[AMRadio] Hallicrafters S38B


Jim Candela jcandela at prodigy.net
Sun Dec 31 13:30:35 EST 2006


Jack,

   I have never owned a S38B, but I did own a S40B and used it as a Novice on 80/40/15 meters CW. It was pretty terrible actually for CW, but a good 'first' receiver. On AM it was decent in many respects like you mention with your S38B. 

   You did well installing the polarized line cord, and planning to use an isolation transformer is also a good idea. That said, there are no 'incremental design enhancements' that will transform a S38B into a 75A4 or a SP-600. You can compensate somewhat by using your brain as a DSP filter to ignore audible QRN & QRM stuff blasting from your speaker. I did that with my S40B.

My suggestion with receivers  like this is to  look at them  for what it is, and be amazed that it does so well  for how simple a receiver it is.

Don't go away Jack. I for one like your stimulating the topics of discussion on this reflector. On occasion one of us crosses an invisible line, and it hits the fan. Don't believe for 1 minute that your the first to do that. Actually I think I just did it too! ;-)

Regards,
Jim
JKO

----- Original Message ----
From: Jack Schmidling <jack at schmidling.com>
To: Discussion of AM Radio in the Amateur Service <amradio at mailman.qth.net>
Sent: Sunday, December 31, 2006 7:53:16 AM
Subject: [AMRadio] Hallicrafters S38B

I started my career as a ham with an S38B so yesterday I bought one to 
relive the good old days.

It worked so well that I am going to set it up as my regular AM receiver.

I was not too impressed with a wire hung around the room but when I put 
the dipole on it, it really came alive.  After doing a little welding 
(learning about AC/DC radios) I got it hooked into the system so I can 
push to talk.

I will get an isolation transformer but in the mean time, I put on a 
correctly polarized plug and put 100 pf caps in series with the antenna 
coax leads as an additional precaution.

Anyway, the only serious problem with it is that the "BFO" does not 
work.  A little research pointed out that it is not a BFO but just 
regenerative feedback that makes it squeal.  The fix is to diddle with 
the position of a wire snaked between to pins of the detector tube socket.

I was unable to establish a reasonable sounding heterodyne this way but 
when I clipped a very small cap to one of the pins and the switch, it 
worked very well at the expense of lots of sig strength.

I can't seem to find any info on this issue and wonder if anyone has 
been there.

I also note with glee that even though the BFO does not work properly, 
the sigs get vastly louder when in the CW mode.  It is obviously 
operating in a regen mode but not what is needed for a BFO.

Seems like there should be some way to control this business and improve 
the inherent sensitivity of the S38B but I think I am over my pay grade 
here.

Any ideas?

JACK K9ACT

-- 
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