[Boatanchors] General question...frequency shift with RF gain

[Dale Parfitt]

Depending on how much it is shifting, a simple Zener regulator on the VFO supply may fix it, or there are  solid state high voltage regulators that are a lot stiffer than a Zener.

Just out of curiosity, how much does the voltage change from  min to max RF gain. I would also suspect then that very strong signals (big AGC change) might also “FM” the signals. Of course many of the early rigs w/o a product detector did not have AGC on CW/SSB where the change would be most noticeable.

 

Dale W4OP

 

From: John Saxon [mailto:johnbsaxon at yahoo.com] 
Sent: Friday, January 15, 2016 11:30 AM
To: parinc1 at frontier.com
Cc: Boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] General question...frequency shift with RF gain

 

Yes, I am seeing a voltage change on the HFO with RF gain adjustments.

 

--

John

K5ENQ

 

 

  _____  

From: Dale Parfitt <parinc1 at frontier.com>
To: 'John Saxon' <johnbsaxon at yahoo.com> 
Cc: Boatanchors at mailman.qth.net
Sent: Friday, January 15, 2016 10:15 AM
Subject: RE: [Boatanchors] General question...frequency shift with RF gain


While I have never experienced this I would wonder if changing the RF Gain changes the current drawn by the front end stages that are controlled by the AGC line. This may change the loading on the  receiver's HV supply.
That little change may then cause a change in the RX VFO voltage, thus causing a small frequency shift. Easy enough to check with a good voltmeter.

Dale W4OP


-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of John Saxon via Boatanchors
Sent: Friday, January 15, 2016 10:55 AM
To: Boatanchors Mail List
Subject: [Boatanchors] General question...frequency shift with RF gain

On the Hallicrafters list a fellow reported a receiver that shifted frequency with RF gain adjustments.  Several folks responded that they had had a similar experience. I am having the same issue with a National NC-101X.  Just out of curiosity:  Is a frequency shift with RF gain adjustment common?  uncommon?  in-between?
Just wondering...
--JohnK5ENQ


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