7360/6AR8 mixer configs

[Tim Shoppa]

Looking at how I would configure a 7360-type mixer in the front end of
a low-band (say 80M and 40M) receiver.

Method A: To me, the most obvious way to do it is to feed the RF into
the 7360's grid, and feed the deflection plates with balanced local
oscillator input at circa 10 or 20 V P-P. Put a center-tapped
transformer to the anodes and pull the output out of a winding.

BUT... that's not what I see being done in the various app notes.

Method B: I see, for example, feeding RF into a single deflection
plate, and putting a pot for fine-tuning the balance on the other
plate. LO is injected into the 7360's grid. (e.g. page 6 of
http://www.ab4oj.com/1st/hb/7360/7360.pdf ). I think the intention
here is not to saturate the deflector beam inputs into switching mode,
but to keep the amplitudes small where it'll be linear.

What's the advantages and gotchas of doing it each way? Method A takes
a lot of LO amplitude and has the highest gain for the RF. Method B
takes less LO amplitude but I think has lower gain. Method A cancels
out the LO, and Method B cancels out the original RF. Right?

Of course two 7360's would let me do a doubly-balanced mixer... can't
afford 7360's but I do have some 6AR8's!

Tim N3QE.

[Tio Pedro]

Post by Tim Shoppa
Looking at how I would configure a 7360-type mixer in the front end of
a low-band (say 80M and 40M) receiver.
Method A: To me, the most obvious way to do it is to feed the RF into
the 7360's grid, and feed the deflection plates with balanced local
oscillator input at circa 10 or 20 V P-P. Put a center-tapped
transformer to the anodes and pull the output out of a winding.
BUT... that's not what I see being done in the various app notes.
Method B: I see, for example, feeding RF into a single deflection
plate, and putting a pot for fine-tuning the balance on the other
plate. LO is injected into the 7360's grid. (e.g. page 6 of
http://www.ab4oj.com/1st/hb/7360/7360.pdf ). I think the intention
here is not to saturate the deflector beam inputs into switching mode,
but to keep the amplitudes small where it'll be linear.
What's the advantages and gotchas of doing it each way? Method A takes
a lot of LO amplitude and has the highest gain for the RF. Method B
takes less LO amplitude but I think has lower gain. Method A cancels
out the LO, and Method B cancels out the original RF. Right?
Of course two 7360's would let me do a doubly-balanced mixer... can't
afford 7360's but I do have some 6AR8's!
Tim N3QE.

Why not take a peek at the old Sanders articles that ran in the 1960s in
QST? Or, take a lot at the schematics for the Squires-Sanders RX on
BAMA for some real world applications.

Pete

[Tim Shoppa]

Post by Tio Pedro

Post by Tim Shoppa
Looking at how I would configure a 7360-type mixer in the front end of
a low-band (say 80M and 40M) receiver.
Method A: To me, the most obvious way to do it is to feed the RF into
the 7360's grid, and feed the deflection plates with balanced local
oscillator input at circa 10 or 20 V P-P. Put a center-tapped
transformer to the anodes and pull the output out of a winding.
BUT... that's not what I see being done in the various app notes.
Method B: I see, for example, feeding RF into a single deflection
plate, and putting a pot for fine-tuning the balance on the other
plate. LO is injected into the 7360's grid. (e.g. page 6 of
http://www.ab4oj.com/1st/hb/7360/7360.pdf). I think the intention
here is not to saturate the deflector beam inputs into switching mode,
but to keep the amplitudes small where it'll be linear.
What's the advantages and gotchas of doing it each way? Method A takes
a lot of LO amplitude and has the highest gain for the RF. Method B
takes less LO amplitude but I think has lower gain. Method A cancels
out the LO, and Method B cancels out the original RF. Right?
Of course two 7360's would let me do a doubly-balanced mixer... can't
afford 7360's but I do have some 6AR8's!
Tim N3QE.

Why not take a peek at the old Sanders articles that ran in the 1960s in
QST?  Or, take a lot at the schematics for the Squires-Sanders RX on
BAMA for some real world applications.

Indeed, the Squires-Sanders receivers show the 7360's being used
exactly like I would use them - feed RF into grid, local oscillator
fed in a balanced way into deflector beam plates, take output from
anodes through a balanced transformer.

But much of the other 50's/60's era notes show deflector beam tubes
being used in other mixer configs, e.g. LO on grid and RF into plates.
LO on grid might just be a derivation from the self-excited 7360
configs.

What year/month were the Sanders articles in QST? I have most of the
late 50's and 60's on my shelves but haven't had a good excuse to look
through them lately.

Tim.

[Michael Black]

Post by Tim Shoppa
What year/month were the Sanders articles in QST? I have most of the
late 50's and 60's on my shelves but haven't had a good excuse to look
through them lately.

It's 1963 for the article(s), I seem to recall there was a second article
about the noiseblanker but I'm not sure. The QST review of the receiver
wsa in '64 or maybe '65.

I know the years because I never had QST from 1963 for some reason, though
I have '62 and '64, so I've never actually seen the Squires article.

I can pull a few books off the shelf from the prime hobby use of the 7360,
and when I get around to it, I'll see if there is much variation in the
use of the tube or not.

Of course, for a lot of the articles, there was a point of introduction
and the others followed. So if there is a definite trend in one method,
it might be just as simple as others using what was in the first article.

Michael VE2BVW

[Tim Shoppa]

Post by Michael Black

Post by Tim Shoppa
What year/month were the Sanders articles in QST? I have most of the
late 50's and 60's on my shelves but haven't had a good excuse to look
through them lately.

It's 1963 for the article(s), I seem to recall there was a second article
about the noiseblanker but I'm not sure.  The QST review of the receiver
wsa in '64 or maybe '65.
I know the years because I never had QST from 1963 for some reason, though
I have '62 and '64, so I've never actually seen the Squires article.
I can pull a few books off the shelf from the prime hobby use of the 7360,
and when I get around to it, I'll see if there is much variation in the
use of the tube or not.
Of course, for a lot of the articles, there was a point of introduction
and the others followed.  So if there is a definite trend in one method,
it might be just as simple as others using what was in the first article.

The 7360 is prominently featured in the 60's ARRL Handbooks, that's
for sure. There's one exciter that uses three of them!

I do recall a one or two-band receiver in a 60's handbook that 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!

Tim N3QE

[Michael Black]

Post by Tim Shoppa
I do recall a one or two-band receiver in a 60's handbook that 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 SSB Handbook from 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 RSGB Handbook have 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

[Tim Shoppa]

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.

[N***@aol.com]

Post by Michael Black
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).

The article is called "Some Thoughts on Home Receiver Design". The
second
conversion to 455 kc. was to avoid having the BFO on the lots-of-gain
IF, and to
permit the use of a crystal controlled BFO, yet have it be adjustable
by moving
the 2215-to-455 oscillator freq.

The first IF is 2215 kc. If you can find a junked Sierra 126B
selective voltmeter,
it has nearly-identical filters inside. Some other models of Sierra
selective voltmeter
may have them too.

Post by Michael Black
 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.

The Squires article was in Sept. 1963 QST.

Post by Michael Black
 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).

It was necessary on the higher bands. The IF was only 2215 kc., and on
15 meters the image rejection wasn't too good with just a single tuned
circuit.
The quick solution was an RF Q multiplier. But it seems to me to be an
add-on;
what it does is to boost the desired signal by increasing the
effective Q, rather
than rejecting the unwanted by adding more poles.

IMHO the better solution would be a double-tuned input circuit.

Post by Michael Black
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.

"An Experimental Receiver For 75 Meter DX Work", by W1KLK, February
1972.
Uses a 7044 computer duotriode as a grounded-grid RF amp, followed by
a 7360 mixer.
There are no less than four tuned circuits before the mixer, and you
have to retune the
preselector often. Not for idle bandscanning; this RX is for digging
out the weak ones.

The 6AR8 is reportedly microphonic, and other types are preferable.
7360 was considered
a transmitting tube, which is why you find it in the Transmitting Tube
manual, and why
almost nobody but RCA made them.

Alternatives are the 6JH8 and 6ME8, which are less expensive and more
common. They were
used in TV sets. At least one ham rig maker (Swan) changed from using
the 7360 as a
balanced modulator to the 6JH8.

The Southgate Type 7 receiver section uses a 7360 mixer (google my
call to see).

73 de Jim, N2EY

[geek]

Hi,

<snip>

Post by N***@aol.com
Alternatives are the 6JH8 and 6ME8, which are less expensive and more
common.

I've done some experiments with the 6ME8 and it's horribly noisy compared
to the 7360.... or even a 6BE6 for that matter :-\

Cheers,
__
Gregg

[Michael Black]

Post by geek
Hi,
<snip>

Post by N***@aol.com
Alternatives are the 6JH8 and 6ME8, which are less expensive and more
common.

I've done some experiments with the 6ME8 and it's horribly noisy compared
to the 7360.... or even a 6BE6 for that matter :-\

You're not going to get a balanced mixer out of a single 6BE6 either.

But, on does have the advantage that beam deflection tubes aren't just
used as first mixers. Balanced modulators and mixers in SSB transmitters.
Product detector in a receiver. There, noise isn't the same issue
as in a first mixer.

Michael VE2BVW

[geek]

Post by Michael Black

Post by geek
Hi,
<snip>

Post by N***@aol.com
Alternatives are the 6JH8 and 6ME8, which are less expensive and more
common.

I've done some experiments with the 6ME8 and it's horribly noisy compared
to the 7360.... or even a 6BE6 for that matter :-\

You're not going to get a balanced mixer out of a single 6BE6 either.
But, on does have the advantage that beam deflection tubes aren't just
used as first mixers. Balanced modulators and mixers in SSB transmitters.
Product detector in a receiver. There, noise isn't the same issue
as in a first mixer.
Michael VE2BVW

Indeed!

My tests were based on the first mixer for a SW receiver (gah, which I
have still to build >.< )

Cheers!
__
Gregg

[Jimmie D]

Post by Tim Shoppa
Looking at how I would configure a 7360-type mixer in the front end of
a low-band (say 80M and 40M) receiver.
Method A: To me, the most obvious way to do it is to feed the RF into
the 7360's grid, and feed the deflection plates with balanced local
oscillator input at circa 10 or 20 V P-P. Put a center-tapped
transformer to the anodes and pull the output out of a winding.

Its been a long time since I used a 7360 but I did it exactly as you
described.
I used a toriod broadband transformer to feed the 7360 deflection plates
because I didnt want to have to switch in tuned circuit.
The band switching arrangement was cumbersome enough asit was. This was the
front end for a rx project I never finished. It did seem to work pretty well
when used it as a rx converter in front of an old Halicrafter radio.

Jimmie