TB 9-5985-313-40
NOTE
Minimize time expended between measurements in (5) above
and (10) below.
(6) Record voltage at bridge 1 as V2 and bridge 2 as V1.
(8) Adjust RF power amplifier controls for approximately 50 W forward power as
shown on RF power meter.
(9) Set V-REM-'V switch on each power bridge to 'V.
(10) Measure voltage at RVG terminals on each bridge, using multimeter. Record
voltage at bridge 1 as 'V2 and at bridge 2 as 'V1.
(11) Substitute values recorded in (6) and (10) above in the following formula and
solve for K1.
K1 = (2V1 - 'V1) 'V1 Ko
(2V2 - 'V2) 'V2
K1 = Input calibration factor of TI at the applicable frequency.
K0 = Output calibration factor of directional coupler (A2) at applicable frequency as listed on test
report.
(12) Repeat (1) through (11) above for each applicable TI frequency.
(13) Adjust RF power amplifier output control to minimum. Deenergize each
power bridge.
(14) Disconnect thermistor mounts from each power bridge and reconnect them to
opposite power bridge.
(15) Energize each power bridge, wait 3 minutes, and repeat (3) through (12) above.
(16) Determine average of the four values calculated for K1 and record the average
as the TI's input calibration factor for the applicable frequency.
b. Adjustments. No adjustment can be made.
10. VSWR Check
a. Performance Check
NOTE
The following check is an operational check only. TIs should
not be rejected if normal indications are not obtained; however,
the user should be notified not to use the TI near the frequency
at which abnormal VSWR is indicated.
Satisfactory
performance of the VSWR check indicates that TI can be used
for wattmeter calibration throughout its frequency range.