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@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%. -- Created on and sent from a Unix like PC running and using free and open source software:

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@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@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%. > > -- > Created on and sent from a Unix like PC running and using free and open > source software: > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. >