[Hallicrafters] SX-42 Alignment

[Roy Morgan]

At 03:06 PM 2/19/2007, you wrote:
>>Yes, indeed.  Saint Peterr has a special list of folks who have tried to 
>>align
>>an SX-42.  They all get special arrangements upon arrival!
>
>Can you guarantee this?  ;-)

Uh... well.. I can't Guarantee it, heheh (I can hope, though.)

>>Do you have ANY kind of sweep generator?
>
>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.


>>If you have not replaced any mica caps in the RF transformers, stand by to do
>>so.  They may well be shorted or shifted in value by this age.
>
>I have no way to test them, perhaps I should just replace them....

Don't replace them unless they are not working, at least not yet.

>With your other receiver, make sure the local oscillator is running at 
>near the
>>right frequency
>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.

Rodger mentioned "little Japanese "DC to daylight" receivers ". What he 
means is small battery sets that tune from at least the broadcast band way 
up to high frequencies.  Some people have a dedicated communications 
receiver (for example an R-388) at the test bench for such purposes. Others 
find a little portable radio at a swap meet or at Rat Shack, and it does 
just fine.


Roy




- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
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