diy IF transformers: first attempt.

[Amie]

I keep thinking about the shorten quater wave transmission line used in the oscillator of the Leak Trough Line:

http://www.adventuresinhifiaudio.com/18/...er-design/

I wonder i can make a FM  oscillator rig with a coaxial copper pipe as 1/4 transmission line.

A year or so ago I did have some success with a vhf circuit, (again an FM band superregen that used a twin triode for detector + AF amp that used a transmission line for tuning that I called a trombone tuner*. It was a U shape piece of heavy tinned wire, (think 100 amp fuse wire that had a coil incorporated on one end that was loading for the top end of the FM band), it was tuned by  pulley and cord system that pulled a sliding contact along between the parallel section of wire. I have the notes and dimensions for that with the actual device, unfortunately not here! (In a biscuit tin two counties away!) The only real problem with that was having the connections to the valve from the tuned circuit short enough... That performed best with the detector changed to a UHF triode.

More by luck than judgment the bandwidth of that tuned circuit was just right, and reasonably noise free slope detection was possible, and although a simple self quenched design, its quench ran at about 30 kHz and the audio is acceptably entertainment quality: listening to music with it, is a pleasant enough experience.

*The project was encouraged by "Kalee20" (Peter) and "reset" (Greg).