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HQ 170 CW sidetone monitor

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Author Topic: HQ 170 CW sidetone monitor  (Read 308 times)
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« on: April 10, 2019, 11:03:07 PM »

Has anyone modified an HQ 170 so that when it is muted, a sidetone signal is still enabled?  My "Elmer" made a change to my receiver in the 1960's that provided a sidetone with muting.  Lots of time has passed - and I have forgotten as much as I knew at the time as to what was done.  Forward 55 years later and a different receiver.   I have a fairly stock HQ 170 paired with a Heathkit Apache.  The antenna to the receiver is bypassed during transmit using the classic Dow Key relay and the accessory contacts cut regulated voltage to the screens of the first several stages RF-IF in the receiver.  Would reducing this voltage instead of interrupting this via the relay provide usable signals to sidetone levels without damaging the receiver?  Would a series resistance instead of open circuit  across the mute terminals allow some signal for sidetone?  It seems this would have been a common modification but I cannot find one in a reasonable search.  Also, my retired brain was never a good tube/signal analysis guy.

Thanks, NS7H
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