Tait T855 - Page 166

C3.12 T856/857 Initial Tuning & Adjustment M850-00
31/09/98 Copyright TEL
3.9.3 Limiter Adjustment
Note:
If the T856/857 will be used over the whole 8MHz switching range, you
must set the deviation for each channel. However, if the module will be
used on frequencies that cover only a 1MHz (or less) switching range, you
can set the deviation on the middle channel and use this value for all other
channels with the “fill” option in PGM800Win.
Set the links in the audio processor section as required (refer to Section 3.5).
Inject 1kHz at -10dBm into the line input (D-range 1 (PL100) pins 1 & 4; and pins 2
& 3 shorted; refer to Section 2.2 of Part F).
Adjust RV210 (line sensitivity) fully clockwise and key the transmitter by earthing
the Tx-Key line. Adjust IC220 via PGM800Win “deviation” to set the peak devia-
tion to ±4.7kHz (±3.8kHz) [±2.3kHz] (you can use either the mouse or up and
down arrow keys).
Sweep the audio frequency from 100Hz to 4kHz and ensure that the maximum
deviation does not exceed ±4.7kHz (±3.8kHz) [±2.3kHz]. Readjust IC220 if neces-
sary via PGM800Win “deviation”.
3.9.4 Line Level Without Compressor
This section assumes that the compressor is not used. If the compressor is required,
refer to Section 3.9.5.
Adjust the line sensitivity as follows:
• set the injected signal at the line input to the required line level (typically -10 to
-20dBm);
• adjust RV210 (line sensitivity) to provide ±3kHz (±2.4kHz) [±1.5kHz] devia-
tion.
3.9.5 Compressor
The compressor may be used on the line input only, the microphone input only, or on
both the line and microphone inputs. If the compressor is used, refer to one of the fol-
lowing sections as appropriate.
3.9.5.1 Compressor On Line Input Only
Set RV210 (line sensitivity) fully clockwise and key the transmitter by earthing the
Tx-Key line.
Reduce the line level to -50dBm at 1kHz and set RV220 (compression level) fully
clockwise.