Service manual

8000 SERIES RECEIVER DECODER MODULE (RDM)
2-8
March 2000
Part No. 001-3139-502
2.10.2 DIVERSITY AND SQUELCH THRESH-
OLD LEVEL
1. Establish the 0 dB reference for quieting as
described in Section 2.10.1. Adjust the LOCAL
AUD control so that audio can be heard from the
speaker when the receiver unsquelches.
2. Switch diversity control switch S1 on the receiver
board to the enter "DIV" position.
3. Increase the unmodulated generator output so that
the audio unsquelches. Then decrease the generator
output and the audio should squelch when approxi-
mately 7 dB quieting is reached. If not, refer to
Section 2.8.8.
2.10.3 RECEIVE DATA LEVEL
1. Connect a signal generator to the appropriate
receive antenna jack. Set the generator output for the
receive channel frequency with an output level of
100 µV, modulated with 150 Hz at ±800 Hz
deviation.
2. The data signal at TP8 on the logic board should be
0.56V P-P or 0.20V RMS. If not, refer to
Section 2.9.
2.11 RDM ALIGNMENT
2.11.1 EQUIPMENT REQUIRED
• Frequency counter with 10:1 probe.
• IFR signal generator (or equivalent).
• AC Voltmeter
• DC Voltmeter
• Distortion Analyzer
• Oscilloscope
• Transmission Test Set
• Multi-Net Encoder/Decoder Box
2.11.2 CLOCK ADJUSTMENT
Verify the clock frequency of the microprocessor.
1. Measure the frequency at U1, pin 19 with a fre-
quency counter and 10:1 (10M ohm) probe.
2. Frequency should be 11.059 MHz ±500 Hz.
3. Adjust C5 if necessary.
2.11.3 RECEIVE AUDIO LEVEL
1. Set the IFR signal generator to the receive channel
frequency with an output modulation set to 1 kHz at
±1.33 kHz deviation for 900 MHz or ±1.5 kHz devi-
ation for 800 MHz at a level of -70 dBm.
2. Connect the generator to antenna 1 (J6).
3. Verify that S1 on the receiver board is set to
"Ant 1".
4. On the Decoder board set S1, Sections 1/2 "On",
3 "Off" and reset the RDM.
5. Using a transmission test set verify that -20 dBm is
measured at TP3.
6. Adjust R29 if necessary.
7. Verify that -12 dBm is measured at TP4.
8. Adjust R35 if necessary.
2.11.4 RECEIVE DATA DEVIATION
1. Set the IFR signal generator to the receive channel
frequency with an output modulation set to 100 Hz
at ±800 Hz deviation at a level of 100 µV.
2. Connect the generator to antenna 1 (J6).
3. On the Decoder board set S1, Sections 1/2 "On",
3 "Off" and reset the RDM.
4. Using an AC voltmeter, verify that 0.34V RMS or
0.56V P-P is measured at TP1.
5. Adjust R20 if necessary.