[Hallicrafters] SX-42 Alignment

[Rich Soennichsen]

Thank you Roy, see below....

> >Mine does have a sweep mode, how do I use it?
>
> This is a topic for another series of posts, but basically, you get the
> generator to sweep through the frequency of interest (in the case of most
> FM radios 10.7 mc IF frequency) and watch the detector output on a scope.
> You synch the scope with the sweep (the method depends on your sweep
> generator and your scope).  Then you look for the right shape of waveform
> on the scope and tune things up watching the scope.
>

I think I'll hold off on this until I can get a basic alignment done.

> >How do I use another receiver to check the LO?
>
> 1) Locate the local oscillator tube (in the SX-42, this is a type 6F8 dual
> triode tube, front most under the tuning capacitor cover.)
>
> 2) Wrap a sniffer wire around the tube (a turn or two is fine) and hook the
> other end of the wire to the antenna input of the other receiver. (Note:
> this is likely to work even with metal tubes, although as far as I know,
> all Loctal tubes are glass, so the signal will easily leak out and get to
> the sniffer wire.)
>
> 3) Figure out where the local oscillator should be running.  According to
> Rodger in an earlier post:
>
> "... On the SX-62 the oscillator will
> be offset by the ~455 khz. IF frequency on the 4 lower ranges and by the
> 10.7 mhz. IF frequency on the 2 upper ranges.  So for example, on band 1 if
> you tune the SX-42 to 600 khz. you should hear the oscillator at 1055 khz.
> and at a receiver frequency of 1600 khz. you should hear the oscillator at
> 2055 khz. "  (And on the highest bands with the FM IF strip in use, the
> difference will be 10.7 mc.  - which way I don't know.)
>
> 4) Tune the other receiver to the expected frequency and tune around.
> You'll come across a strong signal that will change frequency if you tune
> the SX-42 main tuning dial.
>
  I have a Yaesu FT-840 on the desk.  I attached a small antenna and
was able to find the LO oscillator signal.  With the SX-42 tuned to
550 kc I found the LO at about 965 kc which gives an IF of ~415kc.  If
I tune to the other end of the bc band the IF is only ~230kc.  Hmm
seems to me this non-linearity is a problem...  I don't know whether
this needs to be addressed directly or if the RF alignment will take
care of it.

Rich