M850-00
T856/857 Initial Tuning & Adjustment
C3.9
Copyright TEL 31/09/98
3.6 Synthesiser Alignment
• Ensure that the T856/857 has been programmed with the required frequencies
using PGM800Win software.
• Single Channel Select a channel using PGM800Win.
Multichannel Select the middle channel via PGM800Win.
• Connect a high impedance voltmeter to the long lead of L1 in the VCO (this meas-
ures the synthesiser loop voltage).
• Key the transmitter by earthing the Tx-Key line.
Single Channel Tune VCO trimmer C6 for a synthesiser loop voltage of
10V.
Multichannel Tune VCO trimmer C6 for a synthesiser loop voltage of
10V on the middle channel.
If there is no middle channel, tune C6 so that the channels
are symmetrically placed around a loop voltage of 10V.
All channels should lie within the upper and lower limits
of 16V and 3V respectively.
Do not attempt to program channels with a greater fre-
quency separation than the specified switching range
(8MHz).
• Check that the exciter output power is 1W ±300mW (T857 only).
• Measure the exciter output frequency and adjust the TCXO (=IC700) trimmer if
required.
Caution:
This trimmer is susceptible to physical damage. Do not exert a down-
ward force of more than 500g (1lb) when adjusting.
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