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 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 , (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. in the field or at the factory. provides five measurement ranges The 430B Power Meter has now from 0.1 milliwatt full scale to 10 rate bias current-selecting switch is been redesigned so that it will milliwatts full scale. located at the lower right of the directly accommodate the coaxial Bias current in the new instru front panel. This switch is marked with three main current ranges tWm. Gallagher and B. P. Hand. "New Conven ment has been made independent iences for Microwave Power Measurements," Hew of the power range switch. A sepa- which provide for bias currents from lett-Packard Journal, Vol. 5, No. 11, July, 1954. 0 to 16 ma. The upper two ranges COAXIAL MOUNTS are divided into a number of cur rent steps which simplify selection of a required current. A dual "Coarse - Fine" control in the lower center of the panel acts as a vernier for the switch steps.

0.05% REGULATOR WAVE GUIDE MOUNTS Besides increasing the amount of bias power that the instrument will supply, the new 430C has been de signed to have an unusually high order of regulation in its d-c cir cuits. This feature offers important benefits when measuring small powers where most of the bias power that the instrument applies to the bolometer element is d-c power. If line fluctuations change the d-c power into the bolometer ele ment by more than a few microwatts on the 0.1 milliwatt range of the *Negative temperature coefficient elements can also be used in these mounts. instrument, the result will appear See Hewlett-Packard Journal, Vol. 3, No. 3, Not'., 195J. as a drift or fluctuations in the

© Copr. 1949-1998 Hewlett-Packard Co. meter pointer. For this reason the NOTES ON BOLOMETER ELEMENTS regulation of the d-c circuits in the The -hp- Model 430C Microwave Power Meter use should be carefully distinguished from their 430C for ± 10% line voltage changes will operate with either positive temperature use as bolometer elements in power measure coefficient bolometer elements (usually called is maintained within at least 0.05%. ments. In detector use the barretter is used in "barretters") or negative coefficient elements the same manner as a silicon crystal. Detection In practice this means that meter (called "thermistors"). These elements are avail occurs because the resistance of the barretter pointer drifts resulting from line able in a variety of shapes and types of con changes with the modulation cycle. A constant current effects in the power meter struction, but -hp- mounts generally use a cart current through the barretter will thus result in amount to only two or so of the 2 ridge style barretter or a capsuled or uncap- an audio voltage across the barretter. The re suled thermistor. microwatt divisions on the meter sponse of barretters used as detectors is closer Pertinent electrical characteristics of a number to a true square-law response than is the re face and this occurs only on the low of 100- and 200-ohm bolometer elements which sponse of crystals. est range of the instrument. can be used with the -hp- 430B and 430C power The sensitivity of barretters when used as meters are shown in the table. detectors is about 20 db below that of silicon BOLOMETER MOUNTS Certain instrument fuses may also be used as crystals at a frequency of 1,000 cps. Instrument A wide range of -hp- bolometer barretters as is done in the -hp- Model 475B fuses may also be used as detectors, but their mounts is available for making and the 476A. For this use, however, the fuses sensitivity is about 3 db below that of conven power measurements in both coaxial must be selected and subjected to a special but tional barretters. and wave guide systems. Charac simple treatment. Thermistors are generally preferred for meas Barretters are sometimes used in standing- teristics of these mounts are sum uring the average value of pulsed power be wave measurements as detector elements. This cause they generally have longer time constants. marized in the accompanying table. BOLOMETERS Included are both tuned and un tuned mounts, i.e., mounts which must be manually tuned for the r-f frequency used and mounts which do not require tuning. A number of typical set-ups using these mounts are diagrammed in Vol. 5, No. 11 (July. 1954) of the Hewlett-Packard Journal. -Don Carmean

SPECIFICATIONS -hp- MODEL 430C MICROWAVE POWER METER POWER RANGE: 5 ranges, front panel selector. Full scale readings of 0.1, 0.3, 1, 3, and 10 milliwatts. Also calibrated in db to give continuous reading from — 20 dbm to ^-10 dbm (0 dbm— 1 mw). Power range can be extended with attenuators or directional couplers. EXTERNAL BOLOMETER.- Frequency range de pends on bolometer mount. Bolometers can All values of current and power are approximate. operate at resistance levels of 100 or 200 ohms and can have positive or negative temperature coefficients. Any DC bias cur rent up to 16 ma is available for biasing VISIT THE hp- BOOTH INSTRUMENTS AVE. positive or negative temperature coefficient bolometers. DC bias current is continuously At the March 21-24 IRE Radio Engi adjustable and independent of bolometer resistance and power level range. Sufficient neering Show in New York -hp- will latitude is provided to insure operation over have on exhibit a number of unusu usual room-temperature range. TELEVISION AVE. ACCURACY: Within 5% of full scale value. ally interesting instruments. Included i 1— T — i 1 — r • POWER SUPPLY: 115/230 volts ±10%, 50/1000 among these will be a pre-showing , . I ! ! ! ! cycles approximately 75 watts. of a system for measuring the r-f fre [INFORMATION | | REGISTRATION RO* SIZE: Cabinet: 73/8" wide, 11V2" high, 12'/4" deep. Rack Mount: 19" wide, 7" high, 12'/2" quency of r-f pulses — a system with a deep. high definition such that r-f frequency WEIGHT: Cabinet: Net 20 Ibs.; shipping 32 Ibs. Rack Mount: Net 23 Ibs.; shipping 35 Ibs. shifts during an r-f pulse can be ACCESSORIES FURNISHED: 1— AC-16D cabl. measured. assembly, consisting of 44" RG-58/U 50- ohm coaxial cable terminated on one end Additional instruments to be shown with UG-88'U BNC connector. include -hp-'s new 15-21 kilomega- KINGSBRIDGE ARMORY NEW YORK CITY ACCESSORIES AVAILABLE.- -hp- Stock No. G- 28A selected instrument fuses (200-ohms at cycle , a simple indus The -hp- booth will be located at 8.75 ma at 25= C ) for use with -hp- 475B trial counter which will speed many or as a single element, 10 for $10.00. Usable the corner of Radio Road and Instru up to 4,000 me. production measurements, a coaxial ments Avenue, -hp- engineers from PRICE: Cabinet: S250.00 f.o.b. Palo Alto, Cali directional coupler, a new 41 5B and both factory and field will be on fornia. Rack Mount: $255.00 f.o.b. Palo Alto, California. 430C described in this issue, and hand. You are most cordially invited Data subject to change without notice. others. to stop by.

© Copr. 1949-1998 Hewlett-Packard Co.