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Need to correct a few misconceptions in the last post.
TV started in London on 2nd November 1936 from Alexandra Palace. The first regular high definition service in the world.
It closed down at the outbreak of WW2 (Septemeber 1939) for 3 main reasons. One was that it was a luxury that couldn't be afforded during wartime. Another was the fear the transmissions could act as beacon to guide enemy aircraft. The third was that the skilled engineers and technicians were needed for work on radar.
The Alexandra Palace transmitter was used during WW2 to counter the "Y" beam navigation system used by the Luftwaffe. There are also persistent stories of the studios being used late in the war for TV demonstrations. Exactly what happened is still unclear.
After WW2 the service was restarted in time for the victory parade in 1946. This used exactly the same equipment as before WW2. Much maintenance was needed but no rebuilding of the studios or tower at Ally Pally.
Transmission was moved from Ally Pally to Crystal Palace in 1956. Studios remained at Ally Pally.
The 1936 fire at Crystal Palace destroyed the Baird company's laboratories there. The BBC TV transmissions were not affected.
BBC2 started in 1964 on 625 lines, UHF with transmissions from Crystal Palace. At that point the original BBC TV service became known as BBC1.
The 702 was one of the original sets released in 1936 for the start of the TV service.
The relationship between TV and radar in the the UK is interesting. A lot of technology was common to both. There is no truth in the often repeated suggestion that the UK government deliberately encouraged the development of TV in order to provide a good basis for radar. However in the UK we were fortunate to have developed CRTs, VHF techniques etc before WW2. TV also gave us a pool of skilled engineers and factories capable of making radar equipment. Radar IF was 45MHz (same as BBC TV vision) for many years, due to the good performance of a TRF TV receiver made by Pye which used the then new EF50 valves.
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