Re: [Qucs-help] Q: Vacuum tube schematic symbols & SPICE models

[Danny H. <dgh...@gm...>]

Jeez, love to talk tubes, love to design and build tubes. Started at the
original Raytheon tube plant in Waltham till it closed. Worked at Litton,
what became of the ITT plant, what became of Varian and even at what became
of Thompson CSF.

Modeling and simulation of microwave tubes are time domain calculations of
the relevant physics with a few circuit models adding value. You might use
an S parameter characterization in QUCS, but forget about full blown
klystron design.

Man, I miss the field, but judging from my work history you'll understand
how it was bad for me on a personal level - like a tempestuous lover.

On Thu, Jan 23, 2020, 6:48 PM Gene Heskett <ghe...@sh...> wrote:

> On Thursday 23 January 2020 18:32:20 Dr. David Kirkby wrote:
>
> > On Thu, 23 Jan 2020 at 19:24, Federico Miyara
> > <fm...@fc...>
> >
> > wrote:
> > > Gregg,
> > >
> > > Vacuum tubes are by no means a fossile specimen buried in technology
> > > ancient history. Most electric guitar players will die for a good
> > > tube preamplifier. It may be arguable, but these are the facts.
> > >
> > > Federico Miyara
> >
> > At the high power end they win too. You can get a couple of MW
> > continuously out of a tube amp. I suspect that for short pulses 1 GW
> > is practical.
> >
> > I used to work at Marconi. On the same site was E2V which was part of
> > the Marconi group of companies. Before they could run some of their
> > big valves, they had to get permission from the National grid, because
> > the power they used was so great. I suspect that one tube would take
> > close to 4 MW of power.
>
> As a retired broadcast Chief Engineer, with extended time in the care and
> feeding of klystrons back in their heyday, since I became an occasional
> user of Qucs, I have often wondered if there were ways to synthesize
> their operation in Qucs?  Those would have to have a way to plug in the
> effects of E=mv2 from Einsteins theory as that is the only way to
> explain the waveform distortions they introduce to the output signal,
> and which we had only very rudimentary means to correct by
> pre-distortions.  The Ward Equalizer was king, but had no means to
> correct for its variable group delays due to the instantaneous power
> levels.
>
> Simply put, its electrical length varied with the instant power level due
> to the non-linear effect of not being able to speed the beam up by the
> same velocity change to match the slowdown on the other half cycle of
> the sine wave input.  Said another way, at 20kv for beam voltage, the
> electrons in the beam were moving at speeds where E=mv2 could be
> observed. Because they got more mass when sped up they put that energy
> into their mass so they didn't speed up as much, and lost mass when
> slowed down so the same energy slowed them easier, the beam appeared to
> get longer when that variation was at the high power end, sync tip power
> in a ancient mary (VSBF) tv transmitter by 100ns or more.
>
> Better ways to make shorter tubes were invented at about the same time,
> reducing that distortion at about the same time ways to pre-distort in
> the time domain AND the dc power level were developed. These new tubes,
> called klystrodes were a bit cheaper than the $100,000+ for a klystron,
> and considerably more efficient, so in just 5 years or so, the reduced
> power bills bought most UHF broadcasters a new transmitter with the
> savings. Quite a few couldn't finance it and went dark too.  That was
> all 40+ years ago. Yeah, now I'm an old man, and my parts list is
> beginning to look like Lee Majors. But theres been a heck of a lot of
> been there and done thats in my time here.
>
> Cheers, Gene Heskett
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> If we desire respect for the law, we must first make the law respectable.
>  - Louis D. Brandeis
> Genes Web page <http://geneslinuxbox.net:6309/gene>
>
>
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