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1946 Why 405 lines?

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peterscott
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I know this topic has been discussed before but I was looking for the official enquiry/report leading to the decision and found an on-line copy of the Hankey Television Committee that was appointed as early as September 1943 to examine the question. I agree with the findings but I think it still makes interesting reading.

Here is the list of witnesses:

Hankey Witnesses

Peter

www.nostalgiatech.co.uk

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Topic starter Posted : 23/03/2020 9:38 am
Till Eulenspiegel
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From the July 1961 Radio Constructor: Should Britain introduce a 625-line television system?

Of course it was the right decision at the time.

Radio Constructor July1961
Radio Constructor July1961 2

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Posted : 23/03/2020 10:40 am
peterscott
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@till

It's interesting that the principal advantage of the 625 line system over 405 is the 55% increase in vertical resolution giving a large reduction in picture "lininess" but using the 8MHz channel bandwidth only gives a 20% increase in horizontal resolution over 405 line sets with 2.5MHz bandwidth and no advantage if the 405 line sets has 3MHz bandwidth.

Peter

www.nostalgiatech.co.uk

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Topic starter Posted : 23/03/2020 11:35 am
Cathovisor
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One of the biggest advocates of moving to 625 lines was Charles Orr Stanley of Pye, who saw it as a way to export more of his television receivers and studio equipment to Europe. Of course, Stanley never saw in his greed that the market could work both ways, and that more reliable 625-line receivers could come to the UK from the Continent and show the British public that you could buy a TV set that didn't leave you on first-name terms with the local repair man.

If you've ever read Radio Man you get the impression that Stanley wasn't the nicest of individuals, but nowhere near as much of a bar steward as the philandering narcissist that was Peter Eckersley.

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Posted : 23/03/2020 11:41 am
peterscott
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Posted by: @cathovisor

If you've ever read Radio Man you get the impression that Stanley wasn't the nicest of individuals, but nowhere near as much of a bar steward as the philandering narcissist that was Peter Eckersley.

Very interesting and a very fair point about competition from foreign manufacturers.

Peter

www.nostalgiatech.co.uk

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Topic starter Posted : 23/03/2020 12:05 pm
Cathovisor
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It's tempting to draw comparisons with a recent political event to discuss the laws of unintended consequences, but I am definitely NOT going down that path!

I remember the much-missed Geoffrey Dixon-Nuttall pointing out how rapidly Pye build quality went downhill after Stanley's takeover in the early 30s (culminating in the unspeakably nasty model MP) and how their post-war radios were unusually, of much better quality than their pre-war stuff. What does interest me is that pre-war, they had links with Telefunken; I think (BICBW) that the massive "Paramphonic" two-part radiogram used the superlative Telefunken TO1000 pickup. That link with Telefunken was to prove invaluable in developing a workable system of flyback EHT ahead of all the rest.

However, if Pye hadn't had been as big a company as it was, a certain TV receiver would have sunk them in much the same way that EMI's size saved them from the notorious 1807.

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Posted : 23/03/2020 12:27 pm
Cathovisor
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Posted by: @peterscott

[...] but using the 8MHz channel bandwidth only gives a 20% increase in horizontal resolution over 405 line sets with 2.5MHz bandwidth and no advantage if the 405 line sets has 3MHz bandwidth.

This was something I wonder how many people noticed when people moved to 16:9 receivers on 625 lines - they still had the same bandwidth but produced a softer picture.

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Posted : 23/03/2020 12:37 pm
Nuvistor
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@cathovisor

Probably very few, for many it’s possible that picture quality above a certain level becomes secondary to content. That picture quality level may be quite low for some.

Frank

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Posted : 23/03/2020 1:10 pm
peterscott
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@nuvistor

I must admit that sitting 10' away from our 32" set, like I do, I don't really see a significant difference between SD and HD 1080 although it's very obvious if I move closer.

Peter

www.nostalgiatech.co.uk

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Topic starter Posted : 23/03/2020 2:36 pm
Cathovisor
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If you've a good TV the difference at that distance is indeed negligible. The only difference is on captions, I've found.

But I'm still watching a 24" 4:3 CRT!

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Posted : 23/03/2020 3:22 pm
Till Eulenspiegel
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I reckon it's OK to show this picture again.

405 versus 625.

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Posted : 23/03/2020 7:24 pm
peterscott
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@till

That's just because the tube was too big.

Big Tube

Peter

www.nostalgiatech.co.uk

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Topic starter Posted : 23/03/2020 7:32 pm
Till Eulenspiegel
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Hi Peter,   Your huge tube picture is from the same 1961 Radio Constructor magazine as the 405 or 625 topic on pages 942 and 943.

The huge 30" Dumont CRT was never marketed in the UK. Imagine watching 405 pictures on this tube.  From the ETF:   https://www.earlytelevision.org/dumont_ra-119.html

I still have that 1958 24" KB "Regina" TV to look at some.

Last night I watched Sunday Night at the London Palladium on the 23" Pye V600. The 405 line pictures were good. The line structure wasn't too noticeable.

Till Eulenspiegel.

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Posted : 23/03/2020 7:51 pm
peterscott
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Posted by: @till

Hi Peter,   Your huge tube picture is from the same 1961 Radio Constructor magazine as the 405 or 625 topic on pages 942 and 943.

Till Eulenspiegel.

Yes, and it was you that took me there!

Peter ?

www.nostalgiatech.co.uk

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Topic starter Posted : 23/03/2020 7:59 pm
Till Eulenspiegel
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The 24" KB

KB PV100

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Posted : 23/03/2020 8:22 pm
Katie Bush
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@till Before we all bought Japanese then? ?

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Posted : 23/03/2020 9:15 pm
Katie Bush
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@till I had a big EKCO around that size of screen, can't remember the model No. but it was a lovely set, pin sharp focus, and despite the obviously visible line structure, you never really noticed it if the programme content was absorbing enough. I think it's the age old thing about just how much we actually see Vs. what we think we see.

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Posted : 23/03/2020 9:20 pm
PYE625 liked
Till Eulenspiegel
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EMI had access to certain RCA patents including interlaced scanning.

The original EMI standard was to be 243 lines interlaced, the intention was that it would compete with the sequential scanning Baird 240 line system. The EMI system would offer a flicker free picture. The EMI line timebase repetition rate would be 6,075c.p.s. Almost matches the Baird 6.000c.p.s.

EMI employed five divide-by-three circuits = 243 supplied from the 12,150 c.p.s. master oscillator. Increase the master oscillator frequency to 20.250c.p.s. and replace one of the count down circuits to divide-by-five the result is 405. Of course other parameters have to be considered, 2.7Mc/s video bandwidth being the one needing attention, something not easy to achieve in 1934!

The aspect ratio of the original 405 line system was 5:4 and was replaced in the late forties by 4:3. With a 5:4 aspect ratio the maximum bandwidth is 2.75Mhz. When the aspect ratio was changed to 4:3 the bandwidth is 3Mhz for the same horizontal definition. The active video part was 83 microseconds and in the '60s when 625-405 converters came into use the active video part became 79 - 80 microseconds.

Till Eulenspiegel.

Mod Note:Fixed post formatting ? 

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Posted : 24/03/2020 9:06 pm
Nuvistor
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Wasn’t the reason for interlace two fold, one flicker the other bandwidth, 405 none interlaced would have require twice the bandwidth when 2.7Mhz was a challenge?

Frank

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Posted : 24/03/2020 10:14 pm
Cathovisor
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@nuvistor

It was, Frank - a very early form of data compression if you will! Certainly at work you find that things that didn't seem to matter at 1.5Gbits/second (the data rate for standard HD video) suddenly get a little more critical at 3Gbits/second (that's switching from 50i to 50p).

12Gbits/second (for UHD TV) is a whole new ballgame!!

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Posted : 24/03/2020 11:57 pm
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