Similarly but not identically, and the top of the curve is what's important
in a switching application where you're trying to saturate the device. You
want something with as abrupt a transition in the curve as you can get, and
something with a huge amount of gain.

You mean, the device needs to be nonlinear?

But you also want something that
switches really, really fast.

Like the 12AF4 or one of the other tubes used in VHF tuners?

Honestly, if you just want the carrier, though, it doesn't buy you anything
over normal Class C operation.

Then why are people putting so much store by class E operation for CW
amplification?

I guess back to the drawing board. What I was thinking was to use a
genny as VFO to
inject a carrier into a buffer amp driving a CW amplifier.

wrote:
Similarly but not identically, and the top of the curve is what's important
in a switching application where you're trying to saturate the device. You
want something with as abrupt a transition in the curve as you can get, and
something with a huge amount of gain.

You mean, the device needs to be nonlinear?

It sure helps if it is. You're really fighting things otherwise.

But you also want something that
switches really, really fast.

Like the 12AF4 or one of the other tubes used in VHF tuners?

Hmm... maybe. A sharp-cutoff pentode for VHF service might do the trick.

Honestly, if you just want the carrier, though, it doesn't buy you anything
over normal Class C operation.

Then why are people putting so much store by class E operation for CW
amplification?

Damned if I know. Class C already gets you extremely good efficiency,
and it's not like with the legal limit being what it is that you're going
to save much on your power bill. If you're running 250KW, of course, every
little bit counts, and the ability to do AM modulation at the same time
makes it very valuable for high power broadcast applications.

I guess back to the drawing board. What I was thinking was to use a
genny as VFO to
inject a carrier into a buffer amp driving a CW amplifier.

What is a "genny?"
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
wrote:
Similarly but not identically, and the top of the curve is what's important
in a switching application where you're trying to saturate the device. You
want something with as abrupt a transition in the curve as you can get, and
something with a huge amount of gain.

You mean, the device needs to be nonlinear?

It sure helps if it is. You're really fighting things otherwise.

But you also want something that
switches really, really fast.

Like the 12AF4 or one of the other tubes used in VHF tuners?

Hmm... maybe. A sharp-cutoff pentode for VHF service might do the trick.

Honestly, if you just want the carrier, though, it doesn't buy you anything
over normal Class C operation.

Then why are people putting so much store by class E operation for CW
amplification?

Damned if I know. Class C already gets you extremely good efficiency,
and it's not like with the legal limit being what it is that you're going
to save much on your power bill. If you're running 250KW, of course, every
little bit counts, and the ability to do AM modulation at the same time
makes it very valuable for high power broadcast applications.

I guess back to the drawing board. What I was thinking was to use a
genny as VFO to
inject a carrier into a buffer amp driving a CW amplifier.

What is a "genny?"
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

'Genny' means "regenerative receiver circuit", typically a direct
conversion regenerative mixer/oscillator followed by an audio amplifer.
Sometimes preceded by an RF amplifier to help prevent the carrier from
radiating back into the antenna.

There's plenty of them out there but only recently did I see a few that
used tubes wired in space charge mode for 12V operation. One of the
designs slapped on a crystal oscillator as QRP transmitter to create a
full transciever, but why not simply use the regenerative oscillator as
a VFO into the transmitter?

The Eternal Squire

wrote:
I guess back to the drawing board. What I was thinking was to use a
genny as VFO to
inject a carrier into a buffer amp driving a CW amplifier.

What is a "genny?"

'Genny' means "regenerative receiver circuit", typically a direct
conversion regenerative mixer/oscillator followed by an audio amplifer.
Sometimes preceded by an RF amplifier to help prevent the carrier from
radiating back into the antenna.

Where's the PWM coming from? You could have a stock sine wave oscillator
driving a PWM modulator built as a relaxation oscillator, but somewhere you
need the modulation.

(Of course, doing this in the analogue domain kills most of the advantage,
but it still might e worth trying).

There's plenty of them out there but only recently did I see a few that
used tubes wired in space charge mode for 12V operation. One of the
designs slapped on a crystal oscillator as QRP transmitter to create a
full transciever, but why not simply use the regenerative oscillator as
a VFO into the transmitter?

Because the regenerative oscillator isn't exactly stable, to begin with.
Also, if you're running a switching output stage, you need a PWM signal
whose duty cycle in some way corresponds with the waveform you want to
produce, and that takes a bit more than just a simple free-running oscillator
(which is what a regenerative amplifier is if you crank that regen control
up too much).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."