Re: How good were 1950's/1960's Band 1 TV receivers?

Mark Carver wrote:

I can't remember seeing black level clamping on many b/w sets, 625 or
405, though I'm a bit too young to remember 405 lines that well.

My memory is that most of the earlier (50s & 60s) B/W sets tended to have sync-tip DC restoration (diode clamp) after the demodulator (always an envelope detector in those days of course) and were then DC-coupled through a pentode video o/p stage to the CRT. However the great majority had mean-level AGC, gated AGC being found only on distinctly up-market sets.

By the mid-70s, when B/W was on its way out, the inevitable cost-engineering had led to AC coupling throughout, with no attempt at clamping at all. Programme producers in that era, ISTR, avoided dark scenes which would display as indifferent mid grey on most viewers' equipment. That era really was the nadir of TV set design, with some really horribly unreliable components in use, plus all the nastiness of dual-standard switching still being around.

The other point about impulse interference being less visible on
negative modulation pictures, well is it in practice ? Surely
overshoot within the receiver's circuity would give any black dot a
nice white edge ?

I'm sure you're right, c.f. the recent thread ("dodgy lamp ...") on the same subject in uk.tech.digital-tv.

--
Andy
.