Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Martin Brown <'''newspam'''@nonad.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: Who remembers how bad analogue television was?
Date: Thu, 27 Feb 2025 09:49:30 +0000
Organization: A noiseless patient Spider
Lines: 63
Message-ID: <vppcfb$3281d$1@dont-email.me>
References: <m2a9coFaisuU1@mid.individual.net> <vpp6l0$319r5$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Injection-Date: Thu, 27 Feb 2025 10:49:32 +0100 (CET)
Injection-Info: dont-email.me; posting-host="052168c8cf9e588ccfae26430d72ece1";
	logging-data="3219501"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+JLlEjKinqDF69DP2dxCKh8nHJas0qk3l+yk5UXFmFgQ=="
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:DthEgnaa2jR7hX/18S3Pg1DlROU=
Content-Language: en-GB
In-Reply-To: <vpp6l0$319r5$1@dont-email.me>
Bytes: 4287

On 27/02/2025 08:10, Jeff Layman wrote:
> On 27/02/2025 04:52, Sylvia Else 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 suspect this same poor AGC was responsible for a shift in the
>> detection of the sync pulse such that the text would be moved to the
>> right of its proper position, which could result in distortion of the
>> letters as the average brightness varied line by line.
>>
>> In the early days of television, using thermionic valves, it was
>> probably a miracle that these things worked at all, but surely in the
>> transistor age, something better could have been provided.
>>
>> Were studio monitors any better, anyone know?
> 
> I suppose that's one of the problems with being "first past the post" - 
> you get stuck with the system. The US had NTSC, valves, and 525 lines.

I always believed that made it impossible for them not to have 
newscasters with flesh that slowly shifted between ghastly green and 
purple tones (or was clamped to unnatural pale orange like the 
Donald's). NTSC was called Never Twice the Same Colour in the UK for 
good reason. PAL was self correcting. My Japanese sets could do both.

However, when I was in Japan I saw US style NTSC TV implemented 
correctly. It seems there was no reason that it could not be made to 
work well only that US makers couldn't be bothered to do it right.

> In the UK colour broadcasting didn't start until over 12 years later - 
> July 1967 - using PAL, transistors, and 625 lines. Most of western 
> Europe was the same as the UK, but in France and eastern Europe it was 
> SECAM and 819 lines. From what I understand, PAL was better than NTSC, 
> and from what I remember, analogue colour in the UK wasn't bad at all.

Very early sets the colour was in pastel shades until they started 
doping the front screen with neodymium to take out the unwanted yellow 
component in the early phosphors (especially the blue). Barely gets a 
mention now but it made a big difference to colour saturation and 
purity. Put sets with and without Nd doping together and the difference 
was huge. But either one on their own would satisfy a punter. Premium 
price for the one with better more saturated colours.

https://en.wikipedia.org/wiki/Cathode-ray_tube#Constructions

Main problem though was reliability I recall the service engineer 
spending lots of time fiddling with valve swaps. ISTR the original valve 
EHT stack rectifier gave off X-rays and had a lead shield around it.

-- 
Martin Brown