Magamp oscillator

[Bill Beaty]

On Tuesday, November 3, 2015 at 10:03:19 AM UTC-8, Piotr Wyderski wrote:

You don't need to challenge me, I have exactly the same
experience after nontrivial amount of googling. There's
nothing about it.

I recall seeing (about 10yrs ago) a ref to math showing that it's not possible; that even the ideal case, mag amp operating point is outside the gain/phase for oscillation. I didn't look up the ref though.

It was in an article on historical development of electronics, claiming that the first oscillators had to wait for vacuum tubes, since even though mag amps existed earlier, oscillators weren't possible. (But even Faraday coulda made one, if he had Nyle Steiner's burned zinc oscillator.)

Also: "impractical" means that hobbyists do it all the time for laughs, while "impossible" means that no hobbyist has succeeded, ever.

Separate topic: is an all-inductors diode possible, using magnet-biased saturable reactors? I recall a Tesla patent claiming this. If real, why all the rotary converters, and why were selenium or copper-oxide rectifiers such a big deal?

 

On Thursday, 5 November 2015 07:30:05 UTC, Bill Beaty wrote:

On Tuesday, November 3, 2015 at 10:03:19 AM UTC-8, Piotr Wyderski wrote:

You don't need to challenge me, I have exactly the same
experience after nontrivial amount of googling. There's
nothing about it.

I recall seeing (about 10yrs ago) a ref to math showing that it's not possible; that even the ideal case, mag amp operating point is outside the gain/phase for oscillation. I didn't look up the ref though.

how is that possible? If you have gain you only need add R&C to get time shift aka phase shift.

> It was in an article on historical development of electronics, claiming that the first oscillators had to wait for vacuum tubes, since even though mag amps existed earlier, oscillators weren't possible. (But even Faraday coulda made one, if he had Nyle Steiner's burned zinc oscillator.)

arc oscillators came before vacuum tubes, relying on negative reistance. 'singing arc.' Not to be confused with spark gap technology. And fwiw there were also electromechanical oscillators such as bells, relays, etc well before valves.

Also: "impractical" means that hobbyists do it all the time for laughs, while "impossible" means that no hobbyist has succeeded, ever.

Separate topic: is an all-inductors diode possible, using magnet-biased saturable reactors?

Inductor rectifiers were one of the standard types in the early days of radio

> I recall a Tesla patent claiming this. If real, why all the rotary converters, and why were selenium or copper-oxide rectifiers such a big deal?

inductor rectifiers were a relatively reliable tech, but had poor sensitivity. How would you get mere millivolts to cause a significant shift in an inductor's operating point.


NT

 

[legg]

On Wed, 4 Nov 2015 23:29:59 -0800 (PST), Bill Beaty <billb@eskimo.com>
wrote:
<Snip>
>Separate topic: is an all-inductors diode possible, using magnet-biased saturable reactors? I recall a Tesla patent claiming this. If real, why all the rotary converters, and why were selenium or copper-oxide rectifiers such a big deal?

The 'set' and 'reset' reactors are, in their extreme control settings,
biased to allow current flow in one direction only. They require a
non-reversible current during their control phase, or in a coupled
control winding which is only really practical using a synchronous
switch or rectifier.

One maintains unidirectional current to keep the part in saturation
prior to application of reverse voltseconds, the other applies
restting voltseconds only, to avoid conduction in the forward phase.

Energy is derived for oontrol either from the source input, or the
(un)regulated output - for wider control (or blocking voltsecond)
range, both control methods can be applied to the same part.

Kotlarewski (sp) in Ottawa published a definitive article on these in
the 90s.

A certain amount of self-maintained bias can be induced by placing
hard magnetic material in series with the flux path, but these tend to
be mechanically difficult to construct, short-lived,lossy and of low
relative permeability.

RL

 

[whit3rd]

On Wednesday, November 4, 2015 at 11:30:05 PM UTC-8, Bill Beaty wrote:

> Separate topic: is an all-inductors diode possible, using magnet-biased saturable reactors? I recall a Tesla patent claiming this. If real, why all the rotary converters, and why were selenium or copper-oxide rectifiers such a big deal?

A rectifier, with an AC source, produces DC EMF; but any magnetic field
that produces in a winding a DC EMF, must have

d(flux)/dt ~= dotproduct( (area) ,dB/dt ) >0

in a net average over time. That's a ramp in B that never every decreases: you can not
do that, over any sufficiently long period of time the B field will exceed your magnetic
material limits (or current supply capability, or material strength limits).

The best you could do, is with some moving-parts switching to reverse a winding
direction (the commutator on a DC generator reverses the winding polarity); so
an AC motor/DC generator or other 'rotary converter'. That doesn't rely on the
dB/dt to be always-increasing, it changes the orientation of the 'area' and flips the sign
in the dot product so that the product is never negative.

 

On Thursday, 5 November 2015 21:08:03 UTC, whit3rd wrote:

On Wednesday, November 4, 2015 at 11:30:05 PM UTC-8, Bill Beaty wrote:

Separate topic: is an all-inductors diode possible, using magnet-biased saturable reactors? I recall a Tesla patent claiming this. If real, why all the rotary converters, and why were selenium or copper-oxide rectifiers such a big deal?

A rectifier, with an AC source, produces DC EMF; but any magnetic field
that produces in a winding a DC EMF, must have

d(flux)/dt ~= dotproduct( (area) ,dB/dt ) >0

in a net average over time. That's a ramp in B that never every decreases: you can not
do that, over any sufficiently long period of time the B field will exceed your magnetic
material limits (or current supply capability, or material strength limits).

The best you could do, is with some moving-parts switching to reverse a winding
direction (the commutator on a DC generator reverses the winding polarity); so
an AC motor/DC generator or other 'rotary converter'. That doesn't rely on the
dB/dt to be always-increasing, it changes the orientation of the 'area' and flips the sign
in the dot product so that the product is never negative.

https://en.wikipedia.org/wiki/Magnetic_detector


NT

 

[John Larkin]

On Wed, 4 Nov 2015 23:29:59 -0800 (PST), Bill Beaty <billb@eskimo.com>
wrote:

On Tuesday, November 3, 2015 at 10:03:19 AM UTC-8, Piotr Wyderski wrote:
You don't need to challenge me, I have exactly the same
experience after nontrivial amount of googling. There's
nothing about it.

I recall seeing (about 10yrs ago) a ref to math showing that it's not possible; that even the ideal case, mag amp operating point is outside the gain/phase for oscillation. I didn't look up the ref though.

It was in an article on historical development of electronics, claiming that the first oscillators had to wait for vacuum tubes, since even though mag amps existed earlier, oscillators weren't possible. (But even Faraday coulda made one, if he had Nyle Steiner's burned zinc oscillator.)

Pre-tube, big radio transmitters, hundreds of KW things, used
negative-resistance arcs to make true oscillators.

Not to be confused with spark gap transmitters, that just made ringing
oscillations.

https://en.wikipedia.org/wiki/Arc_converter



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Robert Baer]

John Larkin wrote:

On Wed, 04 Nov 2015 08:49:10 -0800, Robert Baer
robertbaer@localnet.com> wrote:

John Larkin wrote:
On Tue, 3 Nov 2015 16:19:34 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

If you mean a DC powered circuit that oscillates using only passive
parts and diodes, no relays or such, I've never seen it done.

I'm not sure if you can call a magnetic amplifier a passive part.
It can exhibit admirable power gain, but needs to be powered by AC,
for example:

http://sparkbangbuzz.com/mag-audio-amp/mag-audio-amp.htm

The guy claims it has the gain of 2000. So recently, I have
started to wonder if you can use such a device as a DC-powered
oscillator. I agree, the answer "yes" would be a surprise, but
maybe it is "yes" indeed?

Best regards, Piotr

You can also make an amplifier or an oscillator using varicap and
rectifier diodes, but it also needs an AC pump.

Since nobody has done what you suggest in about 200 years of
tinkering, I suspect it can't be done.



And the bee cannot fly.

Some things are actually impossible.

Bees can obviously fly. What idiot decided that they can't?

If you can design an oscillator that meets Piotr's requirements, we'd
love to see it.

Am not so good at designing with nonlinear components.
Know of the trick using nonlinear inductors in a discrete L,C PFN to
get faster risetimes; not sure how helpful that maybe in this case.
First i need to find nonlinear inductors/transformers that do not
need excessive power to act that way.
And the play with them.
I do know that as the excitation is increased on the Ma Bell ring
generator, that there is some point that it starts to become unstable,
and finally (as an oscillator to run at 20Hz) settle down in the
preferred mode; that info is not helpful.
If you have other clues, please let me know.

 

[Robert Baer]

tabbypurr@gmail.com wrote:

On Thursday, 5 November 2015 21:08:03 UTC, whit3rd wrote:
On Wednesday, November 4, 2015 at 11:30:05 PM UTC-8, Bill Beaty wrote:

Separate topic: is an all-inductors diode possible, using magnet-biased saturable reactors? I recall a Tesla patent claiming this. If real, why all the rotary converters, and why were selenium or copper-oxide rectifiers such a big deal?

A rectifier, with an AC source, produces DC EMF; but any magnetic field
that produces in a winding a DC EMF, must have

d(flux)/dt ~= dotproduct( (area) ,dB/dt )>0

in a net average over time. That's a ramp in B that never every decreases: you can not
do that, over any sufficiently long period of time the B field will exceed your magnetic
material limits (or current supply capability, or material strength limits).

The best you could do, is with some moving-parts switching to reverse a winding
direction (the commutator on a DC generator reverses the winding polarity); so
an AC motor/DC generator or other 'rotary converter'. That doesn't rely on the
dB/dt to be always-increasing, it changes the orientation of the 'area' and flips the sign
in the dot product so that the product is never negative.

https://en.wikipedia.org/wiki/Magnetic_detector


NT

Humph. "Maggie" was the term used in radar as a short term for the
magnetron..

 

[John Larkin]

On Thu, 05 Nov 2015 15:45:37 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

John Larkin wrote:
On Wed, 04 Nov 2015 08:49:10 -0800, Robert Baer
robertbaer@localnet.com> wrote:

John Larkin wrote:
On Tue, 3 Nov 2015 16:19:34 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

If you mean a DC powered circuit that oscillates using only passive
parts and diodes, no relays or such, I've never seen it done.

I'm not sure if you can call a magnetic amplifier a passive part.
It can exhibit admirable power gain, but needs to be powered by AC,
for example:

http://sparkbangbuzz.com/mag-audio-amp/mag-audio-amp.htm

The guy claims it has the gain of 2000. So recently, I have
started to wonder if you can use such a device as a DC-powered
oscillator. I agree, the answer "yes" would be a surprise, but
maybe it is "yes" indeed?

Best regards, Piotr

You can also make an amplifier or an oscillator using varicap and
rectifier diodes, but it also needs an AC pump.

Since nobody has done what you suggest in about 200 years of
tinkering, I suspect it can't be done.



And the bee cannot fly.

Some things are actually impossible.

Bees can obviously fly. What idiot decided that they can't?

If you can design an oscillator that meets Piotr's requirements, we'd
love to see it.


Am not so good at designing with nonlinear components.
Know of the trick using nonlinear inductors in a discrete L,C PFN to
get faster risetimes; not sure how helpful that maybe in this case.

Saturating magnetics can do cool high-power stuff that would destroy
semiconductors. Like the nonlinear delay lines you mention. I've seen
some biggish eximer lasers that used saturating magnetics to make the
big pulse drives into the discharge tubes. Very rugged.

First i need to find nonlinear inductors/transformers that do not
need excessive power to act that way.
And the play with them.
I do know that as the excitation is increased on the Ma Bell ring
generator, that there is some point that it starts to become unstable,
and finally (as an oscillator to run at 20Hz) settle down in the
preferred mode; that info is not helpful.

Do you mean the old central office ring generators? There is very
little online about them, but they seemed to be rotating
motor-generators mostly. The CO stuff did all ultimately run off 48
volts DC.

Do you know of a non-rotating, non-semiconductor, DC powered ring
generator? Bell was pretty good with magnetics.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[whit3rd]

On Thursday, November 5, 2015 at 2:21:25 PM UTC-8, John Larkin wrote:

Pre-tube, big radio transmitters, hundreds of KW things, used
negative-resistance arcs to make true oscillators.

Not to be confused with spark gap transmitters, that just made ringing
oscillations.

Even after tubes were available, the spark-gap oscillator was a standby
of diathermy/induction heating. Crude, effective, and in a welding
shop you need to ventilate against other gas buildup, so why not
against ozone?

 

[piglet]

On 06/11/2015 00:39, John Larkin wrote:

Do you mean the old central office ring generators? There is very
little online about them, but they seemed to be rotating
motor-generators mostly. The CO stuff did all ultimately run off 48
volts DC.

Do you know of a non-rotating, non-semiconductor, DC powered ring
generator? Bell was pretty good with magnetics.

I think you're correct. I saw this:
<http://www.telephonetribute.com/switches_survey_chapter_12.html>
which seems to say that the subharmonic mag-amps were energized by
utility 60Hz power and DC rotary convertors handled power outages.

US patent US2452239 shows a local application but again the ringing
generator is pumped at 60Hz.

piglet

 

[piglet]

On 04/11/2015 10:00, whit3rd wrote:

Magnetic amplifiers are in the general class of 'parametric amplifiers'; I think
some of the ferroresonant tricks were given names such as "parametric
transformer", but one would have to search a lot of old sales brochures to be sure.

Many thanks for clarifying - makes mag-amps seem less terrifying when I
can relate them to varactor para-amps!

piglet

 

[Hul Tytus]

Phil - do you know of a source for tunnel diodes? Preferably less than
$100.

Hul

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 11/03/2015 10:54 AM, John Larkin wrote:
On Tue, 3 Nov 2015 16:19:34 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

If you mean a DC powered circuit that oscillates using only passive
parts and diodes, no relays or such, I've never seen it done.

I'm not sure if you can call a magnetic amplifier a passive part.
It can exhibit admirable power gain, but needs to be powered by AC,
for example:

http://sparkbangbuzz.com/mag-audio-amp/mag-audio-amp.htm

The guy claims it has the gain of 2000. So recently, I have
started to wonder if you can use such a device as a DC-powered
oscillator. I agree, the answer "yes" would be a surprise, but
maybe it is "yes" indeed?

Best regards, Piotr

You can also make an amplifier or an oscillator using varicap and
rectifier diodes, but it also needs an AC pump.

Since nobody has done what you suggest in about 200 years of
tinkering, I suspect it can't be done.



Well, tunnel diodes work.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[John Larkin]

On Wed, 4 Nov 2015 08:55:37 +0000, piglet <erichpwagner@hotmail.com>
wrote:

On 03/11/2015 10:45, Piotr Wyderski wrote:
Is it at all possible to build an oscillator entirely from
non-linear magnetics (OK, solid state diodes are allowed)?

Best regards, Piotr

There is such a thing as the "parametric transformer" about which I know
nothing but assuming it works like a varactor diode parametric amplifier
then I suppose it could be made to oscillate, I guess it needs a higher
frequency pump to provide the power source?

piglet

Right. Core saturation creates a nonlinear element that can do things,
but it needs an AC pump.

Here is a diode acting like a subharmonic oscillator. Same sort of
idea.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/SubHarmonic.jpg

Quick proof-of-concept hack. Could be optimized.






--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Phil Hobbs]

On 11/06/2015 03:50 PM, John Larkin wrote:

On Wed, 4 Nov 2015 08:55:37 +0000, piglet <erichpwagner@hotmail.com
wrote:

On 03/11/2015 10:45, Piotr Wyderski wrote:
Is it at all possible to build an oscillator entirely from
non-linear magnetics (OK, solid state diodes are allowed)?

Best regards, Piotr

There is such a thing as the "parametric transformer" about which I know
nothing but assuming it works like a varactor diode parametric amplifier
then I suppose it could be made to oscillate, I guess it needs a higher
frequency pump to provide the power source?

piglet

Right. Core saturation creates a nonlinear element that can do things,
but it needs an AC pump.

Here is a diode acting like a subharmonic oscillator. Same sort of
idea.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/SubHarmonic.jpg

Quick proof-of-concept hack. Could be optimized.

That happens in active peak detectors too, if you get the time constants
wrong.

Cheers

Phil Hobbs




--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[jeroen Belleman]

On 06/11/15 21:50, John Larkin wrote:

On Wed, 4 Nov 2015 08:55:37 +0000, piglet <erichpwagner@hotmail.com
wrote:

On 03/11/2015 10:45, Piotr Wyderski wrote:
Is it at all possible to build an oscillator entirely from
non-linear magnetics (OK, solid state diodes are allowed)?

Best regards, Piotr

There is such a thing as the "parametric transformer" about which I know
nothing but assuming it works like a varactor diode parametric amplifier
then I suppose it could be made to oscillate, I guess it needs a higher
frequency pump to provide the power source?

piglet

Right. Core saturation creates a nonlinear element that can do things,
but it needs an AC pump.

Here is a diode acting like a subharmonic oscillator. Same sort of
idea.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/SubHarmonic.jpg

Quick proof-of-concept hack. Could be optimized.

You brought this up some time ago when I asked about passive
circuits generating lower frequencies from a single higher input
frequency. (The equivalent of what a BBO crystal does with light.)

But this doesn't work. What you're really seeing in this circuit
is just the switch-on transient response of the tank, and which
dies out pretty quickly.

Jeroen Belleman

 

[jeroen Belleman]

On 06/11/15 22:34, Phil Hobbs wrote:

On 11/06/2015 03:50 PM, John Larkin wrote:
On Wed, 4 Nov 2015 08:55:37 +0000, piglet <erichpwagner@hotmail.com
wrote:

On 03/11/2015 10:45, Piotr Wyderski wrote:
Is it at all possible to build an oscillator entirely from
non-linear magnetics (OK, solid state diodes are allowed)?

Best regards, Piotr

There is such a thing as the "parametric transformer" about which I know
nothing but assuming it works like a varactor diode parametric amplifier
then I suppose it could be made to oscillate, I guess it needs a higher
frequency pump to provide the power source?

piglet

Right. Core saturation creates a nonlinear element that can do things,
but it needs an AC pump.

Here is a diode acting like a subharmonic oscillator. Same sort of
idea.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/SubHarmonic.jpg


Quick proof-of-concept hack. Could be optimized.

That happens in active peak detectors too, if you get the time constants
wrong.

Cheers

Phil Hobbs

In active circuitry, sure. I'd like to see some passive circuit that
does this. Non-linearity is not enough. You need a bifurcation in
the phase space trajectory.

Something with a tunnel diode would work.

Jeroen Belleman

 

[Phil Hobbs]

On 11/06/2015 05:41 PM, jeroen Belleman wrote:

On 06/11/15 22:34, Phil Hobbs wrote:
On 11/06/2015 03:50 PM, John Larkin wrote:
On Wed, 4 Nov 2015 08:55:37 +0000, piglet <erichpwagner@hotmail.com
wrote:

On 03/11/2015 10:45, Piotr Wyderski wrote:
Is it at all possible to build an oscillator entirely from
non-linear magnetics (OK, solid state diodes are allowed)?

Best regards, Piotr

There is such a thing as the "parametric transformer" about which I
know
nothing but assuming it works like a varactor diode parametric
amplifier
then I suppose it could be made to oscillate, I guess it needs a higher
frequency pump to provide the power source?

piglet

Right. Core saturation creates a nonlinear element that can do things,
but it needs an AC pump.

Here is a diode acting like a subharmonic oscillator. Same sort of
idea.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/SubHarmonic.jpg



Quick proof-of-concept hack. Could be optimized.

That happens in active peak detectors too, if you get the time constants
wrong.

Cheers

Phil Hobbs

In active circuitry, sure. I'd like to see some passive circuit that
does this. Non-linearity is not enough. You need a bifurcation in
the phase space trajectory.

Something with a tunnel diode would work.

Jeroen Belleman

You don't think that a 1N5819 and a tank circuit is passive?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Hobbs]

On 11/06/2015 05:30 PM, Hul Tytus wrote:

Phil - do you know of a source for tunnel diodes? Preferably less than
$100.

Hul

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 11/03/2015 10:54 AM, John Larkin wrote:
On Tue, 3 Nov 2015 16:19:34 +0100, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

If you mean a DC powered circuit that oscillates using only passive
parts and diodes, no relays or such, I've never seen it done.

I'm not sure if you can call a magnetic amplifier a passive part.
It can exhibit admirable power gain, but needs to be powered by AC,
for example:

http://sparkbangbuzz.com/mag-audio-amp/mag-audio-amp.htm

The guy claims it has the gain of 2000. So recently, I have
started to wonder if you can use such a device as a DC-powered
oscillator. I agree, the answer "yes" would be a surprise, but
maybe it is "yes" indeed?

Best regards, Piotr

You can also make an amplifier or an oscillator using varicap and
rectifier diodes, but it also needs an AC pump.

Since nobody has done what you suggest in about 200 years of
tinkering, I suspect it can't be done.



Well, tunnel diodes work.

Cheers

Phil Hobbs

You can get back diodes, which are similar but not exactly the same as
TDs for oscillators and triggers.

My stash all came from eBay. Most of the old-style TDs had gross
amounts of capacitance, like 200 pF. If you want speed, you have to
find diodes with 100-200mA peak currents. Most of mine are only a few mA.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Phil Hobbs]

On 11/06/2015 05:29 PM, jeroen Belleman wrote:

On 06/11/15 21:50, John Larkin wrote:
On Wed, 4 Nov 2015 08:55:37 +0000, piglet <erichpwagner@hotmail.com
wrote:

On 03/11/2015 10:45, Piotr Wyderski wrote:
Is it at all possible to build an oscillator entirely from
non-linear magnetics (OK, solid state diodes are allowed)?

Best regards, Piotr

There is such a thing as the "parametric transformer" about which I know
nothing but assuming it works like a varactor diode parametric amplifier
then I suppose it could be made to oscillate, I guess it needs a higher
frequency pump to provide the power source?

piglet

Right. Core saturation creates a nonlinear element that can do things,
but it needs an AC pump.

Here is a diode acting like a subharmonic oscillator. Same sort of
idea.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Oscillators/SubHarmonic.jpg


Quick proof-of-concept hack. Could be optimized.

You brought this up some time ago when I asked about passive
circuits generating lower frequencies from a single higher input
frequency. (The equivalent of what a BBO crystal does with light.)

But this doesn't work. What you're really seeing in this circuit
is just the switch-on transient response of the tank, and which
dies out pretty quickly.

Jeroen Belleman

I don't understand your point. The waveform is periodic with twice the
period of the fundamental, but not at the fundamental frequency. How is
that not a subharmonic?

Degenerate parametric amps (pump = input) can also generate
subharmonics--you can buy packaged "frequency halvers" that just use
varactors. See e.g. http://tinyurl.com/p5kpgbj

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net