Tweakers' Asylum

Posted by mrh (Mark Hardy) (A) on July 02, 2003 at 04:50:57

In Reply to: Easy DIY FM tuner on a chip wanted - ideas anyone? posted by Morse on July 01, 2003 at 12:58:56:

... that you start with an AM receiver? As has already been noted, RF circuit design and construction is a in a way different league than AF. The amps and preamps we play with can be almost trivially simple circuits (must be, if I can even sort of understand them!). Plus, after you build a radio, you need to align it, which is a) not trivial for a neophyte and b) requires somewhat esoteric equipment (RF/sweep generator and oscilloscope).

Now an AM radio, even a superheterodyne receiver, is reasonably easy to understand, and there are complete circuits, with description, in places like the RC-19 receiving tube manual from RCA. All parts (or reasonable facsimilies thereof) including coils and transformers should be available from Antique Electronic Supply (link below).

I'll also second the suggestion of considering a crystal/diode set. AES has a number of books and kits (including a book on making an FM crystal radio), including a "two stage, hi-fi" AM crystal tuner! If you've NEVER built a crystal set, do yourself a favor and try one... it's a fascinating experience. Only problem is that wavelengths for AM (MW) are LONG, so you'll really need a LONG antenna (or a powerful local station) to get decent reception.

Keep us posted on your adventures!

all the best,
mrh

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