FM broadcast... tubes for hams

[exces3]

I have been away from the electronics industry
for a long time. A quick internet-search look at
commercial FM transmitters shows, power output
up to 1KW or so. or I missed some.

what's going on at higher powers?

what happens to pulled tubes?
3-500
4-400
4-1000
(glass, remember those things?)

ceramic,
8877
others

do any show up at hamfests?

or are Russian tubes and guitar stuff
the only thing left

__... ...__

 

[Captain Kilowatt]

Commercial FM's up to 1 Kw? Commercial AM and FM transmitters are all solid state now with power levels up to 20 Kw plus. Everything is modules now with each module adding to the total output. Pull a module for service while still on the air and drop power by a mere fraction of the total output. The 3-500, 4-400 and 4-1000 were mainly used in AM transmitters withe the 4-400 being very popular in the 1 Kw class with a pair in the RF section and another pair in the modulator section. Most stations have scrapped these older transmitters or have one simply as a backup. pulls are often available for next to nothing or even free if the station engineer is a good guy. All you need to do is call the station and ask to speak to he station engineer and ask him.

 

[KM3F]

Yes you have been out of touch a long time.
There are vertually no glass tubes made in America any longer.
The 3-500 and 572 are all made in China.
Most FM and TV transmitters are all solid state into the hundreds of Kw range.
They use push pull modules with combiners in and out of get to those powers.
Hi power Ham amplifiers are still using the 3-500, 572, 8877 and some other types.
The medical field has gone solid state as well so not many 'pulls' anymore.
The used market and new old stock is about all that's left.
Russian tubes are still plentifil but you still need to build power a supply that can cost more than the RF deck.
Better to consider an amplifier from the market either tube or solid state.
By the time you get done building you have more into it than buying one.
Good luck.

 

[neutron]

New guy here... couldn't pass up this thread! I used to work for a company that designed and manufactured wideband RF amps. They've done up to 50 kW using transistors (and lots of RF power combiners) with continuous rated coverage from 400 MHz to 1.0 GHz.

Sold for an ungodly sum, but it was a Big Guv project and they were the lowest bidder!

The last time I went to an RF industry trade show (2011), I don't recall having seen any tube-based amplifiers.

Everyone seemed more concerned about bandwidth filtering and amps that could provide a specified gain with high peak-to-average modulations.

Loved working in RF!