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From: john larkin <jl@glen--canyon.com>
Newsgroups: sci.electronics.design
Subject: Re: Who remembers how bad analogue television was?
Date: Thu, 27 Feb 2025 12:27:41 -0800
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On Thu, 27 Feb 2025 20:12:00 +0100, Lasse Langwadt <llc@fonz.dk>
wrote:

>On 2/27/25 17:40, john larkin wrote:
>> On Thu, 27 Feb 2025 08:37:32 -0800, john larkin <jl@650pot.com> wrote:
>> 
>>> On Thu, 27 Feb 2025 09:47:22 +0000, liz@poppyrecords.invalid.invalid
>>> (Liz Tuddenham) wrote:
>>>
>>>> Sylvia Else <sylvia@email.invalid> wrote:
>>>>
>>>>> Leave aside the ghosting, which could largely be addressed by having a
>>>>> decent antenna.
>>>>>
>>>>> But my memory of a Philips Colour TV (1984ish) was that it had rubbish
>>>>> automatic gain control (AGC), and odd interactions between brightness
>>>>> and picture position.
>>>>>
>>>>> The AGC should have been based on the amplitude of the sync pulses,
>>>>> which was 30% of the total. I'm sure this could have been done, but my
>>>>> experience was that instead it was based on the average amplitude of the
>>>>> demodulated signal. A black image containing large white text, such as a
>>>>> title screen, would show a clear darkening to the sides of the text,
>>>>> while being decidedly grey over the rest of the screen.
>>>>
>>>> I think you may be mis-remembering; something similar to the fault you
>>>> describe was prevalent on B&W televisions which were built down to a
>>>> price.  Some of it was caused by average AGC and some was due to lack of
>>>> DC coupling, or skimped DC restoration, in the video amplifier.  Some of
>>>> the better sets used back-porch AGC and, for the enthusiast, add-on
>>>> circuits were published in Wireless World (designed by Mothersole, I
>>>> think).
>>>>
>>> >From the beginnings of colour television the designers recognised that
>>>> all three video amplifiers had to be DC coupled but the AGC was much
>>>> simpler because they used inverted modulation, so a sync pulse
>>>> corresponding to 100% modulation was always available.  I can't imagine
>>>> Philips would have produced a model with such gross errors as you
>>>> describe,.  Was your own set faulty or was this a common insurmountable
>>>> problem caused by NTSC and positive modulation on the system in use in
>>>> the U.S. at the time?
>>>>
>>>> In Europe, Philips and Mullard (their UK valve-making subsidiary)
>>>> published large quantities of material to aid set designers and help
>>>> them get the best out of their range of valves.  I read it several years
>>>> before the colour television service started in England and it included
>>>> details on DC coupling and AGC. (The BBC did a lot of their preliminary
>>>> experimental work using NTSC - but eventually decided to use PAL for the
>>>> public broadcast system).
>>>
>>> When I was a kid we had an RCA 12" round-tube B+W TV, in a giant piece
>>> of furniture cabinet with a 12" speaker. It was all AC coupled, so the
>>> screen always averaged grey.
>>>
>>> It made a pretty good liquor cabinet, after I scrounged it for parts.
>> 
>> We only had three channels, but the programming was better than what
>> we have now.
>> 
>
>https://en.wikipedia.org/wiki/Rosy_retrospection  ;)

Early TV had documentaries, science, concerts, live Play Of The Week,
Kukla Fran and Ollie, westerns, variety shows.

Now we have superheroes, ultraviolence, and nonstop swearing.

We do get about an hour or so per week of decent stuff on PBS. Miss
Marple or All Creatures sorts of things. Not much.