8525B/8528 Technical Service Manual Adjustments 7-7
Publication No: 15-02036 Issue 6
7.3.5 45MHz IF Alignment—Receive
1. Ensure the dual coax socket is connected to the PA and Filter PCB.
2. Connect the signal generator to the antenna socket.
3. Select a channel (USB) and adjust the signal generator output to the
selected channel frequency plus 1kHz.
4. Increase the signal generator output until the signal is heard from the
loudspeaker.
5. Connect the audio voltmeter to the Demodulator output on the Audio
and IF 1650kHz PCB (TP2).
6. Adjust the 45MHz IF trimmer capacitors (outermost holes in shield lid)
to half mesh i.e. screwdriver slots parallel to the long edge of the shield.
7. Adjust L29 and L32 (centre holes) for a maximum signal on the audio
voltmeter.
8. Reduce the signal generator output and repeat step (7) until no further
increase can be obtained on the audio voltmeter (below AGC
threshold).
7.3.6 1650kHz IF Alignment
1. Align the 45MHz IF as above.
2. While still in Rx, peak the audio voltmeter reading by adjusting L1, L2,
and L3 (on the Audio and 1650 IF PCB) and reducing the signal
generator output to remain below AGC threshold.
3. When no further increase in the audio voltmeter reading can be
achieved, check that the signal generator output is below 0.35µV PD for
10dB SINAD.
7.3.7 45MHz IF Alignment—Transmit
CAUTION
THE PROCEDURE WHICH FOLLOWS INVOLVES ALTERNATELY
APPLYING A SIGNAL GENERATOR TO THE ANTENNA SOCKET TO
SET RECEIVER ADJUSTMENTS AND SWITCHING TO TRANSMIT TO
SET TRANSMIT ADJUSTMENTS. THE SIGNAL GENERATOR WILL BE
DAMAGED IF IT REMAINS CONNECTED WITH THE TRANSCEIVER IN
TRANSMIT.
1. Align the 45MHz IF in receive as above.
2. Align the 1650kHz IF as above.
3. DISCONNECT SIGNAL GENERATOR FROM ANTENNA
SOCKET.
4. Disconnect dual coax socket from PA and Filter PCB.
5. Connect audio two-tone source to microphone input and switch
transceiver to transmit.
6. Connect CRO across TP1 on the RF Mixer and Dual Synthesizer PCB.
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