Squelch problem with GME 3400

I have the above with the main bit under the seat and the control bit on the centre console.
The problem is that on channel 20 I have a problem with the squelch. All other channels work fine.
On 20 whilst I can initially squelch and unsquelch successfully with the button as soon as someone transmits on 20 and my unit picks it up the squelch is activated and can't be eliminated via the button. I have to manually switch to another channel and then back to 20 - at which stage the squelch is again working. Until the next transmission is received!
Yes I know I could avoid 20, but it happens to be our Club channel.
Any ideas before I head off to see the local repairer?
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Reply By: Member - Bucky - Monday, Jan 18, 2010 at 17:00

Monday, Jan 18, 2010 at 17:00

Have you checked to see if you can adjust squelch on individual channels..
That might be possible..

Otherwise drop an email to GME, or Prestige communications.

AnswerID: 400045

Follow Up By: Moose - Monday, Jan 18, 2010 at 17:04

Monday, Jan 18, 2010 at 17:04
Thanks Bucky
I have already emailed GME.
If I read the manual correctly I can set the overall squelch to minimum, moderate and maximum (may not be correct terminology) but it applies to all channels.
Cheers from the Moose
FollowupID: 669148

Reply By: Member - joc45 (WA) - Monday, Jan 18, 2010 at 23:12

Monday, Jan 18, 2010 at 23:12
Does the problem occur in one location or everywhere? The source could be a spurious rf product from some other electronic equipment nearby which is opening the mute. This can be from a nearby transmitter site, or from electronics within the vehicle. It will usually manifest itself on only one channel.
Hysteresis in the squelch circuit means that changing channels, then back can quieten the receiver.

AnswerID: 400111

Follow Up By: Moose - Tuesday, Jan 19, 2010 at 09:08

Tuesday, Jan 19, 2010 at 09:08
Thanks for that joc45.
It happens everywhere. Which would indicate that the vehicle is the source of the problem. 100 series V8 auto.
But if it was the vehicle itself producing the "signal" why is it that the problem will only manifest itself after picking up someone elses transmission? If there is no communication from outside then it remains silent. But immediately upon a transmission ceasing that damn noise persists.
Cheers from the Moose
FollowupID: 669279

Follow Up By: Member - joc45 (WA) - Tuesday, Jan 19, 2010 at 12:14

Tuesday, Jan 19, 2010 at 12:14
Hi Moose,
The most probable source is the ECU, but there are a mulltidude of things which run microprocessors (a common source) these days, incl auto trans, electric aerials and windows. Even my dumb GU 4.2 diesel emits spurious signals which interfere with a mid-band VHF 2-way. The source often can be easily located, but stopping it is another thing (ask Disco and 100-series T-diesel owners). And I have a spurious signal from a nearby mobile base station near home.
The reason why you get the squelch staying open after a transmission is due to the hysteresis in the circuit; it will operate at one level of signal and drop out at a different level. The spurious signal is enough to keep the squelch open after a transmission, but not enough to open the squelch from zero signal.
Without getting too technical, it is possible for one particular design of receiver to pick up an unwanted signal, but another receiver will not. Sometimes the frequency of the unwanted signal is totally different to the receiver frequency, but design of the receiver dictates whether it rejects that unwanted signal or not.
Sorry I can't be of more help.

FollowupID: 669304

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