Characteristics of Naval Fire . Control Radar

Home , Feed horn, Rangekeeper

COPY~ CO NFI oP 1895·

CHARACTERISTICS OF ,. NAVAL FIRE .CONTROL RADAR

• ~

-i8Nfi6ENtiAt•

ABUREAU OF ORDNANCE PUBLICATION

~ OP 1895

CHARACTERISTICS OF NAVAL FIRE CONTROL RADAR

12 NOVEMBER 1954 DEPARTMENT OF THE NAVY BUREAU OF ORDNANCE WASHINGTON 25, D. C.

12 November 1954

ORDNANCE PAMPHLET 1895 CHARACTERISTICS OF NAVAL FIRE CONTROL RADAR

1. Ordnance Pamphlet 1895 describes both the fundamental principles of operation of radar equipment in general and the characteristics of specific United States Naval fire control radar equipment.

2. This publication is intended for use by all personnel concerned with radar operation in general, and with the application of basic radar principles to fire control radar.

3. This publication does not supersede any existing publication.

4. This publication is El8N¥'1!HU! AitL and shall be safeguarded in ac cordance with the security provisions of U. S. Navy Regulations. It is for bidden to make extracts from or to copy this classified document, except as provided for in Article 0910 of the United States Navy Security Manual for Classified Matter.

M. F. ScHoEFFEL Rear Admiral, U. S. Navy Ohief, Bureau of Ordnance

.tONFIDENTIAL- 'i!Qt 'FilEt 'IJ,ll

CONTENTS

Chapter Page Chapte1· Page FOREWORD vi 2. Close-in Targets ...... 28 (cont) Merging Targets ...... 28 PART I-GENERAL Propeller Modulation ...... 28 1. PRINCIPLES OF THE RADAR ART 1 Geographical and Atmospheric The Echo Principle ...... 1 Conditions ...... 28 The Radio Echo at Work ...... 1 Low-flying Targets ...... 29 Radar Measurements ...... 2 Land Echoes ...... 29 Factors Affecting Radar Radar Countermeasures ...... 31 Measurements ...... 6 Spotting Surface Gun Fire ...... 32 Power and Range ...... 6 Range Spotting ...... 33 Horizon and Range ...... 6 Deflection Spotting ...... 33 Antenna Gain ...... 7 Spotting Salvos ...... 35 Beamwidth ...... 7 Radar Chronograph ...... 35 Targets as Reflectors ...... 8 Radar Charting for Shore Bombard- Echoes and Noise ...... 8 ment ...... 35 Pulse Length and Pulse Rate ... . 9 Radar Beacons ...... 37 Radar Navigation ...... 37 2. PRACTICE OF THE FC RADAR Corner Reflectors ...... 38 ART ...... 10 Identification, Friend or Foe (IFF) 38 Radar and the FC Problem ...... 10 Emergency Uses of FC Radar ..... 38 Scanning ...... 11 Sector, Spiral, or Elliptical Scan PART 2-EQUIPMENT DATA for Search and Acquisition ... . 11 3. RADAR EQUIPMENT MK 8 ...... 39 Conical Scan for Tracking ...... 12 4. RADAR EQUIPMENT MK 12 ...... 45 Circle Scan for Spotting ...... 12 5. RADAR EQUIPMENT MK 13 ...... 50 Scopes ...... 12 6. RADAR EQUIPMENT MK 22 ...... Scope Sweeps ...... 12 55 7. RADAR EQUIPMENT MK 25 ...... 59 A-scopes ...... 14 8. RADAR EQUIPMENT MK 26 ...... 64 B-scopes ...... 17 9. RADAR EQUIPMENT MK 28 ...... 68 E-scopes ...... 19 10. RADAR EQUIPMENT MK 34 ...... J-scopes ...... 19 74 11. RADAR EQUIPMENT MK 35 ...... 80 PPI-scopes ...... 20 12. RADAR EQUIPMENT MK 39 ...... 85 T&E-scopes ...... 20 13. RADAR SET AN /SPG-48 ...... Evaluating Scope Indications ...... 23 90 Scope Comparisons ...... 23 Interpretation and Judgment ... . 23 PART 3-REFERENCE DATA Stratification and Trapping ... . 25 14. PERFORMANCE CHARACTERIS- Resolution ...... 25 TICS ...... 97 Interference and Corrective Meas- 15. GLOSSARY ...... 109 ures ...... 27 16. BIBLIOGRAPHY ...... 112 Neighboring Radars ...... 27 17. "AN" NOMENCLATURE SYSTEM. 113 ... CONS:ist..,._ III A I Ill 88~ IFIPEIC IIAt

ILLUSTRATIONS

Figure Page Figure Page 1. Sound Echo Ranging ...... 1 27. PPI-scope ...... 20 2. Typical Antenna for Radio Ranging. . 1 28. T&E-scope ...... 21 3. Basic Radar Set, Block Diagram . . . . . 2 29. Scope Comparisons of Same Radar 4. Pip Position on Time-base Represents View ...... 22 Target Range ...... 3 30. Angular Width of Target Varies with 5. Time-base Expansion Increases Accu- Range ...... 23 racy of Range ...... 4 31. Target Aspect Alters Appearances of 6. Fixed Range Marks Indicate Distances 5 Pips ...... 24 7. Movable Range Step for Range Meas- 32. Range Resolution of Targets at Same urement ...... 5 Bearing ...... 26 8. Antenna Gain Represents Increase in 33. Bearing Resolution of Targets at Power when Energy is Focused. . . . 6 Same Range ...... 26 9. Principle of Beam Width ...... 7 34. Interference from Other Radars. . . . . 27 10. Target Nearest Beam Axis Returns 35. Thunderstorms or Electrically Charged Strongest Echo...... 8 Clouds ...... 28 11. Echo Pulse (Target Pip) Seen 36. Water Reflections Produced by Low Through Random Noise ...... 9 angle Target ...... 29 12. Sector Scan ...... 10 37. Detecting Low-angle Target Approach- ing over Shoreline ...... 30 13. Spiral Scan ...... 11 38. Targets within Coastline Shadow Area 14. Elliptical Scan ...... 11 are Obscured ...... 31 15. Conical Scan ...... 12 39. Radar Spotting ...... 32 16. Circle Scan ...... 13 40. Salvos Produce Multiple Echoes. . . . . 32 17. Main Sweep Views Long Range 41. Deflection Spotting ...... 33 Targe~ ...... 13 42. Salvo with MPI at -603 Yards...... 34 18. Precision Sweep Views Segments of Main Sweep ...... 14 43. Determination of Initial Velocity by Radar Tracking ...... 34 19. A-scope ...... 15 44. Off-shore Reference Points for Shore 20. AIR-scope ...... 15 Bombardment ...... 35 21. Pip Matching with A-scope ...... 16 45. Radar Charting ...... 36 22. B-scope and E-scope ...... 16 46. Corner Reflectors Increase Reflecting 23. Distortion on B-scopes ...... 17 Properties ...... 38 24. ~E-scope ...... 18 47. IFF System, Block Diagram...... 38 25. Double-E scope ...... 19 48. Antenna for Radar Equipment Mk 8, 26. J -scope ...... 19 Shown on Gun Director Mk 34. . . . . 39

iv CQb'S'Pit 4I lA&

ILLUSTRATIONS

Figure Page Figure Page- 49. Radar Equipment Mk 8, Functional 72. Control-Indicator Unit (with Com- Schematic ...... 40 puter Mk 13) ... 0 .. 0 ...... 66 50. Antenna Assembly, Front Open...... 41 73. Antenna for Radar Equipment Mk 28, 51. Radar Operator's Station, Typical on 40-mm Twin Mount ... 0.... o 0 . 68 Arrangement ...... 42 74o Units for Radar Equipment Mk 28, on 52. Auxiliary Indicator ..... 0 .. 0 ...... 43 Gun Director Mk 37 . 0 .. 0 . 0...... 69 53. Antenna for Radar Equipment Mk 12 75. Radar Equipment Mk 28 with GFCS (Right), atop Gun Director Mk 37 45 Mk 63, Functional Schematic 0 .. 0. 70 54. Radar Equipment Mk 12, Functional 76. Below-decks Radar Equipment ... 0 . . 71 Schematic ...... 46 77. Antenna for Radar Equipment Mk 34, 55. Range Control Unit .. 0 .. 0 ...... 47 on 3"/50 Mount 0 ... 0 ...... 7 4 56. Radar Equipment at Pointer's Station 47 780 Antenna for Radar Equipment Mk 34, 57. Main Frame in Radar Transmitter on Gun Director Mk 57 ..... 0 . . . . 75 Room ...... 0. 0 .. 0. 0..... 48 79. Radar Equipment Mk 34 with GFCS 58. Antenna for Radar Equipment Mk 13, Mk 63, Functional Schematic . . . . . 76 on Gun Director Mk 34...... 50 80. Radar Components in Rack . 0...... 77 59. Radar Equipment Mk 13, Functional 81. Antenna for Radar Equipment Mk 35, Schematic ..... o...... 0 ...... 51 on Gun Director Mk 56 ... 0 ...... 80 60. Control Console ...... o...... 0 . . . . 52 82. Radar Equipment Mk 35, Functional 61. Remote Range-and-Train Indicator.. 53 Schematic .... 0... 0...... 81 62. Antenna for Radar Equipment Mk 22 (Left), on Gun Director Mk 37.... 55 83. Control Console, Containing both Ra- 63. Radar Equipment Mk 22, Functional dar and Fire Control System Com- Schematic ...... 56 ponents ...... 82 64. Control Panel ...... 57 84. Antenna for Radar Equipment Mk 39, 65. Indicator Unit . 0..... 0 ...... 57 on Gun Director Mk 57 ... 0 ...... 85 66. Antenna for Radar Equipment Mk 25, 85. Radar Equipment Mk 39, Functional on Gun Director Mk 37. 0 . 0 ...... 59 Schematic ...... 0 ...... 86 ... 67. Radar Equipment Mk 25, Functional 86. Radar Console ... 0 . 0 ...... 87 Schematic . 0 0.... 0 o 0 . 0 ... 0 . . . . . 60 87. Target Acquisition Unit .. 0. 0 ...... 88 68. Radar Console .. o. 0. 0. 0..... 0..... 61 69. Radar Control Unit (Trainer) ...... 61 88. Antenna for Radar Set AN /SPG-48, on 3"/50 Mount (Gunar Mk 1).... 90 70. Antenna for Radar Equipment Mk 26, on Gun Director Mk 52 .. 0 .. 0 . . . . . 64 89. Radar Set AN /SPG-48, Functional 71. Radar Equipment Mk 26, Functional Schematic . 0 ... 0 ...... 91 Schematic o ... o...... 65 90. Radar Console . o.. o...... 93

\1elli'QE"ilAL v 0014Pft521WIIJtL

FOREWORD THE SHOOTING EYE OF THE FLEET In the fire control world of today, radar has become the shooting eye of the fleet. This volume is for you who are responsible for keeping this shooting eye sharp. The pressure of modern operations leaves a busy ship's officer little time to read and comprehend even some of the material on the general subject of radar, much less the mass of specific instructional material on individual radar equip ment aboard. Therefore, this manual was prepared to help you with this problem; it con tains information on gun fire control radar-pertinent information that has been culled from thousands of pages of OP's and technical data on the subject. Familiarization with its contents can save the ship's officer the time and trouble of wading through a mass of written material. In brief, it is hoped that this manual will help to sharpen the shooting eye of the fleet-painlessly! PLAN OF THE BOOK This is no ordinary OP; it is not intended to be. This manual was planned and designed for a specific reader-those officers who are responsible for admin istration of all phases of the use of fire control radar. Neither is this manual intended to be a "sugar coated" version of the compre hensive information to be found in the OP's on specific fire control radar equipments. Obviously, acquaintance with the details of those OP's is desirable and helpful, and reference to them is, at times, absolutely essential. However, in lieu of the opportunity to make greater use of the individual equipment OP's, this manual will serve as a refresher and as a reference to the significant points of fire control radar. To attain this objective, the content has been organized into three major parts: Part 1 includes two chapters, Principles of the Radar Art and Practice of the Fire Control Radar Art. Part 2 includes Equipment Data and Part 3 provides Reference Data. · - Principles of the Radar Art, in the main, will serve as a refresher for most officers on the fundamentals of radar. It is important that the reader thoroughly comprehend these fundamentals for they provide the foundation on which the information in the succeeding topics is built. Practice of the Fire Control Radar Art, is a resume of the salient factors of operat on. This section discusses actual operational equipment, interpretation of the information presented by radar, and the functional or operational situa tions encountered. Equipment Data supplies information condensed from the applicable OP's on specific fire control radar equipments. These data will usually suffice to give the officer what he needs to know about individual systems or equipment. Reference Data is composed principally of performance characteristics tables providing a ready reference on the operational aspects of the various radar equipments. vi CGhiFiil!f 4?1N..

PART 1-GENERAL

Chapter I PRINCIPLES OF THE RADAR ART

The Echo Principle The fundamental concept of radar is based on the echo principle. An echo is a reflection. Echoes occur nearly every time wave energy strikes an object, whether the energy be light waves, sound waves, or radio waves. Although the energy may be reflected in many directions, usually it is only that energy which is returned to the location of its origin that is useful in de termining the presence of an object. Seafaring men have, for years, used this echo ,~ principle to detect obstructions in their ship's course or to determine their ship's position during fog or at night. The seaman could, for example, find his posi tion relative to a dangerous cliff jutting out into the sea. By shouting through a megaphone, figure 1, or by sounding a fog horn, and by then timing the interval required to receive an echo and noting the direction from which Figure 2-Typical Antenna for Radio Ranging. it came, he could determine the range and bearing of the cliff. The Radio Echo at Work A radio echo may be used in a similar man ner. Instead of a megaphone, figure 2 shows a sharply directive antenna which transmits a . ·~·' series of extremely short pulses of radio energy in a narrow beam. During the interval between pulses, a receiver "listens" for the echoes and the distance to the object is measured by elec tronically timing the round-trip travel time of the radio waves. The bearing of the antenna, when the strongest echo is received, is the rela tive bearing of the object being sought. - , . Radio waves are far more useful than sound '· "• ~ r - \ waves for such detection and measurement. I ;..' ... - "\. \ / --~..,_ _, Sound waves do not travel rapidly enough to , I /{ _,_..?--, \ I I / • ' present accurate information about fast moving I ' ..~\".. \ . ' I ·., objects. Therefore, a sound wave, in the form ...... \ of an echo, returns to the point of its origin "" some time after the object has left the position Figure J-Sound Echo Ranging. at which it was struck by the transmitted ceunel!t4ll u.. OP 1895 Qet4FI61!1 ~AL wave. Furthermore, sound waves are not easily There must be a source of radio energy (the transmitted over great distances. transmitter), a timer to pulse this energy, a However, radio waves travel at nearly a directional antenna to beam the pulses of en million times the speed of sound waves. Even ergy, a receiver to detect the echoes, and finally, at distances of a hundred miles or more, the a means of measuring how much time has round trip time for a pulse of radio energy is elapsed between the moment of transmission measured in microseconds, or millionths of a and the moment of the reception of the echo, as second. Also, it is comparatively simple to gen well as a means of indicating the relative direc erate pulses of radio energy that can travel over tion from which the echo came. a hundred miles to an object and still return as echoes strong enough to be detected. Radar Measurements An advantageous fundamental of the echo The pulses transmitted by fire control radars principle is the fact that the target object does consist of short bursts of ultra-high frequency not contribute energy to the pulse that strikes radio energy. Radio energy, of the frequencies it; the target merely serves as a reflector for involved, obeys essentially the same laws as that pulse, and a small part of the incident light. Therefore, like light, this energy travels energy is returned as an echo. It is this utiliza in a straight line, can be focused into a beam, tion of the echo principle, employing electro and has a constant speed of approximately magnetic waves as the transmitting medium, 186,000 miles per second, or 328 yards in a that makes radar a unique method of location millionth of a second (microsecond). Therefore, by radio. the round trip time (in microseconds) for a Radar, then, is the generic name for a family single pulse is a measure of the distance between of RAdio Detection And Ranging techniques the pulse source and the object. The distance based on the radio echo. to the object, and also its elevation and relative It follows that there are certain pulse gener bearing, can be conveniently portrayed graphi ating and echo measuring components which cally by means of luminous markings on the are common to every radar set. See figure 3. face of a cathode ray tube indicator.

GENERATES PULSES OF RADIO ENERGY THAT ANTENNA RADIATES PULSES OF RADIO ENERGY ARE FED TO ANTENNA WHEN TRANSMITTER IS CONNECTED TO IT.

TRANSMITIER H~"'T""'.--t~ ALSO PICKS UP ECHO SIGNALS FROM ANY TARGET WHICH HAS BEEN STRUCK BY THE RADIATED PULSES.

PRODUCES START AND STOP AUTOMATIC SWITCH THAT CONTROL PULSES FOR TIMER DISCONNECTS RECEIVER FROM ANTENNA TRANSMITIER AND INDICATOR '--""""'-_. WHENEVER TRANSMITTER IS OPERATING

DETECTS AND AMPLIFIES ECHO SIGNALS SUFFICIENTLY TO ACTUATE INDICATOR

INDICATOR

VISUAL DISPLAY OF INTERVAL (RANGE) BETWEEN TRANSMITTED PULSES AND ECHO SIGNALS

figure 3-Basic Radar Set, Block Diagram.

2 CObUilliUit ITPJII\L 'iQftFIBiti~.L PRINCIPLES OF THE RADAR ART

------1: 65,600 YOS. 400 MICROSECONDS ------=1 16,400 YDS .-·1 ------(-~------~- . ... Lt ...... ------1---- 65,600 YOS.----~ ---

ECHO

Figure 4-Pip Position on Time-base Represents Target Range.

Usually, in making distance measurements, a from an object which is at a distance from the luminous trace, called a time base line, is used radar set corresponding to the length of the to sweep across the face of the tube. The length luminous trace to the pip. of this line represents increments of time, start For example, in figure 4 the radar antenna ing from zero at the left where the trace begins. is represented as beamed on two target ships Changing the amount of time required to sweep at the same relative bearing, one at 65,600 the trace across the face of the cathode ray tube yards and the other at one-fourth that range, or indicator, or scope, alters the time base of the 16,400 yards. Therefore, the two target pips, line and affords a means of measuring the dis on the illustration of the scope, are at equivalent tances to objects at varying ranges. distances from the pip of the transmitted pulse, Vertical distortions of this line are called thereby indicating the ranges to the targets in pips; they are produced by received pulses terms of the time base line on the scope. In this (echoes) of the transmitted radio energy. The scope illustration, the target farthest away is first pip, which is produced by the transmitted at the maximum range (65,600 yards) that can pulse, is at zero time, and therefore at zero be represented with a 400 microsecond time range. Each succeeding pip represents the echo base.

GOb!FiiEt' ... ' 3 OP 1895

-.....__ 21 ------

-- --- THE RANGE OF EACH OBJECT --- IS INDICATED IN NAUTICAL MILES

100- MILE DISPLAY TIME BASE 1233 MICROSECONDS

50-MILE DISPLAY TIME BASE 617 MICROSECONDS

10-MILE DISPLAY TIME BASE 123 MICROSECONDS

figure 5-Time Base Expansion Increases Accuracy of Range. 4 oea 'E'Diia w•L PRINCIPLES OF THE RADAR ART Most indicators are provided with a means Fundamentally, all that must be known to of changing the sweep time of the time base determine bearing, as well as elevation, is the line. The longer the sweep time, the greater the direction of the beam of radio energy when it distance that can be measured. A shorter sweep strikes an object. The echo that returns from facilitates more accurate range measurement of the object is received by the same directional echoes from nearby objects, due to the expanded antenna that beamed the pulse a few micro scale as illustrated in figure 5. seconds before. Thus, angular measurements of Actual measurement of the target range is the relative bearing and the elevation of the usually accomplished in one of two ways. Some antenna, which correspond to the direction in indicators are provided with electronic range which the antenna is oriented when an echo is marks, as shown in figure 6, which are accu received, provide a means of measuring the rately timed to appear on the scope at points bearing and elevation of the object producing corresponding to definite distances. These range the echo. The angular position of the antenna marks usually appear as sharper pips than the can also be shown graphically as luminous echo pulses. marks on the face of a cathode ray tube. A more common type of range mark is a movable range step or notch, figure 7, that is used much like a cursor on a slide rule. The step, and any chosen target pip, can be brought adja cent to each other by turning a knob or hand wheel geared to a counter. The counter is cali TARGET brated in units of the distance represented by PIP the position of the range step in the time base line. Target range is read directly on this counter when the range mark coincides with the RANGE STEP desired target pip. When the mark and the target echo are so aligned, B of figure 7, the echo is said to be "gated".

TRANSMITTER RANGE MARKS 10 MILES APART A-UNGATED PULSE ON A 50-MILE BASE

8-GATED

figure 7-Movable Range Step figure 6--fixed Range Maries Indicate Distances. for Range Measurement. ~II Ei 18214 IIAl 5 Factors Affecting Radar Measurements true; radio wave energy is dissipated during its In view of the foregoing discussion, it may transmission through space at a great rate-a seem evident that the success of radar measure much greater rate than that which is propor ment depends only upon the reception of an tional to the distance of transmission. This rate echo sufficiently strong to be discernible to the of dissipation is in accordance with an inverse receiving system as a signal. However, much square law. This means that the radiated pulses more is involved. There are many factors affect grow weaker as the square of the distance from ing radio detecting and ranging which are all the transmitter. The same law applies to the reflected pulse; it, too, grows weaker as the closely related and which interact in a complex square of the distance from the target. Conse manner. quently, the strength of the echo pulse varies Some of these factors are inherent, uncontrol with the inverse fourth power of the range from lable characteristics of radio wave propagation, the radar set to the target. and others can be controlled within design limits built into the equipment before it is in Horizon and Range. Since radio waves travel stalled aboard ship. An acquaintance with these in a straight line, as noted earlier, the curvature factors can be gained by first considering what of the earth limits the range of radar for sur happens to the transmitted pulse on its trip to face use. While the optical horizon must there the reflecting object and during its return as an fore be considered the maximum attainable echo, and second, by studying the character of range for surface targets, it should be remem- the pulse. For example, an analysis of what may happen to the transmitted pulse on its microsecond journey to and from the reflecting object brings to mind many questions: If the transmitter power is increased, is the range increased pro portionately? If the pulse in its round trip hits objects other than the target, or is transmitted through varying conditions of weather, does this have an effect on the echo signal? How does the shape, size, aspect, and material of the target affect the quality of the echo signal? And further, considering the character of the trans A mitted pulse, how do variations in pulse length, pulse rate, and wavelength affect the range of radar? Under what conditions is it best to alter these controllable pulse characteristics? These factors are discussed, under appropri ate headings, in the ensuing paragraphs. A fore .. knowledge of them will provide. a key to the optimum performance attainable by a particu lar radar system. Power and Range. A radar set, to be useful, must be able to detect an echo signal from a distant object-as distant as possible. It would seem reasonable then, to assume that an in crease in the power of the transmitted pulse 8 would result in a proportionate increase in the strength of the echo pulse, and therefore, a proportionate increase in the effective range Figure 8-Antenna Gain Represents Increase in that can be covered. But this assumption is not Power when Energy is Focused. 4Qt IFI6!14,1AL 6 CQbJFIQii:bm A I PRINCIPLES OF THE RADAR ART

INTENSITY OF FIELD AT A AND B (BEAM WIDTH) IS HALF THE INTENSITY AT X ALONG THE AXIS OF THE BEAM

, Figure 9-Principle of Beam Width.

bered that the optical horizon is extended by point X is much greater than when the field was raising the height of the eye. Consequently, transmitted equally in all directions. raising the antenna of a radar set will increase Antenna gain, then, represents the increase its range. This is a factor to be borne in mind in power in a given direction when the radio when appraising comparable radar installations energy is focused by an antenna, over the power aboard various types and classes of ships. measured at the same point when the antenna Antenna Gain. Since a target lies in a particu is radiating the same amount of energy equally lar direction in relation to one's own ship, it not in all directions. only would be wasteful to radiate the power Focusing radio energy results in a beam equally in all directions, but by so doing, it which has the greatest amount of energy dis would be impossible to determine direction. tributed along its axis. This concentration les Therefore, the antenna configuration is always sens as the side boundaries are approached, as made in such a manner as to direct an optimum illustrated in figure 9 by the diminishing black amount of energy in the desired direction. The tone toward the edges of the beam. The more increase in power that is afforded by such direc narrow the beam, the greater the strength along tivity is called antenna gain. For example, A of the axis of the beam. An antenna which focuses figure 8 illustrates, by black-to-white tone the energy in a narrow beam has a higher gain values, the decreasing intensity of a radio than one which produces a broad beam. This energy field that is transmitted equally in all characteristic makes possible a more accurate directions from a point source. The intensity is determination of target bearing. greatest at the source (black) and rapidly Beamwidth. Beamwidth, then becomes an im diminishes to gray, then toward white at the portant factor in putting a strong signal on a fringe of the effective transmitting range. target. In order to establish side boundaries, Therefore at point X, the intensity of the field is beamwidth is arbitrarily defined as the angular the same as for any other point that is on a distance between two directions in space where circle having the same radius from the source the radiated power has half the maximum value of transmission as the point X. of the power along the axis. This principle is In B of figure 8, the radio field has been illustrated in figure 9; the intensity of the field focused into a beam which is projected in the at points A and B (as represented by tone same direction from the source as the point X. values) is half the intensity of the field at X on However, now the intensity of the radio field at the axis of the beam.

•&If JFIBEI lltN. 7 L

The antenna may be considered as a point surface that is struck by the beam, and the source, or the apex of a solid angle that is greater the chance that part of this surface will formed by the diverging beam. It may be seen be at right angles to the beam. This surface will in figure 10 that the closer a target is to the vary in its reflecting properties according to its center of the beam, the greater will be the abil composition. Although rain and clouds will re ity of the radar receiver to detect the target turn an echo, metals are by far the best reflec because the transmitted pulse is strongest at tors of radio energy. It is apparent, then, that that point, and as a result, the echo will be the amount of incident radio energy that is stonger, producing a more discernible target reradiated as an echo depends on the aspect, pip on the scope. shape, size, and composition of the target. Echoes and Noise. The strength of the echo Targets as Reflectors. The strength of the echo pulse as compared to the transmitted pulse is is also governed by the effective cross-sectional extremely weak. This echo must be detected and area and the composition of the target. Any amplified by the receiver. However, electrical reflection toward the source of the transmitted noise generated within the receiver itself, as energy is due to those surfaces of the target well as random echoes produced by rain, hail, which are at right angles to the line of approach clouds, the sea, etc., make it difficult to distin of the beam. Such surfaces constitute the radar guish between these extraneous signals, which cross-section of the target. Since the beam di appear on the scope as "grass", and the target verges, the larger the target, the more reflecting pip. Each echo pulse has a timed relation to

figure Jo-Target Nearest Beam Axis Returns Strongest Echo.

8 GOIQPIOEI\ I lAP. PRINCIPLES OF THE RADAR ART

AVERAGE OF 10 PULSES

AVERAGE OF 30 PULSES

A TARGET PIP AVERAGE OF 100 PULSES ~ A ~ I ' ..., • , ... t'W - ...... figure 11-Echo Pulse (Target Pip} Seen Through Random Noise.

other similar pulses which have been reflected feet in space, no energy will have returned sequentially from a target; these persist on the before the pulse has been completely trans scope at the same location as compared to the mitted. The slight interval which results from changing character and location of the random · such an arrangement permits a distinction to signals or "grass". See figure 11. If the aver be made between the transmitted pulse and its age signal power for a given series of echo echo. The shorter the pulse, the closer an object pulses exceeds the average random noise power may be to the radar antenna and still be dis for the same interval, as shown by the indica tinguished. tions in figure 11, it is possible to distinguish A series of pulses is required for proper rec the target pip. ognition of the echo signals at the receiver. The time interval between successive pulses must be Pulse Length and Pulse Rate. The length of a long enough to allow each pulse to reach the transmitted pulse signal affects the minimum target and to return before the following pulse range of detection. Imagine the pulse to be of is transmitted. This interval, controlled by the an arbitrary length, much like an elongated pulse repetition rate, must be greater than the burst of smoke from a skywriting plane. A pulse echo time required for the most distant target. of one microsecond duration occupies a distance Thus, pulse length and pulse repetition rate are of about 1000 feet in space. If this pulse strikes important in determining the minimum and an object slightly less than 500 feet away, some maximum ranges, respectively, of the radar set, reflected energy will have returned to the an and since these factors are usually controllable tenna before the transmitter has stopped send (within limits) it is important that proper ad ing the pulse. However, if the pulse length is justments be made when putting the radar set one-half microsecond, thus occupying only 500 in operation.

SOb'PRP ltli tb 9 Get4flo!N ""[

Chapter 2 PRACTICE OF THE FIRE CONTROL RADAR ART

Radar and the Fire Control Problem the optical equipment. In some installations, the Radar can be used in various ways, depending radar operators are stationed below decks, upon the particular design, to facilitate solution rather than in or about the director proper. of the fire control problem. It may be employed They control the gun fire control system only in detecting the target, establishing its present by means of radar ranging, pointing, and train position, tracking it to supply constantly chang ing. In either case, the radar operators are ing data for the computation of gun orders, and usually coordi~ated by a control officer. spotting. Because radar sight is not affected by In most tactical procedures, the operators are low visibility, radar may be employed to aid all dependent on one another. If an operator shifts of these functions against an obscured target. the range suddenly with the result that the pip Even under optimum conditions of visibility, drops out of the range gate, the chances are that radar may be used to track a target at greater the associated operators will no longer have ranges than when optics are used. And, auto indicator signals on which they may point and matic tracking radars can follow a violently train. Similarly, during brief periods of signal maneuvering target more closely than a director fading when the distinctive luminous pips may operating tracking by means of optics. Fleet disappear from the faces of the indicator scopes, experience has shown that radar accuracy re radar operators usually allow the computer to mains stable during action whereas a director drive the director if it is in automatic control; operator's accuracy decreases. in local control, they continue ranging, pointing It must be recognized, however, that the and training at a steady rate until the signal human factor also imposes a limitation on the returns. If the operators train and elevate effectiveness of radar equipment. If the equip erratically, they run the risk of losing the target ment is to be useful under all conditions, the altogether. By the same token, bearing accuracy radar crew members must operate as a team. is dependent, to a large degree, on an operator's These operators are often an integral part of a ability to detect small differences in image sizes gun fire control system crew. They can cause a or positions. These considerations emphasize gun director to train, elevate, and range on a the need for teamwork in order to make the target by using either the radar equipment or most efficient use of the radar equipment.

EFFECTIVE SECTOR COVERAGE ..

Figure J2-Sector Scan.

10 &QtJFiiEI 4I tAt QQtlFIBEIQ I IAE' PRACTICE OF THE FIRE CONTROL RADAR ART

EFFECTIVE SPIRAL ANTENNA AXIS SCAN COVERAGE

PATH OF BEAM AXIS

Figure 13-Spiral Scan.

EFFECTIVE ELLIPTICAL SCAN COVERAGE

ANTENNA AXIS

OF BEAM AXIS Figure 14-EIIiptical Scan. Scanning bears a different relation to the antenna Scanning may be defined as systematic and reflector. periodic movement of the radar beam in space. Sector, Spiral, or Elliptical Scan for Search Such beam movement is necessary in radar and Acquisition. Search and acquisition require equipments for rapid target acquisition, for a comparatively large coverage in space. This blind tracking, and for spotting. Different scan coverage is provided in different equipments ning motions, which produce different patterns by the use of sector, spiral, or elliptical scan. in space, are each suited for one of these em In sector or B-scan, the beam is caused to ployments. Most radar equipments are there search to and fro through a horizontal arc as fore designed to use several scanning motions, shown in figure 12. The center of the scanning or types of scan, if they are intended to perform arc is rigidly aligned with the director line of all three functions-acquisition, tracking, and sight so that when the director is trained on a spotting. target, accurate bearing indication is given by Scanning is accomplished either by movement the radar. In spiral scan, the radar beam is of the entire radar antenna assembly or by rotated with a spiral motion, as shown in figure displacement of the point source of radiation 13. Elliptical scan is illustrated in figure 14. The with respect to the antenna reflector. Displace movement of the radar beam in an elliptical ment of the source may be mechanical or elec pattern is best suited for acquisition of air trical, the latter involving switching among targets, particularly when designation does not several point sources of radiation, each of which include target elevation.

Conical Scan for Tracking. Conical scan per luminous screen. These electrons produce lumi mits blind tracking by providing a means of nous markings on the screen, and, in accordance determining the relative position of the target with the relative position and timed relationship with respect to the axis of the antenna. Conical of the sweep of the electron stream across the scan is accomplished by moving the antenna so screen, these markings can be used to graphi that the radar beam describes a narrow cone cally portray one or two coordinates of the in space as shown in figure 15. The strength of target. the reflected signals within this cone varies in Scope Sweeps. The timed relationship of the intensity as the beam is rotated. This variation sweep of the electron stream is an important in strength is used to control the position of the controllable factor in the interpretation of tar target indications on a radar scope. get locations on the scope. There are three types Circle Scan for Spotting. Circle scan is similar of sweeps in general use on fire control radar to conical scan except that the beam describes equipments: main sweep, expanded sweep, and a wider circle about the axis of the antenna. precision sweep. Not all equipments have all See figure 16. Since circle scan presents a three types of sweep, but most equipments have wider field and flickerless indication, it is par at least two types. The purpose of these sweeps ticularly effective for spotting shell splashes is to permit greater accuracy in making target during surface firing. measurements. Scopes On a main sweep, an operator can view the full range of the radar set. In some sets the Radar scopes are cathode ray oscilloscopes total range appearing on the scope at any time that provide graphic presentations of radar may be varied from about half the full range data. Depending upon the type of scope, these to the maximum range, figure 17. In the exam present the operator with indications of the ple shown at A in figure 17, the operator has an range, bearing, or elevation of a target, or com adjusted field of view of 50,000 yards. He can binations of these target coordinates. view any 50,000 yard section of the maximum There are several standard types of scopes range of 80,000 yards by using a control which in general use with fire control radar equip moves the field of view across the scope. ments. These are the A-scope, B-scope, E-scope, J-scope, PPI-scope, and T&E-scope. All of these The expanded sweep available on some radar scopes are similar in principle, having an inside sets produces the same presentation as the main coated luminous face or screen. The echo from sweep except that the expanded sweep covers the target, after amplification, is used to con from zero to some range less than the main trol a stream of electrons impinged upon the sweep.

FECTIVE CONICAL SCAN COVERAGE

figure 15-Conica/ Scan.

12 CO~IIPlgl!t 4'1"1:AL CQ.I'I!;.',.IiiAl PRACTICE OF THE FIRE CONTROL RADAR ART

EFFECTIVE CIRCLE SCAN COVERAGE

Figure 16-Circle Scan.

I I I I I I I I I I I I I T6 1- l I I I IT5- j I I I II I II I I T.-' ' MAIN SWEEP ADJUSTED TO 80,000 YARDS

MAIN SWEEP ADJUSTED TO 50,000 YARDS

·~~

Figure 17-Main Sweep Views Long Range Targets.

CQbi~IPEbiTI .._ 13 vr 10"10 G Precision sweep is a nominal interval of main sweep which may be selected by the operator for accurate measurement in the area portrayed. On this sweep, the operator can also view out to the full range of the equipment, but only in small segments. He chooses these segments by using the range crank in the manner of a win dow roller shade to control the movement of the -r, field that is visible on the scope. See figure 18. A-scopes. A-scopes present range data. On in dicators of this type the .range-determining mechanism works in conjunction with a mov able break in the trace that is known as the 2.000 range step. See figure 19. Range is constantly YDS . measured to this step. When a target echo is received, it appears in the form of a pip or spike along the trace or sweep line. An echo is said to be "gated", figure 19, when the range step coincides exactly with the left or leading edge of the target pip. At the same time there will be a drop in amplitude of the target pip and of all other echoes and "grass" along the YDS. sweep line due to action of automatic gain con trol. Range is then read accurately on a counter or measured on the tube face by means of elec tronic range markers. A modified form of the A-scope is the AIR scope u·sed for accurate rangefinding. The AIR scope presents a main sweep and a precision sweep simultaneously on the same indicator. A typical AIR-scope is shown in figure 20. -r, The lower A trace in this example, extends from 0 to 30,000 yards. Scribe marks on the scope face indicate 10,000-yard intervals. The range notch is movable and can be set on the target pip. The upper R trace is the expansion of the A trace; it extends 500 yards on either side of the range notch, its total length thus represent ing 1000 yards. The range step remains fixed near the center of the R trace and coincides in range with the range notch. Echoes from sta tionary objects and 1000-yard range markers (only one of which is visible at any time) move past the range step as the range notch moves figure J 8-Precision Sweep Views along the A trace. Segments of Main Sweep. Some A-scopes are used to obtain accurate bearing data. This is accomplished by lobing and pip matching. In lobing, the radar beam is transmitted alternately from each side of the

14 08UFI81!14'b:l(f! PRACTICE OF THE FIRE CONTROL RADAR ART

rARGET UNGATEO TARGET GATED

' -, ,' \ · ---- -~--- -4'* ----_ ___.. I __- \ I ' I

figure J9-A-scope.

PIP FROM ANOTHER TARG ET

RANGE STEP ------

PIP FROM ANOTHER TARGET

figure 20-A/R-scope.

COb'E'PSb'TI 'Is 15 OP 1895

LEFT LOBE~ ---

RIGHT LOBE

Figure 2l-Pip Matching with A-scope.

B-SCOPE E-SCOPE

Figure 22-B-scope and E-scope. 16 CONf!tO!I\ I fJitl PRACTICE OF THE FIRE CONTROL RADAR ART antenna centerline, and the returning echoes produce a double indication of the target on the A-scope, as shown in figure 21. If the centerline of the antenna is not on the target, the indica tions or pips will differ in height. To center the antenna on the target, and thereby obtain accu rate bearing data, the operator must train the antenna until the pips are matched in height.

B-scopes. B-scopes are used as all-purpose dis YDS. MAIN SWEEP plays to determine the range and bearing of point targets, or groups of targets, when little or no importance is attached to the shapes of extended targets, or to the relative locations of widely separated targets at close range. PRECISION SWEEP Whenever the radar equipment views a tar get, the echo from that target appears as a -41,000} - 40,000 YDS. bright spot in the B-scope as typified in figure 22. The vertical center lines coincide with the ~- 39 , 000 director line of sight. When the field of view - starts at zero range, the wide horizontal line at the bottom of the scope marks the trans 31,000} mitted pulse. All ranges are measured upward - 30,000 YDS . from this horizontal line to the movable range 29,000 mark, a narrow horizontal line. The B-scope does not show the true plan view relationship of a group of targets but displays a picture somewhat distorted in range and bear 21 ,000 } ing. However, neither kind of distortion in any 20,000 YDS . way affects the accuracy of range and bearing 19,000 determination of a specific target, the echo of which is properly centered on the range and bearing lines. Range distortion which is usually insignificant, is due to the fact that arcs of 11 ,000} circles, drawn with own ship as center, appear 10,000 YDS. on the scope as straight lines. Bearing distor 9,000 tion in a B-scope should be understood because all targets in the scanned sector will appear on the scope in a distorted plan view. _;...-~.; ~ \\!=-.... Figure 23 illustrates this distortion. Three ~;; s target ships, each 2000 yards apart, are ap ~t; ·::.:" proaching the ship carrying the radar, in straight, parallel courses. As they advance, the Figure 23-Distortion on 8-scopes. pips indicating the two outside ships will di verge until they leave the screen at 20,000 yards while the center echo will continue along the center bearing line. Thus, a wedge-shaped sector of the earth's surface is displayed on the scope as a rectangular area.

17 POSITION 2

I I

POSITION l

POSITION 1 POSITION 2

•

Figure 24-~E -scope. 'Q8t4FI81!1 ff'IM: , <:gNE'DBm • • PRACTICE OF THE FIRE CONTROL RADAR ART E-scopes. The E-scope, see figure 22, dis plays range horizontally and elevation verti cally. Range is shown by the horizontal dis placement of the target indication from the left side of the scope. Elevation, with respect to the axis of the antenna, is shown by the vertical position of the target indication in the present ation. In the basic E-scope the presentation remains stationary across the center of the scope. In the 6.E-scope the presentation moves from the bot tom to the top of the scope as the antenna is elevated as shown by positions 1 and 2 of figure 24. Graduations on the scope face provide a means of measuring the elevation of the an tenna. In some radar equipments the 6-E-pres entation is normal, while the basic E-scope is termed an expanded presentation. The range mark appears as a bright vertical line, the width figure 25-Double-E scope. of the elevating trace, whereas the target echoes appear as short vertical lines. The translucent can be brought to the horizontal crossline on the face may be marked off in degrees of elevation. face scope, thus centering the target in eleva The Double-E scope, figure 25, shows range tion. and elevation in a similar manner. However, J-scopes. The J-scope provides range data the indication is shifted back and forth in step only. In the J-scope the time-base line appears with the moving beam, thus producing two pips. as a circle, representing either a long-range One pip represents the strength of the echo main sweep or a short-range expanded sweep, picked up in the right vertical half of the radar as selected by the operator. The target pips beam orbit (usually on elliptical scan) ; the appear as radial deflections (1, 2, and 3, as other pip represents the strength of the echo shown in figure 26) which can be matched by a picked up in the left vertical half of the orbit. mechanical pointer against range markings on If the antenna axis is to the right of the tar attached concentric scales. get, a stronger echo will be picked up in the left half of the orbit. Conversely, if the axis is to ENGRAVED 6000 the left of the target, the right half of the orbit CIRCLE will pick up the stronger echo. Most radar POINTER equipment is wired so that the target echo from the left half of the orbit appears as the right pip on the scope, and the target echo from the right half of the orbit appears as the le:it pip. 9000 Thus, by moving the antenna in the direction of the weaker of the two pips until each is of equal intensity, the axis of the beam can be brought to the same bearing as the target. And similarly, the elevation position of the target above or below the horizontal axis of the an tenna, can be determined by noting the position CIRCULAR TARGET of the target pips with reference to the hori TIME BASE PIPS zontal graduations on the face of the scope. By elevating or depressing the antenna, the pips figure 26--J-scope. (M>tlliiiBEt likhtl 19 OP 1895

....._ ------~-o· ~ --- ____ .- , ~-- _-:--- it,~------~-~\---

/ 180"

Figure 27-PPI-scope.

PPI-scopes. The PPI (plan position indi T&E-scopes. In the T&E-scope (train and cator) presents a plan view of the area around elevation scope), shown in figure 28, a target own ship. Targets appear at bearings and pip does not appear on the screen until the echo ranges relative to own ship. The result is a map, has been gated. Instead, a circle is centered on the cross-hairs. When the range operator gates as shown in figure 27. a target, the circle changes to a spot and moves to a position on the screen which corresponds Although the origin of the PPI sweep is to the position of the target relative to the axis usually at the center of the cathode ray tube, of the antenna. The director pointer uses the thus giving an equal field of view in all direc target spot of a T&E-scope for blind tracking tions, it may be displaced far off the tube face, in the same manner that he would track a vis in order to give a maximum expansion to a ible target with a telescope. He moves the direc particular region. An indicator of this type is tor in train and elevation until the centering of called an off-center PPI; it shows a sector the spot on the cross-hairs indicates that the display. antenna is on the target.

20 edi~HdEmT.i([ .. Q&t4P'Ibd\ I IJQ&a PRACTICE OF THE FIRE ·CONTROL RADAR ART

7 '

-~\ I \ I ---- ' '

TARGET OUTSIDE OF SCANNED AREA

TARGET ON EDGE OF SCANNED AREA OFF IN BEARING AND ELEVATION

I', N I \

\ I ------~'..... ,'

TARGET WELL WITHIN SCANNED AREA OFF IN ELEVATION

17 ' I \ ~

\ I ------~'... /

ON TARGET

Figure 28-T&E-scope. 'Sfi't JPI8!1 ITII\L 21 OP 1895 ceJMf!iDENTIAL

TRUE ELEVATION - 40•

ANTENNA IN SPIRAL SCAN

t:. E-SCOPE

A/R SCOPE B-SCOPE

RANGE

RANGE EXPANDED BEARING

figure 29-Scope Comparison of Same Radar View. 22 get •r1121 c1 Bt!t:t JVOt 15ill84'1z'cla PRACTICE OF THE FIRE CONTROL RADAR ART

Figure 30-Angular Width ol Target Varies with Range.

Evaluating Scope Indications covered by this spiral scan appear on the "A" Most radar equipments employ several types sweep and on the E-scope. T5 does not appear of scopes, each contributing part of the required on any scope because it is outside the scanned target data. An understanding of the contribu area. Tl does not appear on the B-scope because tion made by each type of scope is best gained it is more than 1000 yards from the range mark. by comparing the presentation of each for the Targets Tl and T4 do not appear on the "R" same target, or targets, as shown in figure 29. sweep because they are not within the ranges covered by this precision sweep. Scope Comparisons. The example shown in Interpretation and Judgment. The size and figure 29, compares the presentation of the same shape of the scope indications can often tell a targets on an AIR-scope, a B-scope, and a skilled operator a great deal about the targets E-scope with the equipment in spiral scan and from which the echoes were reflected. Changes having just acquired target T3. Therefore the in range, size of target, target angle, and re pip from T3 is at the beginning of the range ceiver gain will alter the shape and size of the notch in the "A" sweep, at the step on the "R" target pip. For example, as the distance to the sweep, at the center of the trace in the E-scope, target increases, the angular width of the tar and at the center of the B-scope. All targets get and its echoes decreases. See figure 30.

C?tiE!OEtln *i 23 L _/~3 LINE OF SIGHT ----- TARGET ANGLE 00 ------·--I ~...,..., ..

------TARGET ANGLE 315' ------

figure 3J-Target Aspect Alters Appearances of Pips.

24 t;Qb'F'PB lil.t .. PRACTICE OF THE FIRE CONTROL RADAR ART

A change in target angle will bring about a extends the range limit of radar equipment well similar result, shown in figure 31, that demon beyond the horizon if the transmission path is strates how aspect alters the signal return from nearly horizontal. an object. Here, using a ship as a target, two Substandard as well as superstandard radar superimposed echoes may appear at slightly dif ranges also can be caused by such refractive ferent ranges for target angles of 00 and 180 anomalies. For example, attenuation resulting degrees. For target angles of 090 and 270 de from precipitation or water vapor occurs as a grees, one long echo will appear. At all other result of absorption and scattering of energy angles, two or three fairly distinct, overlapping out of the beam by raindrops, sleet, snow, etc. echoes may appear. These different echoes may result from the reflections from the bow, the This phenomenon, which extends or limits the superstructure, and the stern. As range in range of radar sets, is called "trapping". The creases, the bow and stern masses will return conditions which cause trapping are invisible weaker echoes and may eventually fade out. On and often mislead radar operators into false most radar equipments, the superstructure of evaluations of the overall performance of their a battleship will reflect radiation from as great equipment, especially when long range targets a range as 50,000 yards. Awareness of these are used for performance checks. facts permit the skilled operator to detect a An even more serious operational conse change in target angle from the change in the quence of trapping involves security of radar size and appearance of the echoes. transmissions. When certain stratification is Stratification and Trapping. Radar data in present, a duct is formed which aids radio en terpretation is also affected by unpredictable ergy transmission so that the enemy may inter cept both radar pulses and VHF communication · irregularities in the range of radio energy prop agation. Radiation, at the wavelengths used by at far greater ranges than normal. This possi most radar sets, theoretically travels in straight bility should be kept in mind constantly when a vessel is operating in waters where trapping lines. Although it would seem that the range is known to be common. limit is therefore the horizon, in practice it is found that horizontal stratification of the at Resolution. Resolution may be defined as the mosphere of the earth causes refraction of radio ability of a radar to discriminate between two energy rays. These rays usually are bent down or more targets in the beam, so as to permit ward so that they tend to follow the surface of tracking and ranging on a single target to the the earth more closely. Certain stratification, exclusion of other targets. Resolution in range which is caused by surface evaporation, seems depends upon pulse length and gate width. Reso to exist most of the time over large areas of the lution in bearing (and elevation) depends upon oceans of the world. This stratification often beam width.

25 OP 1895 CQUFI8EIUihh

figure 32-Range Resolution of Targets at Same Bearing.

SCANNED ARE.A

figure 33-Bearlng Resolution of Targets at Same Range. 26 OQt lliiiBZIQ I IXL - CQt IFIBP!I tTIJ ,L PRACTICE OF THE FIRE CONTROL RADAR ART

Resolution of targets at the same bearing FTC passes individual echo pulses with some but different ranges is illustrated in figure 32. differentiation by greatly attenuating long jam As the radar pulse moves out from the antenna ming pulses within certain frequency ranges. it strikes target Tl. Before leaving Tl it also This differentiation circuit, however, is of no strikes T2, since the latter is less than the pulse value if the receiver is overloaded by strong length beyond Tl. A single echo is therefore signals. When such overloading occurs, the sen returned to the receiver from Tl and T2, pro sitivity of the receiver must be reduced. As long ducing only one target pip on the scope. As the as the jamming signal is of constant strength, pulse continues beyond the first two targets and manual gain control is satisfactory to accomplish strikes T3, a separate echo for T3 is returned to the sensitivity reduction. However, if the radar the receiver because this target is separated antenna is scanning, or if the jamming signal is from targets Tl and T2 by a distance greater modulated, IAGC is used because it provides an than the pulse length. instantaneous and automatic method of com However, it is not possible to track in range pensating for variation in the strength of the unless one target echo is gated and others are echo signal. kept outside the range gate. Generally, radar sets employing a narrow Resolution of two targets at the same range beamwidth and short pulse lengths are com but at different bearings theoretically requires paratively difficult to jam. Such equipments the targets to be separated by approximately receive radiation from a relatively small portion one beamwidth. This problem is illustrated in of space and, for that reason, are not affected by figure 33. Since targets Tl and T2 are separated electronic jamming unless the jamming is initi by less than one beamwidth, the radar beam ated at or near the target. Furthermore, sharp strikes both targets simultaneously, returning a beams comprising pulses of short duration are single echo and producing a single target pip on effective against "window" or "rope" metal foil the scope. As the beam continues its scanning dropped from the air to create false signals and motion it leaves these targets and strikes T3, confuse the radar. which is more than a beamwidth from either Tl Neighboring Radars. Other radars operating or T2. T3, therefore, returns a separate echo and at the same repetition rate and frequency, either produces a separate pip on the scope. · on own ship or accompanying ships, may cause interference. This interference takes the form Interferences and Corrective Measures of multiple sharp pips, as shown in figure 34, The reception of unwanted echoes from many actual targets is not the only difficulty en countered in radar data interpretation. Other types of extraneous radiation will impair the effectiveness of the radar. These interferences may be man-made or natural. Man-made interference includes intentional jamming by enemy action. Accordingly, many receivers are equipped with antijamming provi sions. If tuning the receiver or the entire trans mitter receiver system to another part of the band does not reduce the interference by avoid ing the jammed frequency, the operator may be able, depending upon the design of the equip ment, to change the repetition rate of the trans mitted pulse or choose one or more of the following receiver circuits; FTC (Fast time con stant), or IAGC (Instantaneous automatic gain control). Figure 34-lnterference from Other Radars. 27 32 3489 0 - 54 - 3 OP 1895 travelling across the screen in either direction. by interfering radars that operate at the In some cases these indications may be elimi same repetition rate, figure 34. Furthermore, nated by changing the repetition rate, or by when propeller modulation is present during changing the operating frequency. However, the automatic radar tracking, it causes the radar radar can be operated effectively with this inter antenna to "hunt" in train and elevation. Never ference present because the characteristic pat theless, such interference occasionally can be tern is unchanging and is easily recognized. useful in helping to determine whether a target is a single or multi-engine aircraft. Close-in Targets. Another form of interference is caused by strong echoes from nearby targets. Geographical and Atmospheric Conditions. These echo signals appear on the indicator Land, rough sea, and storm clouds reflect a con screens as "double echoes", due to the fact that siderable amount of radio energy and therefore the reflected energy from the target may hit can interfere with detection of objects which are own ship and then be reflected a second time viewed by a radar against such backgrounds. In from the target ship. This second echo will some areas, electrically charged clouds and thun always appear at twice the range of the original derstorms are common and may produce indica target echo, and may be distinguished by ob tions on the scope which are most often charac serving its appearance and range as compared terized by the unsteadiness of the echoes. See with the original echo. figure 35. Extraneous signals of this type, that would Merging Targets. When tracking a target with tend to clutter up the indicator, are eliminated an automatic tracking radar, the tracking cir in most radar sets by a "sensitivity time con cuits may lock on a stronger echo which may trol'' (STC). This is a circuit which reduces the merge with the desired echo. For example, an receiver sensitivity considerably at the instant enemy aircraft target, while making an attack each pulse is generated and then allows the may attempt to fly close to a friendly vessel. The sensitivity to return to its normal value as the tracking circuits will follow the target echo until echo pulse is received. it merges with the stronger echo of the friendly vessel. The tracking circuits may then lock on the stronger pip, losing the target and endanger ing the friendly vessel. To prevent the tracking circuits from locking on the wrong echo, the radar operator may press a "coast" button just before the target echo merges with the interfering echo. This "freezes" the tracking rates at the rates prevailing when the button was depressed. As soon as the inter fering echo is left behind, the button is released. If the target has not greatly changed its course and speed, the generated rates should keep the beam close enough to the target for the auto matic tracking circuits to lock on target again. Propeller Modulation. A possible source of error in bearing and elevation measurement is propeller modulation of the received signal. This type of interference results from partial syn chronization between the propeller speed of a target aircraft and the scanning rate of the radar. Such a phenomenon causes random move ment of the spot on a T&E-scope or is seen on Figure 35-Thunderstorms or Electrically other scopes as a pattern similar to one caused Charged Clouds .

28 .Q&IIi Qz:tq I tAL Cfiila tFii rat 4fls\b::a. PRACTICE OF THE FIRE CONTROL RADAR ART

- - --:--+------

Figure 36-Water Reflections Produced by Low-angle Target.

Any unwanted signals that are returned from second reflection from the surface of the sea, at close range are therefore not permitted to affect some point between own ship and the target. the indicator circuits. However, the STC has a See figure 36. Certain radar equipments are disadvantage in that its controls must be ad designed specifically to discriminate between .. justed manually for varying conditions. these signals and thus provide accurate eleva Low-flying Targets. Air targets such as tor tion determination at low position angles. When pedo planes, approaching over water at angles a radar set cannot provide the required eleva of less than approximately one degree of eleva tion accuracy, the elevation rate which is nor tion, as viewed by the radar, will produce in mally transmitted to the computer is cut out accurate elevation indications because of radio or reduced to zero, thus preventing the genera energy reflections from the surface of the sea. tion of erratic elevation rates. Even roughness of the sea may be a determin Land Echoes. Land masses may interfere ing factor here. with the detection of both air and surface tar In certain ~ases, two elevation signals will be gets. These land masses produce echoes which received from a single target, one reflected blanket low-flying air targets or surface targets directly from the target and the other by a near shore.

29 OP 1895

(A) AIR TARGET APPROACHING LOW OVER SHORELINE WILL NOT BE DETECTED BECAUSE OF LAND INTERFERENCE. LAND ECHOS AND PLANE ECHOS WILL BE AT SAME RANGE.

(B) PLANE APPROACHING OVER HIGH SHORELINE MAY BE DETECTED BY POINTING HIGH, SO THAT LOWER EDGE OF BEAM IS JUST ABOVE LAND. THE TARGET CAN BE TRACKED IN RANGE AND BEARING.

(C) WHEN THE PLANE HAS REACHED A POSITION WHERE ITS PIP DOES NOT MERGE WITH THE SHORE LINE INDICATIONS, THE PLANE CAN BE TRACKED IN THE NORMAL MANNER.

figure 37-Detecting Low-angle Target Approaching over Shoreline.

30 eei4Pi~ Axr: Glit 4P'I8Et Iii hi PRACTICE OF THE FIRE CONTROL RADAR ART

•

figure 38-Targets within Coastline Area are Obscured. In the case of air targets flying over land the opposition's radar and thus facilitates jam- masses, the operator may be able to eliminate ming by mechanical ?r electronic me~ns. the land echo by elevating the antenna so that Mechanical jammm~ of radar _Is usually the lower edge of the radar beam barely clears accomplished by dr?ppmg m~tal fml from the the land. See figure 37. air to reflect false signals which clutter up t_he indicator. This foil, often called "rope" or "wm- The echoes of surface targets near shore may dow" usually can be combatted effectively if be obscured by a shadow area created by the the ;adar's pulse length is shortened. Radars land mass. Interference from a low, flat sh?re- with narrow beams are usually more effective line may be eliminated by reducing receiv_er against "rope" than those with broad beams. sensitivity so that the ta.rget echo may be dis- Electronic jamming is produced by the trans- criminated from the relatively weak land echoes mission of strong signals at the operating ire- appearing on the scope. However, very rugged quency of the radar being jammed. These coastlines present particular~y strong and trou- signals clutter or saturate the receiver circuits blesome land echoes. DetectiOn of surface tar- and make recognition or tracking difficult, if gets near such coastlines is dependent upon the not impossible. angle of radar view, because the depth of the Since an enemy has no means of gauging the shadow area varies with this angle, and upon effectiveness of his jamming other than by the distance of the target from the shore, as intercepting the signals and observing the oper- illustrated in figure 38. ation of the jammed radar, it often is desirable ;e to continue operation of the radar, even when Radar Countermeasures. In most instances, scope pictures are unintelligible, in order to the enemy will attempt to prevent radar recog- deny the enemy the knowledge that his jam- nition and radar-directed fire by employing ming is successful. This policy of continued radar countermeasures. These countermeasures radar operation has the effect of immobilizing comprise any means employed to obtain infor- the enemy jammers on a particular frequency, mation about an opposing force by interception thereby increasing his need for more jamming of its radar and any means used to thwart equipment if all frequencies are to be blocked. radars which are seeking target information. Radar may be deceived by reflective floating Interception of radar beams forewarns of the decoys. This deception often is used to ~imulate presence of other vessels or planes carrying submarine periscopes. However, ~n ~bJect can radar. It also reveals certain characteristics of be revealed as a decoy by comparmg Its plotted

&II h ibti$11AC 31 OP 1895 eoMFIDEIQ I IAL: track with the speed and direction of the sur Spotting Surface Gunfire face wind. When the track of an object, which Fleet experience has proved the value of appears to be a periscope or schnorkel, is un radar for spotting shell splashes in range and related to the velocity and direction of the wind, the target must be regarded with suspicion deflection. With certain equipments, radar spot until its identity can be established. ting, even at long ranges, is accurate and reli Thorough training in recognizing false sig able. Radar makes fire control independent of nals and reading through jamming, is the the conditions of visibility; blind spotting is soundest measure against deception. possible with blind firing. • ---

SHELL ~ SPLASH ' ------\~TARGET ~ .(., ;------1 - I - -:1,./1 ~ I I - DISTANCE I I ~ SHORT4 f----i AIR SCOPE

Figure 39-Radar Spotting.

•

B·SCOPE

Figure 40-Salvos Produce Multiple Echos.

32 cer~rtr5!14 1tAt Q&it JJii8Er4'flsJtb PRACTICE OF THE FIRE CONTROL RADAR ART

Spotting does not entail tracking the projec Deflection Spotting. The measuring stick used tile. The radar tracks only the target, because in deflection spotting is one beamwidth. It is attempts to range or train on the splash echoes assumed that an average splash echo is 18 mils wide in the example shown in figure 41. interfere with the smooth transmission of tar Deflection spotting is based on the relative get range and bearing. When a gun is fired, the proportion of a splash echo which appears on return of radio energy from the projectile either side of the bearing center line. View "A" produces a small, weak, moving echo which of figure 41 shows that with zero deflection appears initially at the minimum range on the error, the splash echo is bisected, i.e., approxi scope and moves out toward the target pip. If mately 9 mils of the echo are on either side of the projectile stays within the vertical limits the center bearing line. Views "B" and "C" of figure 41 show deflection errors which have been of the radar beam, its flight to the point of estimated by determining those fractions of the .. impact can be followed on the scopes of most splash pips that appear on either side of the radar sets on main or expanded sweep. At the center bearing line. point of impact, the echo stops moving and grows larger as the splash builds up, figure 39. A -50 MILS 0 +50 MILS Shell splashes appear on B-scopes as fluctuat • • • ing echoes which last up to several seconds, • • depending on the range to the target and the • • • - ~ size of the projectile. The large column of water • • • thrown up by a shell produces a single echo, • /~· whereas salvos produce larger or multiple • • echoes as shown in figure 40. Echoes from shells which fall directly on a target usually are lost I I ZERO DEFLECTION ERROR in the target echo. Salvos which straddle the target may envelop the target pip in a mist of B splash pips on the scope. Splash pips are most • • • widely separated by a precision sweep. There • fore, precision sweep is generally used for all • • • spotting. --- ~ -- · ---- ///// Range Spotting. The length of the echo (nom • • inally 100 yards) is used as the measuring unit • • • • in range spotting. The true length of the echo ERROR - 3 MILS RIGHT on individual equipment indicators should be determined before firing commences. Since the thickness of the range line itself may represent c as much as fifty yards in range, the radar tech nicians adjust this line so that it will be as thin • -·• • as possible. Operators, and others who do radar 't • • • spotting, determine the range in yards covered ~ • ~ ------by the precision sweep of their equipment. • /f// . • Splashes which are over or short of the target • . ....• are easy to spot by estimating the position of • • • the echo on the scale established by the nominal ERROR - 9 MILS LEFT distance from the range line to the top or bot tom of the scope. Figure 41-Deflection Spotting. C&J .P'I5EI 4 l'tfrL 33 u¥ I 41 IDEI 41 IAL

figure 42-Salvo with MPI at -603 Yards.

•------3000YARDS------~1 Ii-o•------1000 YARDS ·I· 2000 YARD TEST INTERVAL ~ --~------

figure 43-Determination of Initial Velocity by Radar Tracking.

34 Q lilJ 14flb8G I IJI

Spotting Salvos. When salvos are spotted, several echoes (single or merged) usually are visible on the scope at the same time. With large salvos, shells often fall so close together that individual splashes cannot be distinguished. However, the MPI (mean point of impact) of salvos, which is the point that marks the average distance from the target of all shell splashes, can be spotted in a manner similar to the method used to spot single splashes. The error in deflection of the MPI is estimated from the appearance of the splashes on the B-scope. Figure 42 illustrates the MPI of salvos and the corresponding estimate of deflection error. Radar Chronograph The radar chronograph furnishes a means of determining actual projectile initial velocity at the time of firing. Such determination was for merly made by estimates of the various factors governing I. V. Radar makes possible the meas urement of the velocity of a projectile during flight under service conditions. In those fire control systems that employ the chronograph, the radar tracking unit locks on the projectile echo during flight, and an asso ciated timer unit measures the time elapsed while the projectile travels over a specified in terval (2000 yards as illustrated in figure 43) between two ~ed range points. To find the de sired I.V., it is necessary to compare the calcu lated average velocity with the average velocity under standard conditions. (This value can be determined from range tables.)

... Radar Charting for Shore Bombardment Radar equipments with type B presentations and good discrimination are especially suited to " problems of shore bombardment. However, it is much more difficult to interpret scope patterns of shorelines and shore targets than it is to interpret individual echoes from surface tar gets. The range discrimination, bearing discrim ination, distortion, sweep time, and receiver sensitivity setting of a radar equipment are all factors which affect the shoreline pattern Figure 44--0R-shore Reference Points lor Shore Bombardment. shown on a B-scope. One method of using radar for shore bom bardment involves the use of offshore objects as reference points, as illustrated in figure 44.

C&'t IFiiEt l'lz'IP 35 OP 1895 ceunaEm IAt

BEAM WIDTH LAID OUT ON NAVIGATIONAL CHART

MILS + 100 75 50 25 0 25 50 75 100 1,000 800 600 + 400

600 800 1,000 WITH REDUCED GAIN NORMAL GAIN

figure 45-Radar Charting.

36 CQNf1QfNI'AJ PRACTICE OF THE FIRE CONTROL RADAR ART Such objects-rocks or isolated lighthouses, for gain) is shown in the lower left-hand corner of example-may be picked up on the B-scope by figure 45. It should be noted that with normal reducing the receiver sensitivity until these gain the echo from the reference point is not objects appear as separate echoes. discernible and the shore shadow area is in creased. Then, if the relative positions of the offshore objects and the desired shore targets are shown on an accurate navigation chart, the radar bear Radar Beacons ing and range data can be used as a reference Radar beacons are used to provide accurate point for offset firing. reference points for shore bombardment. These Another method involves preparation of a beacons consist essentially of a receiver, which radar chart, from navigational charts and other picks up transmitted pulses, and a transmitter, similar data, which will show the probable ap triggered by the output of the receiver. Upon ~ pearance on the B-scope of a shore which is to triggering, the beacon transmitter sends out be bombarded. coded signals to be detected by an interrogating A radar chart is based on various positions of ,radar set. These beacons are usually carried the ship on its bombardment course. Prominent ashore by landing parties and put into opera objects and landmarks are marked on the chart tion near the target area. When triggered by and copies are given to officers and operators pulses from the ship's radar, they transmit for reference during the approach. Thus, it is coded signals which establish their identity and possible to brief and coach operators in the position. By use of these positions, offset firing appearance on their scopes of the target area is then employed to bombard the target area. previous to the action. The ranges and bearings of objects on the charts can be readily obtained Radar Navigation and unexpected targets, such as ships offshore or in harbors, can be discerned. Search radars are generally employed to aid navigation at night or in fog-bound waters. An example of the preparation of a radar Occasionally, the search radars may fail, or cir chart is illustrated in figure 45. A beam approxi cumstances may require that own ship's posi mating the radar's scan (11.5° in the example tion must be determined more accurately than illustrated) is laid out to scale on a navigational is possible with search radar. Fire control chart from the position at which the ship will radars may then be employed to give ranges be when the chart is to be used. In this example, and bearings on neighboring objects. In navi the reference point is a large metal seaplane gating narrow channels at night, radar sets hanger at the shoreline. with low minimum ranges may be used to par ticular advantage because they can furnish " The outer and inner range lines on the chart accurate positional data on isolated buoys and represent the. limits of the areas covered by the rocks. precision sweep of the radar. This interval is subdivided by other range lines. For conven Radar sets which are designed particularly ience in plotting, the 11.5 degree sector is for detection of low-angle targets are often divided by 25-mil bearing lines drawn on the excellent navigational aids for the detection of chart. Thus, each small block represents 200 small icebergs, which show only 5 or 10 feet yards in range and 25 mils in bearing. For dif above the water, and growlers (chunks of ice ferent ranges or chart scales, other convenient so small that they rise and fall with the motion values can be used, based upon the scanning of the waves). area covered by the particular radar. However, if the fire control radar equipment Next, the shore outline which will be observed is used for navigation or for search and early on the precision sweep is plotted. The appear warning, the life of the director roller paths, ance of the shoreline on the scope (with reduced train motors, etc., may be decreased. 37 Ul" IHY!)

Corner Reflectors beacon interrogation and coded response which It is often desirable to increase the radar identifies on the radar screen those echoes that reflecting properties of various objects, to make are returned from friendly ships and aircraft. their echoes stand out more clearly on indicator A simplified diagram of an IFF system is shown screens. This effect can be accomplished with in figure 47. Because it depends upon direct corner reflectors. See figure 46. pulses rather than reflected pulses, IFF also aids in determining the range and bearing of These reflectors aid a mother ship in keeping friendly craft at distances greater than the track of landing craft and may prevent these smaller vessels from being run down when vis maximum normal operating range. ibility is poor. Corner reflectors are also used Ships or planes which are equipped with IFF on target rafts, on buoys to aid radar pilotage can also produce distress calls on the radar screens of other vessels by radiating an excep along a channel, and on meteorological balloons to aid radar tracking. tionally wide emergency signal. Emergency Uses of Fire Control Radar Identification, Friend or Foe During conditions which require radar si IFF, an abbreviation of "Identification, Friend lence, most radar receivers may be operated as or Foe", is primarily a system of automatic direction finders. Received signals can be maxi mized by manipulation of the receiver coarse and fine tuning controls and by training the antenna. Some radar equipment can be operated for two-way code communication by means of a telegraph key for transmission and a headset for reception. A transmission speed of no more than ten words per minute is used under these conditions. Radar equipment also is useful in forecasting the weather, since abnormal atmospheric condi tions are reflected in scope presentations. In an figure 46-Corner Reflectors Increase emergency, fire control radars equipped with Reflecting Properties. PPI's or B-scopes may be used for this purpose.

DIRECT BEACON PULSE, IN FORM OF CHALLENGE SIGNAL, AUTOMATICALLY INTERROGATES TRANSPONDER ON AIRCRAFT

----

PROPER CHALI,ENGE SIGNAL TRIGGERS TRANSPONDER TO TRANSMIT CODED REPLY TO INTERROGATING RADAR figure 47-lff System, Block Diagram. 38 CQtJIEI?III I tAr C~!EI_DSNQA,L

PART 2-EQUIPMENT DATA

Chapter 3

RADAR EQUIPMENT MK 8 MODS I. 2. 3

Radar Equipment Mk 8 Mods 1, 2, 3 is used of the area beyond this range to a limit of in conjunction with Gun Directors Mk 34, fig 60,000 yards. ure 48, and Mk 38 for control of 6-, 8-, and 16- The functional arrangement of Radar Equip inch guns. The radar accurately determines ment Mk 8 is shown in figure 49. Detailed char range and bearing of surface targets to a dis acteristics of this radar are given in Part 3, tance of 44,000 yards and permits observation Reference Data. ..• :r.

figure 48-Antenna for Radar Equipment Mk 8, Shown on Gun Director Mk 34.

~-~ tJIIIt IEJ U 39 Ut' I ts'f!>

RF TRANSMITIER ANTENNA r- RECEIVER I

TRIGGERJ BEARING LINE ~ PULSE .... ! ...J ""::I VIDEO AUXILIARY "- MODULATION "- r GENERATOR INDICATOR .... :t "" (.?z ex ,... I BEARING ~ PULSE AUXILIARY CJ) ) INDICATOR

IF TO VIDEO "-+ AMPLIFIER

AUXILIARY INDICATOR VIDEO ABOVE DECKS

BELOW DECKS SYNC PULSE

RADAR SYNC PULSE SELECTOR SWITCH CONTROL ~ INDICATOR VIDEO

VIDEO AND DEFLECTION CONTROL l SYNC PULSE ....0 c RANGE PULSE > I COUPLING COUPLING RANGE AMPLIFIER AMPLIFIER UNIT

I . (MECHANICAL .• SHAFT) .•

PULSE RATE AUXILIARY RANGE RANGE TO I""" CONTROL UNIT INDICATOR TRANSMITIER RANGEKEEPEif MKS

VIDEO

figure 49-Radar Equipment Mk 8, functional Schematic.

40 OQt lfiBLFfi lOMe' CQb'Fiillit li*t.L EQUIPMENT DATA

figure 50-Antenna Assembly, Front Open.

Operational Units per second. An 11.5-degree sector can be cov ered by the scan without movement of the gun Radar Equipment Mk 8 Mod 3 is in greater director. The operator can substitute a dummy use than Mods 1 and 2. It comprises a number antenna and an echo box for this antenna so of major units which are in general located at that the performance of the equipment can be forward and after main battery gun directors, checked in radar silence. the main battery plotting room, and after fire I A locking pin permits locking the antenna in control station. Additional units are located in the "dead ahead" position. Other controls in the the fire control tower or forward fire control antenna assembly are a cut-off switch, which station. disconnects power from the antenna motor, and The location of the various radar units will a manual operating knob, provided for emer vary with the type and class of ship, and with gency operation of a waveguide switch. The the type of main-battery gun director. In most transmitter-receiver is bolted to the inside of installations a control ind.icator and auxiliary the gun director. .. indicators with type B presentation are pro The radar operator's station in the plotting vided in the gun director, in main-battery plot, room or fire control station contains the main and in the fire control tower or fire control control indicator, figure 51. This indicator, stations. The center, or zero bearing line on which is used by the range operator, is a B-scope these indicators represents the bearing line of with a five-inch screen. On a main sweep, the the radar antenna on top of the director. This operator can view out to 60,000 yards, although antenna is accurately aligned with the director actual range measurement by the range unit is line of sight so that a target is brought to the limited to 44,000 yards. Expanded sweep pro center line by training the director. Tracking duces a scope picture of from zero to 20,000 in the range coordinate then can be controlled yards. Precision sweep extends to 44,000 yards, from the director, from the plotting room, or but only a 2000-yard segment is visible at any from a rangekeeper. one time. In addition to the standard scope con trols on this indicator, there are a switch which The antenna on top of the director, figure selects either the radar or the dummy antenna, 50, rocks horizontally back and forth five times a zero-range correction knob, and a knob for each second, thereby accomplishing ten scans adjustment of receiver gain.

881 trt1!M!UTIJ it 41 OP 1895 oer.Aam 1IXr

POWER CONTROL UNIT RANGE UNIT CONT'L INDICATOR

figure 51-Radar Operator's Station, Typical Arrangement.

Five identical auxiliary indicators are pro In the plotting room, a power control unit vided. See figure 52. These repeat the B-scope provides a central operating point for the dis presentation of the main control indicator on tribution, measurement, and control of power three-inch screens in the director, in plot, and to the various other units. The switches and in the fire control station. The sweeps on these controls on or behind the panel of this unit screens are controlled remotely by the sweep govern the power conditions of the radar equip switch on the main control indicator. ment from secured through standby and oper The location of the range line on the scopes ate. is indicated on a range counter in the plotting room range unit. The radar range operator Operating Personnel there signals the rangekeeper operator that a The radar crew, except for the two. range target is accurately ranged by pressing his operators, is part of the director crew. A listing range mark key. The rangekeeper operator man of the crew and their principle radar duties ually transfers these range readings to the follows. rangekeeper. The range unit setting also is transmitted automatically to range indicators Control Officer. at the rangekeeper's station, in main battery 1. Determines and orders the type of range plot, in the gun director, and in the fire control tracking to be employed tower or fire control station. 2. Spots gun fire as required.

42 cet lrma'Jiht G?tllii8Et4'h\b EQUIPMENT DATA

Trainer. 1. Trains on target in bearing 2. Spots gun fire as required.

Typical Operating Procedure In typical operations with a main-battery fire control system, Radar Equipment Mk 8 provides range data and aids target acquisition and tracking. When the approximate range and bearing of the target have been designated, the trainer slews the director to the designated bearing and watches for a target pip on his B-scope, using main sweep or expanded sweep, according to the range of the target to be picked up. When a target appears, he trains the direc tor with his handwheel so that the center bear ing line on the B-scope bisects the target pip. At the same time, the radar operator in the plotting room, or the radar range operator in the director, cranks the range unit to the desig nated range. When the designated target has been ac quired, the radar range operator switches to precision sweep and adjusts the range unit to Figure 52-Auxiliary Indicator. place the lower edge of the target pip in co incidence with the upper edge of the range line. Plotting Room Radar Range Operator. Once the range unit has been so adjusted, the 1. Ranges on the target with the radar operator depresses the range mark key behind range unit the range crank to signal to the rangekeeper 2. Controls selection of sweeps on all indi operator that the range shown on the range cators indica tors is correct. As soon as the rangekeeper 3. Controls power conditions of radar has generated a range-rate solution, the range equipment keeper operator can take over control of rang 4. Performs anti-jamming procedures as ing. If the rangekeeper solution is correct, the required. target pip will stay in coincidence with the Director Radar Range Operator. The director range line. radar range operator views range on an aux iliary radar indicator. However, he gets on tar When the auxiliary computer in the after fire get with units which are not part of the radar control station is used instead of the range equipment as follows: keeper in plot, generated range rates are not 1. Ranges on target with a range slewing supplied to the radar range unit. Therefore, the pushbutton radar range operator in the gun director, or the 2. Reads the range on a range indicator radar operator in the fire control station, must 3. Transmits this range to the plotting keep the pip in coincidence with the range line room on a range transmitter. by manual operation of the range crank.

43 3Z3489 0 - 54 - 4 OP 1895 CiiCPibm'i IXL

Conditions of Readiness requires about five minutes to reach its final SECURED. All power is off. operating temperature. However, the receiver can be operated from a cold start after one NORMAL SHUTDOWN. Power is on to heaters minute, but during the first few minutes, the and convenience outlets. operator may have to adjust the tuning fre STANDBY. Only the high voltage rectifier quently. switch and the antenna control switch are in the OPERATE. The entire equipment is in opera "off" position. One tube in the radar receiver tion.

NOTES ON YOUR SHIP'S INSTALLATION

Cgb'RiP II I~ est 'f'DFNT! A I • •

Chapter 4 RADAR EQUIPMENT MK l2 MODS 0,

Radar Equipment Mk 12 Mods 0, 1 is used in However, elevation measurements by Radar conjunction with Gun Fire Control System Mk Equipment Mk 12 are subject to serious errors 37 and associated all purpose 5-inch guns. Its between elevation angles of one degree and antenna is carried atop Gun Director Mk 37, eight degrees. This low angle limitation is elim figure 53. The radar determines the range, inated by Radar Equipment Mk 22, used in bearing, and elevation of targets to a distance conjunction with Radar Equipment Mk 12 to of 50,000 yards. provide pointing data in the low angle region .

Figure 53-Antenna for Radar Equipment MK 12 (Right), atop Gun Director Mk 37.

45 OP 1895 C6NPI'm:N I lA[ Radar Equipment Mk 32 (IFF) also is used The functional arrangement of Radar Equip with Radar Equipment Mk 12 in some installa ment Mk 12 Mods 0, 1 is shown in figure 54. tions to determine the friendly or enemy char Detailed characteristics of the equipment are acter of targets detected by the main radar. given in Part 3, Reference Data.

ANTENNA

t RF )

RANGE OPERATOR'S CONTROL TRANSMITIER INDICATOR OFFICER'S RECEIVER INDICATOR

OPERATOR'S POWER TRAIN TRAIN CONTROL INDICATOR METER UNIT CONTROL t J

RANGE ELEVATION ELEVATION CONTROL INDICATOR METER UNIT J RATE CONTROL SIGNALS

ABOVE DECKS ·-··· BELOW DECKS RANGE MOTOR CONTROL SIGNALS

TRIGGER 1 RANGE f AUTO RANGE COMPUTER RANGE MAIN IF (ECHO) MKl UNIT FRAME RANGE RATE RANGE NOTCH PULSE TRIGGER PULSE

TRAIN AND ELEVATION SIGNALS )

figure 54-Radar Equipment Mk J2, functional Schematic. 46 Cdi4J!ib214fi~L CQb'f'DfNII +' EQUIPMENT DATA and computer aided tracking. In most installa tions this range unit is located below decks and its control functions are governed from a range control unit in the director, figure 55. Under normal operating conditions, the radar equipment will range automatically within ±20 yards of a target in the range notch. Radar data concerning range, together with data on director position and antenna elevation, are normally furnished continuously to the com puter. Whenever weak targets do not return a sufficient signal to permit continuous automatic tracking control, computer aided tracking may be used to cause the director and the radar range notch to follow the target pip. Four identical indicators are provided in the director for the control officer, the range oper ator, the trainer, and the pointer. The indicator at the pointer's station is illustrated in figure Figure 55-Range Control Unit. 56. A selector switch on each indicator affords a choice of four presentations: Operational Units The antenna of Radar Equipment Mk 12 is mounted in an assembly on top of the director shield. The antenna, antenna drive unit, and transmitter-receiver assembly of Radar Equip ment Mk 22 are mounted on the antenna of the Radar Equipment Mk 12 as shown in figure 53. The transmitter-receiver assembly of Radar Equipment Mk 12 consists of a cabinet in the director which houses both the usual transmit ting and receiving components and a test unit. The test unit permits a rapid check of the over all operation of the unit as well as enabling the operator to tune the receiver to the transmitter frequency. The operator's control unit in the director provides the range operator with power con trols, receiver sensitivity, and manual or auto matic gain controls. At the range operator's station, a range unit controls the position of the range notch on the indicators. The range of a target pip in the notch is indicated in 10-yard increments on the dials of this unit. In addition, switches are pro vided to cut in automatic ranging, rate control, Figure 56--Radar Equipment at Pointer's Station. Qlt lfllitllh'f! 47 OP 1895 (;Cf41 ibm'fTAL

presence of a target pip in the notch is made known to both operators by two small lights on the face of each meter. When the radar is "on target" in range, train, and elevation, the meter pointers are centered and the lights are on. A main frame is located in the radar trans mitter room below-decks, figure 57. This main frame contains most of the equipment of the Radar Mk 12 which is too bulky for director mounting. A test scope and portable sweep unit are mounted on a bracket attached to the side of the main frame.

Operating Personnel The principal duties of those members of the director crew who operate the Radar Mk 12 are as follows: Control Officer. Aids the operation of the range operator, trainer, and pointer. Although figure 57-Main Frame in Radar Transmitter he has no direct control over the positioning of Room. the target indication in range, train, or eleva tion, the control officer can give specific direc 1. Range presentation. This is an A-presenta tions to the operators who manipulate the tion with a movable range notch on a 50,000 controls. yard sweep. It features a 1200-yard expanded Radar Range Operator. region consisting of a 400-yard notch centered 1. Turns on power from a cold start between two 400-yard intervals. The position of 2. Turns on power from standby this notch is controlled by the range unit. By 3. Tunes the transmitter-receiver observing the number of superimposed target 4. Ranges on target. pips in the notch, the range operator can deter Director Trainer. mine whether or not the tr!'liner or pointer are 1. Controls position of director in train on target. 2. Acquires target by means of radar 2. Train presentation. The indication in train 3. Tracks the target in train consists of two sweeps, one slightly displaced 4. Spots in deflection when required. horizontally from the other. Therefore all tar get pips appear double on the scope. When the Director Pointer. pips are of equal height, the radar beam is on 1. Controls the axis of the beam in eleva target in train. tion 3. Elevation presentation. The indication in 2. Acquires the target in elevation by elevation is the same as that for train. However, means of radar when the pips are of equal height in this pres 3. Tracks the target in elevation. entation, the beam is on target in elevation. 4. Train and elevation presentation. This is a Typical Operating Procedure T&E-scope, presenting a spot indication for a In typical operations with GFCS Mk 37, in gated target. formation on a target's designated position is In addition to the indicators, the trainer and received in the director by synchro. The pointer, pointer are provided with meters, figure 56. trainer, and radar range operator match dials These meters indicate target error in train or to bring the director and radar antenna to the elevation by deflection from center zero. The designated bearing and elevation.

48 Cbl4rit5214liAL GQNSJgiiiblililrko EQUIPMENT DATA When the radar range operator sees a target Conditions of Readiness pip on his A-scope, he centers the range notch SECURED. All power is off. under the pip to gate it, causing the pointer's NORMAL SHUTDOWN. Power is on to heaters scope and trainer's scope to show target indi and convenience outlets. cations. STANDBY. Filaments are lit, About 1112 min utes of warm-up is sufficient to permit safe The trainer and pointer match the pips on application of high voltage in the operation their respective scopes by training or pointing condition. Nevertheless, the range notch may until the pips are of equal size; they then switch be unstable unless the warm-up period is ex to the T&E presentations. To stay on target, the tended to 10 minutes. pointer and the trainer either keep the spots OPERATE. The entire equipment is in oper- centered in the crosshairs of their scopes, or ation. keep the needles centered on the elevation and NOTE: For emergency starting, with train meters. At target elevation angles of less some hazard of failure, the time delay than 8 degrees, where Radar Equipment Mk 12 switch (S5) inside the operator's con is inaccurate because of water reflections, the trol unit may be set in the "out" posi pointer and the range operator use Radar tion. The system will then operate as Equipment Mk 22 to supplement the elevation soon as the filaments reach operating data supplied by Radar Equipment Mk 12. temperature.

NOTES ON YOUR SHIP'S INSTALLATION

QQt llilf5EN I I~ 49 oii8t Cl'lbEN I IAt

Chapter 5 RADAR EQUIPMENT MK I 3 MOD 0

Radar Equipment Mk 13 Mod 0 is used in conjunction with Gun Directors Mk 34, 38, and The radar may be employed to determine the 54 for control of 6-, 8-, 12-, and 16-inch guns range and bearing of surface targets to a dis aboard cruisers and battleships. This radar is tance of 50,000 yards, and to permit observation also used on Antenna Mount Mk 23 (in place of of targets to 80,000 yards. The functional a director), aboard ships of the CL144 class. arrangement of the radar is illustrated in figure Figure 58 shows the antenna of Radar Equip ment Mk 13 on Gun Director Mk 34. 59. Detailed characteristics of the radar are given in Part 3, Reference Data......

Figure 58-Antenna for Radar Equipment Mk 13, on Gun Director Mk 34. 50 Gi t 4iiiJI5Ei4 Ilftfl! 88141 IOEIQ II'Jii

BEARING PULSE BEARING SWEEP ANTENNA I RF

RANGE AND RF WAVE GUIDE RF TRAIN SWITCHING INDICATOR UNIT

IF IF RECEIVER GAIN TRANS · RECEIVER GAIN RECEIVER GAIN TRANS· .....0.. MITIER MITIER ..... RECEIVER :1: RECEIVER RECEIVER 0 1/) TUNING !e...... TUNING ( TUNING ..... 0 z 0: ~ al TRANSMITIER REMOTE RANGE SWITCHING RANGE INDICATOR UNIT CONTROL

ABOVE DECKS )"!;'; )i;{ ' """ /it ·''''' "i BELOW DECKS LLIO ~ != Z::ELLI 0-LLI ~ to- .... al SYNC PULSE

RANGE PULSE RANGE CONTROL MAIN VIDEO

PRECISION SWEEP AMPLIFIER CONTROL RANGE CABINET PRECISION VIDEO CONSOLE MAIN SWEEP

BEARING PULSE POWER TO RECTIFIER VARIOUS UNITS CABINET BEARING SWEEP

figure 59-Radar Equipment Mk J 3, functional Schematic.

Operational Units substitute a dummy antenna and an echo box The antenna of Radar Equipment Mk 13 is for this antenna. A manual operating knob on mounted atop the gun director. During opera the antenna permits emergency manipulation tion it scans by rocking back and forth five of a wave-guide switch. Two identical trans times a second, thus completing ten scans per mitter-receivers can be used interchangeably to second. feed this antenna, each being standby to the In order to check the performance of the other. Their frequencies differ slightly to afford system in radar silence, the radar operator can a choice in case of jamming.

CQJ 4PIIif l!lji 51 OP 1895

•

figure 60-Control Console. A radar console in the plotting room below The radar operator has a B-scope range and decks, figure 60, contains most of the radar train indicator, and the necessary controls to controls for power, range tracking, and receiv slew the radar in range. He also can read range ing. To establish the conditions of readiness, on a range repeater comprising coarse and fine the console operator may select the power con dials, and on a long range control on the front dition, control the scanning motor of the an panel which provides a coarse measurement of tenna, choose one of the two transmitters, and range out to 80,000 yards on a dial graduated short out interlock circuits to achieve a battle in 500-yard increments. short condition. The console also affords adjust In addition to the B-scope in the console, ments of the pulse rate, time constant, receiver remote range and train indicators are provided tuning and receiver gain, and local oscillator · in the director, in the main-battery plotting frequency control. These adjustments are part room, and in the fire control station. Each of of the anti-jamming provisions. these remote indicators, figure 61, can display

52 Q I I Cflm.¥4 I lA! cet IE'PSt'JW\L EQUIPMENT DATA Operating Personnel The radar crew, except for the two range operators, is part of the director crew. A listing of the crew and its principal radar duties . follows. Control Officer. 1. Determines and orders the type of range tracking to be employed 2. Spots gun fire as required. Plotting Room Radar Range Operator. 1. Ranges on the target with the radar range unit 2. Controls power conditions of radar equipment 3. Performs anti-jamming procedures as required. Director Radar Range Operator. The director range operator views range on his remote range and train indicator. However, he gets on target with instruments which are not part of the radar equipment, as follows: 1. Ranges on target with a range slewing pushbutton Figure 6J-Remote Range-and-Train Indicator. 2. Reads the range on a range indicator 3. Transmits this range to the plotting room on a range transmitter. one of three range sweeps, selected by means of Trainer. a switch on the indicator. On a main sweep, the 1. Trains on target in bearing operator can view from zero to 80,000 yards. 2. Spots gun fire as required. This total sweep range on the screen may be Typical Operating Procedure varied from 40,000 to 80,000 yards. On pre In typical operations with a main-battery fire cision sweep-normal range, the operator can control system, Radar Equipment Mk 13 is em view from zero to 50,000 yards, but only 2000 ployed for target acquisition, tracking, and • to 4000 yards of this distance at one time. On range measurement. The target is designated precision sweep-long range, the field covered is to the gun director by synchro, and the director from zero to 80,000 yards. This latter sweep is is trained to the designated bearing. The an used for observation only, because it is not as tenna scans the area, picking up the target accurate as a normal range sweep; therefore, echoes on main sweep. When the trainer has range values normally transmitted to the range positioned the director so that the bearing line keeper are not transmitted during long range on his B-scope bisects the target pip, the radar operations. operator at the console ranges on the target. The radar operator continues to turn his In an emergency, tracking in range can be range track crank to hold the echo at the range performed at an amplifier cabinet below decks line, thus transmitting range continuously to by using the range crank provided there. The the rangekeeper. As the gun director transmits monitoring indicator in the amplifier cabinet target bearing, the rangekeeper solves the fire can be used as an auxiliary range and train control problem and transmits gun train and indicator, or as an A-scope. gun elevation orders to the turrets.

GQtlliiiDSblil tJ 53 Ul" I H'fb

Targets may also be tracked in range from not apply if the previous switch position was the remote control unit in the director or from "operate". the rangekeeper. Once the rangekeeper has gen OPERATE. The entire system is in operation. erated correct tracking rates, the target pip will (One of the two transmitter-receivers is in remain in coincidence with the range line with standby.) The normal and long range units out further movement of the range track crank. should be zero-set after 15 minutes warm-up. REMOTE CONTROL CONDITION. The remote con Conditions of Readiness trol unit at the director control officer's station governs the standby-operate power selection. SECURED. All power is off. EMERGENCY CONTROL CONDITION. Only the NORMAL SHUTDOWN. Power is on to heaters normal range unit can be operated from the and convenience outlets. amplifier cabinet. The monitoring indicator dis STANDBY. Tube filaments are warmed up plays a type B presentation on which range is after one minute has elapsed (if the equipment read on the counters of the range unit and drive was normally shut down). This interval does assembly in the rack below.

NOTES ON YOUR SHIP'S INSTALLATION

ce1 c1 a::Jm 1a cb& COI>I&IIi>Et Ill/it c

Chapter 6 RADAR EQUIPMENT MK 22 MODS o. I

Radar Equipment Mk 22 Mods 0 and 1 is an Radar Equipment Mk 22 is shown in figure 63. auxiliary radar operated with Radar Equipment Radar Equipment Mk 22 provides pointing Mk 12 (or Mk 4) in conjunction with Gun Fire accuracy down to a position angle of approxi Control System Mk 37. See figure 62. mately 0.6 degrees and affords better tracking Radar Equipment Mk 22 is used to determine accuracy than the main radar at all angles of the elevation of low-angle targets, since Radar elevation. The narrow beam of this auxiliary Equipment Mk 4 is subject to elevation inaccu radar often provides complete discrimination racies with targets below 12 degrees and Radar where the main radar fails because of land Equipment Mk 12 is subject to inaccuracies clutter. Detailed characteristics of this equip below 8 degrees. The functional arrangement of ment are given in Part 3, Reference Data.

•

Figure 62-Antenna for Radar Equipment Mk 22 (LeftJ, on Gun Director Mk 37. COI4PH!S!ItJIJ\L 55 OP 1895 Clrtl iBLKffAt - Operational Units with the main radar system. Power conditions Radar Equipment Mk 22 cannot be operated and receiver tuning are governed at a control independently of Radar Equipment Mk 12 (or panel located in a blister on the director shield, Mk 4). The antenna of the auxiliary radar is figure 64. attached to the antenna of the main radar, as The indicator unit, figure 65, of Radar shown in figure 62 and is aligned with the main Equipment Mk 22 is mounted in the director antenna in train, elevation, and crosslevel. How above the elevation indicator. The face of the ever, the auxiliary antenna scans independently scope of this indicator unit is reflected in a of the main antenna, rocking in a vertical plane mirror at the left of the unit, and shows the through an angle of ±q degrees about a zero director line of sight as a bright, horizontal point established by the axis of the main an- mark. The rocking motion of the antenna ap tenna. · pears as a faint vertical trace with a relatively The transmitter-receiver assembly of the brighter leading edge. A short, bright vertical .. auxiliary radar is also mounted on the antenna strip on this trace represents only the target in of the main radar. It is pulsed in synchronism the notch of the main radar scope. The position

TRANSMITIER RF ANTENNA RECEIVER UNIT

ANTENNA DRIVE UNIT MODULATOR PULSE """' ABOVE DECKS ./: '>> }) / BELOW DECKS ELEVATION MARK I MODULATOR I 1 IF ~ INDICATOR SYNC PULSE FROM RECEIVER TUNING CIRCUIT UNIT ASSOCIATED RADAR RANGE NOTCH FROM J ASSOCIATED RADAR VIDEO

RECEIVER GAIN

RANGE SWEEP SYNC ! ELEVATION RANGE INDICATOR INDICATOR

t ELEVATION SWEEP

Figure 63-Radar Equipment Mk 22, Functional Schematic.

56 COUFIBZI4 I IX[~ CQb'F'PFb'I161 s EQUIPMENT OAT A

Figure 65-lndicator Unit.

Operating Personnel

-, No additional personnel are required for oper ~ ....,lllr ation of Radar Equipment Mk 22. When a -...... ·r:f..*_·.~·l .. fr, ~--~ ..: target moves into a region where pointing is ~~ I I, ' ' inaccurate with the main radar, the pointer uses the indicator of Radar Equipment Mk 22. Operating personnel of the main radar control ~ lllfTU lrQ'ltft~ Mk 22, and their duties, are as follows : ~~ ':.0."'' .,_ ,..-, fir.; ...-- ••• :- ' ' ' ' Radar Range Operator. .. 1. Turns ·on power 2. Tunes and adjusts receiver 3. Turns on antenna drive. 4. Instructs trainer verbally during emer gency tracking in train when main radar is not effective. Director Pointer. 1. Bisects target echo by elevating or de pressing antenna 2. Operates rate control signal key to in Figure 64-Control Panel. form computer operator that correct target of the strip on the trace, relative to the hori elevation is being transmitted zontal mark, corresponds to the position of the '3. Tracks target in elevation target above or below the director line of sight. 4. Corrects computer solution by rate con Radar Equipment Mk 22 Mod 1 differs from trolling only when the motion of the target Mod 0 in offering additional facilities which changes. provide range presentation, sensitivity time Director Trainer. In emergency tracking, control (STC) and automatic frequency control tracks in train according to verbal instructions of the sweep. In this mod scopes are provided from range operator. (Trainer is on target when at both the pointer's and range operator's echo pip on scope of Mk 22 is at maximum stations. height.) Ci'tt ISZIQ I IAt 57 OP 1895

Typical Operating Procedure width of the beam depends on the receiver sen In typical operations with Radar Equipment sitivity setting; high settings at short ranges Mk 22, the procedures employed in acquiring cause reception of multiple echoes from a single and tracking targets are largely dependent on target that is being illuminated by minor lobes those procedures used in the main radar in con of the beam. junction with Gun Fire Control System Mk 37. Radar Equipment Mk 22 is used primarily to Conditions of Readiness provide accurate data in the low angle region SECURED. Radar Equipment Mk 22 is com in which the main radar proves ineffective. To pletely shut down. get on target in elevation, the pointer in Gun STANDBY. The 400-cycle power and the an Director Mk 37 elevates or depresses the main tenna drive are off. The main radar may be in radar antenna until the target indication on the full operation or in standby. However, the main scope of Mk 22 is bisected by the horizontal radar must be in full operation before Radar • range mark. The degree of accuracy in deter Equipment Mk 22 is switched from standby to mining target elevation angles is determined by operate. A one-minute delay must elapse be the pointer's ability to bisect the target signal tween the turning on of 400-cycle power and indication. A good operator can point on a tar actual operation of the transmitter. get flying between 25 and 1000 feet in altitude, OPERATE. The main radar is in full operation. with errors of less than ±3 mils. (This condition is a vital prerequisite to opera However, such accuracy can be achieved only tion of Radar Equipment Mk 22 to prevent if the operator is aware of several factors serious damage to it.) Radar Equipment Mk 22 peculiar to a radar of this type. The effective is in full operation.

NOTES ON YOUR SHIP'S INSTALLATION

58 C~SPEIC I Ott .__ CQtCI IDEIQ I IAE •

Chapter 7 RADAR EQUIPMENT MK 25 MODS 2. 3. 5 Radar Equipment Mk 25 Mods 2, 3 is an auto increase in RF power output. Furthermore, the matic tracking fire control radar which is used Mod 3 will track reliably at greater ranges and with dual-purpose Gun Fire Control System at increased target rates. In addition, provision Mk 37. An exterior view of Gun Director Mk 37, has been made in the Mod 3 for automatic range mounting components of Radar Equipment Mk designation. 25 Mod 2, is shown in figure 66. A functional Radar Equipment Mk 25 Mod 5 is the radar arrangement of the radar units is illustrated component of Gun Fire Control System Mk 67. in figure 67. The most important difference between the Mod 5 and earlier mods is the location of the radar Radar Equipment Mk 25 Mod 3 differs from console below decks instead of in the director. the Mod 2 primarily in its increased range. This Characteristics of this radar and differences ,. improved performance is achieved in the Mod 3 between mods are shown in the characteristics by use of a new transmitter with a substantial chart in Part 3, Reference Data.

Figure 66--Antenna for Radar Equipment Mk 25, on Gun Director Mk 37. CQb'512114,~L 59 3Z3489 0 - 54 - 5 OP 1895 CQII 41 iBEI"IAL Operational Units The majority of the operational controls used The Mk 25, with its antenna mounted on top with GFCS Mk 37 are located in the director on of the director, can track targets either man a radar console, figure 68, from which the ually or automatically in range, bearing, and radar range operator can govern normal opera elevation. Operation in each of these coordin tion and adjustment of the radar system. In ates may be manual or automatic, regardless of GFCS Mk 67, this console is below decks. Con the modes of operation in the other coordinates. sole controls include power, receiver tuning,

REFERENCE I SCAN AND ANTENNA I RADAR CONTROL RADAR RADAR VOLTAGE I I POWER CONTROL UNIT (TRAINER) IND. ASSY. IND. ASSY. MKl MOO 0 MK2 MOD 0 • RANGE SLEW t t RF SWEEP CONTROL

AUTO CONTROL RANGE DATA )_ TRIGGER f RF RADAR RADAR RANGE RATE RANGE XMTR IF ECHO BOX CONSOLE CONTROL SWITCH SELECTOR CONTROL CIRCUITS J TRACK RANGE DATA J CONTROL G.O. CONTROL ( RANGE RATE MECHANISM TRANS SWITCH CONTROL (PART OF GUN (AUTO· MAN) DIRECTOR MK3n INCREMENTS OF GENERATED ABOVE DECKS PRESENT RANGE

BELOW DECKS TRAIN AND ELEVATION TRAIN AND ELEVATION CORRECTION 1 ENABLING ~ COMPUTER RADAR TRAIN AND RADAR CORRECTION MKl OF '--+ UNIT ELEVATION TRACKER DATA G.F.C.S. MK37 ASSEMBLY ERROR

t ELEVATION DATA J SYNC

RANGE PULSE RADAR RANGE ERROR RANGE UNIT ASSEMBLY RANGE CONTROL CIRCUIT VIDEO

SWEEP VOLTAGES AND CONTROL

Figure 67-Radar Equipment Mk 25, Functional Schematic. 60 CQt li IDEJQ I I'Xt C1!l1E'Sft 'I' :a: EQUIPMENT OAT A gain, modulation selection, repetition rate, sweep selection for all indicators, antenna-echo box selection, anti-jam circuit selection (STC, IAGC, or FTC), three-man to one-man opera tion selection, and range controls for the range unit below deck. The console also contains range and designated range dials, and two indicators for the console operator. The left console indicator is a 3-inch screen which provides a type-A presentation for the range operator. To its right is a 5-inch screen offering a B or E presentation, selectable by means of the display switch mounted above it. • · Indicators with a selection of either a type-B or type-E presentation are provided also for the control officer and trainer. An indicator display- "' ing either a type-E or a type-aE presentation is mounted at the pointer's station. Two range sweeps are provided on all of these indicators. The main sweep extends from zero to 50,000 yards (Mods 3 and 5: 100,000 yards), of which any 30,000-yard section may be viewed at one time. The precision sweep allows the operator to view arty 4000-yard portion of the main sweep at any one time.

NAVY llPARTIIOO-- UUU Of OiMIIU ,.,;;ttnl --fl~

figure 69-Radar Control Unit CTrainerJ.

:;.,.;_. ::;.,_J " The radar equipment as a whole may be oper ~ ·~ ated by the range operator, trainer, and pointer together, or by the trainer alone. This latter one-man watch condition is achieved by the use - il of a radar control unit (trainer). This unit, located at the director trainer's station, is shown in figure 69. It can be used whenever the trainer control switch on the console is in the "on" position. The trainer may then put the equipment in standby or operate power condi tion, slew range, choose either main or precision sweep, and select conical, spiral, or circle scan. Either the trainer, using his control unit, or the range operator, using the console controls, figure 68-Radar Console. can set the equipment for automatic tracking.

~Qb'S'PEbiiJ ._ 61 OP 1895 CQt Jfilld 4PTA£ In the automatic condition, an automatic Typical Operating Procedure tracker below decks controls the motion of the In typical operation of Radar Equipment Mk director in train, and the director optics and 25 with the GFCS Mk 37, the control officer re radar antenna assembly in elevation. However, ceives target information on target designation the automatic tracker functions only when a dials and by telephone. He uses his slew sight switch on the console or on the radar control to place the director line of sight in bearing and unit (tracker) is turned to automatic and the elevation. If the target is not visible, he slews foot switches (automatic-manual) are de to match pointers with the designation dials. At pressed. Tracking is then automatic after the the same time, the radar range operator re target is acquired. ceives the target information on a designated Anti-jamming features of the equipment in range dial, and slews the range notch to match clude single control tuning of both transmitter range indices on the dial. and receiver, switch selection of several repeti With GFCS Mk 67, the target is designated • tion rates, an IAGC circuit, and an FTC circuit. from a remote station by synchro signals. The An STC circuit is incorporated in the receiver target designation can be accepted by a push to minimize sea return and equalize echoes from button control which causes the director to slew .. near and far targets. to synchronization with the designation signals. The control officer observes his indicator and Operating Personnel coaches the trainer and the pointer on target. The trainer places the director on target in train The radar crew, which is part of the director by using his handwheel to center the target pip crew, consists of a control officer, range oper on his B-scope. He then operates his footswitch ator, trainer, and pointer. An outline of the to ready the radar for automatic tracking. The principal duties of these personnel follows. pointer places the director on target in elevation Control Officer. The principal duty of the con by using his handwheel to center the target pip trol officer is to determine and order the type of on his .6.E-scope. He then switches to the E-pres tracking to be employed. entation and operates his footswitch to ready Range Operator. The range operator is usu the radar system for automatic tracking. When ally known as the radar operator. His principal the track lamps light on the indicators, auto duties are: matic tracking commences. 1. Turns on the power 2. Evaluates scope indications Conditions of Readiness 3. "Gates" target in range 4. Prevents the automatic tracking circuits SECURED. All power is off. from locking on interfering echoes NORMAL SHUTDOWN. Convenience outlets in 5. Performs the radar anti-jamming pro the power supply, range, transmitter-receiver, cedures and radar unit cabinets are energized. In addi 6. Spots in range as required. tion, the heater circuits in the radar antenna and the range unit oven are energized. This Trainer. The director trainer is responsible condition is used during periods when circum for the following: stances permit a 3-minute time delay in putting 1. Trains director the equipment in the operate power condition. 2. Selects antenna scan (circle, spiral, or conical) STANDBY FILAMENT POWER CONDITION. All 3. Spots in deflection as required tube filaments are energized. The blowers in the 4. Performs target acquisition and track power supply and range unit cabinet are operat ing in one-man watch. ing. This condition is used during periods when Pointer. The director pointer's principal the equipment may be subject to use without radar duty is tracking in elevation. delay.

62 CQt 151 21 4I ;)fto COD,IS'?it •• I 1 EQUIPMENT OAT A

STANDBY TEST CONDITION. All power is avail vides selection of the standby or operate power able except to the transmitter circuits. Sweep conditiOns. traces appear on all radar indicators. This con dition is used for direction finding and test OPERATE WITH EMERGENCY POWER. An emer purposes. gency power switch on the control unit (power) OPERATE. The entire system is in radar opera performs the function of the power control tion. It may also be used for communication pushbuttons on this unit and on the radar con purposes. sole. A battle short pushbutton shorts out all OPERATE DURING ONE-MAN WATCH. A push interlocks. A wave-guide switch manually se button on the radar control unit (trainer) pro- lects antenna or echo box positions.

NOTES ON YOUR SHIP'S INSTALLATION •

Q! I t"IBEI 4I ~cL 63 allllli'?Etlflftl

Chapter 8 RADAR EQUIPMENT MK 26 MODS 3, 4

Radar Equipment Mk 26 is a fire control mounted on the gun director above decks, fig radar designed for use with Gun Fire Control ure 70, where it is positioned by the director System Mk 52 for control of 3"/ 50 and 5"/ 38 pointer and director controlman as the director caliber guns. The radar provides only range is moved to track the target. Radar operational data to the system. Blind tracking is not possi controls and an indicator are located below ble with this fire control system because there decks in a control room that houses other com is no radar indicator at the director and no error ponents of the fire control system. The func detection circuit in the radar system. tional arrangement of the radar is illustrated The antenna of Radar Equipment Mk 26 is in figure 71. • ..

Figure 70--Antenna for Radar Equipment Mk 26, on Gun Director Mlc 52.

CQt IPII II "12\~ CQNE'Pfk'™ L EQUIPMENT DATA

ANTENNA

ABOVE DECKS ----- & BELOW DECKS

TRANSMIITER HOUSING ,------~------l

' TRANSMIITER : TRIGGER PULSE l MODULATOR J • SIGNAL RF

.. TRIGGER

RF TO IF osc AFC CONVERTER MIXER

AFC ) ----~--t------TO VIDEO l VIDEO I CONTROL lrCONVERTER I I INDICATOR I

figure 7J-Radar Equipment Mk 26, functional Schematic.

Radar Mk 26 has a reliable range of about the train and elevation lead angles so that the 12,000 yards for an air target, although this axis of the radar beam remains pointed along figure may be modified by antenna height and the line of sight to the target. These offsets are by atmospheric conditions that affect radar accomplished manually by the director control propagation. When several targets are in the man who stands beside the director and sets in beam, the radar can resolve them if they are values of the lead angle by means of knobs separated in range by approximately 100 yards. which are accessible on either side of the direc Detailed characteristics of Radar Equipment tor. These lead angle offsets of the radar an Mk 26 are given in Part 3, Reference Data. tenna for a particular target may be predeter mined by reference to a chart which shows Operational Units optimum positions of the antenna for different The radar antenna assembly on Gun Director target speeds and target angles. Mk 52 has a parabolic reflector that moves with The antenna is connected to a transmitter the director in train and elevation as the direc receiver mounted in a horseshoe-shaped trans tor axis moves in or parallel to the line of fire mitter and housing unit, located at the base of during tracking of the target. However, the the director pedestal in some shipboard installa antenna dish must be offset by the amount of tions, below decks in others. JVQt 1&111!14 I I"& 65 OP 1895 COt IPIDEN HAL

A control-indicator unit is mounted with of which may be selected by means of a range Computer Mk 13 in the below decks control switch on the control-indicator panel. One scale room, figure 72. The control-indicator unit is graduated from 1000 to 11,000 yards for AA contains all of the operating controls of Radar ranging, but this scale can be used for range Equipment Mk 26 with the exception of a range measurement down to 800 yards. The other handwheel on the computer. The range pointer scale extends from 2500 to 27,500 yards for sur on the face of the scope in the control-indicator face ranging and for detection of AA targets at unit is kept matched with the target pip by ranges above 11,000 yards. turning the range handwheel on the computer. Range rate is not determined by the radar, The range pointer on the face of the scope indi but is developed by Computer Mk 13 when the cator and the range dial on the computer display system is used for AA fire. An aided tracking the same range information simultaneously. mechanism in the computer facilitates range The radar indicator is a J-scope with a circu tracking so that the radar operator need make lar timebase that shows range increasing clock adjustments only for changes in the target's • wise. There are two scales on this scope, either range rate. There is also a control lever on the left side of the computer case that provides direct control of the range rate. After the radar operator has finished running up range on an outgoing target, he may use this lever to re verse the range rate in the computer from plus to minus so that the radar can pick up an in coming target without delay.

Operating Personnel The radar crew is part of the operating per sonnel of Gun Fire Control System Mk 52. The operators and their princip3tl radar duties are: Control Officer. 1. Selects the target (if ship's doctrine does not provide for designation by another source) 2. Estimates range and target angle. Director Pointer. 1. Slews the director to the designated bearing of the target 2. Tracks the target in bearing and ele vation. Director Controlman. 1. Adjusts radar dish to keep radar beam on target 2. Readjusts dish according to coaching from radar operator whenever pip gets weak. Radar Operator. 1. Controls operation of all below decks radar equipment COMPUTER MK13 2. Gates pip and reports target range and relative position of pip if more than one target Figure 72--Corrtrol-lndicator Unit (with Computer Mlc I 3). appears 66 OQII tPII!I4ll/da.. cgwsmn III OJ, EQUIPMENT DATA

3. Coaches director controlman in offset offsets the radar antenna dish to keep the beam ting dish on target when the director gun sight case is 4. Spots in range as required positioned along the line of fire. During action, 5. Makes operational checks and adjust the radar operator reports changes in pip size ments of all radar equipment. to inform the director controlman when the echo is getting weaker so that the dish may be Typical Operating Procedure readjusted. In typical operations, the director pointer Conditions of Readiness acquires the target optically. At the same time, SECURED. All power is off. the control officer estimates range to the near est 1000 yards. The director controlman calls NORMAL SHUTDOWN. Power is on to heaters this estimated range to the radar room below and convenience outlets. decks so that the radar operator will know STANDBY. All power is on except high voltage where to look for the target pip. When several to the transmitter circuits. targets are attacking, the control officer adds OPERATE. All circuits are energized. At least designation data to his range estimate so that one minute must elapse before the equipment the radar operator will know which pip to track. can be brought from standby to operate on an As soon as the radar operator is tracking, he initial warm-up of the radar. The equipment reports the range and relative position of the must be on for at least ten minutes before a pip in the group. When the director pointer correct zero setting of the range pointer can be commences tracking, the director controlman made.

NOTES ON YOUR SHIP'S INSTALLATION

., .

•

CQI II J£11 !JtktL 67 Chapter 9 RADAR EQUIPMENT MK 28 MODS 2, 3

Radar Equipment Mk 28 Mod 2 is an integral to 36,000 yards at range rates to ±450 knots, part of antiaircraft Gun Fire Control System and determines bearing and elevation of targets Mk 63 Mods 0, 1, 3, and 4 used for 40-mm twin in the range gate with an accuracy of -+-2 mils. or quad mount guns. Radar Equipment Mk 28 Mod 3 is installed instead of Radar Equipment Range data is supplied automatically and con Mk 12 used with Gun Fire Control System Mk tinuously to the lead computing sight on Gun 37 for 5"/ 38 caliber guns on certain vessels of Director.Mk 51 Mod 6 used with GFCS Mk 63, the DD and DMS type. and to Computer Mk lA used with GFCS Mk 37. Radar Mk 28 facilitates observation out to The bearing and elevation information permits 60,000 yards, measures linear range of targets blind tracking with both systems.

Figure 73-Antenna for Radar Equipment Mk 28, on 40-mm Twin Mount. 68 CQNE'PP ITIJ it • CONf'PEbl!! t I. EQUIPMENT DATA Operational Units The units described here are those that affect the radar's operating characteristics or its con tribution to the solution of the fire control problem. Detailed characteristics of Radar Equipment Mk 28 are given in Reference Data. The functional arrangement of the radar units of Radar Equipment Mk 28 Mod 2 is shown in figure 75. In GFCS Mk 63, the antenna and its parabolic reflector are installed on Antenna Mount Mk 19, mounted on one of the guns in the battery. The antenna mount moves in train with the gun mount and in elevation with the gun, in accord ance with gun orders transmitted by the direc tor. For search, the antenna assembly can be caused to nod in elevation with reference to the antenna mount, to a maximum of -+-15 degrees of gun elevation, at the discretion of the target acquisition operator below decks. For tracking, the antenna assembly may be driven a maximum of -+-20 degrees in train and elevation, with reference to the antenna mount, by an electromechanical servo controlled by lead angle si~als developed in the director sight. These positioning arrangements permit the gun Figure 74-Units for Radar Equipment Mk 28, to be directed along the computed line of fire on Gun Director Mk 37. while the antenna assembly remains pointed along the line of sight to the target. Lead angle signals to the antenna drive on the antenna When a target is gated, its position relative mount are transmitted only when the system is to the axis of the radar antenna is shown to the operated in the track condition. director operators on train and elevation indi In GFCS Mk 37, the antenna and its parabolic cators. On Gun Director Mk 51, there is a T&E reflector are mounted as an assembly on top of scope in the gun sight. In Gun Director Mk 37, Gun Director Mk 37 by Antenna Mount Mk 12 an elevation indicator is mounted at the point Mod 11. The entire antenna assembly and an er's station and a train indicator at the trainer's tenna mount move with the director in train. • station. The train and elevation information is The antenna assembly is pointed in elevation repeated to the r~dar operator below decks, relative to the director by a mechanical coupling where the main units of the radar equipment to the pointer's handwheel. For crosslevel cor are installed. rection, the antenna mount is mechanically cou When Radar Mk 28 is used with GFCS Mk 63, pled to the rangefinder. the antenna is carried on the gun mount in a Antenna scanning is accomplished by a disturbed line-of-sight arrangement. See figure motor-driven movement of the antenna feed to 73. With GFCS Mk 37, the antenna is mounted produce a conical pattern. The antenna is con atop the director in an undisturbed line-of-sight nected by a coaxial cable to a transmitter arrangement. This antenna mounting and the receiver assembly attached to the front of the location of the trainer's and pointer's indicators gun mount in GFCS Mk 63. No coaxial cable is is shown in figure 7 4. needed with the GFCS Mk 37, as the antenna 69 OP 1895 ti II tf11BEN I tAt and the transmitter-receiver assembly are tuning is possible when circumstances require it. mounted as an integral unit. The target acquisition unit, used only with Transmitter and receiver operations are con the GFCS Mk 63, presents a double-E scope trolled by several units in the radar room below indication. Bearing designation information for decks. These and the major operational units the Tacu appears on dials. A relative director are mounted in a radar rack. See figure 76. train dial shows the position of the director and Switches on the power control unit supply the the guns. Target elevation also is designated on main power for the entire radar system and put a dial. All of these dials are follow-the-pointer the transmitter in standby or operate condi mechanisms that automatically develop error tions. Keying pulses for the transmitter come signals whenever the director is out of corre from the modulation generator, which has con spondence with the designation signal. trols on its front panel for pulse length and During search, the Tacu sends electrical sig repetition rate. An automatic frequency control nals to the T&E-scope in the director gun sight unit governs the receiver, but manual receiver to move a spot indication on the screen off

GUNSIGHT ANTENNA _...

TRAIN AND ELEVATION RF DEFLECTION VOLTAGES ABOVE DECKS

,:,:,:,:,.,: ... ·:;. ·:==~:::::::.:n~:,::::: ·=··=~· . .. .. ,... :::::~ ,.. .• j BELOW DECKS

SYNC MODULATION TRIGGER TRANSMITTER TACU PULSE GENERATOR PULSE RECEIVER

FREQUENCY SYNC J CONTROL PULSE ( ..... IF c: f AFC z CJ RANGE UNIT ;;; RANGE MARK UNIT a:: i ....a:: .... RANGE J SYNC PULSE CONTROL .. INDICATOR 1- RANGE RATE RANGE PULSE

VIDEO · TRAIN AND ELEVATION RANGE STOP INDICATOR CONTROL AGC VOLTAGE

2 ~ REFERENCE VOLTAGE

figure 75-Radar Equipment Mlc 28 with GfCS Mlc 63, functional Schematic. 70 CQtJFIB!I4~AL EQUIPMENT DATA

center in the direction of the target designation. indicate the position of the target relative to The Tacu operator watches the double-E scope the center of the radar beam. The director oper so that he may coach the director pointer to ator may bring either the spot image or the ward the target. As the director is pointed to optical image into prominence in his gun sight cancel the error, the spot on the T&E-scope eyepiece by means of a variable density filter becomes centered in the gun sight reticle. that is controlled by a knob in the right handle Once either optical or radar tracking com bar of the director. mences, the Tacu is switched out of the circuit, In GFCS Mk 37, no Tacu is used. The scopes and pointing error signals in the T&E-scope at the pointer's station and at the trainer's

'1i

~ TRAIN AND ELEVATION , INDICATOR-:----~-;-

TARGET ACQUISITION UNIT

MODULATION GENERATOR ..

•

RECTIFIER

Figure lt-Below-decks Radar Equipment. sar IPAikm t • .. 71 OP 1895 station are used for blind tracking whenever Operating Personnel the target has been gated by the below decks The radar crew is an integral part of the radar operator. On the pointer's scope, the spot operating crew of GFCS Mk 63 or GFCS Mk 37. representing target elevation with respect to The operators and their principal duties with the director line of sight is shown relative to a regard to radar operation of GFCS Mk 63 are horizontal crossline on the screen; on the train summarized below. GFCS Mk 37 requires no er's scope, the spot representing target bearing Tacu operator and the director trainer handles with respect to the direc.tor line of sight, is the train coordinate. shown relative to a vertical crossline. For both fire control system radar installa Control Officer. tions there is also a spot indication below decks 1. Selects the target (if it is not designated on the train and elevation indicator control unit by another source) in the radar rack. Two operational controls are 2. Issues action orders for the director also mounted on this unit: a switch to select system crew and the battery under his control. automatic or manual gain control and a knob to Director Pointer. adjust the gain manually. 1. Slews the director to the designated .. The control indicator unit in the radar rack bearing of the target has a 5-inch A-scope on which can be shown a 2. Searches and tracks in train and ele main sweep of zero to 60,000 yards, an expanded vation sweep of zero to 10,000 yards, or a precision 3. Makes all operational checks at the sweep of any 2500 yard interval from zero to director. 36,000 yards. A switch on the front panel of the Radar Operator. control indicator unit selects any one of the 1. Controls operation of all below-decks sweeps. The range marker appearing on these radar equipment with the exception of the Tacu sweeps is a movable step that is controlled by a 2. Gates pip and reports target range range unit. 3. Spots in range as required The range unit has a slewing control that 4. Makes operational checks and adjust enables the operator to slew the range step ments of all radar equipment. toward the target pip at approximately 6000 yards per second without affecting the tracking Target Acquisition Operator. rate. Control of the tracking rate is facilitated 1. Aids radar operator in starting proce by a mechanically-coupled handcrank or by dure aided tracking circuits. With aided tracking, the 2. Operates target acquisition unit to crank functions as a control of the range-rate coach director pointer on target during search mechanism so that the operator does not have 3. If required during tracking, reads radar to follow the target pip continuously by hand. range to director talker every 500 yards. A time switch provides a choice of two ratios of the range change produced by the crank to Typical Operating Procedure the change in rate set by the same movement In typical operations with GFCS Mk 63, of the crank. These aided range features enable Radar Equipment Mk 28 aids target acquisition the operator to track a target smoothly regard and tracking, and supplies range and range less of whether the target range rate is fast rate data. Acquisition with the target acquisi or slow. If the range of a target is changing at tion unit is usually preferable to above-decks a uniform rate, the aided tracking circuits will acquisition with the director alone. A new tar keep the range step moving adjacent to the get generally will be spotted first by the search target pip. radar, and its bearing and range will be deter A range-rate dial, located to the right of the mined by that equipment. In some instances, an range crank, displays the rate in knots at which the range is being changed by the aided track estimation of target elevation may be available. ing unit; the quantities displayed are shown as If no target elevation designation is available, increasing or decreasing range rates. the Tacu operator and the director pointer may 72 EQUIPMENT OAT A

conduct an organized search about the desig With the target gated, target indications also nated bearing sector. appear on the train and elevation indicator con The Tacu operator can cause the antenna to trol unit. nod in elevation either 5 degrees or 15 degrees Once the system is in the tracking mode, the relative to the line of sight while the director Tacu is out of the circuit, the antenna stops pointer cycles the director through the desig nodding, and the pointing error signals to the nated bearing sector in accordance with signals gun sight T&E-scope enable the director pointer from the Tacu. This sector search is repeated to perform blind tracking. with the Tacu sending increasing director eleva tion orders to the pointer's scope. Such a search Conditions of Readiness pattern allow8 for increasing target elevation SECURED. All power is off. as the target closes range. When the target is somewhere in the beam, NORMAL SHUTDOWN. Power is on to heaters but is not yet gated, an indication appears on and convenience outlets. the radar operator's A-scope and on the Tacu STANDBY. On initial starting, a one minute operator's double-E scope. The Tacu operator delay must elapse before the plate circuits can ,. uses the pointing indications on the double-E be energized. The equipment may be cycled scope to coach the director pointer squarely on from standby to operate at any time after the the target. The radar operator then can gate the time-delay relays have operated. target pip on his A-scope and adjust the range OPERATE. The equipment is in complete elec rate in his range unit to keep the target gated. trical operation.

NOTES ON YOUR SHIP'S INSTALLATION

73 Chapter 10 RADAR EQUIPMENT MK 34 AND MODS

Radar Equipment Mk 34 Mods 2, 6, and 16 is different calibers, switches are provided in the an integral part of the antiaircraft Gun Fire associated radar equipment to alter the com Control System Mk 63 for the control for 40-mm puted electrical values to compensate for the and 3"/ 50 guns. See figure 77. ballistic differences of the several types of guns. Radar Equipment Mk 34 Mods 3, 4, 7, 8, 9, 10, Radar Equipment Mk 34 measures range out 11, 12, 13, and 14 is used as part of antiaircraft to 40,000 yards, permits observation out to Gun Fire Control Systern Mk 57 for the control 60,000 yards, provides range-rate data, and in of 40-mm guns or as a standby system for 5- dicates the bearing and elevation of the target. inch or 6-inch guns. See figure 78. This target information is furnished automati Since GFCS Mk 57 and GFCS Mk 63 are de cally to the associated computer whenever the signed to control the fire of guns of two or three system is tracking in radar control.

figure 77-Antenna for Radar Equipment Mk 34, on 3" I 50 Mount.

74 CQNFI9 5 b'l' til EQUIPMENT DATA

Figure 78-Antenna for Radar Equipment Mk 34, on Gun Director Mk 57.

The functional arrangement of Radar Equip scan. During tracking the antenna is offset from ment Mk 34 is shown in figure 79. Detailed char the line of fire to remain on the target. acteristics of the radar are given in Part 3, Target indications are available to the direc Reference Data. tor pointer on a T&E-scope which in the GFCS Mk 63 is part of the gun sight and in the GFCS Operational Units Mk 57 is part of the director indicator. In both The antenna used in Radar Equipment Mk 34 systems target range information is presented with GFCS Mk 57 is mounted in a fixed position to the range operator below decks on an A-scope on the director. An antenna drive motor moves control indicator, while indications of the point the antenna feed to produce a conical scanning ing error are repeated on a T&E-scope. In the pattern. GFCS Mk 63 target information is also shown The antenna used in mods which are part of on the double-E scope of a target acquisition GFCS Mk 63 is mounted on the gun slide as unit. shown in figure 77. During search, the antenna In those radar equipments which are part of reflector is held in line with the gun bore but the GFCS Mk 63, the spot in the T&E-sc~pe is the antenna feed nods through 10 degrees or 30 superimposed on the optical image in the direc degrees in elevation while performing conical tor gun sight. This arrangement simplifies the C0141 IJEIQIIAL 75 3Z3489 0 - 54 - 6 OP 1895 .tliil81WIIII tliJI\~ problem of getting on target for the director panded sweeps shows the area out to 18,000 or pointer. During search the position of the spot 27,000 yards on the scope. Precision sweep dis is controlled from the target acquisition unit. plays any selected 2500-yard interval of the In radar equipments used with GFCS Mk 57, main sweep, out to 40,000 yards. the director indicator containing the T&E-scope A 2-inch T&E-scope in the radar control also houses an A-scope and an artificial horizon. unit duplicates the presentation in the gun sight The A-scope displays a sweep line with a maxi or director indicator above decks. This arrange mum range of 15,000 yards. ment permits close coordination between the The radar indicator (control), in the radar radar operator and the director pointer. rack below decks, figure 80, displays any one · The range unit in the radar rack measures of three sweeps on a 5-inch A-scope. Main target range, registers range on a counter, de sweep extends to 60,000 yards. A choice of ex- termines and displays range rate, and transmits

RANGE RATE

RANGE ANTENNA GUNSIGHT

NODDING VOLTAGE

ABOVE DECKS """ "'" BELOW DECKS

VIDEO POINTING TARGET CONTROL ACQUISITION UNIT ~ INFORMATION UNIT POINTING INFORMATION (INDICATOR) ... t__ Q: .... ::.: 0 (!' Q: .... z < 0 < :IE ,------, Q: > ~ RELAY ~ 1 TRANSMITIER ~ RANGE RANGE RANGE INDICATOR 1 MK13 ' UNIT MARK (CONTROL) J (PART OF ~ --__,1 G.F.C.S. MK63) - I ~ ...... ~ ...... ~ J SYNCHRONIZING PULSE J

ECHOES (

MODULATION TRIGGER TRANSMITTER GENERATOR RECEIVER

Figure 79-Radar Equipment Mk 34 with GFCS Mk 63, Functional Schematic.

76 SQbiE'RP R ' I CO.IFIIii'S'Il'il' EQUIPMENT DATA

... ,.

G£N£RATOR UNIT

Figure 80-Radar Components in Rack. QQtiFIBEI t•L 77 OP 1895 00141 IIIIHI~ both range and range rate to the system com Target Acquisition Operator. puter. An aided tracking mechanism supple 1. Aids radar operator in starting pro ments manual controls to permit tracking of cedure high-speed targets. 2. Operates target acquisition unit The control unit (power) is the central control 3. If required during tracking, reads radar and distribution point for power. Switches in range to director talker every 500 yards. this unit govern the power operating conditions of the other units of the system. Typicai Operating Procedure The target acquisition unit, used only with In typical operation of the GFCS Mk 57 with GFCS Mk 63, compares director train and eleva Radar Equipment Mk 34, the target is desig tion with the designated target bearing and nated to the control officer by telephone. His elevation. The Tacu transmits signals to the gun talker repeats the designation data to the direc sight or to the director indicator which move tor crew and to the radar crew. The radar oper the spot on the T&E-scope in tlie direction of ator below decks slews to a range beyond the the target designation. As the director is moved reported range and watches for the target pip. to cancel the pointing error, the spot becomes The control officer helps slew the director to the centered in the cross-hairs, and the director po designated bearing and then slowly oscillates the sition coincides with the designation. A double director approximately 5 degrees either side of E-scope on the Tacu indicates to the target the designated target bearing. At the same time, acquisition operator the remaining pointing the director pointer searches in elevation by errors once the target is picked up in the beam, moving the director up and down between zero permitting him to coach the pointer in centering and 30 degrees or 15 degrees on either side of the the target in the beam. designated target elevation. Operating Personnel When the target pip appears on the below decks indicator, the radar operator gates it, the The radar crew is part of the operating per circle in the director T&E-scope diminishes to sonnel of GFCS Mk 57 or GFCS Mk 63. The a spot, and the director pointer commences operators and their principal duties are: tracking. The director is on target and in com Control Officer. plete radar control. 1. Selects the target (if it is not designated In typical operation of the GFCS Mk 63 with by another source) Radar Equipment Mk 34, target acquisition is 2. Estimates range and range rate guided from the Tacu below decks. Target in 3. Issues action orders for the battery un formation is transmitted through the target de der his control. signation system to the Tacu operator and to the Director Pointer. radar operator. The radar antenna on the gun 1. Slews the director to the designated mount nods when the search-track switch on the bearing of the target Tacu is set at search. The Tacu signals guide the 2. Searches and tracks in elevation as well director pointer who moves the director in re as traverse sponse to the spot indication in the same way 3. Assists control officer in identifying tar that he would respond to a target indication. gets and in estimating range When a pip appears on the double-E scope, the 4. Makes all operational checks at the target acquisition operator centers the target director. in the beam by further guiding the movements Radar Operator. of the director pointer. As soon as the director 1. Controls operation of all below-decks and antenna are on target, the Tacu operator radar equipment with the exception of the Tacu switches to track to stop the antenna nodding 2. Gates pip and reports target range and to disconnect the Tacu from the circuit. The 3. Spots in range a.s required spot in the gunsight indicator is then controlled 4. Makes operational qhecks and adjust by the radar and the director is tracking in ments of all radar equipment. radar control. 78 w&t'SJDH'P • I. EQUIPMENT DATA

Conditions of Readiness delay in putting the entire director system in the action condition. SECURED. All power is off. STANDBY FOR IMMEDIATE READINESS. Power is maintained to all units. The only circuit not fully NORMAL SHUTDOWN. Power is on to heaters and convenience outlets. energized is that of the radar transmitter, which can be put into operation in a matter of seconds. STANDBY FOR HALF-HOUR READINESS. Power OPERATE. The equipment is in complete oper is furnished to the radar equipment from ship's ation. (Approximately two hours are required 115-volt a-c supply. This condition is used during to bring the equipment from the secured con periods when circumstances permit a half-hour dition to the action condition from a cold start.)

NOTES ON YOUR SHIP'S INSTALLATION

79 Chapter II

RADAR EQUIPMENT MK 35 AND MODS

Radar Equipment Mk 35 is an automatic power supplies, is mounted on the director above tracking fire control radar which functions as decks. See figure 81. Radar indicating and an integral part of antiaircraft Gun Fire Con operating controls are part of a control console trol System Mk 56. for the entire fire control system. This control The radar components are physically a part console, together with power supplies and the of various elements of the gun fire control sys majority of the fire control system components, tem. The radar antenna, together with an asso is located in a control room below decks and ciated transmitter-receiver assembly and certain controlled by a radar operator and radar tracker.

figure 8J-Anfenna for Radar Equipment Mk 35, on Gun Director Mk 56.

80 EQUIPMENT DATA

The radar's fire control function in the GFCS Operational Units Mk 56 is to acquire obscured targets and to pro The transmitter-receiver assembly is mounted vide automatic tracking of targets in range, on Gun Director Mk 56. Although the transmit bearing, and elevation. The functional arrange ter is powered by a below-decks supply, the re ment of the radar is illustrated in figure 82. ceiver derives power from an adjacent supply Under optimum conditions, Radar Equipment chassis mounted in a compartment of the gun Mk 35 can acquire a target within a reliable director. Power and operational control of the acquisition range of 15,000 yards. Once a target transmitter-receiver is accomplished remotely is acquired, the radar can track it in range at from the below-decks console. A transmission speeds as fast as 650 knots within range limits line assembly of wave-guide sections joins the of 250 to 30,000 yards. When several targets are transmitter-receiver to the radar antenna in the beam, their pips can be resolved if they are separated in range by 40 yards, or if they assembly. are separated in angle by llf2 degrees. Accurate The antenna assembly on Gun Director Mk tracking is possible down to llf2 degrees above 56 moves with the director in train but is driven It If the horizontal as viewed by the radar. Gun Di independently of the director in elevation. is rector Mk 56, which carries the radar antenna, stabilized by a gyro in this director. Essentially, has a maximum traversing rate of 35 degrees the antenna assembly consists of an antenna per second. wave-guide feed, a parabolic reflector, and a Detailed characteristics of Radar Equipment scanning mechanism which nutates the antenna Mk 35 are given in Part 3, Reference Data. feed in spiral or conical scan.

VIDEO TRANSMITIER RF 30 ..,., REFERENCE ANTENNA RECEI,VER SIGNALS

AGC ANDJ t MODULATOR TRIGGER STC ABOVE DECKS ··::,:, rr I\!}> )) )i .

RANGE ERROR MOVABLE MOVABLE SIGNAL MARKERS MARKERS - RANGE DEMODULATOR SYNCHRONIZER CONDENSER ANGLE ERROR FIXED FIXED • SIGNAL MARKERS MARKERS ..,a: TRIGGER J

30 V"' REFERENCE SIGNAL _.)

figure 82-Radar Equipment Mk 35, Functional Schematic.

81 OP 1895 0 I FlPI&I CI IAL

In spiral scan, the antenna nutates at 30 the scan mechanism with a choice of spiral, con cycles per second, moving the 2-degree beam ical, or off positions. Indirect control of the scan through a 12-degree spiral pattern for search pattern is afforded by a footswitch located cen about a given target designation. In conical trally at the bottom of the console. The foot scan, the antenna nutation produces a 3-degree switch is available to both the radar operator cone for tracking the target. and the radar tracker, but it is usually operated by the radar tracker. The type of antenna scan is determined by a The control console, figure 83, serves as the scan-control switch on the console in the control operational center of the entire gun fire control room. This switch provides direct control of system.

Figure 83-Control Console, Containing both Radar and Fire Control System Components. 82 QQt lflbi!M I IJ te' ca~JFiistl!l o1 a EQUIPMENT DATA Two of the three indicators in the console are For targets that are being tracked through used by the radar operator. The left-hand indi clutter, or for low-flying aircraft that pass near cator, an AI R-scope, displays a 30,000-yard friendly surface craft or near other airplanes, A-sweep, and a 1000-yard R-sweep which shows the Mk 35 is equipped with a coast pushbutton a 500-yard expansion on each side of the range on the console which freezes the prevailing gate. During search and acquisition operations, tracking rates so that the radar will not track target pips appear on the A-trace. When the the stronger echo from the interfering object. target is gated and is being tracked automati Radar Equipment Mk 35 is relatively difficult cally, a pip appears in the notch of the A-sweep to jam. Its narrow beamwidth and short pulse and at the foot of the step in the R-sweep, while duration enable it to see through "window", and range marker blanks move horizontally to show in most cases, enable a skilled operator to track whether target range is increasing or decreas through "window" and other forms of jamming. ing. There are also scribe marks on the scope The narrow beamwidth enables it to break face that mark off the range scale at 10,000- through most electronic jamming unless the yard intervals. jamming device is on the target or very near it. Other anti-jamming provisions are essentially The center indicator also operated by the STC, receiver tuning, repetition-rate control, radar operator, is an E-scope that shows range and conical scan-rate control. horizontally from zero to 30,000 yards, and Radar Equipment Mk 35 can also be operated shows director true elevation vertically from in conjunction with a Chronograph Mk 1 to fur -10 degrees to +90 degrees. Curved scribe nish projectile velocity data for the computation marks on the face of the scope furnish an indi of initial velocity. cation of target altitude in yards. In spiral scan for search and acquisition, the trace appearing Operating Personnel on the E-scope is a 12-degree band. The center The operating personnel of the radar equip of this band moves vertically on the scope as the ment are a control officer stationed in the direc radar antenna is elevated, thus representing the tor and two men who operate the radar from true elevation of the director line of sight. If the below decks. spiral scan presentation is expanded, as required for surface firing, the trace covers about one Control Officer. The control officer is stationed half of the screen and remains fixed at the cen at the director where he is able to slew the direc ter of the scope. tor, thus bringing the antenna on target in bearing and elevation. He controls the switching A coarse range mark, called a range strobe on between radar tracking from the below-decks the E-scope, is slewed on the target pip by the console and optical tracking from the director. radar operator. The target then appears on the • Radar Operator. The radar operator is usually precision B-scope and on the R-sweep of the the senior operator below decks. He works with AIR-scope. the radar tracker to perform the following The tracker's precision B-scope, on the right duties: • hand side of the console, shows the target pip 1. Slews range when the radar operator has the range gate on 2. Controls antenna elevation his A-scope within 1000 yards of the target. 3. Performs "coast" procedures to keep the The B-scope covers only a range interval of automat~c tracking circuits from locking on in 1000 yards on either side of the range strobe. terfering echoes It shows bearing horizontally for 6 degrees 4. Performs radar anti-jam procedures either side of director train. The bearing trace In addition the radar operator is responsible appears as a vertical band with a width of 12 for starting operations, for setting the computer degrees in bearing for spiral scan, and 3 degrees to handle air targets, low-angle air targets, or in bearing for conical scan. Target pips appear surface targets, and for setting sight angle and on the trace as horizontal .Iines equal in length sight deflection for any special surface fire pro to about 3 degrees of bearing. cedures. ~Ill ibbN I ilt 83 OP 1895 • Qlf IFI8214'f1Ar Radar Tracker. The radar tracker works with switch to shift the antenna to conical scan in the radar operator to perform the following readiness for automatic tracking. When the duties: radar operator sees the tracking circuits lock on 1. Positions the director in bearing during the pip on his A/R-scope, he reports to the con radar search procedures trol officer that the pip is gated. The automatic 2. Uses aided range once target is on pre tracking circuits keep the director on target and cision B-scope keep the pip gated while the below-decks opera 3. Controls antenna scan and operation of tors observe the progress of tracking on their the automatic tracking circuits scopes. When the target is destroyed, or has 4. Performs aided tracking in bearing dur passed beyond effective range, the control officer ing surface modes of firing. orders the console operators to switch to spiral scan and to restore other preliminary settings in Typical Operating Procedure preparation for a new target. In a typical operation, a target designation Conditions of Readiness station assigns a target to the system. To accept the designation, the radar tracker presses the SECURED. All power is off. target designation button on the console to syn NORMAL SHUTDOWN. Power is on to heaters chronize the system with the designated values. and convenience outlets. The antenna performs spiral scan for search STANDBY. All power is on and all filaments about the designated position. Both of the con are warmed up. Transmitter power to the an sole operators watch the E-indicator for the tenna is not on. In initial standby condition, target pip. When the target pip is visible on the time-delay relays must operate for three min E-scope, the radar operator slews the range utes before they will permit the equipment to be mark close to the pip and cranks elevation to switched to operate condition. center the pip on the trace. As soon as the pip OPERATE. The entire equipment is in opera is visible on the B-indicator, the radar tracker tion. Recycling from standby to operate, after cranks range to center the pip vertically and the equipment has been in operation and has cranks bearing to center the pip horizontally. been returned to standby, can be accomplished The tracker then presses the scan-control foot- in less than five seconds.

NOTES ON YOUR SHIP'S INSTALLATION

84 CO~JFIIEII&AL

Chapter 12 RADAR EQUIPMENT MK 39 MODS 3. 4

Radar Equipment Mk 39 Mods 3 and 4 is an to 30,000 yards, provides range-rate data, and integral part of antiaircraft Gun Fire Control indicates the bearing and elevation of the target. System Mk 57 Mods 4 and 11. The radar antenna Range and range rate are furnished auto is shown mounted on Gun Director Mk 57 in matically to the associated computer when the figure 84. The radar equipment measures range system is tracking normally.

Figure 84-Antenna for Radar Equipment Mk 39, on Gun Director Mk 57. 85 OP 1895 £Qb'§'PP '71 I ... Since GFCS Mk 57 is designed to control the Operational Units fire of guns of different calibers, the electrical The radar antenna is mounted on the front of value of the range rate used can be altered to the director with the electrical axis of the an correct the ballistic values for the different guns. tenna held coincident with the director line of A switch permits the operation of Radar Equip sight. An antenna-drive motor moves the an ment Mk 39 Mod 3 with 40-mm and 5"/38 guns; tenna feed to produce an elliptical scanning and of Mod 4 with 3"/ 50, 5"/ 54, and 6" / 47 guns. pattern for search, or a conical pattern for tracking. The functional arrangement of Radar Equip The radar transmitter-receiver is mounted ment Mk 39 is shown in figure 85. Detailed char below decks near the director. It is tuned acteristics of the radar are given in Part 3, remotely from a radar console in the system Reference Data, control room.

RADAR FILAMENT TRANSFORMER INDICATOR VOLTAGE (FILAMENt) REFERENCE (DIRECTOR) ~ ANTENNA I ~ I J VOLTAGE • AMPLIFIED ECHO (VIDEO) RF J 2ND RANGE MARK ABOVE DECKS

~ BELOW DECKS

AMPLIFIED AND RADAR RADAR DETECTED ECHO (VIDEO) TRANSMITIER INDICATOR RECEIVER (CONSOLE)

t RECEIVER TUNING \. TRAIN AND ELEVATION DEFLECTION AUTOMATIC GAIN CONTROL VIDEO

l GATED ECHO TARGET POWER ACQUISITION SUPPLY UNIT TRAIN AND ELEVATION UNIT """ • - DEFLECTION TRAIN AND ELEVATION J DEFLECTION

SYNC SIGNAL RANGE RADAR CONTROL VOLTAGE } TO AMPLIFIER RADAR PULSE RANGE (PART OF RANGE MODULATOR UNIT GFCS MK57) NOTCH INDICATION RATE

CONTROL PULSE (MODULATOR TRIGGER) J SWEEP TRIGGER

figure 85-R.adar Equipment Mk 39, Functional Schematic. 86 1 3 COb 5'%t' ' OJ EQUIPMENT DATA An inicator is mounted on the director for sweep can be adjusted between the limits of use by the pointer in acquiring or tracking a tar 8000 and 25,000 yards. get in radar control. This unit consists of a The control console, below decks in the radar T&E-scope, an E-scope, and an artificial horizon room, houses a modulator, range unit, indicator indicator. The E-scope nominally shows ranges unit, power supply unit, and fuse and terminal from zero to 20,000 yards but the length of the box. See figure 86.

FUZE AND • • TERMINAL BOX - c•• •• • •

RADAR POWER • SUPPLY UNIT

RADAR INDICATOR UNIT (CONSOLE)

,. • ...... '- • "' RADAR .., RANGE UNIT J

.. RI~ I: ~• · •- - II •-- •.A .a .a d ll

LA TOR

Figure 86-Radar Console. 87 OP 1895 fCOb'Etsn lia.tla: The modulator pulses the transmitter circuits move the dot on the cathode ray tube in the of the transmitter-receiver unit. A main power direction of the target designation. As the di toggle switch and a battle short switch are lo rector is moved to cancel the pointing error, the cated on the front panel of the modulator unit. spot becomes centered in the cross-hairs and the The range unit ranges on a moving target director position coincides with the designation. with an aided tracking mechanism during A double-E scope on the Tacu indicates the normal operations. Values of range and range direction the director must be trained after the rate can be read on the face of the range unit, target has been picked up, to center the target and both are transmitted electrically to the fire in the beam. control computing system. The power supply furnishes the voltages In an emergency, the aided tracking mecha needed to operate the rest of the equipment. nism may be disengaged and manual tracking Among the controls on the front panel are a performed. Under this condition, the range rate switch to change from manual to automatic tun is not transmitted automatically to the com ing, a tuning knob for manual tuning, and puter, but it may be found by timing the change switches to cut in the FTC or IAGC circuits for in the counter readings. A knob and dial ar anti-jamming purposes. rangement enables the operator to set in such • range rates for emergency transmission to the Operating Personnel computing system. The radar crew is part of the operating per The radar indicator consists essentially of a sonnel of GFCS Mk 57. The operators and their 5-inch A/R scope and a 2-inch T&E monitor principal duties are: scope. The main sweep of the A/R-scope extends Control Officer. from zero to 30,000 yards. The precision sweep 1. Selects the target (if it is not designated of this scope displays 1000 yards on each side of by another source) the range notch. Whenever the target is in the 2. Estimates range and range rate notch, a spot on the T&E-monitor shows the 3. Issues action orders for the battery un relation of the target to the radar beam axis. der his control. The target acquisition unit or Tacu, figure Director Pointer. 87, compares director train and elevation with 1. Slews the director to the designated the designated target bearing and elevation. It bearing of the target transmits signals to the director indicator that 2. Searches and tracks in train and eleva tion 3. Assists control officer in identifying tar gets and in estimating range 4. Makes all operational checks at the direc tor. Radar Operator. 1. Controls operation of all below-decks radar equipment with the exception of the Tacu 2. Gates pip and reports target range 3. Spots in range as required 4. Makes operational checks and adjust ments of all radar equipment. Target Acquisition Operator. 1. Aids radar operator in starting proce dure 2. Operates target acquisition unit 3. If required during tracking, reads radar figure 87-Target Acquisition Unit. range to director talker every 500 yards. 88 Gilt 151 214 I.-. EQUIPMENT OAT A Typical Operating Procedure Conditions of Readiness In a typical operation of the GFCS Mk 57, tar SECURED. All power is off. get search and acquisition are controlled by the target acquisition operator below decks. Signals NORMAL SHUTDOWN. Power is on to heaters from the Tacu guide the director pointer to the and convenience outlets. designated bearing and elevation. If target ele vation is not designated, the Tacu operator con STANDBY FOR HALF-HOUR READINESS. Power ducts a search in elevation about the designated is furnished to the radar power supply equip bearing. ment from ship's 115-volt a-c supply. This condi Search is normally conducted with elliptical tion is used when circumstances permit a half scan. However, as the maximum detection range hour delay in putting the entire director system with elliptical scan is about 5000 yards less than in the action condition. that with conical scan, the latter may be used in STANDBY FOR IMMEDIATE READINESS. Power search for long-range targets. is maintained to all units. The only circuit not When the target comes into the beam and a fully energized is that of the radar transmitter, • pip appears on the Tacu double-E-scope, the which can be put into operation in a matter of Tacu operator guides the director pointer to seconds. center the target in his indicator. As soon as the director is on target, the scan is shifted to OPERATE. The radar equipment is in complete conical and the Tacu is disconnected from the operation. (Approximately two hours are re system. The spot in the director indicator is quired to bring the equipment from the secured then controlled by the radar, and the system is condition to the action condition from a cold tracking in radar control. start.)

NOTES ON YOUR SHIP'S INSTALLATION

- ..

89 Chapter 13 . RADAR SET AN/SPG-48

Radar Set AN /SPG-48 is an automatic track In a gunar system, the antenna on the gun ing fire control radar which is an element of mount, moves with the mount in train, and cor Gunar Mks 1, 2, and 3 for the control of AA fire responds by independent drive with the gun in of 3"/50, 3"/70, and 5"/54 caliber guns. Figure elevation: The mount serves as the director for 88 illustrates the installation of the antenna on the gunar system by responding in train and the 3"/50 Mount (Gunar Mk 1). elevation to automatic tracking signals devel- ,

•

figure 88-Antenna for Radar Set AN/SPG-48, on 3"I 50 Mount CGunar Mk J J. 90 '!Klurua"' !i m c. Jib it ) 1 4 EQUIPMENT DATA oped by the radar equipment when the radar is transmitter and associated power supplies are locked on a gated target. As the mount moves usually located in a nearby below-decks com to track the target, an antenna drive automati partment. The functional arrangement of Radar cally responds to the gunar system computing Set AN/ SPG-48 (Gunar Mk 1) is shown in circuits to offset the antenna axis from the gun figure 89. axis by the amount of the computed lead angles. Under optimum conditions, Radar Set AN/ Mount positioning can also be handled by re SPG-48 has a reliable acquisition range of 24,000 mote manual control by means of hand wheels yards. Once a target is acquired, the radar can on a control console located in a below-decks track it in range at speeds as high as -+-1115 gunar control room adjacent to the mount. This knots within range limits of 350 to 45,000 yards, console contains indicators and operating con with an accuracy of ±10 yards +0.025% of trols for handling radar functions. The radar measured range. When several targets are in the

REFERENCE VOLTAGE ANTENNA

t RF

ABOVE DECKS

_ ~., ,~~-·-··'·!-~:~,,.,.,,,.,,,.,:,:-~;:,··,······· -- ·-· .•. ,_ .. ,.• -----~·· ~-~··~-· :::~:: .. -. -·-·.·.··.·:::·;·::::::::.:::.~;;;J~~;;::::.::;:::;::;::.:'r· -~.:~~:.:.: ~~-:·: ...•• E .- .•. -~-....;•::.-.-~;;_,.. _ ...... ,.;2~ - .. ;:.·;.:,;:•:·: ?t'i n '~ BELOW DECKS

SYNCHRONIZING TIMING MODULATING MODULATOR TRANSMITIING ,.-- SYSTEM SYSTEM PULSE SYSTEM

+ TIMING VIDEO VIDEO SIGNAL RECEIVER RF SYSTEM SYSTEM

Lo.l VIDEO SIGNAL (!' z c a:: ( ....., ELEVATION ERROR •ANGLE TIMING RANGING ERROR SYSTEM DETECTING I. SYSTEM BEARING ERROR ~

TO >- CONSOLE RANGE MK7 ACQUISITION ACQUISITION SIGNALS RANGE SYSTEM DESIGNATION ERROR

RANGE ~

DESIGNATION INFORMATION -'

figure 89-Radar Set AN/SPG-48, Functional Schematic.-

91 3Z3489 0 - 54 - 7 OP 1895 <;QtiE

beam, their pips can be resolved if they are sep is determined by radar circuits that detect the arated in range by 80 yards, or if they are sepa difference in echo power received from different rated in angle by 2.2 degrees. Accurate tracking sectors within the radar beam. The gun-mount is possible down to 1 degree above the surface drives receive successive radar tracking error of the ocean as viewed by the radar. signals as tracking rates and operate to cancel Other pertinent characteristics of Radar Set positional tracking errors, thus bringing the AN /SPG-48 will be found in Part 3, Refer radar tracking line and the line of sight into ence Data. correspondence. The rest of the radar elements are located Operational Units below decks. The antenna on the mount is con The antenna of Radar Set AN/SPG-48 is in nected by a waveguide to a below-decks trans stalled on the gun carriage of 3"/50 Mod 0 mitter. The transmitter housing is a single cabi mounts by Antenna Mount Mk 32 Mod 0. The net that contains test components of the trans , antenna is carried on the front of the gun house mitting system and the initial functional stages on 5"/54 Mod 1 and 3"/70 Mod 1 mounts by of the receiving system in addition to the trans Antenna Mount Mk 32 Mods 2 and 3. mitter. Essentially, the antenna is an assembly con The radar console, figure 90, is the control sisting of a feed-horn radiating element, a para center of the system. For radar functions, it bolic reflector that concentrates the energy into contains controls for the operation of the radar a 2.2 degree beam, and a nutating mechanism. set, and indicators and controls for the range, This antenna-nutating mechanism can be oper elevation, and bearing coordinates, ated in spiral or conical scan by means of a scan The radar set controls include essentially control switch on the radar console below decks. power control switches to place the equipment For normal operation, a foot-switch, operated by the radar operator at the console, changes the in the desired power condition, a scan control antenna scan from spiral to conical, or vice switch that selects the antenna scan pattern, versa. and a radar-chronograph switch that enables the radar to supply data to a chronograph unit In spiral scan, used for acquisition, the 2.2- which furnishes initial velocity information to degree beam is moved continuously through a the gunar system. 12-degree spiral pattern for search about a given target designation. In conical scan the Controls for the radar transmitter and re ;mtenna nutation produces an effective 3.6- ceiver consist of an automatic gain control degree cone for tracking the target. (AGC), a manual gain control, separate trans During search and acquisition, the antenna mitter and receiver controls, adjustable repeti assembly is positioned by elevation and traverse tion rate, and anti-jam controls (STC, FTC drives in the antenna mount so that the axis of and IAGC). There is also a coast pushbutton the radar scanning pattern is effectively coinci that freezes the prevailing tracking rates so dent with the axis of the gun barrel. During that the radar will not lock on a stronger echo tracking, the antenna assembly is displaced by from a larger target when the target in the the antenna drives so that the a,xis of the scan gate passes near surface targets or near other ning pattern is offset from the axis of the gun airplanes. barrel by sight angle and sight deflection. The range indicator is an A/R-scope with a For tracking, the antenna assembly must be 40,000-yard main sweep and a 2000-yard pre positioned continuously so that the geometric cision sweep. The range step on the A-sweep is axis of the reflector, if projected, would pass controlled automatically or manually. In auto through the target. This axis is called the radar matic control, the location of the range step is tracking line. The positional tracking error that governed by the target designating station or represents the displacement between the radar by the radar range error detecting circuits. In tracking line and the line of sight to the target manual control, the range step is positioned by

92 L EQUIPMENT DATA

:~1 l f1.·.···· or r

- ~ --,.::.. ~~-- -

{? ~a ~ ~_.. n ~· ~~

•

Figure 90-Radar Console.

either of two controls on the console : a range The R-sweep is a 2000-yard segment of the tracking handwheel affording manual or aided main sweep that is centered at the range gate. tracking, and a range slew switch. Any targets At the center of this precision sweep is a range indicated on the A-sweep that are within 1000 notch, the left edge of which represents the pre yards on either side of the range step are also cise range measurement of the range gate as shown on the R-sweep. determined by the radar ranging system. There

93 OP 1895 are also 1000-yard range markers, appearing as this spot becomes a small circle and settles at blanked segments of the R-sweep, that move the center of the screen. across the trace to show whether a gated target is increasing or decreasing in range. Operating Personnel The elevation indicator displays either a type The radar crew consists of a radar operator, E presentation with main or precision sweep, or stationed at the left side of the radar console, a t..E presentation, as selected by the operator. and a radar tracker, stationed at the right side The type-E presentation shows range horizon of the console. The principal duties of these men, tally, and elevation beam deflection vertically also referred to as console operators are as above and below the center of the indicator follows: screen. The t..E presentation is essentially the Radar Operator. same except that the horizontal center of the 1. Evaluates range and elevation scope in presentation is displaced vertically from the dications bottom of the screen by an amount proportional 2. Controls in range and elevation during to the true elevation of the gun line between the search and acquisition operations limits of -15 degrees to +85 degrees. A cali 3. Controls changeover to automatic track brated scale on the indicator facilitates estima ing mode tion of the true elevation of the radar tracking 4. Monitors range during automatic track line. During search modes, the gun line and the ing mode radar tracking line are coincident. However, 5. Prevents the automatic tracking circuits during tracking, the radar tracking line is offset from locking on interfering echoes from the gun line by the elevation lead angle, so 6. Performs the radar anti-jamming proce that the horizontal center of the t..E presenta dures tion represents true elevation only of the gun 1. Tunes the transmitter and receiver. line. For actual control of the gun line, there is an elevation slew switch on the console for fast Radar Tracker. or slow elevation slewing. An elevation hand 1. Turns on the power wheel provides manual or aided tracking control 2. Controls the changeover to target desig in elevation. nation mode 3. Controls in bearing during search and The bearing indicator is a B-scope with a acquisition operations choice of a main sweep of 40,000 yards in range 4. Monitors in bearing during automatic or a precision sweep representing a 2000-yard tracking mode. range segment centered about the range gate. Each sweep is brightened at a point correspond ing to the position of the range gate. A slewing Typical Operating Procedure control switch facilitates fast or slow slewing In typical operations, a target designation of the gun mount in train. Manual or aided station designates a target to the gunar system. tracking control of the mount in train is pro The below-decks operators observe designation vided by a handwheel. Present true and relative lamps on their console and press an accept desig bearing and designated bearing are shown on nation button to synchronize the system with dials located above the B-scope. the transmitted values of target bearing, eleva tion, and range. The radar operator then re There is also a T&E-scope on the console that leases the target designation button and the sys shows a bright spot, in a position relative to the tem is operated under manual radar control. If center of the scope, that corresponds to the posi the target is not visible on the radar indicators tion of the gated target relative to the radar when the system has been synchronized, the con tracking line. When the echo signal is less than sole operators use the handwheels to conduct an the amount required for automatic tracking, organized search about the designated position.

94 ~L EQUIPMENT OAT A When the pip appears, the radar operator Conditions of Readiness gates it in range on his A/R-scope and centers it SECURED. All power is off. on the E-scope ; the radar tracker centers it on his B-scope. The radar operator then presses the NoRMAL SHUTDOWN. Power is on to heaters footswitch to put the system in automatic radar and convenience outlets. tracking. STANDBY. Low voltage rectifiers deliver power In automatic tracking, the radar tracking cir in one minute. A time-delay relay, which cannot cuits provide signals which cause the gunar sys be bypassed, cycles through four minutes before tem to follow the target in bearing, elevation, power can be applied to the magnetron for radi and range while the radar crew only observes ation in the operate condition. the progress of tracking and makes corrections if the system drops out of automatic. The gunar OPERATE. The entire radar system is in opera computer generates lead angles with which the tion. Once the equipment has reached readiness radar tracking line is offset from the gun line for this condition of operation, it may be and continues computation until a solution is switched from operate to standby and then back reached and the gun line is positioned along the to operate without requiring recycling of the required line of fire. time-delay relays.

NOTES ON YOUR SHIP'S INSTALLATION

95 OP 1895 I J'

NOTES ON YOUR SHIP'S INSTALLATION

96 a a: 18214 ""L.

PART 3-REFERENCE DATA

Chapter 14 PERFORMANCE CHARACTERISTICS

RADAR EQUIPMENT MK 8 MOD 3 Range data Range, maximum, yards ...... 44,000 ;, Range, minimum, yards ...... 200 Accuracy, yards ...... -+- (15 + 0.1% R) Target acquisition Type ...... Manual Tracking accuracy, mils Bearing ...... ±3.62, reset -+- 1.5 Receiving system Antenna coupling ...... Waveguide IF frequency, megacycles ...... 60 IF bandwidth, megacycles ...... 5.0 Frequency control ...... Manual Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 8815 -+- 75 Peak RF power, kilowatts ...... 35 to 45 Pulse rate, pulses per second ...... 1500 -+- 5% Pulse length, microseconds ...... 0.3 RF lines, type ...... Waveguide Power consumption 4 Total, kilovolt-amperes ...... 3.3 Antenna Type ...... Rocking, truncated paraboloid • Size, feet (approximate) ...... 8 x 2 Gain, decibles* ...... 39 Beam width, degrees In the horizontal plane ...... 0.9 In the vertical plane ...... 3.6 Scan Type ...... B-Scan Angle, degrees ...... 11.6 Coverage, degrees: In the horizontal plane only ...... 12.5

• Approximate for one-way transmission

97 OP 1895 ,Q?t15i1PB 'if:AJ

RADAR EQUIPMENT MK 12 MODS 0, I Range data Range, maximum, yards ...... 50,000 Range, minimum, yards ...... 400 Accuracy, yards ...... ± (20 + .025% R) Slew rate, yards per second ...... 3500

Target acquisition Type ...... Manual

Tracking accuracy, minutes • Bearing and elevation* ...... +-10, reset +-4

Receiving system Antenna coupling ...... Coaxial IF frequency, megacycles ...... 30 . IF bandwidth, megacycles ...... 4 Frequency control ...... Manual

Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 920 to 970 Peak RF power, kilowatts ...... 99 to 110 Pulse rate, pulses per second ...... 48 +- 5% Pulse length, microseconds ...... 1.2 RF lines, type ...... Coaxial

Power consumption Total, kilovolt-amperes ...... 3.1

Antenna Type ...... Double, cylindrical paraboloid Size, feet (approximate) ...... 6 x 6 Gain, decibels** ...... 22 Beam width, degrees : In the horizontal plane ...... 10 In the vertical plane ...... 10

Scan Type ...... Lobe switching Angle, degrees ...... 5 Coverage, degrees*** : In the horizontal plane ...... 15 In the vertical plane ...... 15

• Elevation accuracy at an angle above 10 degrees •• Approximate for one-way transmission ••• Angle between line of sight and centerline of beam pattern

98 L PERFORMANCE CHARACTERISTICS

RADAR EQUIPMENT MK 13 MOD 0

Range data Range, maximum, yards ...... 80,000 Range, minimum, yards ...... 250 Accuracy, yards ...... + (15 + 0.1% R) Slew rate, yards per second ...... 3000

Target acquisition Manual Type ... · · · · · · · · · · · · · · · · · · · ·· · · · · · · · · · · · · · · · ......

Tracking accuracy mils +3.62 reset ± 1.5 Bearing...... ·. · · · · · · · · · · ·····················- ' Receiving system Antenna coupling ...... Waveguide IF frequency, megacycles ...... 60 IF bandwidth, megacycles ...... 9 Frequency control ...... Manual

Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 8815 -+- 75 Peak RF power, kilowatts ...... 50 Pulse rate, pulses per second ...... 1800 ± 10% Pulse length, microseconds ...... 0.3 RF lines, type ...... Waveguide

Power consumption Total, kilovolt-amperes ...... 3.9

Antenna Type ...... Rocking, truncated paraboloid Size, feet (approximate) ...... 8 x 2 e Gain, decibels* ...... 39 Beam width, degrees : In the horizontal plane ...... 0.9 In the vertical plane ...... - ...... 3.6

Scan Type ...... Sinusoidal horizontal Angle, degrees ...... 11.5 Coverage, degrees : In the horizontal plane only ...... 12.5

"' Approximate for one-way transmission

99 OP 1895

RADAR EQUIPMENT MK 22 MODS 0, I

Range data Range, maximum, yards ...... 45,000 Range, minimum, yards ...... 250 Accuracy, yards ...... + (25 + 0.1% R)

Tracking accuracy Bearing, degrees ...... 0.5 Elevation, mils ...... ±3.0

Receiving system Antenna coupling ...... Waveguide IF frequency, megacycles ...... 60 IF bandwidth, megacycles ...... 5 Frequency control ...... Automatic

Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 9375 + 30 Peak RF power, kilowatts ...... 30 to 40 Pulse rate, pulses per second : With Radar Mk 4 ...... 1640 With Radar Mk 12 ...... 480 Pulse length, microseconds ...... 0.5 RF lines, type ...... Waveguide

Power consumption Total, kilovolt-amperes ...... 2

Antenna Type ...... Section of paraboloid Size, feet (approximate) ...... 6 x 1% Gain, decibels* ...... 37 • Beam width, degrees: In the horizontal plane ...... 4.5 In the vertical plane ...... 1.2

Scan Type ...... Sinusoidal vertical Angle, degrees ...... 12 Coverage, degrees: In the horizontal plane ...... 4.5 In the vertical plane ...... 13

* Approximate for one-way transmission

100 PERFORMANCE CHARACTERISTICS

RADAR EQUIPMENT MK 25 MOD 2 Range data Range, maximum, yards ...... 50,000 Range, minimum, yards ...... 350 Accuracy, yards ...... + (15 + 0.1% R) Slew rate, yards per second: Slow speed ...... 0 to ± 500 High speed ...... +6000

Tracking acquisition Manual Type ... · · · · · · · · · · · · · · · · · ...... Bearing and elevation accuracy, mils Manual radar tracking ...... 5.0 Automatic radar tracking ...... 1.1 Receiving system Antenna coupling ...... Duplexer IF frequency, megacycles ...... 59 IF bandwidth, megacycles ...... 9 Frequency control ...... Automatic Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 8500 to 9600 Peak RF power, kilowatts ...... 50 Pulse rate, pulses per second ...... 1800 to 2200 Pulse length, microseconds ...... 0.25 RF lines, type ...... Waveguide Power consumption Total, kilovolt-amperes ...... 2.7 Antenna Type ...... Paraboloid Size, feet (approximate) ...... 5 .. Gain, decibels* ...... 38 Beam width, degrees: In the horizontal plane ...... 1.6 p In the vertical plane ...... 1.6 Beam shift, degrees** : Conical scan ...... 0.5 Circle scan ...... 5.0 Spiral scan ...... 0.5 to 5.0 Scan Coverage, degrees : Conical scan ...... 2.6 Circle scan ...... 12.0 Spiral scan ...... 2.6 to 12.0

* Approximate for one-way transmission ** Angle between line of sight and feed

101 OP 1895 ..SQt'F'Rst !TW L RADAR EQUIPMENT MK 25 MOD 3 Range data Range, maximum, yards ...... 100,000 Range, minimum, yards ...... 300 Accuracy, yards ...... -+- (15 + 0.1% R) Slew rate, yards per second Slow speed ...... 0 to ± 1000 High speed ...... -+- 10,000 Target acquisition Type ...... Manual Bearing and elevation accuracy, mils Manual radar tracking ...... 5 Automatic radar tracking ...... 1.1 Receiving system Antenna coupling ...... Duplexer IF frequency, megacycles ...... 59 IF bandwidth, megacycles ...... 9 Frequency control ...... Automatic Transmitting system Transmitter ...... Magnetron Frequency, megacycles ...... 8500 to 9600 Peak RF power, kilowatts ...... 250 Pulse rate, pulses per second ...... 1320 -+- 10% Pulse length, microseconds ...... 0.25 RF lines, type ...... Waveguide Power consumption Total, kilovolt-amperes ...... 3.7 Antenna Type ...... Paraboloid Size, diameter, feet ...... 5 Gain, decibels* ...... 38 Beam width, degrees : In the horizontal plane ...... 1.6 In the vertical plane ...... 1.6 Beam shift, degrees** : Conical scan ...... 0.5 Circle scan ...... 5.0 Spiral scan ...... 0.5 to 5.0 Scan Coverage, degrees; Conical scan ...... 2.6 Circle scan ...... 12.0 Spiral scan ...... 2.6 to 12.0

* Approximate for one-way transmission ** Angle between line of sight and feed 102 PERFORMANCE CHARACTERISTICS

RADAR EQUIPMENT MK 26 MODS 3, 4

Range data Range, maximum, yards ...... 27,500 Range, minimum, yards ...... 600 Accuracy, yards ...... •...... +75

Receiving system Antenna coupling ...... Duplexer IF frequency, megacycles ...... 30 IF bandwidth, megacycles ...... 2 Frequency control ...... Automatic

Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 3000 Peak RF power, kilowatts ...... 30 Pulse rate, pulses per second ...... 540 to 660 Pulse length, microseconds ...... 0.5 RF lines, type ...... Flexible coaxial cable

Power consumption Total, kilovolt-amperes ...... 1020

Antenna Type ...... Truncated paraboloid Size, diameter, inches ...... 36 Gain, decibels* ...... 26 Beam width, degrees : p In the horizontal plane ...... 10 In the vertical plane ...... 10

* Approximate for one-way transmission

103 OP 1895 egm Ellfh\L

RADAR EQUIPMENT MK 28 MODS 0, 2, 3

Range data Range, maximum, yards ...... 40,000 Range, minimum, yards ...... 400 Accuracy, yards ...... ± (15 + 0.1% R) Slew rate, yards per second ...... +6000 Target acquisition Type (Mods 0, 3) ...... Manual Type (Mod 2) ...... TACU

Bearing and elevation accuracy Manual radar tracking ...... ±2 reset

Receiving system Antenna coupling ...... Duplexer IF frequency, megacycles ...... 60 IF bandwidth, megacycles ...... 5.0 Frequency control ...... Automatic

Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 2992 to 3019 Peak RF power, kilowatts ...... 30 Pulse rate, pulses per second ...... 1800 +- 10% Pulse length, microseconds ...... 0.5 RF lines, type* ...... Rigid coaxial cable Power consumption Total, kilovolt-amperes ...... 1.7 Antenna Type ...... Paraboloid Size, diameter, inches ...... 45

Gain, decibels** ...... 27 ) Beam width, degrees : In the horizontal plane ...... 6.7 In the vertical plane ...... 6.7 Beam shift, degrees*** ...... 4.5 Scan Type ...... Conical Angle, degrees ...... 4.5 Coverage, degrees: In the horizontal plane ...... 11.2 In the vertical plane (tracking) ...... 11.2 In the vertical plane (with nodding) ...... 41.2

* Flexible coaxial cable for Mk 28 Mod 2 ** Approximate for one-way transmission *** Angle between line of sight and feed

104 g PERFORMANCE CHARACTERISTICS

RADAR EQUIPMENT MK 34 MODS 2 THROUGH 16 Range data Range, maximum, yards ...... 40,000 Range, minimum, yards ...... 350 Accuracy, yards ...... ± (15 + 0.1% R) Slew rate, yards per second* ...... +6000

Target acquisition With GFCS Mk 57 ...... Manual With GFCS Mk 63 ...... TACU

Bearing and elevation accuracy, mils t Manual radar tracking ....•...... +2.0 Receiving system Antenna coupling ...... Waveguide IF frequency, megacycles ...... 60 IF bandwidth, megacycles ...... 5.0 Frequency control ...... •...... •...... Manual

Transmitting system Transmitter oscillator ...... Magnetron Frequency, megacycles ...... 8740 to 8890 Peak RF power, kilowatts ...... 50 Pulse rate, pulses per second ...... 1800 + 180 Pulse length, microseconds ...... 0.3 RF lines, type ...... Waveguide

Power consumption Total, kilovolt-amperes ...... 1.5

Antenna ~ Type ...... Paraboloid Size, diameter, inches ...... 30 Gain, decibels** ...... 32 . Beam width, degrees : In the horizontal plane ...... 3.0 In the vertical plane ...... 3.0 Eeam shift, degrees***, Conical scan only ...... 1.5

Scan Type ...... Conical Coverage, degrees ...... 4.5

* Mods 11 and 14, ± 5000 u Approximate for one-way transmission ***Angle between line of sight and feed

105 OP 1895 GQ~- r··- ...... _, --~~------

RADAR EQUIPMENT MK 35 MOD 2 Range data Range, maximum, yards ...... 30,000 Range, minimum, yards ...... 350 Accuracy, yards ...... + (20 + 0.025% R) Slew rate, yards per second ...... 4000 Target acquisition Type ...... Manual

Bearing and elevation accuracy, degrees Automatic radar tracking ...... 0.7 Receiving system Antenna coupling ...... Duplexer IF frequency, megacycles ...... 60 IF bandwidth, megacycles ...... · ...... 11 Frequency control ...... Automatic Transmitting system Transmitter ...... Tunable magnetron Frequency, megacycles ...... 8500 to 9600 Peak RF power, kilowatts ...... 50 Pulse rate, pulses per second ...... 3000 + 5% Pulse length, microseconds ...... 0.1 RF lines, type ...... Waveguide

Power consumption Total, kilovolt-amperes * Antenna Type ...... Paraboloid Size, feet (approximate) ...... 4 Gain, decibels** ...... 39 Beam width, degrees : In the horizontal plane ...... 2.0 In the vertical plane ...... 2.1 Beam shift, degrees*** : Conical ...... 0.6 Spiral ...... 5.0 Scan Coverage, degrees : Conical ...... 3.0 Spiral ...... 12.0

• Included in power consumption of GFCS Mk 56 •• Approximate for one-way transmission *** Angle between line of sight and feed

106 L PERFORMANCE CHARACTERISTICS

RADAR EQUIPMENT MK 39 MOD 3, 4 Range data Range, maximum, yards ...... 30,000 Range, minimum, yards ...... 300 Accuracy, yards ...... + (30 + 0.5% R) Slew rate, yards per second ...... ±2000 Aided tracking rate, knots : Outgoing ...... 450 Incoming ...... 750 Target acquisition Type ...... TACU Bearing and elevation accuracy Manual radar tracking (mils) ...... ±2 reset Receiving system Antenna coupling ...... Waveguide IF frequency, megacycles ...... 30 IF bandwidth, megacycles ...... 3.5 Frequency control ...... Automatic Transmitting system Transmitter oscillator ...... Tunable magnetron Frequency, megacycles ...... 9000 to 9160 Peak RF power, kilowatts ...... 25 to 35 Pulse rate, pulses per second ...... 1800 ± 10% Pulse length, microseconds ...... 0.5 RF lines, type ...... Waveguide Power consumption Total, kilovolt-amperes ...... 2.2 Antenna Type ...... Paraboloid Size, diameter, inches ...... 30 Gain, decibels* ...... 30 Beam width, degrees: In the horizontal plane ...... 3.0 In the vertical plane ...... 3.0 Beam shift, degrees** : Conical scan ...... + 1.0 Elliptical scan; Horizontal ...... + 1.0 Vertical ...... ± 8.0 Scan Coverage, degrees: Conical scan ...... 5.0 Elliptical scan; Horizontal ...... 5.0 Vertical ...... 19

* Approximate for one-way transmission ** Angle between line of sight and feed

107 323489 0 - S4 - 8 OP 1895

RADAR SET AN/SPG-48 Range data Range, maximum, yards ...... 40,000 Range, minimum, yards ...... 350 Accuracy, yards ...... ± (10 ± 0.025 % R) Slew rate, yards per second Slow speed ...... 0 to + 1100 High speed ...... + 10,000

Bearing and elevation accuracy, mils Automatic radar tracking ...... +0.75 reset r Receiving system Antenna coupling ...... Duplexer IF frequency, megacycles ...... 59.0 IF bandwidth, megacycles ...... 9.0 Frequency control ...... Automatic Transmitting system Transmitter oscillator ...... Tunable magnetron Frequency, megacycles ...... 8500 to 9600 Peak RF power, kilowatts ...... 250 Pulse rate, pulses per second ...... 1320 + 10% Pulse length, microseconds ...... 0.25 RF lines, type ...... Waveguide Power consumption Total, kilovolt-amperes ...... 4.2 Antenna Type ...... Paraboloid Size, diameter, inches ...... 30 Gain, decibels* ...... 36.0 Beam width, degrees : In the horizontal plane ...... 2.4 I~ the vertical plane ...... 2.4 Beam shift, degrees** : Conical ...... 0.75 Circle ...... 5.0 Spiral ...... 0.75 to 5.0

Scan Coverage, degrees: Conical ...... 3.6 Circle ...... 10.0 Spiral ...... 12.4

* Approximate for one-way transmission *" Angle between line of sight and feed

108 Chapter 15 GLOSSARY

Aided Tracking. A system of tracking a target Chaff. (See window.) in bearing, elevation, or range in which a Challenge. To cause an interrogator to send out constant rate of motion of the tracking pulses, thus putting an IFF system in oper mechanism is maintained by electro ation. mechanical means so that an equivalent constant rate of motion of the target can Cheese Antenna. A truncated parabolic reflector be followed. equipped with parallel conducting sheets which confine the radiation in such a man Anti-jamming (A/J). The art of minimizing the ner as to produce a plane wave front. affect of jamming in order to permit the echoes from targets detected by a radar to Clutter. Interferring reflections of radio energy be visible on an indicator. from land, rough sea, or storm clouds. Array. A number of antenna elements arranged Corner Reflector. A device, consisting of three so as to produce a concentration of energy mutually perpendicular planes, which re in a desired direction. turns a strong radar echo. Automatic Frequency Control (AFC). As used Countermeasures. The means employed to ob in radar, the AFC is a device for keeping tain information about an opposing force the receiver local oscillator frequency at a by interception of its radar signals and to fixed difference from the transmitter fre thwart similar enemy action by means of quency to insure stability of receiver jamming, deception, or evasion. tuning. Automatic Gain Control. A type of circuit which Deception. Deliberate production of false or mis maintains a constant receiver output, re leading echoes by radiation of spurious gardless of the variations in signal strength signals or by reradiation of radar pulses at the input to the receiver. from reflectors. Small targets may be made Battle Short. A switch which short-circuits all to appear like large ones or echoes may be safety interlocks. made to appear where no genuine target exists. Beamwidth. The angle between half power intensities in a lobe pattern. (See lobe.) Depression. Sensitivity time control (STC) ad- • Beaver Tail Beam. A fan-shaped beam . justment of initial gain at zero range. Bedsprings. See billboard type antenna. Discrimination. (See resolution.) Billboard-type Antenna. A large broadside Dish. A paraboloidal antenna reflector. array with a flat reflector. (Also called a Double Moding. Changing abruptly from one fre bedspring.) quency to another (frequency jumping). Blind Zones. Areas in which echoes cannot be received. Effective Cross-Sectional Area (of a target). Blip. (British.) (See pips.) A quantity which denotes the ability of a target to reflect radar signals. Broadside Array. A directional antenna system designed to give the maximum radiation in Evasion. Tactics that are intended to take ad a direction perpendicular to the plane of vantage of the detection limitations of radar the array. to prevent or postpone discovery by radar.

109 OP 1895

Expanded Sweep (fire control radar). A range Isotropic Radiator. An object which radiates scale shorter than the longest scale pro equally in all directions. vided, but extending from zero range out Jamming. The deliberate radiation or reradia ward. (For comparison, see precision tion of a signal or signals on the frequency sweep.) of the radar or band of radars for the Fast Time Constant (FTC). A anti-jamming cir purpose of obliterating information on cuit which passes individual pulses with enemy radar scopes and confusing their some differentiation by greatly attenuating radar operators. long pulses and modulation frequencies Jitter. Random deviations from true target po within certain frequency ranges. sition due to random fluctuations in received Flak Paper. (See window.) signal strength, random fluctuations in the Flood Lighting. The covering of a wide area of angle of arrival of the received signal, re search with a broad, fixed beam. ceiver noise, or residual servo jitter. Glint. The motion of the effective center of Jitter Pulsing. Random repetition rate which radiation as the target aspect changes. produces only noise on enemy intercept re Grass. Random interference caused primarily by ceivers. circuit noise. (Term describes appearance Kites. Delayed descent or baloon supported re of noise on indicator screen.) flectors which are dropped to simulate targets. Gulls. Balloon supported radar reflectors which are used to simulate targets. Lobe. The two or three dimensional polar rep resentation of the energy distribution of IF. Intermediate frequency. antenna field strength intensities. IFF. Identification, Friend or Foe. A system of automatic interrogation and coded response Lobe Switching. Alternate radiation of two which identifies on the radar screen those beams displaced slightly from the antenna echoes from friendly aircraft and ships. axis. Illuminating. Directing the radar beam at a Maiden's Hair. (See window.) target. Mattress Antenna. Vertical or horizontal an Instantaneous Automatic Gain Control (IAGC). tenna elements arranged in rows, with rows A circuit that provides an instantaneous one above the other and a reflector behind and automatic method of compensating for the array. the variation in the echo strength of a Moonshine. Radar countermeasures deceptive signal. It is usually used as an anti-jam cir device. cuit when the jamming signal is modu- Notch. Rectangular depression in a sweep trace, lated. used as a range mark. Interception. The detection of radar signals by use of a special receiver which facilitates Phantoms. Radar decoys. obtaining a bearing on the signal source Pillbox Antenna. A narrow cylindrical parabolic and determining some of the characteristics antenna reflector with parallel plates cover of the radar equipment at that source. ing the ends. Interference. The reception of confusing signals Pip. The visual indication on the scope which accidentally produced by spurious radiation represents the pulses reflected from an from friendly or enemy electrical apparatus object in the beam. (British-blip.) and machinery, or by atmospheric phe Pipology. Determination of target composition nomena. from appearance and behavior of echo pips. Intermittent Scanning. One or two 360-degree scans of an antenna beam at irregular in Pulse Recurrence Frequency. The number of tervals to decrease the probability of de pulses per second. Identical to pulse repeti tection by intercept receiver. tion rate.

110 GLOSSARY

Racons. Radar beacons which are used for Rope. (See window.) navigational aids, homing, and blind land Scatter. (British)-Interference from extrane ing. Originally a British term. ous echoes. Radar Countermeasures Room. An enclosure oc Searchlighting. Beaming radio energy in the di cupied by jamming transmitters, associated rection of the target. look-through receivers, and intercept re Sea Return. Interfering reflections of radio ceivers. energy from the surface of the sea. Radar Intercept Room. An enclosure occupied by Side Lobe. A portion of the beam, from a radar intercept receivers when they are installed antenna, other than the main lobe and in a separate space. usually much smaller. Radar Jamming Room. An enclosure occupied by Squint Angle. Beam shift in scanning caused by radar jamming transmitters and associated displacement of the radiating antenna or look-through receivers when they are in feedline from the axis of the reflecting stalled in a separate space. paraboloid. Radar Room. An enclosure occupied by radar Squitter. The response to noise or self-triggering and control indicator units. of an IFF system, resulting in radiation of Radex. An exercise used to train operators to unwanted pulses when no challenge is sent read through jamming. or received. Radome. A general name for radar turrets Suppressor Pulse. A pulse used to disable an which enclose antenna assemblies. IFF or beacon transponder during periods Railing. A pattern on a type-A indicator caused when interference may be encountered. by pulse interference or pulse jamming. Temporal Gain Control. (British)-A circuit Range Gate. The range gate is an indicator pulse which facilitates the observation of strong triggered by the range unit and used to signals at short ranges by weakening or isolate the selected target signal. eliminating fainter signals which tend to Range Step. Vertical displacement in a sweep clutter up the indicator. Identical to sen trace-used to mark range like a cursor. sitivity time control (STC) or time varied Resolution. The ability of a radar to discriminate gain in American usage. between two or more targets in the beam, Window. Aluminum foil strips which are so as to permit tracking and ranging on a dropped from planes to cause a multiplicity single target to the exclusion of other of target pips on enemy radar screens, targets. resulting in obliteration of targets desired Ribbon Marker. Intensified annular segment of by the enemy, or false impressions of precision PPI. (Used to indicate B-scope numerical strength. Also called chaff, rope, area on PPI.) flak paper, maiden's hair. •

Ill Chapter 16 BIBLIOGRAPHY

Text Books Naval Fi1·e-Control Radar, NAVPERS 10811. Australia, (Council for Scientific and Industrial Bureau of Naval Personnel. Research, Radiophysics Laboratory), Text Naval Fire-Control Radar, NAVPERS 10931. book of Radar. Perkins, 1947. Bureau of Naval Personnel. Fink, Donald G., Radar Engineering. McGraw Naval Search and Fighter-Director Radar, Hill, 1947. NAVPERS' 10837 and 10927. Bureau of Hallows, R. W., Radar Simply Explained. Sec Naval Personnel. ond Edition, Chapman, 1950. Radar-A Report on Science at War. Joint Board on Scientific Information Policy. Horning, J. L., Radar Primer. McGraw-Hill, The Radar Countermeasures Manual, Radar 1948. bulletin 7. Chief of Naval Operations. Massachusetts Institute of Technology, (Radar School), Principles of Radar. McGraw-Hill, Radar Electronic Fundamentals, NAVSHIPS 900,016. Bureau of Ships. 1946. Radarman 3 and 2, NAVPERS 10146B. Bureau Penrose, H. E., Principles and Practice of of Naval Personnel. Radar. Third Edition, Newnes, 1950. Radar Operations Manual, Radar bulletin 3. Sonnenberg, G. T., Radar and Electronic Navi gation. Van Nostrand, 1951. U. S. Fleet Office of the Commander-in Chief, Navy Department. Reports Radar System Fundamentals, NAVSHIPS Airborne Rada'r Countermeasu1·es Operator's 900,017. Bureau of Ships. Manual, Radar bulletin 12. Office of the The Shipboard Radar Countermeasures Oper Chief of Naval Operations. ator's Manual, Radar bulletin 11. Office of Aircraft Cont'rol Manual, Radar bulletin SA. the Chief of Naval Operations. Office of Naval Operations. The Surface Plotting Manual, Radar bulletin 5. The Air Plotting Manual, Radar bulletin 4. U.S. U. S. Fleet Office of the Commander-in Fleet Office of the Commander-in-Chief, Chief, Navy Department. Navy Department. The Tactical Use of Radar in Aircraft, Radar The Capabilities and Limitations of Shipborne bulletin 2A. U. S. Fleet Office of the Com Radar, Radar bulletin 1A. Office of Naval mander-in-Chief, Navy Department. Operations. Tactical Use of Radar in Small Vessels Radar GIG Manual, Radar bulletin 6A. Chief of Naval bulletin 9. Office of the Chief of Naval Operations. Operations.

NOTE: These publications are not available for distribution by the Bureau of Ordnance.:

112 CQtji! ldQ hAL Chapter 17 *SUMMARY OF JOINT NOMENCLATURE SYSTEM ("AN" SYSTEM} FOR COMMUNICATION-ELECTRONIC EQUIPMENT

TABLE OF COMPONENT INDICATORS

COMP. IND. FAMILY NAME EXAMPLES OF USE (Not to be construed as limiting the application of the component indicator) AB Supports, Antenna ...... Antenna mounts, mast bases, mast sections, towers, etc. All Amplifiers ...... Power, audio, interphone, radio frequency, video, electronic control, etc. AS Antennae, Complex ...... •... Arrays, parabolic type, masthead, etc. AT Antennae, Simple ...... Whip or telescopic, loop, dipole, reflector, also transducer, etc. (See H.) BA Battery, primary type ...... B batteries, battery packs, etc. BB Battery, secondary type ...... Storage batteries, battery packs, etc. BZ Signal Devices, Audible ...... Buzzers, gongs, horns, etc. c Controls ...... Control box, remote tuning control, etc. CA Commutator Assemblies, Sonar .. . Peculiar to Sonar equipment. CB Capacitor Bank ...... Used as a power supply. CG Cable Assemblies, R. F ...... R. F. cables, wave guides, transmission lines, etc., with terminals. CK Crystal Kits ...... A kit of crystals with holders. CM Comparators ...... •...... <...ompares two or more input signals. CN Compensators .....•...... •..... Electrical and/or mechanical compensating, regulating or attenuating apparatus. CP Computers ...... A mecbanicaJ and/or electronic mathematical calculating device. CR Crystals ...... •...... Crystal in crystal holder. cu Couplers .....•...... Impedance coupling devices, directional couplers, etc. cv Converters (electronic) ...... Electronic apparatus for changing the phase, frequency, or from one medium to another. cw Covers ...... •....•... Cover, bag, roll, cap, radome, nacelle, etc. ex Cable Assemblies, Non-R. F ...... Non-R. F. cables with terminals, test leads, also composite cables of R. F. and non-R. F. conductors. CY Cases and Cabinets ...... • Rigid and semirigid structure for enclosing or carrying equipment. D Dispensers ...... •.••••• Chaff dispensers. DA Load, Dummy ...... R. F. and non-R. F. test loads. DT Detecting Heads ...... Magnetic pick-up device, search coil, hydrophone, etc. DY Dynamotors ...... Dynamotor power supply. E Hoists ...... •.••...... Sonar hoist assembly, etc. F Filters ...... ••.•• Band·pass, noise, telephone, wave traps, etc. FN Furniture ...... Chairs, desks, tables, etc. FR Frequency Measuring Devices ... . Frequency meters, tuned cavity, etc. G Generators, Power ...... Electrical power generators without prime movers. (See PU & PD.) GO Goniometers ...... Goniometers of all types. GP Ground Rods ...... Ground rods, stakes, etc. H Head, Hand, and Chest Sets ...... Includes earphone. HC Crystal Holder ...... Crystal holder less crystal. HD Air Conditioning Apparatus ...... Heating, cooling, dehumidifying, pressure, vacuum devices, etc. ID Indicators, Non-Cathode-Ray Tube Calibrated dials and meters, indicating lights, etc. (See IP.) IL Insulators ...... Strain, stand-off, feed-through, etc. 1M Intensity Measuring Devices .... . Includes SWR gear, field intensity and noise meters, slotted lines, etc. lP Indicators, Cathode Ray Tube ... . Azimuth, elevation, panoramic, etc. J Junction Devices ...... Junction, jack and terminal boxes, etc. KY Keying Devices ...... Mechanical, electrical and electronic keyers, coders, interrupters, etc. LC Tools, Line Construction ...... Includes special apparatus such as cable plows, etc. LS Wudapeakers ...... Separately housed loudspeakers, intercommunication station. H Microphones ...... Radio, telephone, throat, band, etc. MD Modulators ...... Device for varying amplitude, frequency or phase. HE Meters, Portable ...... Multimeters, volt-ohm·milliammeters, vacuum tube voltmeters, power meters, etc. MK Miscellaneous Kits ...... Maintenance, modification, etc., except tool and crystal. (See CK, TK.) .HL Meteorological Devices .....•... Barometer, hygrometer, thermometer, scales, etc. HT Mountings ...... Mountings, racks, frames, stands, etc. HX Miscellaneous ...... Equipment not otherwise classified. Do not use if better indicator is available. 0 Oscillators ...... Master freQuency, blocking multivibrators, etc. (For test oscilJators, see SG.) OA Operating Assemblies ...... Assembly of operating units not otherwise covered. oc Oceanographic Devices ...... Bathythermographs, etc. OS Oscilloscope, Test ...... Test Oscilloscopes for general test purposes. PD Prime Drivers ...... Gasoline engines, electric motors, Diesel motors, etc. PF Fittings, Pole ...... Cable hangar, clamp, protectors, etc. PG Pigeon Articles ...... Container, 1oft, vest, etc. PH Photographic Articles ...... Camera, projector, sensitometer, etc. pp Power Supplies ...... Nonrotating machine type such as vibrator pack, rectifier, thermoelectric, etc. PT Plotting Equipments ...... Except meteorological. Boards, maps, plotting table, etc. PU Power Equipments ...... Rotating power equipment except dynamotors. Motor-generator, etc. R Receivers ...... •• Receivers, all types except telephone. RC Reels ...... Reel, cable. (See RL.) RD Recorders and Reproducers ...... Tape, facsimile, disc, magnetic, etc. RE Relay Assemblies ...... Electrical, electronic, etc. RF Radio Frequency Component .... . Composite component of R. F. circuits. Do not use if better indicator is avallable. RG Cables, R. F., Bulk ...... R. F. cable, wave guides, transmission lines, etc., without terminals. RL Reeling Machines ...... Wire and cable reeling machines. (See RC.) RP Rope and Twine ...... Nonelectrical cord, etc. RR Reflectors ...... Target, confusion, etc. Except antenna reflectors. (See AT.)

~L Ill OP 1895 CONFIDENTIAL

COMP. EXAMPLES OF USE IND. FAMILY NAME (Not to be construed as. limiting the application of the component indicator) RT Receiver and Transmitter ...... Radio and radar transceivers, composite transmitter and receiver, etc. s Shelters ...... House, tent, protective shelter, etc. SA Switching Devices ...... Manual, impact, motor driven, pressure operated, etc. SB Switchboards ...... Telephone, fire control, power, panel, etc. SG Generators, Signal ...... Test oscillators, noise generators, etc. (See 0.) SM Simulators ...... Flight, aircraft, target, signal, etc. SN Synchronizers ...... '.. . Equipment to coordinate two or more functions. ST Straps ...... Harness, straps, etc. T Transmitters ...... Transmitters, all types except telephone. TA Telephone Apparatus ...... Miscellaneous telephone equipment. TD Timing Devices ...... Mechanical and electronic timing devices, range device, multiplexers, electronic gates, etc. TF Transformers ...... Transformers when used as separate items. TG Positioning Devices ...... • Tilt and/or Train Assemblies. TH Telegraph Apparatus ...... Miscellaneous telegraph apparatus. TK Tool Kits ...... Miscellaneous tool assemblies. TL Tools ...... All types except line construction. (See LC.) TN Tuning Units ...... Receiver, transmitter, antenna, tuning units, etc. TS Test Items ...... Test and measuring equipment not otherwise included; boresighting and alignment equipment. TT Teletypewriter and Facsimile Apparatus ...... Miscellaneous tape, teletype, facsimile equipment, etc. TV Tester, Tube ...... Electronic tube tester. u Connectors, Audio and Power . .. . Unions, plugs, sockets, adapters, etc. UG Connectors, R. F ...... Unions, plugs, sockets, choke couplings, adapters, elbows, flanges, etc. v Vehicles ...... Carts, dollies, trucks, trailers, etc. Vi! Signaling Equipment, Visual. . . . Flag sets, aerial panels, signal lamp equipment, etc. WQ Cables, Two Conductor ...... Non-R. F. wire, cable and cordage in bulk. (See RG.) WF Cables, Four Conductor ...... Non-R. F. wire, cable and cordage in bulk. (See RG.) WM Cables, Multiple Conductor ...... Non-R. F. wire, cable and cordage in bulk. (See RG.) WS Cables, Single Conductor ...... Non-R. F. wire, cable and cordage in bulk. (See RG.) WT Cables, Three Conductor ...... Non-R. F. wire, cable and cordage in bulk. (See RG.) ZM Impedance Measuring Devices . .. . Used for measuring Q, C, L, R or PF, etc.

TABLE OF SET OR EQUIPMENT INDICATOR LETTERS

INSTALLATION TYPE OF EQUIPMENT PURPOSE

A-Airborne (installed and operated in A-Invisible light, heat radiation A-Auxiliary assemblies (not complete .opo aircraft) B-Pigeon erating sets) B--Underwater mobile, submarine C-Carrier B-Bombing C-Air transportable (inactivated, do not D-Radiac C-Communieations (receivina- and trana.. use) E-Nupac mitting) D-Pilotless carrier F-Photographic D-Direction finder F-Fixed G-Telegraph or teletype G-Fire control or searchlight directing G-Ground, general ground use (includes 1-Interphone and public address H-Recording (photographic, meterologi- two or more ground installations) J-Electro-mechanical (not otherwise cov- cal and sound) K-Amphibious ered) L---Searchlight control (inactivated, use M-Ground, mobile (instslled as operating K-Telemetering "G") unit in a vehicle which has no func L-Countermeasures .Ill-Maintenance and test aaaemblies (in tion other than transporting the equip Ill-Meteorological cluding tools) ment) N-Sound in air N-Navigational aids (including alti· P-Pack or portable (animal or man) P-Radar meters, beacons, compasses, racona, s-Water surface craft Q--Sonar and underwater sound depth sounding, approach and landing) T-Ground, transportable R-Radio P-Reproducing (photographic and sound) U-General utility (includes two or more s-Special types, magnetic, etc.. or com- Q--Special, or combination of purpoees general installation classes, airborne, binations of types R-Receiving. passive detecting shipboard, and ground) T-Telephone (wire) s-Detecting and/or range and bearing V-Ground, vehicular (installed in vehi V-Visual and visible light T-Transmitting cle designed for functions other than W-Armament (peculiar to armament, not W-Control carrying electronic equipment, etc., otherwise covered) X-Identification and recognition such as tanks) X-Facsimile or television

EXAMPLES OF "AN" TYPE NUMBERS

TYPE NUMBER INDICATES

AN/SRC-3( ) ...... General reference set nomenclature for water surface craft radio communication set No. 3. AN/SRC-3 ...... • Original procurement set nomenclature applied against AN/SRC-3( ). AN/SRC-3A ...... Modification set nomenclature applied against AN/SRC-3. AN/APQ-13-T1() ...... , .. General reference training set nomenclature for the AN/APQ-13 set. AN/APQ-13-T1 ...... Original procurement training set nomenclature applied against AN/APQ-l3-T1( ). AN/APQ-13-T1A ...... Modification training set nomenclature applied against AN/APQ-13-Tl. AN/UPT-T3( ) ...... General reference training set nomenclature for general utility radar transmitting training set No. 3. AN/UPT-TS ...... Original procurement training set nomenclature applied against AN/UPT-T3( ). AN/UPT-T3A ...... Modification training set nomenclature applied against AN/UPT-T3. T-61 ( )IARQ-8 ...... General reference component nomenclature for transmitter No. 61, part of or used with airborne radio special set No. 8. T-61/ARQ-8 .... , , ...... Original procurement component nomenclature applied against T-61( )/ARQ-8. T-61A/ARQ-8 ...... Modification component nomenclature applied against T-61/ARQ-8. RD-81( )/U ...... General reference component nomenclature for recorder-reproducer No. 31 for general utility use, not part of a specific set. RD-81/U ...... Original procurement component nomenclature applied against RD-31( )/U. RD-31A/U ...... Modification component nomenclature applied against RD-31/U. 114 CONFIDENTIAL CONFIDENTIAL AN NOMENCLATURE SYSTEM

NOTES Example: Radio Set AN/ARC-3( ) might be assigned for a new 1. This chart was formerly titled SUMMARY OF JOlNT ARMY airborne radio communication set under development. The cognizant NAVY NOMENCLATURE SYSTEM ("AN" SYSTEM) FOR COM development organization might then aasign AN/ARC-S(XA-1), MUNICATION AND ASSOCIATED EQUIPMENT. AN/ ARC-3(XA- 2), etc., type numbers to the various seta developed for test. When the set was considered satisfactory for use, the 2. The system indicator "AN" does not mean that the Army, experimental indicator would be dropped and procurement nomen ... Navy and Air Force use the equipment but simply that the type clature AN/ ARC-3 would be officially assigned thereto. number waa assia-ned in the "AN" system. 3. In the "AN" nomenclature system, nomenclature consists of a Trainiq Seta. A set or equipment designed for training pur name followed by a type number. The type number will consist of poses will be assigned type numbers as follows : indicator )etters shown on this chart and an assigned number. 1. A set to train for a specific basic set will be assigned the basic 4. The type number of an independent major unit not part of or set type number followed by a dash, the letter T, and a number. used with a specific set will consist of a component indicator, a Example: Radio Training Set AN/ ARC-6A-Tl would be the first number, the slant and such of the set or equipment indicator letters training set for Radio Set AN/ARC-SA. as apply. Example: SB-6/PT would be the type number of a port. 2. A set to train for general types of sets will be assigned the able telephone switchboard for independent use. usual set indicator letters followed by a dash, the letter T, and a 6. All requests for nomenclature assignments will be submitted number. Example: Radio Training Set AN/ARC-Tl would be the on the Department of Defense Form DD-61 and in accordance with first training set for general airborne radio communication seta. the Munitions Board Cataloging Agency publication entitled, "Item Description Guides for Supply Cataloging." Parentheses Indicator. A nomenclature assignment with parenthe ses, ( ) , following the basic type number is made to identify an MODIFICATION LETTERS article generally, when a need exists for a more ~reneral identifica Component modification suffix letters will be assigned for each tion than that provided by nomenclature aasigned to specific designs modification of a component when detail parts and subassemblies of the article. Examples: AN/GRC-5( ), AM- 6( )/GRC-6, SB-9 uaed therein are no longer interchangeable, but the component itself ( )/GG. A specific desilln is identified by the plain basic type ia intercban,eeable physically. electrically, and mechanically. number, the basic type number with a suffix letter, or the basic type Set modification letters will be assigned for each modification number with an experimental symbol in parentheses. Examples: not affecting interchangeability of the sets or equipment as a whole, AN/ GRC-6, AN/GRC-6A, AN/ GRC-6(XC-1), AM-SB/GRC-6, SB-9 except that in some special cases they will be assigned to indicate (XE-3)/GG. functional interchangeability and not necessarily complete electrical and mechanical interchangeability. Modification letters will only be assigned if the frequency coverage of the unmodified equipment is NOMENCLATURE POLICY maintained. The suffix letters X, Y, and Z will be used only to designate a (See JANAP 196 for Statement of Policies) set or equipment modified by changing the power input voltage, 1. AN Nomenclature will be aasigned to: phase or frequency. X will indicate the first change, Y the second, Z the third, XX the fourth, etc., and these letters will be in addition A. Complete sets of equipment and major components of military to other modification letters applicable. (For examples see JANAP design. 196.) B. Groups of articles of either commercial or military design which are grouped for a military purpose. ADDITIONAL INDICATORS C. Major articles of military design which are not part of or used Expuimental Seta. In order to identify a set or equipment of an with a set. experimental nature with the development organization concerned, D. Commercial articles when nomenclature will facilitate military the followin~r indicators will be used within the parentheses: identification and/or procedures. XA-Weapons Components Division, WADC, Dayton, Ohio (also see XS a: XY) 2. AN Nomenclature will not be assigned to: XB-Naval Research Laboratory, Washington, D. C. A. Articles cataloged commercially except in accordance with XC- Coles Signal Laboratory, Fort Monmouth, N.J. Paragraph 1. D. XE--Evans Signal Laboratory, Fort Monmouth, N.J. XG- U. S. N. Electronic Laboratory, San Die~ro, Calif. B. Minor components of military design for which other adequate XJ-Naval Air Development Center, Johnsville, Pa. means of identification are available. XM-Squier Signal Laboratory, Fort Monmouth, N. J. C. Small piece parts such as capacitors and resistors. XN-Department of the Navy, Washington, D. C. D. Articles having other adequate identification in joint military XP-Canadian Department of National Defense, Ottawa, Canada. specifications. XR- E111rineer Research and Development Laboratory, Ft. Bel- voir, VL 3. Nomenclature assignments will remain unchanged regardless of XS-Componenta ar.d Systems Laboratory, WADC, Dayton, Ohio. later changes in installation and/or application. XU- U. S. N. Underwater Sound Laboratory, Fort Trumbull, New "London, Conn. IMPORTANT.-AU pen10nnel are cautioned qainat orlclnatinc or XW-Rome Air Development Center, Rome, N. Y. chancinc any part of any nomenelature aaolcnment, indadinc modi XY-Armament Laboratory, WADC, Dayton, Ohio. fication letters, without authorization.

• Apprvved and publioMd by the COMMUNICATION-ELECTRONIC NOMENCLATURE SUBPANEL under authority of the JOINT COMMUNICATIONS-ELECTRONIC COMMITTEE Wuhin~n 25, D. C. 10 April 1952

CONFIDENTIAL 115 CONFIOI: . IUU~------

DISTRIBUTION

SNDL Part 1 (No. 66) and Part 2 (No. 24)

One copy each : 21 ; 22 ; 23 ; 23A ; 24B, 24C, 24F, 24G, 24H; 26F (Norfolk only) , 26H, 26U, 26Z ; 28A (except 6 and 15), 28B, 28C, 28J, 28N; 31A, 31Bl, 31B2, 31C1, 31C2, 31D 31J, 31L, 31M (LST 1153, 1154, 1156, 1158-1167) ; 32C, 32D, 32F (AGS 30, 50), 32K, 32L (AKS 20, 21, 22, 23, 24, 25, 26), 32Nl, 32N2 (TAO 41, 42, 43, 57), 32P, 32Q2, 32U; 38A; 41A, 41B (Atlantic and Pacific); A3 (CNO), A5 (BU PERS); E4 (Chesapeake Bay Annex Attn: Mr. Heller); K11 (NGF only); M46. Two copies each :

24A, 29B, 29D, 29E, 29F, 29M, 29N, 29P, 29Q, 29R; 30D, 30E; 32A, 32E (AG 128 and 152), 328, 32DD, 32MM; 38B; B5; E6 (Alexandria only); F9 (Subic Bay only); J12, J33, J37, J56, J60, J76, J84; K5A (NOPI only), K7 (NOL Corona), Ll (Charleston only) ; M9. Three copies: 24E; Ll (New York only) Four copies: A5 (BUSHIPS) Five copies: 29A, 29G, 29H, 29K, 29Kl, 29L Six copies : Ll (all except New York and Charleston) Twenty-five copies: J91

Requests for additional copies of OP 1895 should be submitted on NAVEXOS 158, Stock Forms and Publications Requisitions, to the District Publications and Printing Office by which addressee is serviced.

19 Nov 1954/3M/l.

CONFIDENTIAL

U S. GOVERNMENT PRINTING OFFICEol~ o-3Z3489