Does anyone (in particular, the 20's superhet gurus) have any articles/data on winding DIY IF coils for a DIY 20's era superhet?
By info, I mean actual winding, construction and test data for various IF frequencies (30-500kHz) and transformer types, including iron-wire cored. It appears that the first, and maybe the last of the transformers in any set, have different parameters to the ones in between, so a short explanation of that would be appreciated.
I have read a lot on Duane's site regarding IF tests but wonder if there is any definitive, general info./articles (contradiction in terms?) on the subject. Info on the net seems to be "pretty thin on the ground".

Thanks.

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A google search on <winding IF transformers> brings up a few sites, after you convince google that you really mean "IF".
Here's one:
http://www.sm0vpo.com:800/blocks/if-txfmr_tube_00.htm

I've also heard of improvising IF transformers by mounting two small rf chokes physically close to each other, with appropriate resonating capacitors.

-Chuck

SM0VPO is Harry Lythall's callsign. He has a message board too, like this one.

I can only tell you what worked for me, and it's for a transistor IF strip - with that in mind, I'm assuming you can simply use a thicker wire for the windings, as the wire I used was 40 SWG (That's not the same as AWG, so be careful).

Since you are using valves, you won't need a centre tap on the tuned side of the transformer. So, 220 turns and 220pF brought the coil into resonance at 455KHz. Note that I used a single tuned transformer, so my secondary coil was only 20 turns, 30 turns and 40 turns (IF 1, IF2 and IF3 respectively). If you want to use a twin tuned coil, your secondary would be 220 turns again with 220pF.

All I can say to you is that it worked for me. Coil former was 7mm O/D polystyrene tube with an M6 thread cut into it with a tap, and then an M6 12mm ferrite tuning slug was added. I got the tube from a model shop - its easy to get hold of, but expensive since it's only really used by model makers and I assume they don't sell a lot of it.

In "The Superheterodyne Book" by Clyde Fitch, 1934, plans are given for making 175 kc IF coils.

Some good info there - thanks guys.

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Try this site--

http://www.tuberadio.it/docs.htm

The Radio News Superhet book can be downloaded from there and several of the designs give coil building data.

Ed.

Done.
Now for some reading.

Thanks, Ed.

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