Troubleshooting
18 Apollo SL40 Field Maintenance Manual
RECEIVER
RECEIVER PERFORMANCE
The following specifications define expected receiver performance.
Class D
Frequency range 118.000 to 136.975 MHz, 760 channels.
Sensitivity 1µV (2µV hard) for 6dB S+N/N with 30% modulation at
1000Hz
Selectivity <6dB variation at ±7kHz > 60dB at 22kHz
Speaker audio output level 12 watts into 4Ω load., 8 watts into 8Ω load.
Headphone audio output level 280mW into 100Ω load, 120 mW into a 500Ω load.
Distortion <5% at rated audio output.
AGC characteristics <3dB variation in audio output from 5 µV to 100mV
input, 15% to 90% modulation.
Squelch control Automatic squelch with manual override
SPEAKER AUDIO TEST
The speaker audio level is measured using the HP8920. This is accomplished by
connecting the speaker audio to the Audio in, (high) of the HP8920. By adjusting volume
control to the desired level, (12W) and measuring the audio power in watts.
Procedure
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 5 as guides.
Press PRESET
Press RX function
Using the CURSOR control knob or the USER keys set:
AUTO MANUAL MANUAL
RF GEN Freq 127.50 MHz
AF GEN Freq 1 kHz
Amplitude 10,000 µ volts
RF OUTPUT RF OUTPUT
AF Freq 1000 / 85%
Ext Load 4 ohms
AC LEVEL units to Watts
2. Connect the speaker load to the HP8920 audio in. Turn the SL40 volume control to
show an output level of 12 watts on the HP8920. Record the Speaker 1000 Hz Distortion
at 12 watts. Value should be < 5%. Set the distortion level to Reference
3. Connect the headset load to the HP8920 audio in. Turn SL40 volume control to show
an output level of 280 m watts on the HP8920. Record the Headset 1000 Hz Distortion at
280 m watts. Value should be < 5%. Set the distortion level to Reference
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