[Hallicrafters] SX-100 BFO Setting

[Frederick Bray]

I will give the injection method a try.   If that doesn't do it,  I will try the other methods.

Thanks to everyone who has responded.

(I have a Mk1, by the way.)

Rodney Bunt wrote:

> Inject 50kHz into the IF and adjust for ZERO beat. inject at pin 1 of V6.
>
> NOTE: the IF freq depends upon which version of XS-100 you have. The IF for a SX-100Mk2 is
> 50.75kHz, for a SX-100Hk1 it is 50.5kHz
>
> A real seat of the pants adjustment is to set selectivity to 500Hz (.5kHz) remove antenna and tune
> the BFO for the lowest pitch noise, it will go down and back up again, adjust the 'whoosh' for
> lowest pitch.
>
> Rodney
> VK2KTZ
>
> --- Frederick Bray <fbray at mminternet.com> wrote:
> > I am finishing up the restoration of my SX-100, but I have had problems
> > adjusting the BFO as described in the manual.  It is probably my own
> > fault that I lost the original adjustment.  When I got the radio, I
> > couldn't the BFO to function, even after re-capping the radio and
> > replacing the tube.  I assumed that the former owner had mis-adjusted
> > the coil tuning and tried adjusting it throughout its range to no
> > avail.  Turned out that one of the resistors in the circuit had
> > increased in value well up into the megohm range, dropping the voltage
> > below what was required.
> >
> > Anyway, after replacing the resistor, the BFO works, but I can't get it
> > adjusted down to the spec's in the manual.  I figure that I could
> > probably set it correctly using my HP freq. counter -- which goes down
> > to 10 Hz. or with a scope.  Unfortunately, I can't find the right point
> > and/or technique to pick up the BFO signal without loading the circuit
> > to the point that I substantially change the frequency.
> >
> > I wonder if anyone has been down this road and can offer suggestions as
> > to where I might pick off the BFO output so that I can set it to 50 KHz?
> >
> > Many thanks.
> >
> > Fred
> > KE6CD
> >
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