Visiting the Post Office Tower

[Nick]

The co-ax feeders were very impressive bits of plumbing. The outer was about 5" diamter, the inner more than an inch. I have a U link from the old analogue installation. I'll try to find a photo.

The old output stages (klystrons) were water cooled. The new transmitters use vapour cooling on IOTs https://en.wikipedia.org/wiki/Inductive_output_tube

This is bringing back soooooo many memories - The klystrons were in cabinets and you could see the water-cooling jacket - was it pyrex or something? - I recall the cabinet being opened and being shown the klystron in situ.

Also recall some mighty PIO capacitors (at least I assumed that they were PIO) with shorting straps on them as there was a huge amount of RF in the transmitter rooms and the caps self-charged. Also saw the "debollocking stick" - a long wooden pole with a hook and earth strap on one end that was used to check that stuff was safe.

Was told a story by the engineers that the core of that coax feeder was a solid 1 inch diameter copper bar... and that they once had a tower short due to bad weather or somesuch that caused the feeder to blow out every 1/2 wavelength... maybe they were winding us schoolkids up? Who knows! 

Also recall the duty engineer was just sitting there monitoring the outputs and that if any of the input feeds failed, up went the "Normal service will be resumed as soon as is possible" or test card etc. Probably most boring job in the world... no automation in those days.

Multiple power feeds in from differing utility providers too... can almost picture the place though I was only 17 at the time...

Another story centred on them finding an armchair on a platform halfway up the tower! Someone had broken in, undetected, over the fence (this was very pre-IRA) and climbed the tower (was there a service lift cage?) with a small armchair, then sat up there admiring the view, before disappearing! They reckoned he (assuming it was a "he") would be possibly sterile as a result...