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From: jfw@ksr.com (John F. Woods)
Newsgroups: rec.radio.amateur.misc,rec.radio.amateur.packet,rec.radio.swap,rec.radio.cb,misc.forsale,ne.forsale,sci.electronics
Subject: Re: TRF Receiver
Message-ID: <3106@ksr.com>
Date: 11 Apr 91 20:42:53 GMT
References: <1991Apr9.124118.27031@mlb.semi.harris.com> <1991Apr9.220744.4049@milton.u.washington.edu>
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In <1991Apr9.220744.4049@milton.u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes:
>In article <1991Apr9.124118.27031@mlb.semi.harris.com> rps@sunman.mlb.semi.harris.com (Ray Sumperyl) writes:
>> Can anybody supply me with a schematic for a tube TRF receiver?
>	No such devices have been built by THAT name in most of a century.
>Any of the '60s vintage Radio Amateur Handbooks, though, will have 'grid-dip
>meter' construction articles, and a grid dip meter is exactly a TRF receiver
>(not terribly sensitive, though, as they usually leave out the
>preamplification).  After mid-60's, the grid-dip meters used MOSFETs (what's
>a 'grid' in a MOSFET?).

Well, in fact the 1963 Radio Amateur's Handbook has schematics for
single-stage tube TRF receivers; you would just build a detector stage
(plate detector, infinite impedance detector, or grid-leak detector) and
wire the antenna to the RF input.  You could then add an RF amplifier,
if you wanted, remembering not to cheat and do any conversion stages ;-).

As for no one building a TRF receiver in most of a century, check out the
Ferranti ZN414 AM Receiver chip (available from Circuit Specialists and
a couple of other places).  It's a 10 transistor TRF receiver (4 amplifier
stages, detector, and AGC) built into a TO-92 transistor package; add
two resistors, two bypass capacitors, an LC tank, and an audio amp, and
you have a complete receiver.

(The 1963 Handbook also has a 110 page advertisement section that will make
you CRY -- MAYBE a quarter of the advertisers still exist)