Troubleshooting
16 Apollo SL40 Field Maintenance Manual
TUNE Freq 127.5 MHz
TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq 1 kHz
Set AF GEN LVL 100 mV and to on
2. Set the SL40 as listed below:
While viewing the frequency display, use the large and small knob on the right
side of the SL40 to select 127.5 MHz.
Toggle this frequency into the Active channel.
Press the PTT button on the test panel.
EXPECTED RESULTS % modulation > 90%
Set AF GEN. LVL 50 mV
EXPECTED RESULTS % modulation > 70%
3. UN key the transmitter.
4. Repeat Steps 1 through 3 for the other MIC jack.
TRANSMITTER SNR (SIGNAL TO NOISE RATIO)
SNR is measured using the HP8920. This is accomplished by presetting the SL40 to the
same channel as the HP8920. Adjust the amplitude of a 1000 Hz tone (input to MIC 1
and/or MIC 2) to obtain 85% modulation. Select the SNR function and the HP8920
Communications Test Set will perform this test automatically.
Procedure:
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 4 as guides.
Press PRESET
Press TX function
Using the CURSOR control knob or the USER keys set:
AUTO MANUAL MANUAL
TUNE Freq 127.5 MHz See NOTE below
TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq 1 kHz
Set AF GEN LVL to read 85% modulation
Set AF meter to SNR
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