X-2 Technical Service Manual Adjustments 7-9
Publication No: 15-02047
3. Remove the coaxial connector P1 on the Rx/Exciter & Control PCB
(removing the exciter output to the PA).
4. Connect a Frequency Counter to Exciter output (Tx and ground).
5. Hold the Tune/Off/Mute switch in the Tune position.
6. Adjust trimmer C51
[D3]
(reference crystal adjust) to a frequency of
17900 kHz ± 5 Hz.
Note: Allow at least five minutes from switch-on before adjusting the
frequency.
7.9.2 Frequency Adjust LSB
To adjust LSB for frequency:
1. First adjust frequency in the USB as detailed in Section 7.9.1. Remain
in the Test Mode and leave the frequency counter connected.
2. Select channel position 4 and the USB/LSB to LSB (this selects test
channel 17903 kHz LSB).
3. While holding the Tune/Off/Mute switch in the Tune position adjust
C97
[E7]
for 17903 kHz ± 5 Hz.
7.10 Mute Adjustment
108-04840
The Mute is located on the Rx/Exciter & Control PCB. The adjustment
procedure is as follows:
1. Connect the Transceiver to an antenna (a short length of wire will do).
Select an unoccupied channel.
2. Select Mute On located on the front panel.
3. Commence with preset potentiometer R358
[E8]
fully counter-clockwise.
Slowly rotate the control clockwise until the mute gate closes and the
receiver noise is heard in the loudspeaker (mute threshold).
4. Rotate the control back in a counter-clockwise direction for 1/4 of a
turn.
5. The mute should now be sensitive enough to operate on the weakest
signal without false triggering on noise pulses. The sensitivity may be
varied from this setting to suit individual requirements (clockwise to
increase sensitivity).
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