FM Transmitters...

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.

solid state up to a kilowatt or so. then add more modules. I don't think valves used anywhere any more. Maybe up at magnetron frequencies

can't beat an 807

or a 6js6c or two or 6146

And many still do...

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 here:

There are still some good-sized vacuum tubes kicking about.

Even their filament power is bigger than all of your rigs put together.

And lots of copper pipe with cooling water running in it.

Paul

QY3-125 or CV2130

it was a long long time ago that was mentioned. But it's till going 24/7.

One of the valve based bits of kit I worked on would stick 10kW of HF out the main feeder, and 16kW of heat out of the top vent (force fed by blowers under a raised floor)[1]. That was a two valve stage design. There was a solid state pre-amp, then a valve based penultimate stage to lift to about 400W, and then a main valve to go to 10kW

Try these klystrons:

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

Puts those tiny 1MW radio and TV transmitters in their place! :-)

You can't beat a DS19/87B radio valve!

Well Klystrons are now no longer in use with the passing of analogue TV back in 2012.

In modern UHF TV transmitters they are using a such as travelling wave tubes solid state doesn't quite rule the roost!...

And companies around who will sell you a new one but as longwave seems to be dying i can see the time 198 Khz will disappear like RTE 252 kHz in Ireland may do it gets reprieved due to Irish here wanting to hear what's going on back home!...

In article <ruon55$pvn$ snipped-for-privacy@dont-email.me, Chris Holmes snipped-for-privacy@gmail.com scribeth thus

For VHF transistors exist around the 1500 watts mark made be Freescale but they are put into modules the modules are connected together to make higher outputs!..

Like this one:)

In article snipped-for-privacy@bancom.co.uk>, tony sayer snipped-for-privacy@bancom.co.uk> scribeth thus

Correction!! IOT's Inductive Output Tubes !!!

There aren't conversions as such, usually the old Valve transmitter is scrapped and a new solid state one goes in its place..

Broadcast transmitters have a very long life the Droitwich long wave one will be kept going until its switched off a decision that the BBC will make..

Nothing to do with the valves plenty of re-builders in Russia and China!..

And new ones are around still..

Really big powers of several kilowatts tend to use Valves still, You can get surprisingly high powers from mosfets but they are still more fragile than the old bottles from the abuse point of view. High powers using semiconductors seems to mean devices parrarelled up and I just wonder what happens to the others if one dies in such a stack? Brian