GNC 400 COMM TRANSCEIVER ALIGNMENT PROCEDURE
P/N 005-00051-55 REV. T
Page 12
3.5.7.2 Modulator Adjustment for 16 Watt comm boards
a.
Recall saved State 7 on the HP8920A/B.
b.
State 7 on Radio Test Set:
•
TX Mode
•
Automatic Tuning
•
AF ANL IN to AM DEMOD
•
DE-EMPHASIS to OFF
•
DETECTOR to RMS*SQRT2
•
AFGEN1 FREQ = 1 KHz
•
AFGEN1 LEVEL = 275 mV
•
Input Port - RF In
•
Audio analyzer set to read Distn.
c.
Key the transmitter and adjust the MIC setting on the display for 90% - 95% modulation
depth.
d.
Unkey the transmitter.
e.
Key the transmitter and increase the MOD DEP setting on the display until the 8920A/B
modulation depth reading just falls below 85%. Decrease the MOD DEP setting one step to
put the modulation reading at, or above 85%. The modulation depth should not exceed 90%
f.
Unkey the transmitter.
3.5.8 Transmitter Sidetone Adjust
a.
Recall saved State 8 on the HP8920A/B.
b.
State 8 on Radio Test Set:
•
TX Mode
•
Automatic Tuning
•
DE-EMPHASIS to OFF
•
AF GEN 1 FREQ to 1 KHz
•
AF GEN 1 Level to 275 mV
•
AF ANL IN to AUDIO IN
•
DETECTOR to RMS
•
AF IN LO to GND
•
Input Port - RF In
•
Audio analyzer set to read Distn.
c.
Key the transmitter and increase the SIDETN setting on the display until the audio level on
the 8920A/B reads 1.4 Vrms +/-0.2 V.
d.
Unkey the transmitter.
Scroll the display to the Store Calibration? field and press the ENT button on the CDI.
Repeat section 3.5 in its entirety at 127.000 and 136.975 MHz. Be sure to set the frequency
on the HP8920A/B and the unit to the proper channel as required.
