7-10 Adjustments 8525B/8528 Technical Service Manual
Issue 6 Publication No: 15-02036
7.3.9 Noise Limiter
1. Connect a DC Voltmeter to TP6 on the RF, Mixer, and Dual
Synthesizer PCB. With no signal applied TP6 should be at
approximately 2.5V DC.
2. Connect a signal generator to the antenna socket, select a channel
(USB) and set the signal generator output to the selected channel
frequency plus 1kHz.
3. Increase the signal generator output until the voltage at TP6 reduces to
2 Volts DC.
4. Adjust L47 for a minimum voltage on TP6.
Note: The null is not well defined.
7.3.10 Frequency Adjustment (USB)
1. Select the highest channel frequency (above 10MHz if possible) that is
not transmit inhibited. Remove the dual coax socket to the PA and
Filter PCB.
2. Connect the frequency counter across TP1 on the RF Mixer and Dual
Synthesizer PCB.
Allow at least 5 minutes warm up before adjustment.
3. Press and hold the Tune pad.
4. Adjust C143 on the RF Mixer and Dual Synthesizer PCB for the correct
frequency for the channel selected.
Note: If the adjustment range of C143 is not enough, the value of
capacitor C142 may be changed. The temperature coefficient of
the replacement capacitor must match that of the factory-fitted
capacitor.
5. Reconnect the dual coax socket.
7.3.11 Frequency Adjustment (LSB)
8525B/8528
1. Perform USB frequency adjustment as above.
2. Select a channel with LSB mode enabled.
3. Press the TUNE pad and adjust C162 until the output frequency (at
TP1) is correct for the selected channel.
4. If the range of C162 is insufficient C161 may be altered to compensate.
To Next Page
Loading...
Need help?
General
