Sheet-beam tubes (6ar8, 7360, etc) as analog multipliers
 

Posted to two newsgroups known to be read by likely respondents ;)

The published literature on pre-solid-state electronic analog
multipliers is scant except for production equipment from
analog computer makers (which by now is difficult to locate).
One example of a useful technique is a four quadrant electron
beam multiplier described he

http://dspace.mit.edu/bitstream/1721...9-04734375.pdf

More exotic tubes with curved deflection geometries followed,
however obtaining such tubes is now difficult.

Has anyone at some point tried using sheet-beam deflection
tubes as were used in synchronous detectors and balanced
modulator designs for analog multiplication? I imagine
that using four tubes each driven by quadrant-limited
amplifiers and whose outputs would be biased and summed
with scaling may work within a few percent of input values
based on a quick look at the characteristic curves published
for these tubes. Another option would be to add a magnetic
deflection yoke over the tubes to provide a proportional
steering of the beam sheet in conjunction with the electro-
static deflection (one of the deflection circuits could be
placed in the negative feedback loop of an op-amp) to
reduce the number of tubes required to two (+/-x, y; +/-x, -y).

It wouldn't take long to breadboard a test circuit for
investigation, but knowing past efforts is always welcome.
Surely someone has evaluated using these tubes in this fashion,
even if just for kicks ;)

Michael

Sheet-beam tubes (6ar8, 7360, etc) as analog multipliers
 

On Mon, 31 Mar 2008 14:05:45 -0600, msg wrote:

Posted to two newsgroups known to be read by likely respondents ;)

The published literature on pre-solid-state electronic analog
multipliers is scant except for production equipment from analog
computer makers (which by now is difficult to locate). One example of a
useful technique is a four quadrant electron beam multiplier described
he

http://dspace.mit.edu/bitstream/1721...9-04734375.pdf

More exotic tubes with curved deflection geometries followed, however
obtaining such tubes is now difficult.

Has anyone at some point tried using sheet-beam deflection tubes as were
used in synchronous detectors and balanced modulator designs for analog
multiplication? I imagine that using four tubes each driven by
quadrant-limited amplifiers and whose outputs would be biased and summed
with scaling may work within a few percent of input values based on a
quick look at the characteristic curves published for these tubes.
Another option would be to add a magnetic deflection yoke over the tubes
to provide a proportional steering of the beam sheet in conjunction with
the electro- static deflection (one of the deflection circuits could be
placed in the negative feedback loop of an op-amp) to reduce the number
of tubes required to two (+/-x, y; +/-x, -y).

It wouldn't take long to breadboard a test circuit for investigation,
but knowing past efforts is always welcome. Surely someone has evaluated
using these tubes in this fashion, even if just for kicks ;)

Michael

Two thoughts:

1: x(1 + y) - x(1 - y) = 2xy. Two beam tubes and a couple of op-amps,
and you're in business. Even with tube op-amps you may use less space
and have less grief from offsets than the space of your quadrant-
switching amp and whatever grief you get from same.

2: There are any number of hot-rod DSP chips that'll fit into a T6-1/2
envelope, complete with ADC's, DAC's and a power supply to run off of
6.3VAC. Sealing the glass up without messing up the DSP may be a
challenge, but you could always fudge and use acrylic.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

Sheet-beam tubes (6ar8, 7360, etc) as analog multipliers
 

msg wrote:
Posted to two newsgroups known to be read by likely respondents ;)

The published literature on pre-solid-state electronic analog
multipliers is scant except for production equipment from
analog computer makers (which by now is difficult to locate).
One example of a useful technique is a four quadrant electron
beam multiplier described he

http://dspace.mit.edu/bitstream/1721...9-04734375.pdf

More exotic tubes with curved deflection geometries followed,
however obtaining such tubes is now difficult.

Has anyone at some point tried using sheet-beam deflection
tubes as were used in synchronous detectors and balanced
modulator designs for analog multiplication? I imagine
that using four tubes each driven by quadrant-limited
amplifiers and whose outputs would be biased and summed
with scaling may work within a few percent of input values
based on a quick look at the characteristic curves published
for these tubes. Another option would be to add a magnetic
deflection yoke over the tubes to provide a proportional
steering of the beam sheet in conjunction with the electro-
static deflection (one of the deflection circuits could be
placed in the negative feedback loop of an op-amp) to
reduce the number of tubes required to two (+/-x, y; +/-x, -y).

It wouldn't take long to breadboard a test circuit for
investigation, but knowing past efforts is always welcome.
Surely someone has evaluated using these tubes in this fashion,
even if just for kicks ;)

Michael

Just a memory from tens of years ago:

The 7360 made a decent balanced modulator, but it is,
by definition, extremely sensitive for external electric
and magnetic fields.

--

Tauno Voipio (OH2UG)
tauno voipio (at) iki fi

Sheet-beam tubes (6ar8, 7360, etc) as analog multipliers
 

Tim Wescott wrote:

snip
2: There are any number of hot-rod DSP chips that'll fit into a T6-1/2
envelope, complete with ADC's, DAC's and a power supply to run off of
6.3VAC. Sealing the glass up without messing up the DSP may be a
challenge, but you could always fudge and use acrylic.


This would be a new acme in solid-state (Fetron-style) replacements ;)

Michael

Sheet-beam tubes (6ar8, 7360, etc) as analog multipliers
 

Jimmie D wrote:
Just a memory from tens of years ago:

The 7360 made a decent balanced modulator, but it is,
by definition, extremely sensitive for external electric
and magnetic fields.

--

Tauno Voipio (OH2UG)
tauno voipio (at) iki fi

You just answered a problem thats had been nagging me for over 30 years.
Now I know why the SSB transmitter I built had such an annoying hum in it.

I never thought about it being affected by a magnetic field.
=========================================
For that reason in 1970s transceivers like Yaesu FT-400/401 the 7360
used as balanced modulator was 'packed' in a tight metal screen bonded
to chassis.

Frank GM0CSZ / KN6WH

Sheet-beam tubes (6ar8, 7360, etc) as analog multipliers
 

Jimmie D wrote:
Just a memory from tens of years ago:

The 7360 made a decent balanced modulator, but it is,
by definition, extremely sensitive for external electric
and magnetic fields.

--

Tauno Voipio (OH2UG)
tauno voipio (at) iki fi


You just answered a problem thats had been nagging me for over 30 years.
Now I know why the SSB transmitter I built had such an annoying hum in it.

I never thought about it being affected by a magnetic field.

Jimmie



Think about a magnetically-deflected TV picture tube.

I noticed the problem, when my Eico 753 (around 1968) worked
fine when the power supply was on the right side, but had
a rough hum reported by other stations, if the power supply
box was moved to the other flank.

--

Tauno Voipio (OH2UG)