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From: asd@cbnewsj.att.com (Adam S. Denton)
Newsgroups: sci.electronics
Subject: Re: TV tuner circuits
Message-ID: <1991Mar26.154701.2149@cbnewsj.att.com>
Date: 26 Mar 91 15:47:01 GMT
References: <4405@orbit.cts.com>
Organization: AT&T
Lines: 39

In article <4405@orbit.cts.com> dougm@pnet51.orb.mn.org (Doug Mcintyre) writes:
>
>help with this stuff. All I've seen is National's old linear data book. I was
>looking for something like a chip that took the standard IF out of the
>mechanical tuner, and fed back its AGC and AFT signals and put out baseband
>video and audio. Anything like this? It is part of a chip in my acient

My choice in this regard is the TDA2540 or TDA2541, available from ECG
and NTE as ECG 1413 or ECG 1545.  Yes, it's expensive from them (NTE1413=$5)
but nobody on the planet other than MCM electronics sells the little bugger
in hobbyist quantities.

It's a 16-pinner with 2-coil design with AFT and AGC with 12V supply.
National used to have it (in their big fat '82 linear book).  They still may.
Look it up there for an applications circuit (signetics also makes it too).
It doesn't have audio, though.  I just stick on a MC1358/CA3065/ECG712
demod chip if I need sound.  These are sold everywhere.

The versions vary as to the polarity of the RF AGC output.  I figure
it's easy enough to level-translate that output with a single xistor
if I need to that I just get whatever version is cheapest.

Some of the chips in the Digi-Key catalog may be what you want, if you
must have a one-chip solution -- check the Samsung chips.  Look 'em up
in the ECG catalog to see if they look like what you'd want.  Getting
data on 'em might be difficult though.

Motorola is working on a ONE-coil design chip...!!!

Also, old TVs are good sources for other things you might need --
like a 4.5MHz ceramic filter and/or SAW (if you find a SAW you're
very lucky!)...

Bear in mind that in the absence of a SAW, you'll need to play games
with "traps" for 47.25 and possibly 39.25 MHz or you'll have adjacent-channel
interference.  Even with a SAW, typically you'll still need the 47.25.

Adam Denton
asd@mtqua.att.com