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Old March 26th 08, 12:36 PM posted to rec.radio.amateur.homebrew
Tim Shoppa Tim Shoppa is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 263
Default 7360/6AR8 mixer configs

On Mar 25, 1:41*am, Michael Black wrote:
On Mon, 24 Mar 2008, TimShoppawrote:
I do recall a one or two-band receiver in a 60'shandbookthat uses a
7360 in the front end. In fact, the more I think about that, the more
I realize that this is the receiver I was thinking of building :-).
Gotta go find it!


The timeline may give some clues. *I've just dug out some books, which
are easier to get ahold of than my old magazines, but some of this
might be useful.

The earliest references were using the 7360 as a balanced modulator
and product detector.

The CQ SSBHandbookfrom 1958 has a couple of beam deflection tube
modulators, though they are 6AR8s. *Audio to the deflection plates,
and RF to the grid in both instances.

QST for March 1960 has "SSB Circuits Using the 7360 Beam-deflection
Tube", and it's about balanced modulators, again audio to the deflection
plates. *A couple of mixers to get up to frequency, and the local
oscillator goes to the cathode or grid, and the IF signal to the
deflection plates.

A December 1960 article shows the 7360 as a product detector, BFO
to the grid and IF to the deflection plates.

Those two QST articles above are in the 1965 ARRL SSB manual, and
all the balanced modulators in the rest of the book show audio to
the deflection plate(s) and oscillator to the grid (or self
excited).

In the August 1961 issue of QST, there's an SSB phasing adaptor
for receivers, again the BFO goes to the grid and the IF to the
deflection plates.

I see no beam deflection tubes mentioned in the 1954 edition of
the ARRL SSB manual, but that's rather expected.

The 1978 edition of "Technical Topics" from the RSGB says the 7360
was introduced in 1960. *It has the Squires circuit (but doesn't mention
the month of the QST article), and that puts the IF on the grid
and the oscillator on the deflection plates. *And it does use
a balanced circuit on the deflection plates.

QST for May 1965 has the "Miser's Dream" that was a pretty advanced
receiver for the time, including a 7360 mixer and an HF IF filter (though
a second conversion to 455KHz for specific design reasons). *I've
always considered that the vector for the 7360 in hobby receiver
mixers, though if I dug out the article, I'm sure it explicitly
referenced the Squires article. *One feature of the receiver is
a q-multiplier at the signal frequency, to improve front end
selectivity given there was no RF amplifier. *I've always wondered
how necessary that q-multiplier was, given later receivers with
high IFs got by fine with limited front end selectivity (I always
wondered if the notion of no RF amplifier was so radical that
they felt a need for the q-multiplier). *For the rest of the
decade, various construction articles would use the same basic
scheme, a 7360 mixer with a q-multiplier at the signal frequency.

I suspect this is the one you may be thinking of.

That receiver feeds the signal into the grid, and the oscillator
goes to the deflection plate (just one), and the blurb (it's
not clear if it's Pat Hawker's interpretation or right from
the article), that it's simpler but warns it might be slightly
more prone to cross-modulation.

A couple of receivers in the 1982 RSGBHandbookhave 7360 mixers,
and signal to the grid, oscillator to the plates (and one or both
of them were balanced).

There was an article by Ray Moore (who I think worked for National)
in the February 1973 issue of Ham Radio about designing receivers
for strong signal handling, and it covers a lot of mixers, including
the 7360. *Either he shows a third topology, or he defines the
7360 in terms of a switching mixer. *I may find that article, I
saw the issue just last week somewhere.

There was a tube receiver in QST about February of 1973 (or was
it '72?), that had to be one of the last described there. *It went
for super strong signal handling, including a 7360 mixer and some
sort of power tube as the RF stage.

* *Michael *VE2BVW


Wow, Michael, that's an incredible survey of the literature! I now
have in front of me the 65 Handbook and the Miser's Dream is indeed
what I was thinking about building. If, for no other reason, than
because they put the oscillator on the deflector plates and the RF to
the grid!

The 7360 tutorials in the 65 SSB book show everything but RF to the
grid and oscillator to deflector plate :-). I think in part because
they thought of it as a product detector, not a front end mixer.

Interesting that the first mention you find is the 6AR8. I always
thought the 7360 came first - but maybe the 6AR8 was more available.
At least one of the rigs in the 65 SSB book uses a 6AR8 too.

Tim.