On 26/01/2021 09:24, 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.

And many still do...

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

Transmitters are just big RF amplifiers.

So while many of the really big amps are still valve or cavity resonator
based designs, there are solid state amps as well.

Much depends on just how much power you need. You can do a few 100's of
watts and into the early kW easily enough in a single solid state amp
module, and can do or more than that by combining the RF output of
multiple amps.

I worked on a 20kW HF amp (for a radar application) where the
fundamental unit of amplification was (IIRC) a 400W MOSFET amp. Those
were combined 4 to module to get a bit over a kW out, then those
combined 4 at a time in a bigger rack mounting unit to get a few kW.
Then finally there were 4 racks combined up to get the required 20kW.

Some pictures of the amp he

https://marconiradarhistory.pbworks....20and%20 JORN




--
Cheers,

John.

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