New TV programme about early television (UK)

Forum for discussion of narrow-bandwidth mechanical television

Moderators: Dave Moll, Andrew Davie, Steve Anderson

New TV programme about early television (UK)

Postby TBlack » Fri Jan 15, 2016 1:35 am

Hello everyone,

I hope you don't mind my intrusion, but I'm putting together a new documentary for a UK broadcaster about the origins of the UK television service, to celebrate the 80th anniversary of the first regular high definition broadcast in the UK, on Nov 2nd 1936.

As part of this film, we are going to build a mechanical 240-line flying spot camera. We aren't going to be building a replica of John Logie Baird's camera from Studio B, but a machine that will provide similar results using the same principles. This will enable us to explain the engineering involved (within our budget..!). The aim is to bring more people into the world of early television and champion mechanical engineering.

I know that many members here have previously built 30-line scanners, and other devices, and basically i'd be really interested to find out more about these builds. Does anyone currently have a working home-made 30-line camera and televisor? and does anyone have a working machine that uses more lines? We're going to be filming the surviving double-8 equipment etc, but it would be wonderful if we were able to see something similar that actually works..!

If anyone is interested in having a quick chat about the project, PM me here or leave a message underneath!

Thanks so much,
- Terry
TBlack
"Fester, enough of the light-bulbs!"
 
Posts: 3
Joined: Thu Dec 17, 2015 10:20 pm

Re: New TV programme about early television (UK)

Postby Klaas Robers » Fri Jan 15, 2016 11:58 pm

The problem of higher line counts when using a Nipkow disc is the loss of light. We see this already with the 30 or 32 lines. The amount of light that you see is always no more than the amount of light that passes through ONE hole. Follow me:

- If we roughly approximate the number of dots in a 32 line picture to be 32 x 32 = 1000,
- then it is clear that the single hole passes only 1 / 1000, or 0.1% of the light available behind the disc.
- This was already true in Bairds time,
- you could only watch the Televisor in a really dark room,
- even the light from the corridor peeping between the door and the threshold was troublesome.
- The neon lamp didn't produce more light.
- Nowadays, using many ultrabright LEDs, we can watch a Nipkow disc in a dimly lit room.

- This is comparable for a camera.
- The attenuation of the light by a factor of 1000
- caused that you need a sensitive photo multiplier behind the disc
- and still the scene should be illuminated brightly.

- The increase of the line number by a factor of 2,
- decreases the light output by a factor of 4 (pixels half the diameter = one quarter of the surface).
- so for 240 lines the light loss is 64 x larger....... 64 000 times.

The trick with intermediate film was a trick to gain light. A film frame can be scanned with a high intensity light spot of a source (arc lamp) that you make yourself. But I never have seen a 240 line mechanical direct view monitor (televisor).
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1656
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: New TV programme about early television (UK)

Postby TBlack » Sat Jan 16, 2016 1:50 am

Forgive me if there's any misunderstanding - we're not going to make a 240-line televisor, we're going to be interpreting the signal on an antique 240/405 line TV set (that still has the switch 'Baird System'/'Marconi system' on it).

We will be using super bright LEDs as our light source (so we don't need to worry about cooling systems etc), and will discuss the infra-red problem separately (as LEDs will not give us the wide spectrum that an arc lamp would have). This is the machine that we are going to approximate:

Image

albeit with a few modern day components to prevent it from being 7ft tall and weighing a tonne or more. It's a flying spot camera, so the subject would in fact be in total darkness in a separate room with the photomultipliers, and the 'camera' would send out a tiny beam of light that would scan the subject.

However, I'm interested in talking to anyone that has previously built a working 30-line or 32-line scanner/televisor that we can see working for a separate part of the programme, dealing with the developments of the technology up to 1936. The double-8 machine at the National Media Museum in Bradford, UK, of course, can't be turned on or activated for us to see how it works, so it would be great to film a working approximation next to it!

Thanks so much!
- T
TBlack
"Fester, enough of the light-bulbs!"
 
Posts: 3
Joined: Thu Dec 17, 2015 10:20 pm

Re: New TV programme about early television (UK)

Postby Klaas Robers » Sun Jan 17, 2016 7:29 am

Terry,
any way I can suggest you to visit the NBTVA convention which will be held in Loughborough somewhere end March - beginning April. There are quite some people bringing their working mechanical televisors / cameras, which you can see and you can talk to them. If you want to have an impression of the Conventions, look on the website www.nbtv.org, select the Gallery and press the arrow to the left button. Then you will see what you can expect.
These are pictures of several years ago, but new Conventions are rather similar than differing.
I never have seen a real-life flying spot scanner of one of the members working.

For the Baird flying spot scanner: realise yourself that it wasn't dark in the studio. The amount of light from the flying spot was very well visible, and I have read that also stroboscopic light was used, flashing during the "sync".

There is a so called "Aurora" scan converter, where you can enter with a normal TV signal, and that will output a varaity of video signal, amonst them 240 line TV and 405 line TV. With that thing you can demonstrate an antique UK TV.
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1656
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: New TV programme about early television (UK)

Postby TBlack » Tue Jan 19, 2016 9:32 pm

Thanks so much for the suggestion of the Aurora scan converter, I think that may end up being an essential piece of kit for us.

Unfortunately, we're having to make and finish the programme before April, although I'll probably still come along to the convention - i'm getting quite into this technology now..!
TBlack
"Fester, enough of the light-bulbs!"
 
Posts: 3
Joined: Thu Dec 17, 2015 10:20 pm

Re: New TV programme about early television (UK)

Postby Lawnboy » Tue Mar 01, 2016 4:51 am

Hi Terry, I just came across this thread today. I would second Klaas' concerns about building a 240 line scanner. That sounds like a very complex (and expensive) piece of machinery. It may be better to feed an ordinary television signal through an Aurora converter, and light the scene the way the original studio was lit.
Regarding the double 8 equipment, club member Don McLean wrote a paper a while back detailing the double 8 and the first published picture of television. It's called "The Achievement of Television: The Quality and Features of John Logie Baird's System in 1926." Although I can't remember where it was published.
I also have a 32 line flying spot scanner built and in somewhat working condition (it's getting there, but still needs a little work), but I live in the USA. I will try to answer any questions you may have about it if you'd like.
Lawnboy
Just nod and pretend you understand me
 
Posts: 285
Joined: Sat Dec 06, 2008 1:02 am
Location: North Brookfield, MA, USA


Return to Mechanical NBTV

Who is online

Users browsing this forum: No registered users and 19 guests