GNC 400 COMM TRANSCEIVER ALIGNMENT PROCEDURE
P/N 005-00051-55 REV. T
Page 7
3.2.2 TCXO Alignment
For –03 and higher 10 Watt comm boards, and 16 Watt comm boards, the integrated circuit
TCXO Y301 is pre-aligned by the manufacturer and no adjustment is required.
AT NO TIME DURING THE TCXO ADJUSTMENT PROCEDURE SHOULD THE
TRANSMITTER BE KEYED. DOING SO COULD DAMAGE THE 8920!
a.
Connect comm transceiver module BNC connector to HP8920A/B ANT IN.
b.
Recall saved State 1 on HP8920A/B.
c.
State 1 on Radio Test Set:
•
TX mode
•
Manual Tuning
•
Tune Frequency of 158.375 MHz
•
Input Port - Ant
d.
Monitor the TX frequency error on the 8920. For –00 and –02 comm boards, adjust C300
until the frequency error is less than
±
50 Hz.
e.
Install the synthesizer cover on the unit.
f.
Remove the BNC cable from the ANT IN port on the 8920 and re-connect it to the RF
IN/OUT port. It is now OK to transmit without damaging the 8920.
3.3 Transmitter Power MOSFET Bias Setting
3.3.1 Bias Settings for –04 and Lower 10 Watt Comm Boards
a.
Turn off the 28V power supply.
b.
Place a DMM configured to read current in line with the 28V supply to the comm. Use the
10A current input and not the 400mA input on the DMM.
c.
Turn on the 28V power supply.
d.
Zero out the current reading on the display using the REL
∆
function on the DMM.
e.
Make sure the potentiometers R530, R563, and R562 have been turned fully CCW as
outlined in section 3.1.1.
f.
On the unit display, set the TX CAL field to CALIBRT. If the current reading on the DMM
increases more than 50mA, send the unit to troubleshoot.
g.
SLOWLY
Adjust R530 until 28V current is 15 mA
±
5 mA.
h.
Zero out the current reading on the display using the REL
∆
function on the DMM.
i.
SLOWLY
Adjust R532 until 28V current is 100 mA
±
10 mA.
j.
Zero out the current reading on the display using the REL
∆
function on the DMM.
k.
SLOWLY
Adjust R563 until 28V current is 100 mA
±
10 mA.
l.
Place the TX CAL field on the display back to normal mode.
m. Turn off the 28V power supply.
n.
Remove the DMM from in-line with the 28V supply and reconnect the 28V supply.
o.
Turn on the 28V power supply.
3.3.2 Bias Settings for –05 and Higher 10 Watt, and 16 Watt Comm Boards
a.
Turn off the 28V power supply.
b.
Place a DMM configured to read current in line with the 28V supply to the comm. Use the
10A current input and not the 400mA input on the DMM.
c.
Turn on the 28V power supply.
d.
Tune the comm to 118.000 MHz.
e.
Zero out the current reading on the display using the REL
∆
function on the DMM.
