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CB Module Tuning Procedure
DC 12.7V
1. RX TUNING
1.VCO
Adjust TC 20P variable capacitor till tolerance of 10MHz reference point is within ±
100Hz.(measure at TP8 by cymometer)
Adjust T12 coil, let VCO output is 1.9V ±0.2V at 40CH.(Measure point is at TP3 by
mechanical Voltage meter)
2. TX.
Press TEST BOX AM/FM button to switch between AM and FM
2.1 AM/FM: Press PTT, adjust TC
output frequency is similar to desire channel such as 27.405MHZ for channel 40.
2.2 AM: adjust VR2
(AM MODULATION TUNING)
and MAX is not over 100%.
2.3 AM/FM: tune T6 T7 T8 and
the
TX POWER and find out the distortion is minimum point. (AM AT 80% MOD,
DIST is less than 10%; FM DIST is less than 8%). After that we have to tune the TX
Power within 3.6W to 4W by adjusting VR200.
2.4 FM: Adjusting VR4
1.7K~1.9K and Maximum is not over 2K.
3. RX TUNING
. Press TEST BOX AM/FM button to switch between AM and FM.
3.1 AM/FM: Adjust L1~L3, T1, T2 to make the best sensitivity and S/N. It should be at
12dB SINAD and the S/N is at least –109dB..
Test Box
SAMPLE
RF Communications
(Frequency Tolerance TUNING),
VR200(TX POWER /TX DIST TUNING) to adjust
(Frequency Deviation)
Spectrum Analyzer
to let AM MOD at 80%~85%
to let FM frequency shift between
so that the
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Summary of Contents for Midland 77321
- Page 1 CB Module Tuning Procedure Test Box DC 12.7V SAMPLE Spectrum Analyzer RF Communications 1. RX TUNING 1.VCO Adjust TC 20P variable capacitor till tolerance of 10MHz reference point is within ± 100Hz.(measure at TP8 by cymometer) Adjust T12 coil, let VCO output is 1.9V ±0.2V at 40CH.(Measure point is at TP3 by mechanical Voltage meter) 2.
- Page 2 3.2 FM : AdjustT3(SENSITIVITY AND S/N) to let the SINAD be the best.. 3.3 AM/FM : Adjust VR1(AUDIO OUTPUT) to let the audio output for FM 0.1~0.32V and AM 0.12~0.16V Adjust VR20(SQ), when INPUT is 62dBuV and OUTPUT would be 3.8V. Testing Point is at TP1.
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