In article ,
(The Eternal Squire) writes:

Has anyone ever implemented a gilbert cell mixer using valves instead
of FETs?
I'm considering this instead of using the increasingly rare and costly
heptode mixer.

To do this, one needs a minimum of three triodes, the top pair
being (essentially) a differential amplifier, the bottom being a
configured constant-current source replacing a moderately-
high common cathode resistor for the differential pair.

That's a LOT of circuit work where a single dual triode could
(and has) work just as well. Connect it as a differential pair
and put the signal in one side, the LO in the other.

Any valve that runs its control grid into the positive region is
going to be operating in a non-linear region and will therefore
"mix" well enough to do some heterodyning.

The name "Gilbert cell" got there in later integrated circuit
times to describe a particular arrangement of BJT junctions
to do mixing or AGC actions. Valve circuitry had other
names and worked for decades as mixers quite will without
fancy names. :-)

Avery Fineman ) writes:
In article ,
(The Eternal Squire) writes:

Has anyone ever implemented a gilbert cell mixer using valves instead
of FETs?
I'm considering this instead of using the increasingly rare and costly
heptode mixer.

To do this, one needs a minimum of three triodes, the top pair
being (essentially) a differential amplifier, the bottom being a
configured constant-current source replacing a moderately-
high common cathode resistor for the differential pair.

That's a LOT of circuit work where a single dual triode could
(and has) work just as well. Connect it as a differential pair
and put the signal in one side, the LO in the other.

Any valve that runs its control grid into the positive region is
going to be operating in a non-linear region and will therefore
"mix" well enough to do some heterodyning.

The name "Gilbert cell" got there in later integrated circuit
times to describe a particular arrangement of BJT junctions
to do mixing or AGC actions. Valve circuitry had other
names and worked for decades as mixers quite will without
fancy names. :-)



But the "Gilbert Cell" mixer also got by for a good long time without
the fancy name.

Nobody used the term in the early seventies when the MC1496 came along.
It was just a double balanced mixer. It was the late eighties when I
started hearing the term, in reference to the NE602, though suddenly
decades of the same circuit was suddenly a Gilbert Cell.

I know I mentioned this at one time in one of the newsgroups, and
there was an explanation, but I can't remember what it was.

Michael VE2BVW

Avery Fineman ) writes:
In article ,
(The Eternal Squire) writes:

Has anyone ever implemented a gilbert cell mixer using valves instead
of FETs?
I'm considering this instead of using the increasingly rare and costly
heptode mixer.

To do this, one needs a minimum of three triodes, the top pair
being (essentially) a differential amplifier, the bottom being a
configured constant-current source replacing a moderately-
high common cathode resistor for the differential pair.

That's a LOT of circuit work where a single dual triode could
(and has) work just as well. Connect it as a differential pair
and put the signal in one side, the LO in the other.

Any valve that runs its control grid into the positive region is
going to be operating in a non-linear region and will therefore
"mix" well enough to do some heterodyning.

The name "Gilbert cell" got there in later integrated circuit
times to describe a particular arrangement of BJT junctions
to do mixing or AGC actions. Valve circuitry had other
names and worked for decades as mixers quite will without
fancy names. :-)



But the "Gilbert Cell" mixer also got by for a good long time without
the fancy name.

Nobody used the term in the early seventies when the MC1496 came along.
It was just a double balanced mixer. It was the late eighties when I
started hearing the term, in reference to the NE602, though suddenly
decades of the same circuit was suddenly a Gilbert Cell.

I know I mentioned this at one time in one of the newsgroups, and
there was an explanation, but I can't remember what it was.

Michael VE2BVW

Gregg wrote:
Behold, Ashhar Farhan signalled from keyed 4-1000A filament:


the greatest valve mixer ever was based on 7360.


snip

How true!!

There were also some tv tubes used in chroma demodulators
that were sorta 7360 ish. The 6AR8 for one, I know there
were a few others.

BTW you had to use mu-metal shields on these for best
results.

Gregg wrote:
Behold, Ashhar Farhan signalled from keyed 4-1000A filament:


the greatest valve mixer ever was based on 7360.


snip

How true!!

There were also some tv tubes used in chroma demodulators
that were sorta 7360 ish. The 6AR8 for one, I know there
were a few others.

BTW you had to use mu-metal shields on these for best
results.

Ken Scharf wrote:

Gregg wrote:

Behold, Ashhar Farhan signalled from keyed 4-1000A filament:


the greatest valve mixer ever was based on 7360.



snip

How true!!

There were also some tv tubes used in chroma demodulators
that were sorta 7360 ish. The 6AR8 for one, I know there
were a few others.

BTW you had to use mu-metal shields on these for best
results.

And if you're going to design anything new, the 7360 is on sale for only
$27 a pop (down from $49!) while the 6AR8 is about $5.

Four diodes and a couple of ferrite cores, on the other hand...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Ken Scharf wrote:

Gregg wrote:

Behold, Ashhar Farhan signalled from keyed 4-1000A filament:


the greatest valve mixer ever was based on 7360.



snip

How true!!

There were also some tv tubes used in chroma demodulators
that were sorta 7360 ish. The 6AR8 for one, I know there
were a few others.

BTW you had to use mu-metal shields on these for best
results.

And if you're going to design anything new, the 7360 is on sale for only
$27 a pop (down from $49!) while the 6AR8 is about $5.

Four diodes and a couple of ferrite cores, on the other hand...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Behold, Ken Scharf signalled from keyed 4-1000A filament:

Gregg wrote:
Behold, Ashhar Farhan signalled from keyed 4-1000A filament:


the greatest valve mixer ever was based on 7360.


snip

How true!!

There were also some tv tubes used in chroma demodulators that were
sorta 7360 ish. The 6AR8 for one, I know there were a few others.

BTW you had to use mu-metal shields on these for best results.

Hi Ken,

I have experimented with those - their noisy as stink above 4MHz :-(

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

Behold, Ken Scharf signalled from keyed 4-1000A filament:

Gregg wrote:
Behold, Ashhar Farhan signalled from keyed 4-1000A filament:


the greatest valve mixer ever was based on 7360.


snip

How true!!

There were also some tv tubes used in chroma demodulators that were
sorta 7360 ish. The 6AR8 for one, I know there were a few others.

BTW you had to use mu-metal shields on these for best results.

Hi Ken,

I have experimented with those - their noisy as stink above 4MHz :-(

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

Some time ago, Barrie Gilbert, for whom the "Gilbert cell" is named,
gave a talk at a local ham club. He began by showing a copy of the
patent for the "Gilbert cell", and emphatically pointed out that his
name isn't on it. As he explained, he didn't invent the circuit nor did
he have anything to do with its invention. At the time it was patented,
he was an application engineer, and he wrote a lengthy article in one of
the trade magazines about the circuit and its applications (and giving
proper credit to the inventor). Shortly after that, through no action of
his own, someone dubbed it the "Gilbert cell". The name stuck, and
Barrie has spent the time since trying to straighten out the record --
without success. As far as I know, he gives the explanation every time
he presents a talk. Ironically, I don't remember the name of the actual
inventor of this very useful circuit -- it's in my notes from that talk,
buried somewhere.

Barrie is an engineer at Analog Devices, and the chief designer of many
of their advanced analog products. He's an exceptionally talented
engineer, a real gentleman, and a humble and honest person. But NOT the
inventor of the "Gilbert cell" -- as he's the first one to point out.

Roy Lewallen, W7EL

Michael Black wrote:

But the "Gilbert Cell" mixer also got by for a good long time without
the fancy name.

Nobody used the term in the early seventies when the MC1496 came along.
It was just a double balanced mixer. It was the late eighties when I
started hearing the term, in reference to the NE602, though suddenly
decades of the same circuit was suddenly a Gilbert Cell.

I know I mentioned this at one time in one of the newsgroups, and
there was an explanation, but I can't remember what it was.

Michael VE2BVW