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Quadrature Detector Adjustment
1. Inject a strong on-channel signal at the antenna jack
modulated with a 1 kHz tone at 3 kHz deviation.
2. Monitor the VOL/SQ HI output at J705-3 with an AC
voltmeter and adjust L509 for a peak on the meter.
Receiver Audio Level
1. Inject a strong on-channel signal at the antenna jack
modulated with a 1 kHz tone at 3 kHz deviation.
2. Monitor VOL/SQ HI J705-3 with an AC voltmeter and
adjust R513 for a reading of 150 mVrms. A+ supply
current should be less than 3.5A with 10 watts of audio
to the external speaker, if equipped.
The external speaker audio has balanced outputs
and must be monitored with the test circuit shown
in Figure 2.
Sidetone Adjustment
The following adjustment requires duplex operation.
The RF signal generator must be isolated from the transmit-
ter RF power by connecting a 15 watt 30 dB attenuator or
other isolation device in series with the RF signal generator.
1. Inject a strong on-channel signal modulated by 1 kHz
tone at 3 kHz deviation at the RF input.
2. Turn the RX audio on (FCN 0 2) and set the volume at
10. Measure the RX audio output at the external speaker:
6.3 Vrms.
3. Turn off the 1 kHz modulation while leaving on the RF
generator signal.
4. Apply a 1 kHz tone to the TX Audio input at TX MOD
jack of the test box (J701-4). Turn on the TX audio (FCN
0 4) and key the transmitter (FCN 0 1). Adjust the 1 kHz
tone level for 3 kHz deviation.
5. Turn on the RX audio (FCN 0 2) and rekey (FCN 0 1).
Measure the RX audio output and adjust R624 & R326
on the Audio Board for a null. The null should be greater
NOTE
than -18 dB down from the 6.3 Vrms reference taken
above. Push END to unkey the transmitter.
TRANSMITTER VERIFICATION
Place the radio in the test mode for the following tests
(FCN A).
Transmit Frequency
Key the transmitter (FCN 0 1) and measure the transmit
frequency (default test mode channel is the first frequency
in the trunk frequency set from which test mode was en-
tered). The measured frequency should be within ±250 Hz.
(Push END to unkey the transmitter.)
Transmit Power
Select channel 649 (CLR 649 CLR) at 814.0000 MHz.
Key the transmitter (FCN 0 1). Power should be a minimum
of 10 watts. (Push END to unkey the transmitter.)
Modulation Limiting
1. Apply a 1 kHz tone at 2 Vrms to the TX AUDIO input
of the test box or J701-4.
2. Select channel 649 (CLR 649 CLR) at 814.0000 MHz.
Turn on the TX audio (FCN 0 4). Turn on the channel
guard tone (FCN 2 5) which also keys the transmitter.
3. The measured deviation should be 4.2 ±0.2 kHz. (Push
END to unkey the transmitter.)
4. Select channel 649 (CLR 649 CLR) at 814.0000 MHz.
Turn on the TX audio (FCN 0 4). Turn on the busy tone
(FCN 2 5) which also keys the transmitter.
5. The measured deviation should be 4.5 ±0.2 kHz. (Push
END to unkey the transmitter.)
Busy Tone Deviation
1. Select channel 649 (CLR 649 CLR) at 814.0000 MHz.
Turn on the busy tone which also keys the transmitter
(FCN 0 6).
2. The measured deviation should be 1 kHz +0.2, -0.3 kHz.
LBI-38953
17
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