12
RECEIVER SQUELCH
The DR-142 is capable of two squelch operating modes. Also, both can operate simultaneously.
See the theory above. The units can be configured as the user requires. When a low level signal appears
the noise squelch opens when the carrier level with 1.5 kHz (3.0 kHz for wideband) deviation is –118 or
greater
.
When the signal appearing is –108dBm or greater the RSSI squelch opens the audio with an
even faster attack time. The above levels are factory set levels. Ambient noise will affect the level at
which the RSSI should be set. The squelch level ideally should be set on the desired frequency, in the
actual location the radio will be used and connected to the desired antenna. The level should be set high
enough to reject most false signals.
If a very fast receiver decay time (or squelching after signal disappears) is needed the noise squelch
should be defeated by turning the R144 pot fully counterclockwise or removing Q110.
To adjust squelch levels for simultaneous use do the following:
Set RSSI squelch level first:
1) Temporarily defeat noise squelch pot by turning R 144 to counterclockwise minimum setting.
2) Adjust RSSI pot R123 fully counterclockwise to squelch audio. Be sure AUX_MON line is high to
allow squelching.
3) Set generator to –108dBm on channel desired with 1.5 kHz deviation ( 3.0 kHz for wideband) and 1
kHz tone. Add any CTCSS or DCS as needed.
4) Turn R123 clockwise until audio opens. Go no further if you want only RSSI squelch functionality.
Now set noise squelch:
1) Select a channel.
2) Adjust squelch pot R144 fully counter clockwise.
3) Adjust the communications test set generator on frequency with an output level of –118dBm. The
deviation should be +/- 1.5 kHz (3.0 kHz for wideband) with a 1 kHz audio signal.
4) Slowly adjust squelch pot R144 clockwise until squelch opens.
5) Reduce generator level until radio squelches.
6) Increase generator level until audio opens. Confirm squelch hysteresis is between 0.5 and 5 dB.
