[time-nuts] TWT's was: Re: Voyager space probe question

[paul swed]

Dave it looks like I can not respond to you directly.
I just wanted to say that I still appreciate TWTs and the magic in them. I
have a number that are operational. 180 W on 10GHz using a Varian/CPI TWT.
Anyhow would like to correspond offline since this is not Time-nuts.
Regards
Paul
WB8TSL

On Mon, Nov 30, 2020 at 4:08 PM Dave B via time-nuts <
time-nuts at lists.febo.com> wrote:

> The power supplies for them are interesting too.
>
> Especially when you get to the multi kW beasties with multiple
> collectors etc.  Floating high power HV supplies, referenced to the more
> negative Cathode potential.
>
> That's one of the things I do for the day job, fix TWTA's.   99% of the
> time, it's a PSU problem.   The tubes themselves are amazingly rugged,
> so long as you do not store too much energy in the PSU on the HV side in
> case there's an arc in the tube.
>
> The secret is the voltage regulation controls and protection circuits.
> Loops within loops etc.   Great if you like analogue control and power
> switching systems.
>
> Can make a mess when things go wrong though.
>
> Current task on the bench though, is refurbishing a pumped oil cooling
> system, not for a TWT, but for a broadband RF power amplifier.  Messy in
> another way.
>
> There are some things solid state can't do economically yet, but it's
> getting close.
>
> But even the high power low microwave solid state amps, much of the bulk
> and complexity again is in the power supply and cooling systems.
>
> Regards.
>
> Dave G8KBV
>
> On 30/11/2020 18:51, time-nuts-request at lists.febo.com wrote:
> > I wouldn't be so sure about the GaN revolution overtaking it. TWTAs are
> > a pretty simple device, easy to get 50-60 dB of gain in a fairly small,
> > robust package with incredibly wide bandwidth (octaves in some cases),
> > and DC to RF conversion efficiency >50%.
>
> --
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>
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