• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

How the Big Boys do it..

180KW of audio. I give fair warning it is in a transmitter, but the size of it is worth looking at.

YouTube

1963 Marconi 250KW transmitter model BD272
@ 19:24 the modulator internals/private parts are shown

Marconi 250KW transmitter model B6124 (next generation)
@ 41:50 the 180KW modulator output tubes shown, not much to see on newer stuff though.

Interesting stuff when things are big.
Woofferton transmitting station - Wikipedia
 
My Dad was the Executive Engineer at Dorchester Post Office Radio Station and we had similar equipment, made by Marconi.
The Radio Station (has been swallowed up as part of Prince Charles's "Poundbury Village" and) was redeveloped in April 1978. The local farmer used to keep race horses and the mushrooms in the "Jap Field" would fill a frying pan on their own!

Here is a link with photographs provided by a good friend of mine, Geoff Watts.
Dorchester Radio Station
 
Last edited:

K.A.B

Member
2005-11-24 3:44 pm
Sweden
Large radio transmitters cool one of the oldest are in Sweden, which has become world heritage and located on the west coast. I have visited it and the antennas are very high and impressive.

Each big transmitter is awesome, they are great inventions how the parts are made impresses, how they have solved the various component functions.


World Heritage Grimeton Radio Station - A site with global reach
 
I used to work at a 100kW short wave station during its upgrade work. Even the modulator tubes were like 3/4 meter high bottles. They were delivered in wooden frames hung on springs, and the carrying containers were strictly forbidden to be turned upside down. I think they were DHT triodes, and probably the filament wires were so fragile. The final tubes were steam cooled beasts. Now this site is a radio museum, too.
 
Interesting to learn that the first stage is a grounded grid. This means the signal comes into cathode at very low impedance, so it would need a whole lot of drive current. Which he explained with the cathode follower driver. Miller capacitance would be very low which is probably the whole reason for using grounded grid in a transmitter like this? To keep the tuning predictable and stable?