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

[Dave B]

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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