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HEWLETT-PACKARD
JOURNAL
T E C H N I C A L I N F O R M A T I O N F R O M T H E - d p - L A B O R A T O R I E S
JLISHED BY THE HEWLETT-PACKARD COMPANY, 1501 PAGE MILL ROAD, PALO ALTO, CALIFORNIA SEPT. -OCT., 1961
A New SWR Meter
with High Gain-Stability
ONE of the important instruments in the micro heretofore but also increase the suitability of this
wave measurement area is basically an audio type of instrument for rf attenuation measurements.
frequency instrument known as a Standing Wave The new instrument is tunable over a 5% range so
Indicator or SWR Meter. This instrument is essen as to accommodate the tolerances and drift that are
tially a very high gain (» 100 db) audio amplifier often encountered in modulating frequency. At the
which is tuned to achieve high selectivity and which same time it has a selectivity that is variable from 15
has an output meter calibrated for standing-wave to 100 cps to meet a variety of measurement condi
work. Although the instrument was originally in tions varying from highest discrimination against
tended for use with a slotted line section to measure noise to fast amplitude response for swept-frequency
vswr, it has seen increasing importance in micro measurements.
wave attenuation measurements using audio substi For attenuation-measuring situations, the instru
tution techniques. It is calibrated for and normally ment is further designed to give high and constant
used with a square-law rf detector, but its high sensi resolution over its complete measurement range. This
tivity and single acceptance frequency also make it is achieved by arranging for each 2.5-db section of
valuable as a detector for audio frequency bridges. the normal 10 db meter scale to be expanded to oc
A new SWR Meter has now been designed which cupy a full meter scale length and one that is roughly
incorporates advances that not only make vswr meas linear for high readability. The arrangement is such
urements easier and more accurate to perform than that 31.5 db of attenuation can be measured with as
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h-TURN ON
115V