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[aprssig] Every; Any; All

Mike Yetsko myetsko at insydesw.com
Mon Sep 27 22:51:50 UTC 2004


> At 10:50 AM 9/27/2004, nc8q wrote:
> >(1) In 2 meter repeater operation;
> >I usually run 'full duplex' at home and sometimes in the car.
>
>          How do you prevent feedback squealing?
>
>          Earl
>

A LOT of repeaters with 'DTMF' control have a 'delay line' in place.
This delay line is chosen so that the system can detect DTMF and lock
on it with a very slight edge and prevent any of the DTMF tones from
going out.  If you listen to 'A/B' from input to output you can notice the
delay.  Usually less than 1/10th second, but enough to usually prevent
feedback.  Although under some circumstances it can produce an echo
chamber effect.






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