As the sunspot cycle is inching forward, I've been considering adding
an upconverter to Charles Kitchin's 50MHz audio-squelched superregen
design, in order to make a sensitive and very quickly tuneable
15-30MHz receiver intended to take the pulse of propagation on the
higher HF bands. The idea came from an unpretentious Russian design.
(No, it wasn't a fremodyne).

In a classic case of mission creep, I observed that a fixed IF lends
itself to a further step. I searched for prior art in inducing super-
regeneration in a resonant cavity.

If that could help narrowing the passband, it would be a nice trick
for upconversion.

I found few and laconic references at almost-otherwordly microwave
frequencies, Gunn diodes, folded spectra, etc etc.

If I could make a resonant cavity in no time I'd not ask for advice
before jumping in, but this would be my very first, and shooting for
40-60Mz IF it risks being somewhat monumental - short of pigtailing
the resonator, or doing a folded design, or some other "Grande
Complication" which might negate the very idea of using a cavity.

****** Prior art pointers, anyone? ******

TIA

Filippo N1JPR






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P.S.: Just to prempt repetitions of the obvious I'll repeat it myself:
Why don't you use a [ superhet ¦ xtal roofing filter ¦ downconversion
¦ cod liver oil ¦ snake oil ]. Sorry I never heard of it, so it's
likely to be a bad idea. Are you a Communist? Never heard of a 40MHz
cavity. A superregen won't demod [ CW ¦ SSB ¦ [QM¦P]SKxx ¦ delta-
sigma ¦ ancient Greek ] ! Is this gonna be a portable receiver in
that you can put it in the back of a SUV - if someone helps you carry
the 6' long cavity, that is? You will need a [ BFO ¦ product detector
¦ AMS ¦ DSP ¦ LPF ¦ postprocessing ¦ Photoshop ]. IF passband will be
too broad, although I have no idea how broad since I never used a
cavity for that. :-o