Major equipment from Lucien

[ppppenguin]

Three pictures of the Harris transmitter.

The TX in position at the museum with the output cubicle open
Combiner unit. This takes the outputs from a pair of 40kW transmitters to make 80kW to send to the antenna
We have two klystrode assemblies. Here they are being loaded in Suffolk

The klystrode or inductive output tube is a variant of the klystron. It's more efficient but lower gain. The cathode runs at -30kV, the beam current can be up to 3A. There is only one other valve in the TX, a deuterium thyratron. This crowbars the 30kV HT supply if there's a fault, saving the klystrode from damage.

We have only the B transmitter. The A transmitter had been raided for spares. Their outputs were combined. Then 80kW of BBC was combined with 80kW of BBC2 to feed the antenna. At Crystal Palace, unusually, ITV and C4 had their own feeder up the mast. At most stations all channels were combined into one feeder.

This TX has a lot of linearisation circuits to allow vision and sound to be amplified by a single output device. Older transmitters used separate sound and vision output devices.

One day we hope to run this TX as a simulation, without power on the klystrode, but actually making RF and faked meter readings as if the PA was running.

PS: I seem to have fixed the picture problem. I've set Irfanview to strip all metadata.