication antennas installed. Although the height above ground may be re- a. Folding Mast. A mast allowing raising and low- stricted in this temporary arrangement, complete or nearly ering the antenna for tuning or repair is the folding type complete operation can be resumed while the permanent shown in figure 7. This type is excellent for holding a tower is being repaired or replaced. simple vertical whip, discone, coaxial, swastika, or a J antenna. 4.-9. RESERVED.

Section 2. EMERGENCY ANTENNA AND FEEDER FABRICATION

10. GENERAL V (when a directive antenna is needed), and the long-wire This section includes temporary antenna structures antenna (for moderate directivity and fast construction). made of wire and tubing, some using wooden members Construction details of each of these antennas are shown, for maintaining their proper dimensions and shape. respectively, in figures 9, 10, and 11. Dimensional information and formulas are provided in the figures or are located in appendix 3. 11. HF ANTENNAS. The three hf antennas most likely to serve in an emer- a. The multiwire receiving doublet antenna will gency are the doublet or multiwire doublet, the inverted operate over a relatively large band. It is constructed

Par 3 Page 9 6580.5 10/16/89 Appendix 9 by paralleling two or more hall-wave dipoles (each cut to (1) To construct this antenna, first make an X- its operating frequency) at the center feed point and frame from wood or other non-metallic material. Make feeding with coaxial cable type RG-11A/U or other 75- it of a size that up to four turns of coaxial cable can be ohm cable. To assist broadbanding, the ends of the accommodated on a diameter of about 2 inches. dipoles are fanned out, as shown in figure 9. (2) Next, solder a length of wire to the center con- b. The inverted V antenna is easy to construct for use ductor pin of a coaxial connector plug that had previously in the hf band. It has moderate directive properties. It is been connected to the end of the transmission line. This is fed at the center with 50-ohm coaxial cable such as RG- the whip radiator. The other end of this wire is passed 213/U. The input impedance of the inverted V is lower through the eye of an insulator and fastened with a clamp as than that of a half-wave dipole. A pole height of about shown in figure 12. With this arrangement, the length of 60 feet (18.2m) provides leg angles of 45º with an apex the whip can be adjusted to operate best on various fre- angle of 90º. Because this antenna functions best as a quencies. In all cases, the whip length, the distance be- resonant antenna (for low swore), the ends of the legs tween the coaxial connector plug and the top insulator must should be left slightly longer than the length so that they be 95 percent of the quarter wavelength at the frequency of can be cut (after erecting) for best transmitter loading at operation. The length in inches is 2800/frequency in MHz. the operating frequency. See figure 10 for details. The length of the skirt (the section between the top of the coil and connector plug tip) should be 25 inches (63.5cm) c. The long-wire antenna is perhaps the fundamental for operation in the air-ground vhf band. The turns of the directive antenna used on high frequencies. It is a fun- coil and lengths of skirt and whip can be varied for opti- damental component of the V and rhombic, which are mum transmitter loading at the frequency required. long-wire arrays. It is usually driven with open-wire feeders, as shown in figure 11, and is fed at one end. b. The Vertical Half-Wave Dipole. Use a vertical The longer antenna provides a basic clover-leaf hori- piece of wood to support the antenna and a rigid metal zontal directivity pattern. The azimuth lobe positions Lubing or rod for the antenna itself. See figure 13. change as the length is increased from a half wave to two and three wavelengths or more. Lobe maxim are at 50º (1) Measure and cut the yard-arm length to about from the 0º to 180º axis for a full wavelength long-wire one-half the overall length of the antenna. antenna. They are at 30º from the axis for a two-wavelength antenna. To obtain the desired directivity, the (2) Mount four standoff insulators on the upright antenna should be oriented by positioning its support as shown in figure 13 and attach two lengths of tubing to poles of azimuth by the number of degrees for the lobe act as the antenna. For a half-wave antenna with 5 per- maxim of the antenna design. cent end effect, the formula is given in the figure.

12. VHF AND UHF ANTENNAS. (3) Drill the tubing so it can be mounted on the The vhf and uhf antennas most likely to serve in an standoff insulators. Otherwise, improvise small clamps emergency are the whip, vertical half-wave dipole, and or tie the tubing to the insulators with wire. the vertical J antenna. As air-ground communication is more efficient with vertical polarization than with hori- (4) Solder a coaxial cable loop to the tubing as il- zontal polarization, it is advisable to construct the emer- lustrated and tie or tape the line to the wooden yard-arm. gency antenna for that polarization. Figures 12, 13, and Leave a slack loop in the downlead to prevent damage 14 provide construction details of the three antennas from too sharp a bend. enumerated above. Figure 13 shows a vertically-polarized half-wave dipole that may be constructed and sup- c. The Vertical J Antenna. This antenna, shown in ported by a yardarm on a tree or mast. Dimensional figure 14, is also constructed of metal tubing or rod. information and formulas are provided in the figures or Mount it with its matching stub without standoff insula- are located in the working data of appendix 3. tors at the metallic strip-a ground at this point will not affect operation of the antenna. Use standard or impro- a. The Whip Antenna. The flexible version of the vised metal clamps at the points where the coaxial or whip is also called the “limp” antenna. It can be hung other transmission line connects to the matching stub. from a branch of a tree, a yardarm, a mast, or any other Determine dimension Z so as to produce normal output convenient support. See figure 12. loading of the transmitter.

Page 10 Par 11 10/16/89 6580.5 Appendix 9 Figure 9. Multiwire Doublet Antenna Figure 9. Multiwire

Par 12 Page 11 6580.5 10/16/89 Appendix 9

Figure 10. Vertical V and Half-Rhombic Antennas

Page 12 Par 12 10/16/89 6580.5 Appendix 9 Figure 11. Long-Wire Antenna Figure 11. Long-Wire

Par 12 Page 13 6580.5 10/16/89 Appendix 9

Page 14 Par 12 10/16/89 6580.5 Appendix 9

13. IMPROVISED FEEDERS. When using tv twin lead as an rf transmission line, considerable loss will occur. When the line is wet, the a. If spare transmission lines are available, which are losses are very high. identical with or similar to that used in the original installation, use improved feeders as a last resort. If the trans- 14. IMPROVISED MATCHING TRANSFORMERS. mission line has been broken, carefully repair the breaks Coaxial cable can be used as matching sections to be with splices. Splice broken coaxial line if you do not have used directly at the feed point of an antenna. Figure 2-61 the proper coaxial fittings to make a good connection. part A, cut a length of flexible coaxial line just 1 bal- Even with proper fittings, when it is important to set up an anced antennas of relatively high impedance with low- installation in a short time, use a simple splice rather than impedance unbalanced cable. take the time to install the fittings. When an improvised antenna is located a considerable distance from a trans- a. To construct the arrangement shown in figure 2-16 mitter, connect several lengths of coaxial line together. part A, cut a length of flexible coaxial line just 1 inch Even if the lines do not have exactly the same character- (2.5om) longer than the required quarter wavelength. istics (one may have a characteristic impedence of 70 Remember to consider the reduced velocity of propa- ohms, the other may have one of 52 ohms), the mismatch gation, which is 0.66 for most coaxial lines of this sort. may be small and the power lost due to mismatch would Remove about 0.75 inch (1.8cm) of the vinyl jacket at probably be considerably less than would occur with an one end of the quarter-wave section. Using a pointed improvised line. instrument, unbraid the exposed outer conductor. Then twist the unbraided strands together to form a pigtail b. Splicing rather than using the proper coaxial fit- connection. Next, remove 0.5 inch (1.2cm) of the ting introduces some discontinuity. However, here again dielectric material to expose the inner conductor. Care- the amount of loss would probably be less than if an fully tin the inner conductor and the outer conductor improvised line were used. In splicing coaxial line, pigtail in preparation for soldering. Remove 0.75 inch solder the two inner conductors together. Then wrap (1.8cm) of the vinyl jacket at the other end of the them with plastic or rubber tape. Next, connect the two quarter-wave section, and remove 0.5 inch (1.2cm) of outer braids together with a short piece of wire. Finally, the braid and dielectric to expose the inner conductor. tape the entire splice. Now solder the inner conductor to the outer conductor to form the shorted end of the section. Next, solder the 0.5 c. Since flexible coaxial line is of such a special pre- inch (1.2cm) of tinned inner conductor at the other end fabricated nature, it can very seldom be improvised. On the to the outer conductor of the coaxial transmission line. other hand, improvise an open-wire line by using any Finally, solder the outer conductor of the quarter-wave available wire and locally constructed spreaders. The section to the inner conductor of the coaxial transmission nature of these spreaders will depend on what material is line. This completes the construction shown in part A of available. Small wooden strips, two to six inches (5 to 15 figure 2-61. om) long, can serve as spreaders in an emergency. For attaching the spreader, use short tie wires tied to the ends of b. In the arrangement shown at figure 2-61, part B, these spreaders and twisted around the wires, making up the the dielectric for the quarter-wave section is mainly air. transmission line. (See figure 15.) Fabricate spreaders from This is true because the shorted section of coaxial line plastic, hard rubber, or any other nonconductor. Drill holes acts as one conductor of a two-wire line in conjunction or attach clips at both ends so that the spreaders can be in- with the outer conductor of the main coaxial line. The stalled between the conductors. velocity of propagation for this section is 0.95. To construct this converter, use a quarter wavelength coaxial d. In using an open-wire line, consider the difference line with the inner and outer conductors shorted together in the characteristic impedance of the improvised line at both ends. Connect one end of this length to the inner compared to that of the original line used with the conductor of the coaxial transmission line at the point equipment. Too great a change may necessitate im- where it is connected to the antenna. Connect the other proving the existing matching transformers or changing end of the shorted length to the outer conductor of the the points of connection on the antenna and transmitter main coaxial line as shown. In order to make this con- to accommodate the new impedance. nection, it is necessary to remove a small amount of the vinyl jacket of the main coaxial line. Maintain an air e. Ordinary electrical wire or television (tv) twin space of about ½ to 1 inch (1.2 to 2.5cm) between the lead can be used to improvise a transmission line. additional section and the main transmission line.

Par 13 Page 15 6580.5 10/16/89 Appendix 9

c. In the arrangement shown at figure 2-61, part C, nally, the inner conductor at the other end of the half an electrical half wavelength of coaxial line is doubled wavelength section is connected to the other side of the back on itself. The outer braids of the half wavelength antenna as illustrated. This system is used to convert the section and of the main coaxial line are all soldered low impedance of an unbalanced line to the high together at the ends. The inner conductor at one end of impedance of a balanced load, and it produces a match the half-wave section is soldered to the inner conductor of 4 to 1. For example, if the unbalanced impedance of of the main transmission line, and both these con- the coaxial line is 75 ohms, then the balanced impedance ductors are connected to one side of the antenna. Fi- is 300 ohms.

Page 16 Par 14 IO/16189 6580.5 Appendix10

APPENDIX 10. CONNECTING ADDITIONAL RECEIVERS TO A SINGLE ANTENNA

1. GENERAL. 3. METHODS OF COUPLING BALANCED- This appendix discusses methods for multipling re- INPUT RECEIVERS ON ONE ANTENNA. ceivers to an antenna. Techniques used for high-frequency (hf) operation differ from those applicable to a. Receivers in Parallel or Series. When the input frequencies above 30MHz. Methods of multipling re-m circuit of a receiver is tuned by antiresonance, its input ceivers also differ if the receivers are of balanced radio impedance normally is higher at the operating fre- frequency (rf) input instead of unbalanced input. quency than at other frequencies. This higher impe- These differences are explained in the following par- dance makes the series connection of receivers prefera- agraphs. The simplest multipling methods connect ble, provided that receivers with balanced inputs are the receivers in series with, or in parallel across, the an- used. For example, assume two receivers Ur and Uz are tenna feeders. Multicouplers are single-input to multi- tuned to materially different frequencies fl and fz, re- ple-output isolation devices, either passive or active. spectively, and are connected in parallel. Then, at Depending on application, they may be in either operating frequency fr, receiver U2 would be a low im- balanced rf or unbalanced rf form. In all multipling ar- pedance and would tend to short out receiver Ur. Assu- rangements that do not use amplifiers to make up los- me, conversely, that they are in series. Then, at the ses, a degree of rf signal loss is to be expected on each operating frequency fl, receiver U2 would drop only a channel involved. However, there may not be a loss in little of the available fi voltage, leaving most of it for signal-to-noise ratio in the detected audio of the re- the operation of receiver Ur. ceiver outputs. (1) With balanced-input receivers located close 2. MULTIPLING OF HF RECEIVERS ON ONE together and connected in series, up to four or five re- ANTENNA. ceivers tuned to different frequencies may be used be- A single broadband antenna, such as the rhombic or fore the losses exceed 10 to 1SdB - compared with a the wave, can be used by several receivers tuned to dif- matched-impedance condition. ferent frequencies. The receivers should be divided into directional groups, with a separate antenna for (2) The use of more than two or three receivers in each group and with individual antennas for those re- parallel, tuned to different frequencies, usually results ceivers that cannot be efficiently grouped. When sev- in large losses. eral receivers, tuned to different frequencies, are connected to the same antenna without a common pream- (3) When several receivers are connected to one plifier (multicoupler), reduction in the signal voltage antenna, interference may be produced in any one of delivered to each receiver must be expected. Such them by spurious outputs from the others. reductions do not necessarily lower the audio signal-to- noise ratio. At times when the hf noise is high, consid- b. Multicouplers. erable loss can be tolerated before receiver set noise becomes an important factor. However, any large (1) A multicoupler is a broadband preamplifier reduction in signal voltage would be likely to reduce with multiple outlets, used to distribute signals to sev- the percentage of usable circuit time over a 24hour eral receivers. A multicoupler reduces or eliminates the period. When a multicoupler is used, its load-carrying effects of spurious receiver outputs and the loss that capacity for all signals received (both wanted and un- occurs when the receivers are connected directly to the wanted) is important. When the load capacity is too antenna or transmission line. However, since a mul- small, interference is produced by intermodulation of ticoupler has a limited load capacity and a broad fre- the various signals in the preamplifier. quency band, strong unwanted signals such as those

Par. 1 Page 1 6580.5 1O/l 6189 Appendix lo

from nearby transmitters can produce interference by checked two or three times to insure good adjustments intermodulation. of all networks for the particular set of operating fre- a quencies. (2) One type of antenna coupler, operating in the range of 4 to 24MHz, is designed to allow operation of d. Resistive Coupling Networks. If a resistor is used up to 10 receivers from a single antenna. Nominal in one antenna lead of paralleled receivers, the loss in input impedances are 75 ohms unbalanced or 156 or signal is increased and the isolation of the receivers 600 ohms balanced. A spurious response (caused by in- from each other is decreased in comparison with the termodulation in the coupler) of less than 2pV will be reactive coupling system. The best value for the isolat- produced @¶Hz away from either of two unwanted ing resistor is (n - 1) AB, where n is the number of par- 5,600~V signals fMHz apart, if f is at least alleled receivers, A is the antenna impedance, and B is 2MHz. Restriction of unwanted signals to 5,600~V the receiver input impedance. For a small number of may necessitate considerable separation from any paralleled receivers, the loss between receiver inputs is transmitting antenna. If f is less than 2MHz, the spuri- too small to control an ordinary spurious receiver out- ous response is larger. put that coincides in frequency with a weak wanted signal. If the resistor value is made larger, this loss in- c. Reactive Coupling Networks. Another method of creases, but the loss in the wanted signal also increases. coupling that avoids the intermodulation of the mul- Thus, resistive coupling networks for feeding a number ticoupler and reduces effects of spurious receiver out- of receivers from the same antenna have a restricted puts. This method parallels all receivers across the field of use. common antenna or transmission line after first insert- ing a series-connected fixed inductor and variable capacitor into one of the leads to each receiver. The reac- 4. MULTIPLING VHF UNBALANCED-INPUT tance of the whole series circuit formed by the induc- RECEIVERS ON ONE ANTENNA. tor, capacitor, receiver, and antenna system impedance Very-high-frequency (vhf) receivers can be series is tuned out at the operating frequency of the particu- multipled on a single antenna by the use of jumper lar receiver. This method reduces the loss caused by coaxial cables if the channel frequencies are at least multipling and produces a maximum signal voltage 1MHz apart. As many as five receivers can be so con- across each receiver. By this method, 5 to 10 receivers nected by 24.5inch (62.2cm) cable lengths; however a may be multipled without excessive loss because no maximum of three receivers is preferred. For installa- standard equipment for this method is available, these tions where the 24.5inch length is too short, an addi- networks should be designed and installed only by tional section 32% inches (82.2cm) long (or multiples qualified personnel. The tuning adjustments of the in- thereof) may be added to the 24.5~inch (62.2cm) dividual series circuits are not entirely independent of length. Refer to TI 6620.2A, Instruction Book, Re- each other when bridged across a common antenna. ceiver Radio, AN/GRR-23 and AN/GRR-24, Volume Therefore, after initial adjustments or whenever any 1, paragraph 3.4, for operation of two solid-state VHF operating frequency is changed, the tuning should be or UHF receivers from a single antenna.

Page 2 Par. 3 Memorandum U.S.Department of Transportation Federal Aviation Administration

? Subject: INFORMATION: Suggested Improvements to Date: ! Order 6580.5, Maintenance of Remote Communications Facility (RCF) Equipments 7 Reply to From: Attn. of: i Signature and Title Facility Identifier To: AF Address Manager, National Engineering Field Support Division, ASM-600

Problems with present handbook. i

Recommended improvements.