RF power stage on Powerful FM Stations

[Nepaliman]

-What kind of RF Power stage has been connected into the FM Stations? Which and what kind of transistors they use? How much powerfull FM can be and exist around the world?

 

[ronsimpson]

Each country has different laws on this subject.
I have worked in 100,000 watt FM stations which is the limit in the US.
The height of the antenna is very important in broadcast FM. At 100mhz the signal is mostly line of sight. My antennas were 200 to 1000 feet tall. My little 20,000 watt station reaches as far as I can see form the top of the antenna with a good signal and about twice as far with a week signal.

The little 100 watt station reached as far as I can see with a OK signal. That area is very flat and with a 500 foot antenna we reached 25 miles.

 

[WTP Pepper]

For very high power transmitters valves are still the preferred method due their physical size having better cooling properties. Huge fans can cool them more efficiently due to their large surface area as oppose to a single chip of silicon in a small area.
Google something like 4CX10000 for transmitter valves.

The smaller 4CX250B valves were often used by radio amateurs as transistors of the time couldn't be cooled fast enough, were extremely expensive and often blew due to the temperature of the silicon when running on full smoke.

In commercial radio/TV there is less of a need to transmit hundreds of KWatts over large regions due to the regional requirements on local radio/TV.
However Crystal Palace and Winter Hill still pump megawatts into the ether in the UK. This will eventually stop largely due to on-line distribution of media.