[R-390] BFO Drift?

[Jon Schlegel]

Hi all,

Tony, try to isolate the oscillator that's moving around.  Roy's 
remark about using another known stable receiver is the way to go 
because it tells you a lot of info quickly.  Lacking a second 
receiver, you may be able to "simulate" a one by using a stable 
signal generator and mixer to mix down to audio to then amplify and 
listen.   A Minicircuits type double balanced mixer would be nice if 
you could latch onto one, otherwise some arrangement using 1N34 type 
diode(s) might do the trick.  Getting enough RF  into the mixer to 
make it work will be the hard part.  You may have to get creative to 
make that happen.

You can take a look at the heater/filament voltages to see if you can 
spot any variation over time.  Another thought along the same lines 
is to operate the BFO heater on a separate supply.  This is a 
complicated test though since I seem to recall that the BFO and PTO 
heaters are in series along with the 3TF7.  Try to isolate which 
oscillator is doing the dance before getting into his kind of thing.

Regards,
Jon WA3MVM

At 12:34 PM 12/11/2008 -0700, ANTHONY CASORSO wrote:
>I have indeed, except that I don't have one. I have also considered 
>trying one of the other 3TF7 replacement variants (including Dallas' 
>voltage regulator idea). However, I think I need to do a little more 
>digging first. I keep saying I am going to get a replacement 3TF7 
>but I have not been motivated to do so until now. My old one went 
>bad about 1 week after I got the receiver. I thought that the 12BY7 
>was doing an OK job for me. Maybe not. We shall see.
>
> >
> > Have you considered reinstating the 3TF7 ?
> >
> > Graham
> > G8OAD
> >
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