[HBR] The I.F transformer problem

[Brian Burns]

Hello All,

I'm new to the HBR list, but have long been interested in ham receiver
design and construction. As K6UCD in 1955 I built one of Byron Goodman's
band imaging receivers for 80 and 40 meters. It was the double conversion
design with a 1700 kc first IF. In that era it was no problem to order up a
Millen transformer for that frequency, though it took an agonizing six
weeks for it to be delivered!

So, having been re-enthused with ham radio after all these years, against
my better judgement, I thought I would like to build another receiver.

I have spent quite a bit of time looking at old handbooks, back issues of
QST, and arguing with fans of regens about the practicality of those old
timers for ham use. I've wanted to see what has risen to the top as some of
the better designs from the tube era. The problem of course is that all of
the superhets specify IF transformers, and//or coils from J.W. Miller,
Millen, etc.

Max Robinson of the funwithtubes list suggested a work-around taken from
one of the NC-300 models, for a capacitively coupled pair of torodial
coils; see attached schematic in .pdf. I'm not sure if this list permits
attachments. If not, I can email you a copy.

So, if there are currently sources for IF transformers, or if anyone has
used Max's scheme, I would really appreciate hearing about it.

Cheers,

Brian Burns   Ex: W5BRO, K6UCD