Synthesiser Alignment; Alignment Of Receiver Front End And If - Tait T880 II Series Adjustment Manual

B3.10 T885 Initial Tuning & Adjustment
3.6

Synthesiser Alignment

• Ensure that the receiver has been programmed with the required frequencies
using the PGM800Win software.
• Connect a high impedance voltmeter to the via next to R520 in the VCO cavity
(this measures the synthesiser loop voltage).
•
Single Channel
Multichannel
• The TCXO =(IC700) output frequency should be trimmed when the IF is tuned -
refer to Section
3.7

Alignment Of Receiver Front End And IF

Note: In this and following sections deviation settings are given first for wide
bandwidth sets, followed by settings in brackets for narrow bandwidth sets
[ ].
Align the synthesiser as instructed in
align the receiver on a frequency in the middle of the required band.
Set RV230 (front panel gating sensitivity) fully clockwise.
Inject a strong on-channel RF signal with ±3kHz deviation [±1.5kHz] at 1kHz into
the antenna socket.
Connect a voltmeter to the RSSI output (D-range 1 [PL100] pin 5 or P238 in the
audio processor cavity) and adjust the helicals (#H900, #H400 and #H401) to give
maximum RSSI voltage. While adjusting the helicals, decrease the RF level to
keep the RSSI voltage below 7V.
Adjust L345 coarsely for maximum line level.
While maintaining a low level unmodulated RF input to the receiver, loosely cou-
ple into the first IF an additional high level signal at 45MHz - you will hear a beat
note.
10/07/00
Tune VCO trimmer CV500 for a synthesiser loop voltage
of 10V.
Tune VCO trimmer CV500 for a synthesiser loop voltage
of 10V on the middle channel.
If there is no middle channel, tune CV500 so that the chan-
nels 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 programme channels with a greater fre-
quency separation than the specified switching range of
6MHz.
3.7.
Section 3.6. For multichannel operation
M880-00
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