HEWLETT-PACKARD JOURNAL TECHNICAL INFORMATION FROM THE -hp- LABORATORIES Vol. 6 No. 7 ^••i LlSHED CALIFORNIA THE HEWLETT-PACKARD COMPANY, 275 PAGE MILL ROAD, PALO ALTO, CALIFORNIA MARCH, 1955 A New Standing Wave Indicator With an Expanded VSWR Scale THE widely-used -hp- Model 41 5 A Stand- instrument retains such former features as ng Wave Indicator is an instrument an alternate high-impedance input channel which measures standing-wave ratios di for use in bridge measurements and a high rectly when used in slotted line set-ups in sensitivity of 0.1 microvolt full scale. combination with detec Basically, a standing-wave indicator is a SEE ALSO: tor elements such as crys tuned audio amplifier of unusually high "New Microwave Power Meter", p. 3 tals or barretters. This sensitivity which is provided with an output instrument has now been meter and an accurate step attenuator. Since redesigned to be even more convenient to the instrument is an audio device which use through addition of an expanded VSWR measures the relative outputs of an r-f de scale, a half-step attenuator which always tector, it must be used with an r-f detector permits readings to be made in the upper and an amplitude-modulated signal (see ac half of the scale, and a new bolometer bias companying set-up diagrams). Commonly, arrangement which permits use of both 8.5 1,000-cps square- wave modulation is used. ma and 4.5 ma bolometer elements as de The Model 415B as supplied is normally tectors. An output jack for operating a re tuned to this frequency. The tuning circuits corder has also been included. The new in the instrument are constructed in the form of an internal plug-in unit, however, and on special order the instrument can be supplied with plug-in units for any desired frequency from 315 to 3,000 cps. Additional plug-in units can be supplied to enable one instrument to be used with different fre quencies by changing plug-in units. When measuring low VSWR's, it is often desirable to be able to make the reading with higher definition than otherwise. For such purposes the meter face on the new Model 415B is arranged with an extra VSWR scale which reads from 1 to 1.3 and which is ex panded so that it occupies the whole meter swing. This scale is shown accented in Fig. 2. A lever switch on the front panel brings the Fig. 1. New -hp- Model 415B Standing Wave Indicator scale into use. The expanded VSWR scale has expanded VSWR and DB scales for easy reading of low VSWR values. is accompanied by an expanded db scale for PRINTED IN US. A. COPYRIGHT 1955 HEWLETT-PACKARD CO. © Copr. 1949-1998 Hewlett-Packard Co. can be used for such purposes, it the "Crystal" position of the input is provided with an alternate high- switch. For detector use, head phones impedance 200,000-ohm channel can be plugged into the "Recorder" which can be selected by the input jack. switch. This order of impedance RECORDER OUTPUT combined with the 3 microvolt full- A recorder output jack is provided scale sensitivity of the high-imped on the instrument for operating 1 HEWLETT MM PAC ance channel permits very sensitive ma d-c recorders of approximately detection of nulls. If the bridge ap 1500 ohms resistance. This arrange plication will permit a 200-ohm de Fig. 2. Meter face used on new 41 5B SWI. ment will permit plots to be made 1-1.3 expanded VSWR scale shown ac tector, of course, up to 0.1 micro cented. Expanded db scale is at bottom of VSWR where this is desired for of meter face. volt sensitivity can be obtained in record purposes. It will also permit applications where it is desired to the instrument to be used where it make readings in db. is desired to monitor a low level sig The same lever switch can be used nal in the 315-3,000 cps range with a to maintain any VSWR reading in 1 ma d-c recorder. -Brunton Bauer the upper half of the meter. This feature is useful when measuring SPECIFICATIONS higher VSWR's where the readings -lip- MODEL 41 SB STANDING WAVE may occur in the more compressed INDICATOR lower half of the meter face. The FREQUENCY: Normally 1,000 cps ±2%. Avail able on special order for other frequencies: switch introduces a half-step atten 315 to 3,000 cps. uation of 5 db. A reading that oc SENSITIVITY: O.I /iv or less provides full scale curs in the lower half of the 10 db Set-tip for measuring VSWR in coaxial deflection on "Crystal" and "Bolo" inputs. systems over 500 - 4,000 megacycle range. NOISE LEVEL: Equivalent noise referred to in range of the meter scale can thus be put less than 0.03 fiy. brought into the upper half by set AMPLIFIER Q: 25 - 35. ting the lever switch and dropping CALIBRATION: For use with square law detec tors. Meter indicates SWR and db. back one position on the main range RANGE: 70 db. Input attenuator provides 60 db switch. in 10 db steps. Accuracy ±0.1 db per 10 db step. SOUE SELECTOR SWITCH: Normal, Expand, BIAS CURRENT and — 5 db. When standing-wave indicators METER SOUES: "Normal", SWR 1 to 4, 3.0 to 10.0 and 0 to 10 db. "Expand", SWR 1 to are used with bolometer elements 1.3. "— 5db", 0 to 10 db (accuracy of at such as barretters, it is customary to tenuator .05 db). GAIN CONTROL: Adjusts meter to convenient operate the bolometer with a d-c reference level. Range approximately 12 db. bias current such as to bias the bolo INPUT.- (a) "Bolo" (200 ohms): bias provided for 8.5 ma bolometer or 1/100 ampere in meter resistance to 200 ohms. The strument fuse; or 4.5 ma low current bolo meter, (b) "Crystal": 200 ohms for crystal new 415B is arranged to supply a Set-up for measuring VSWR in coaxial rectifier, (c) "200,000": high impedance for constant current of either 8.5 or 4.5 systems over 3-11 kilomegacycle range. crystal rectifier or null detector. OUTPUT: For recording milliammeter having a milliamperes, the two bias currents 1 ma full scale deflection and internal re commonly required. The desired sistance of approximately 1,500 ohms. current is selected with a panel INPUT CONNECTOR: Type BNC. POWER: 115 230 volts ±10%; 50/60 cps; 60 switch. A panel jack is also provided watts. so that the bias current can be moni SIZE: Cabinet Mount: 7VÃ" wide, 11 V¿" high, 14" deep. Rack Mount: 19" wide, 7" high, tored by an external milliammeter, 11" deep. should this be desired. The bias cur WEIGHT: Cabinet Mount: 18 Ibs., shipping weight 30 Ibs. Rack Mount: 20 Ibs., shipping rent can be varied by adding ex weight 35 Ibs. ACCESSORIES PROVIDED: -hp- AC-16D Cable ternal resistance in series with the Assembly, BNC connector one end. -hp- meter. 41A-16E Meter Cable. ACCESSORIES AVAIIABIE: -hp- 415B-42B Plug- in Filter for special operating frequency, HIGH IMPEDANCE INPUT 315 to 3,000 cps. $12.00. A high-gain 1,000-cps audio am PRICE: -hp- 415B Standing Wave Indicator, Cabinet Mount, $200.00 f.o.b. Palo Alto, plifier such as the 415B is an excel California, -hp- 415BR Standing Wave Indi cator, Rack Mount, $205.00 f.o.b. Palo Alto, lent detector for use with impedance Set-up for measuring VSWR in wave California. guide systems over 2.6 -11 kilomegacycle bridges. In order that the instrument range. Data subject to change without notice. © Copr. 1949-1998 Hewlett-Packard Co. More Conveniences in the -hp- Microwave Power Meter LVST summer -hp- introduced a mount as well as all other -hp- series of new broadband ther mounts. Further, a number of new mistor mountsf for use in making refinements have been incorporated power measurements in both wave to make the instrument even more guide and coaxial systems. These convenient to use. mounts have proved very popular. The new instrument, known as In particular, the mount for coaxial the Model 430C, will accommodate systems has been widely used be bolometer elements of either posi cause this one mount, when com tive or negative temperature coeffi bined with the -hp- Model 430B cient and of either 100- or 200-ohms Microwave Power Meter, could be operating resistance. A list of such used to measure power over the en elements in general use is shown in tire frequency range from 10 mega the accompanying table. cycles to 10 kilomegacycles. The panel of the Model 430C is To use the coaxial mount with the shown in Fig. 1. At the upper left -hp- 430B Power Meter has required is a switch that adjusts the instru a modification in the meter's bias ment for either positive or negative circuit, since the mount required temperature coefficient elements. At considerably more bias power than the upper right is a switch that ad Fig. 1. New -hp- Model 430C Microwave Power Meter will operate with bolometer conventional mounts. In the past this justs the instrument for use with elements of either positive or negative t-c, modification was made by means of either 100-ohm or 200-ohm elements. 100- or 200-ohm value. Very high d-c regulation is used to minimize drift on a kit which could be installed either The range switch at the lower left low ranges.