[Hallicrafters] SX-42 Alignment

[Roy Morgan]

At 11:59 AM 2/21/2007, Rich Soennichsen wrote: done.

>> >How do I use another receiver to check the LO? ...
>  I have a Yaesu FT-840 on the desk.  I attached a small antenna and
>was able to find the LO oscillator signal.

Rich,

Great!  Your FT-840 I assume will receive on most HF frequencies.

>  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...

There definitely is a problem. Those conditions will get you a very dead 
receiver.

  I would check any mica caps in the local oscillator section.  There are 
trimmers across most of the LO coils, and one or more may not be working right.

First, I would do the LO test on another band, say the next frequency band 
up.  See what happens there.

>  I don't know whether this needs to be addressed directly or if the RF 
> alignment will take care of it.

Yes, it needs to be solved first.  The RF alignment will  not correct what 
you report.

It will be helpful to know that the 455 kc IF is working well at (about) 
that frequency.  Test with a modulated 455 kc signal at the input.  (6SK7 
pin 4)

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
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