Baird Electronic Colour Television (2-sided screen)

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Baird Electronic Colour Television (2-sided screen)

Postby OmegaProductions » Sun Dec 24, 2017 2:12 am

Hello guys in NBTV!! :D
I have some very interesting news for you all! :!: Baird has done an electronic colour television in 1943, one of his last works of television. It is very interesting because the camera tube has two sides, same with the screen! :idea: In two sides have two colours, the first side has orange-red and the second side has blue-green. The name for the camera tube is called "Telechrome". It might be interesting to recreate them. And then it gets received back in the picture tube which reproduces the same colours as the camera tube, or shall I say "Telechrome". Here are some pictures:
pop_mech_3-45-1.jpg
pop_mech_3-45-1.jpg (6.39 KiB) Viewed 3942 times
Baird colour tube diagram.png
Baird colour tube diagram.png (60.2 KiB) Viewed 3942 times

Here is a video all about the "Telechrome" tube and spoken by Ian Baird. Here is the link below:
https://vimeo.com/18118889
And there is another link with more information about his system, on this Early Television Foundation site here below:
http://www.earlytelevision.org/baird_el ... color.html
That's all I have to say! This is me Dylan signing out and goodbye!!!! :D :) :wink:
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Re: Baird Electronic Colour Television (2-sided screen)

Postby ppppenguin » Tue Dec 26, 2017 5:31 am

This "telechrome" tube is well known. It was based on a Hewitic mercury arc rectifier bulb. There was a proposed 3 colour version but I don't think it was ever built.

BTW, it's not a camera tube as you state. It's purely a display tube.
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Re: Baird Electronic Colour Television (2-sided screen)

Postby OmegaProductions » Wed Dec 27, 2017 7:47 am

Oh yeah! pppenguin you are right! :!: It was actually a display tube, not a camera tube. It seems to remind me of an iconoscope tube for some reason but it's not. It is really interesting it is and I noticed that it looks quite a bit similar to this Hewitt mercury arc rectifier bulb. :) I don't know why but when I look at this Hewitt mercury arc rectifier bulb itself, it looks very frightening to me. :shock: The tube that I'm scared of below...
1200px-Quecksilberdampfgleichrichter_in_Betrieb.jpg
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Re: Baird Electronic Colour Television (2-sided screen)

Postby ppppenguin » Thu Dec 28, 2017 3:58 am

My mercury arc on a test rig. One day I'll get round to building some control gear so I can demo it at home.
http://www.borinsky.plus.com/mars.html

Actually the Baird company did build an iconoscope type camera, something that isn't very well known. They couldn't use it because of patents owned by RCA.

https://www.scran.ac.uk/database/record ... chdb=scran
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Re: Baird Electronic Colour Television (2-sided screen)

Postby OmegaProductions » Thu Dec 28, 2017 5:49 am

WOW! I never know that Baird was also experimenting with the iconoscope tube as well! Never know that fact! But just like Philo Farnworth, they also can't build it, because of the RCA patents.

But it would be interesting if you did show the demo of your mercury arc bulb. :idea: :)
Anyways, that's all I have to say! This is me Dylan signing out and goodbye!!!! :D :) :wink:
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Re: Baird Electronic Colour Television (2-sided screen)

Postby ppppenguin » Thu Dec 28, 2017 6:31 pm

Farnsworth had his own camera tube, the Image DIssector. This was grossly insensitive due to lack of charge storage. it later found limited applications such as viewing furnaces where there was loads of light and its ruggedness made it useful.

Philips also developed their own iconoscope type of camera at their Eindhoven labs. Quite possible that others did too.
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Re: Baird Electronic Colour Television (2-sided screen)

Postby OmegaProductions » Fri Dec 29, 2017 12:54 am

Oh yes! Philips did that iconoscope tube for the cameras at Paul Nipkow Television in Germany. But the picture that is shot was not 405-lines, Philips used a lower resolution at 180-lines. Interesting! :!:

Anyways, I realise that John Logie Baird in his electronic colour television system has 600-lines in each two colours, which is actually pretty good quality for it's time!
But I had found this diagram for the 3-colour television system, which was not built. Here is a 3-colour television tube diagram picture here below:
baird_color_system.jpg
baird_color_system.jpg (14.47 KiB) Viewed 3861 times

That's all I have to say! This is me Dylan signing out and goodbye!!!! :D :) :wink:
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Re: Baird Electronic Colour Television (2-sided screen)

Postby ppppenguin » Sat Dec 30, 2017 5:15 am

This paper clearly shows that Philips were experimenting with 405 line interlaced TV.
http://www.extra.research.philips.com/h ... 36-321.pdf

The 3 colour telechome CRT was a clever idea but was never built so far as I know. I don't think it would have worked very well. Having said that, the shadowmask CRT seems like a really daft idea and it was made to work very well indeed.
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Re: Baird Electronic Colour Television (2-sided screen)

Postby Klaas Robers » Mon Jan 01, 2018 3:03 am

Of course Philips was experimenting with 405 line electronic TV in 1936. This was when the 30 line Baird mechanical tv was abandoned by the BBC and electronic TV was not yet introduced. Philips then had two small groups working on television, one leaded by Freek Kerkhof PA0KT on mechanical Baird TV and one on all types of all electronic TV with varying numbers of lines. Nobody knew what the future would bring and then it is best to be available on all possible standards.

During WW2 all transmissions of TV in the UK were stopped, to make mal-useage of the VHF TV transmitters (radio beacons) for flying bombs by the Germans impossible. In 1945 the work on 405 line TV was started up again and at the same time the devellopment of 625 line TV was started. I don't know what the real reason was, but bringing the line frequency from 8 kHz (very well audible) to 16 kHz (much less audible, our ears have some kind of dip on this frequency) will be one of them. I still remember the squeeking sound of the English TV in the small hotel the first time we went to London for holidays around 1970. On the other hand, the visibility of the lines, practically about 180 in the 405 lines system, was although the interlacing fields, still too large. Lines in an interlaced picture are only invisible on a photo from the screen. For your eyes they move and you will follow them, seeing the course half line number structure.

The decision for 625 lines and not 405 lines in Europe was a political one, not a technical decision.
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Re: Baird Electronic Colour Television (2-sided screen)

Postby ppppenguin » Mon Jan 01, 2018 5:37 am

Klaas mentions that the UK TV service was shut down for WW2. The transmitter at AP was used to interfere with the luftwaffe's "Y gerat" beam bombing system. The jamming was very successful. Whether by bad luck or ignorance the germans used a frequency for Y gerat that was in the range covered by the AP transmitter.

https://en.wikipedia.org/wiki/Battle_of ... rmeasure_3

Read RV Jones' book "Most Secret War" for an excellent account of this and much more WW2 intelligence activity.
https://www.amazon.co.uk/Most-Secret-Pe ... 0141042826
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Re: Baird Electronic Colour Television (2-sided screen)

Postby Dave Moll » Mon Jan 01, 2018 6:41 pm

Klaas Robers wrote:In 1945 the work on 405 line TV was started up again and at the same time the development of 625 line TV was started. I don't know what the real reason was, but bringing the line frequency from 8 kHz (very well audible) to 16 kHz (much less audible, our ears have some kind of dip on this frequency) will be one of them.

At the time of first experiencing 625-line television, my ears certainly didn't have such a dip in sensitivity - I found this line whistle far more objectionable than 405 lines. Needless to say, as my ears got older, 16kHz passed beyond the range of my hearing.

By the way, wasn't the 405-line frequency 10kHz rather than 8kHz? (405 x 25 = 10,125, and 625 x 25 = 15,625)
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Re: Baird Electronic Colour Television (2-sided screen)

Postby Steve Anderson » Mon Jan 01, 2018 11:05 pm

Perceived loudness is dependent on level and frequency as well as the individual's particular ear parameters and age. Note the last sentence in the attached...

Dave is correct, 405-lines had a horizontal line frequency of 10.125kHz, 625 is 15.625kHz.

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Re: Baird Electronic Colour Television (2-sided screen)

Postby Klaas Robers » Fri Jan 05, 2018 9:03 pm

When exposed to loud noises, the human ear gets a dip at about 16 kHz. And yes, if you are young this dip might have been not yet developed deep enough. I could still hear the 19 kHz pilot tone of the FM-stereo when listening to a mono FM-radio at an age of about 30 years. At that time the 16 kHz line frequency had gone already.

But there is more. As the 10 kHz of the line deflection of 405 lines was also very well heard by the developpers of the 405 line TVs, they did all they could to suppress this unwanted noise of the line output transformers. The 16 kHz was much less audible by the same aged technicians, so it was not needed to do a comparable effort to suppress this parasitic sound. So it might have been much louder to youngsters, before they went to discos. The loud music there cured this initial problem for them.
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Re: Baird Electronic Colour Television (2-sided screen)

Postby Panrock » Sat Jan 06, 2018 2:09 am

Klaas Robers wrote:But there is more. As the 10 kHz of the line deflection of 405 lines was also very well heard by the developpers of the 405 line TVs, they did all they could to suppress this unwanted noise of the line output transformers. The 16 kHz was much less audible by the same aged technicians, so it was not needed to do a comparable effort to suppress this parasitic sound. So it might have been much louder to youngsters, before they went to discos. The loud music there cured this initial problem for them.

Or this might replace it with their own private 'line whistle': tinnitus! A discussion here: http://www.detinnitiser.com

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Re: Baird Electronic Colour Television (2-sided screen)

Postby Dave Moll » Sat Jan 06, 2018 5:44 pm

Klaas Robers wrote:The 16 kHz was much less audible by the same aged technicians, so it was not needed to do a comparable effort to suppress this parasitic sound. So it might have been much louder to youngsters, before they went to discos. The loud music there cured this initial problem for them.


So that's where I went wrong as a teenager - I don't think I ever went to a disco! :roll:
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