B3.6 T855 Initial Tuning and Adjustment M8SL2-00-002-812
© Copyright Tait Electronics Limited August 2004. All rights reserved.
1kHz into the antenna socket and adjust the helical resonators #FL410 and #FL420
to give best sinad.
Continually decrease the RF level to maintain 12dB sinad.
Readjust FL410 and FL420 to give best sinad.
With PL210 and PL220 connected for de-emphasised audio response, the receiver
sensitivity should be better than –117dBm, assuming that the audio levels are not
being overdriven (refer to Section 3.4.5).
3.4.4 Mute Adjustment
3.4.4.1 Noise Mute
Connect pins 1 and 2 of PL250 to enable the noise mute.
Set the RF level to –105dBm with ±3kHz deviation (±2.4kHz) [±1.5kHz] at 1kHz.
Set RV230 (front panel gating sensitivity) fully anticlockwise.
Adjust RV310 (noise mute gain) fully clockwise to close the mute (if necessary
turn off the RF signal and then turn it on again).
Rotate RV310 anticlockwise until the mute just opens.
Reset the signal generator for the required opening sinad and adjust RV230 clock-
wise until the mute just opens.
3.4.4.2 Carrier Level Mute
Connect pins 2 and 3 of PL250 to enable the carrier mute and disable the noise
mute.
Apply an on-channel signal from the RF generator at the required mute opening
level with ±3kHz deviation (±2.4kHz) [±1.5kHz] at ±1kHz.
Adjust RV235 (carrier mute) anticlockwise to close the mute (if necessary, momen-
tarily turn off the RF), then slowly adjust it clockwise until the mute just opens.
The mute should now open at this preset level.
3.4.5 Line Amplifier Output
Apply an on-channel signal from the RF generator at a level of –70dBm with
±3kHz deviation (±2.4kHz) [±1.5kHz] at 1kHz.
Adjust RV210 (front panel line level) to set the line level to the required output
level.
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