GNC 400 COMM TRANSCEIVER ALIGNMENT PROCEDURE
P/N 005-00051-55 REV. T
Page 9
3.5 Receiver / Transmitter Digital Pot Adjustments
If the comm automated alignment software is to be used, follow the steps in section 3.5.1. If the
digital pots are to adjusted manually, skip to section 3.5.2.
3.5.1 Comm Automated Alignment Instructions
To perform an automated alignment on the comm board:
a.
Click on the icon labeled Align 400.
b.
Push the ‘Set Comm Defaults’ button on the screen. Wait while the Freq MHz box cycles
through frequencies and returns to 118.000.
c.
The manual squelch indicator on the screen must be off. If not, push comm volume knob on
the front of the unit to toggle the squelch.
d.
Push the ‘Auto Align All’ button on the screen.
e.
The alignment program will begin to run. Follow all instructions that appear in the ‘Setup
Instructions’ box.
f.
When the alignment is finished, the ‘Auto Align All’ indicator must be green. If not, repeat the
procedure beginning at step 2.
g.
Stop Here. The comm alignment is complete.
3.5.2 Receiver Preselector Alignment
a.
Recall saved State 3 on the HP8920A/B.
b.
State 3 on Radio Test Set:
•
RX mode
•
RF GEN FREQ = 118.000 MHz
•
RF GEN amplitude = 10
µ
V
•
AF GEN1 OFF
•
ohm/emf = emf on config page
•
RF Level Offset ON - configuration page
•
RF In/Out = -0.3 dB - configuration page
c.
Set the COMM frequency to 118.000 MHz.
d.
Set the channel spacing to 25 KHz
e.
While monitoring the IF AGC voltage on the test panel with a DMM, adjust the HP8920A/B
RF GEN amplitude until the DMM reads 5.0
±
0.1 VDC.
f.
Adjust POLE 1 on the display until maximum IF AGC voltage is achieved.
g.
While monitoring the IF AGC voltage on the test panel with a DMM, re-adjust the HP8920A/B
RF GEN amplitude until the DMM reads 5.0
±
0.1 VDC.
h.
Adjust POLE 2 on the display until maximum IF AGC voltage is achieved.
i.
While monitoring the IF AGC voltage on the test panel with a DMM, re-adjust the HP8920A/B
RF GEN amplitude until the DMM reads 5.0
±
0.1 VDC.
j.
Adjust POLE 3 on the display until maximum IF AGC voltage is achieved.
k.
While monitoring the IF AGC voltage on the test panel with a DMM, re-adjust the HP8920A/B
RF GEN amplitude until the DMM reads 5.0
±
0.1 VDC.
l.
Adjust POLE 4 on the display until maximum IF AGC voltage is achieved.
m. Repeat steps e, g, i, and k to fine tune the preselector poles - it is not necessary to re-adjust
the RF input level each time.
3.5.3 Receiver Noise Squelch Calibration - 25 KHz Mode
a.
Recall saved State 4 on the HP8920A/B.
