Behind the scenes UK experimental colour transmission 1957

[ppppenguin]

Originally Posted by NewVista

1. TV's (even old ones) shouldn't have AC power artifacts. If you see this, I suggest you book the set in for repair.

Keeping hum out of the entire broadcast chain wasn't easy. Hence it's a natural choice to lock field to mains.

I have gone back to the source here. Blumlein et al, The MArconi-EMI tlevision System - The Transmitted Waveform, Journal IEE 1938 p761

"Similarly with interlaced scanning the spot traverses the frame 50 times per sec, thus raising the flicker above that perceptible to the human eye......A frame frequency of the order of 50 was necessary to overcome flicker and the exact value of 50 was chosen on account of the supply frequency of this country...."

I can't be bothered to retype any more of the article but but it goes on to say that hum effects at 37.5Hz were intolerable.

Clearly at the time the decision to use 50Hz was taken it was regarded as essentially flicker free. Especially as the competition was using 25Hz. the question was could they save bandwidth by going lower than 50Hz and the answer was clearly no.

[NewVista]

Originally Posted by ppppenguin

Keeping hum out of the entire broadcast chain wasn't easy. Hence it's a natural choice to lock field to mains.

.

I can see now why they were compelled to do that in those days