GNC 400 COMM TRANSCEIVER ALIGNMENT PROCEDURE
P/N 005-00051-55 REV. T
Page 11
3.5.5 Receiver Carrier Squelch Calibration - 8.33 kHz Mode
a. Recall saved State 5 on the HP8920A/B as in section 3.5.4.
b. Change RF GEN amplitude to 3.0 uV.
c. Set the channel spacing field on the display for 8.33 kHz.
d. Decrease SQ 833 on the display until the squelch just opens (audio turns on).
e. Increase the SQ 833 one level
3.5.6 Transmitter Output Power Calibration
a.
Recall saved state 6 on HP8920A/B.
b.
State 6 on Radio Test Set:
•
Automatic Tuning
•
TX mode
•
AF GEN 1 OFF
•
RF Level Offset ON - configuration page
•
RF In/Out = -0.3 dB - configuration page
•
Input Port - RF in
c.
Key the transmitter.
d.
Monitor the TX Power on the HP8920A/B.
e.
For 10 Watt transmitters: Increase the XMIT PWR setting on the display until the TX carrier
power reaches the first level greater than or equal to 12.0 Watts on the 8920A/B. The power
should not exceed 13.0 Watts.
f.
For 16 Watt transmitters: Increase the XMIT PWR setting on the display until the TX carrier
power reaches the first level greater than or equal to19.0 Watts on the 8920A/B. The power
should not exceed 21.0 Watts
g.
Unkey the transmitter.
3.5.7 Transmitter Modulator Adjust
3.5.7.1 Modulator Adjustment for 10 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.
For –04 and lower boards: Key the transmitter and adjust R558 for 90% - 95% modulation
depth.
NOTE: Only perform this adjustment once at 118.000 MHz. Do not repeat it at
127.000 and 136.975 MHz.
d.
For –05 and higher boards: Key the transmitter and adjust the MIC setting on the display for
90% - 95% modulation depth.
.
e.
Unkey the transmitter.
f.
Key the transmitter and increase the MOD DEP setting on the display until the 8920A/B
modulation depth reading just falls below 80%. Decrease the MOD DEP setting one step to
put the modulation reading at, or above 80%. The modulation depth should not exceed 85%
g.
Unkey the transmitter.
