Assuming they still exist and are interested.
Have you ever looked at the cost of refurbished ordinary ham radio
transmitting valves capable of half a kilowatt?

Not that I have, but I hear that new ones are often crap since the Chinese
never really test them and the assemblies can be poor quality in plating
and construction, but there aware still some big triodes around ex Russian
military that can be pressed into use and the only issue is supplying the
heater current of several amps.

Brian

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"mm0fmf" wrote in message
...
On 26/01/2021 09:52, Chris Green wrote:
Chris Holmes wrote:

One for Brian???

I was wondering back when men were men and Libby Purves worked on the
other
side of the mic, radio transmitters used valves.

Are there now solid state devices (big MOSFETs??) capable of producing
the
necessary output power? Or are valves still used?

There are big semiconductor devices capable.

However old transmitters are expensive to convert to new devices. I
seem to remember that the Radio 4 transmitter on 198kHz is still a
valve and that they only have one more spare.

The only one spare is ********. When the spare is placed into use, the one
removed goes back to the manufacturer to be rebuilt.