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

On Jul 31, 11:19 am, Roderick Stewart
<escapet...@xxxxxxxxxxxxxxxxxxxxxx> wrote:
In article <memo.20070730230534.38...@xxxxxxxxxxxxxxxxx>, Paul Cummins
wrote:

Also, the signal would be far more watchable, since signal errors would
only affect the luminance - making it less defined in shade only, so
intereference would not be so noticeable.

Not sure that I follow that argument. I see someone has already made the
point about ignition sparlkies, but there's also the matter of AGC. With
positive modulation, proper AGC not related to picture content is more
complicated to implement, and in the days of thermionic valves it was
common to economise on components in the interests of costs. Thus, RF AGC
would depend on the average picture brightness, and combined with the
effects of capacitor-coupled video amplifiers, the dynamics of the
pictures displayed in most homes would have been nothing like what was
seen in the studios.

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.

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 ?

.

Relevant Pages

  • Re: How good were 1950s/1960s Band 1 TV receivers?
    ... but there's also the matter of AGC. ... proper AGC not related to picture content is more ... I can't remember seeing black level clamping on many b/w sets, ... negative modulation pictures, ...
    (uk.tech.broadcast)
  • Re: How good were 1950s/1960s Band 1 TV receivers?
    ... only affect the luminance - making it less defined in shade only, ... intereference would not be so noticeable. ... but there's also the matter of AGC. ... proper AGC not related to picture content is more ...
    (uk.tech.broadcast)
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