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From: khayo@sonia.cs.ucla.edu (Erazm J. Behr)
Newsgroups: sci.electronics
Subject: FM receiver
Message-ID: <8631@shemp.UCLA.EDU>
Date: Wed, 14-Oct-87 20:32:37 EDT
Article-I.D.: shemp.8631
Posted: Wed Oct 14 20:32:37 1987
Date-Received: Sat, 17-Oct-87 02:41:48 EDT
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Reply-To: khayo@MATH.UCLA.EDU (Erazm J. Behr)
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Organization: Boelter Hall of Fame
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Hi there; I have a question regarding varactor-tuned circuits.
Since I like to amass nifty little electronic components without
necessarily knowing how they work or how to use them, I recently
got the new Radio Shmuck TDA7000, the FM receiver-on-a-chip. It
seems that with a few capacitors and an external tuning circuit
for the local oscillator one can put together a mono tuner very
easily. Now, I'd like to build a bunch of such tuning circuits
which would give coverage of the more interesting FM bands which
are only found on fancy scanners. I'd prefer to use varactor
diodes - I somehow have more confidence in them than in variable
caps. Two questions:
- what is a typical capacitance range of available varactors?
  will I need some especially stable voltage supply or would
  one of the standard regulator IC's give enough stability?
- which bands (air, police, CB etc.) are "straight FM"? (as you
  see, I'm too lazy to crawl to the library)
Sorry about this stupidity, but maybe some kind soul will have
mercy. I'd appreciate pointers to (preferably more popular)
literature on the subject. Thanks in advance ----     Eric Behr
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          >>>>--------------->         khayo@math.ucla.edu