[AMRadio] Hallicrafters S38B

Jack Schmidling jack at schmidling.com
Sun Dec 31 08:53:16 EST 2006

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 

Any ideas?


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