Behind the scenes UK experimental colour transmission 1957

[Duke Nukem]

Still never have understood why color TV wasn't available in Blighty & the rest of Yoorup til so late

From what I've read in magazines of the period, even in the latter years of the 50's American colour television wasn't that much of a success. By success, I don't mean technically, rather the take-up of colour TV was still low, cost being an issue. Meantime, the UK and I guess Europe too were far less affluent than America so take-up here would presumably been even worse.

TTFN,
Jon

[ceebee23]

I think primary reason for the BBC and the UK not adopting 405 line NTSC was that the EBU had settled on 625/50 as the new European standard in the early 1950s.

This was being progressively introduced across Europe (both west and eastern Europe). (Australia adopted this standard in 1956)

France was running an 819/50 and the UK its 405 line standard both were phased out by the early 1980s.

The UK decided to introduce colour with the 625 line standard. Various investigations into the colour format were undertaken and ultimately PAL was adopted.

But the key to the decision not to proceed with 405 NTSC seems to have been cost and a fear that if they adopted 405 line NTSC colour the public would have seen less reason to adopt the spanking new 625 line standard ... because on the colour receivers of the day 405 line, 525 line and 625 line looked barely different!

I should also point out that the commercial broadcasters, especially ITN's Lord Grade were pushing heavily for colour from the moment they went on air!

[Duke Nukem]

The primary reason for not adopting colour on 405 line would have been that the decision was to introduce 625 line before colour was introduced and to phase out 405-line. So 405-line colour would have been pointless dead end.

The UK's adoption of PAL was almost a last minute thing. The Pilkington Comittee produced a report on the future of TV and gave a plan for the introduction of 625 line within 2 years with colour to follow on the new standard. However, the report preceeded the German PAL system (or at least its announcement in the trade press), so at the time it was almost certain that the plan was for 625-line NTSC (I say almost certain as there had also been experimental broadcasts using the SECAM system).

As to 405 and 625 not looking much different, even in the 50's some firms such as Ekco were already using a spot wobble system on their up-market sets (17"!) to try and mask the line structure and by the time of the Pilkington report early 60's screen sizes were 19" for paupers and 23" for toffs. There would definitely be a difference between 625 and 405 line colour, though in the early/mid 50's when many mono sets couldn't even fully resolve the 405 line system I accept that there 405 and 625 colour might have not shown much difference.

TTFN,
Jon

[Glenz75]

New Zealand never got colour until 1974, a year before I was born...

[ceebee23]

the sad part of the UK not moving into colour broadcasting with 405 NTSC is that all those great programs from the early 60s from the Beeb were only made in b/w

[ppppenguin]

Originally Posted by NewVista

I don't know what GB did in the 30's but can't see how they would achieve the necessary H/V relationship starting w/ 50hz ref. I would like to see a reference/link on this early SPG scheme.

Any SPG was a complex thing in the 1930s. Some were mechanical, like a Hammond tonewheel organ, others used lots of valves (tubes) to do frequency division. FOr 405 you start at 20250Hz. Divide by 2 to get 10125Hz for line pulses, divide by 405 for 50Hz field pulses. 405 = 3*3*3*3*5 The small numbers were essential for early frequency dividers. The 20250Hz master oscillator could be locked to 50Hz mains using a slow acting phase lock.

the sad part of the UK not moving into colour broadcasting with 405 NTSC is that all those great programs from the early 60s from the Beeb were only made in b/w

And many of the tapes were wiped for re-use because they were so expensive. I believe that in the US many shows were shot on film. This was rare in the UK, possibly due to the high cost.

[NewVista]

Originally Posted by ppppenguin

..start at 20250Hz. Divide by 2 to get 10125Hz for line pulses, divide by 405 for 50Hz ..locked [20250]..to 50Hz mains using a slow acting phase lock.
.

Yes, this would be the only way I suppose. Later they would drop the mains lock as SPG's became xtal ref.

My issue remains "why 50 hz ?" [cont. next post]

[NewVista]

Originally Posted by colorfixer

It's more than power supply filtering. Watching 50Hz video under 60Hz non incandescent lighting can be bothersome due to differing flicker rates. In my office, when I watch a 50Hz/Pal feed, the screen noticeably flickers when I light the room with fluorescent lighting. .

My objections to these 'reasons', that you hear now and then, for 50hz countries using 25fps TV are as follows:

1. TV's (even old ones) shouldn't have AC power artifacts. If you see this, I suggest you book the set in for repair.

2. When GB designed 405/50, fluorescent lighting wasn't available*. So it's a non-sequitur to claim "50 hz was chosen to sync flicker with fluorescent lights".

3. Some countries happily enjoy 50hz pwr & 60hz TV (Chile, Japan).

4. Why is there no 12hz beat with my 72hz computer & Fluoro lights ?



*not available commercially until 1939

[ppppenguin]

Originally Posted by NewVista

1. TV's (even old ones) shouldn't have AC power artifacts. If you see this, I suggest you book the set in for repair.

Keeping hum out of the entire broadcast chain wasn't easy. Hence it's a natural choice to lock field to mains.

I have gone back to the source here. Blumlein et al, The MArconi-EMI tlevision System - The Transmitted Waveform, Journal IEE 1938 p761

"Similarly with interlaced scanning the spot traverses the frame 50 times per sec, thus raising the flicker above that perceptible to the human eye......A frame frequency of the order of 50 was necessary to overcome flicker and the exact value of 50 was chosen on account of the supply frequency of this country...."

I can't be bothered to retype any more of the article but but it goes on to say that hum effects at 37.5Hz were intolerable.

Clearly at the time the decision to use 50Hz was taken it was regarded as essentially flicker free. Especially as the competition was using 25Hz. the question was could they save bandwidth by going lower than 50Hz and the answer was clearly no.

[Steve McVoy]

Another factor is the mains derived EHT. The filtering was terrible. The British 405 sets in our museum are powered by 60 Hz and many exhibit severe hum bars even though they are working just as they did when new.

[tubesrule]

Originally Posted by NewVista

My objections to these 'reasons', that you hear now and then, for 50hz countries using 25fps TV are as follows:

1. TV's (even old ones) shouldn't have AC power artifacts. If you see this, I suggest you book the set in for repair.

This is not so straightforward as Jeff and the Blumlein article have pointed out. Firstly, removing ripple from the power supply to an adequate level is VERY difficult to do cost effectively using 1930/40's technology. The required amount of iron and capacitance would make the set very heavy and very expensive. The power supply on the 1936 RCA RR359 prototype sets weighs almost 100lbs by itself due to the size and number of chokes.

The problem is compounded by interlace scanning. Only a very small amount of magnetic interference is required to shift a line enough to ruin the interlace. Just having a power transformer in the set will create enough magnetic interference to show ripple in the image. Magnetically shielded transformers could be used but again are very expensive and large.

Case in point, I have a Sony 9-90UB solid state 405 line set from the 1970's and when I run it here on 60Hz power, feeding it with a 405/50i signal, the picture shows pronounced ripple and line bunching. Even when powered from a battery to eliminate the internal transformer, there is still some noticeable ripple in the image depending on where the set is placed due to stray magnetic fields at 60Hz.

Edit: I see Steve got in there while I was typing This is why the power supply on the RR359 is so big and heavy. They have large chokes and capacitors in the mains derived EHT to try to filter out the ripple. Hardly something that would be practical on a commercial set.

[Steve McVoy]

Even harder to filter at 50 Hz than 60 Hz.

[andy]

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[ppppenguin]

2 video monitors side by side, one locked, the other without a signal. I've seen intereference between them on many occasions. Not with top quality kit but not everything is top quality.

[ceebee23]

I think that you need to remember that 25 frames...50 fields is actually fine ...and flicker is, certainly for most people, hardly ...if at all .. noticeable.

Afterall movie film is 24fps!

I think the key really is the 405 line seemed amazing in 1936 but by 1956 was clearly below the preferred standard.

Everyone in the industry knew colour was coming ...sooner or later.... but reality was the cost in 1955 was exorbitant both for the broadcasters and consumers.... by 1966 the situation was completely different... and the UK began colour broadcasting in 625/50/PAL in 1967/68.