NBSC - Java version!

Forum for discussion of narrow-bandwidth mechanical television

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Postby dominicbeesley » Tue Oct 07, 2008 9:30 pm

Here's an updated version, this one should play more files created by other programs (earlier versions could not handle fact chunks in the wav header).

Thanks to DrZarkov for helping to improve the software

Dom
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Postby DrZarkov » Wed Oct 08, 2008 2:30 am

Very nice, it works! :D

One more wish: Is it possible to turn the picture 90 degrees to get a standard NBTV-picture with vertical lines?
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Postby dominicbeesley » Wed Oct 08, 2008 3:17 am

I'll try and get round to it in the next few days, it shouldn't be too difficult.

Is there any interest in adding other standards such as TeKaDe, 60 lines etc (anything that can fit in a 48/44.k .wav file), and if so do you know of a source of some test samples for the other formats.

As well as adding those formats would there be interest in adding a colour sub-carrier to them?

I'm off down into my basement now to cut up more MDF....

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Postby DrZarkov » Wed Oct 08, 2008 4:54 am

Oh yes, I am very interested! And even if currently everybody here is very quite, the software would be very interesting for others, too! I don't know if you know this very exciting project?
http://www.earlytelevision.org/color_mirror_screw.html
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Postby dominicbeesley » Thu Oct 09, 2008 3:27 am

Do you know of anywhere I might get some TeKaDe samples from? I've had a look round on the net but couldn't find any (my German is hopeless).

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Postby DrZarkov » Thu Oct 09, 2008 5:36 am

There is not much left about TeKaDe, in in Germany you find hardly information about the "Spiegelschraube", the best site in the internet is that from Peter Yanczer, he is *the* mirrorscrew expert. I've made some scans from a German book from the 1980:
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TeKaDe2-small.jpg
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Postby dominicbeesley » Mon Oct 13, 2008 1:54 am

Thanks for the info.

As requested here's a version with a "rotate" option tp play back normal bottom-right to top-left NBTV files.

I've got my B&W Nipkow machine nearly enough working now and a design for a colour decoder working in LTSpice, just waiting for a 30kHz watch crystal and should be able to get colour by the end of next week

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Postby Panrock » Mon Oct 13, 2008 5:17 am

DrZarkov wrote:There is not much left about TeKaDe, in in Germany you find hardly information about the "Spiegelschraube", the best site in the internet is that from Peter Yanczer, he is *the* mirrorscrew expert. I've made some scans from a German book from the 1980:


That last picture of the 'Spiegelschrauben-Fernsempfänger' and the 'Standgerät' (meaning console?) are quite amazing! I have a weak spot for mirror screws. Imagine tuning in, and an image takes shape 'in the air' as if by magic!

Could you kindly post this picture at higher definition so we can read the text?
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Postby DrZarkov » Tue Oct 14, 2008 6:18 am

I'm just back from a little holiday in Bavaria (Bayerischer Wald), so the "HDTV" scans are a little bit late, but here they are: http://www.retrocom.de/tekade.zip
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Postby dominicbeesley » Wed Oct 15, 2008 10:14 am

Thanks for those, shame there's not much info about TeKaDe. Looks like there were a good number of variations of lines/bandwidth though. I'm guessing that these might be difficult to fit into a 44.1kHz audio band.

Are there any surviving examples or replicas?

As for Bavaria, you are lucky! That is where my whole vintage technology obsession started! I bought two radios from a wonderful junk shop in Moosach near Munchen so I could get the BBC while traveling around Europe. I'll go back one day, I hope the shop is still there....I just wish I'd bought one of the televisions

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Postby DrZarkov » Wed Oct 15, 2008 3:24 pm

I've never heard of a surviving TeKaDe mirrorscrew receiver, or a real replica. Maybe we should ask TeKaDe (it became later ITT, now I think it's a part of GE). The problem was, that in Germany the systems changed very fast between 1929 and 1937, when finally 441 lines became standard. I guess that a receiver for let's say 90 lines was disassembled when it became obsolete. Even in 1935, when the Nazis declared the 180 lines system the first "high definition" television system in the world, they changed it shortly after that in 180 lines with interlace (which was possible with a mirrorscrew, you just had to change the mirrorscrew), and only 2 years later to 441 lines. TeKaDe made both, TVs with CRT and mirrorscrew. I know that some early CRT-TVs survived at the post-museum in Nuremberg you can see one. So I wonder how many mirrorscrews were really made.
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Postby Steve Anderson » Thu Oct 16, 2008 1:23 am

DrZarkov wrote:...and only 2 years later to 441 lines.


Now, I find this interesting...441 lines at 25Hz frame rate is a 11.025kHz line-rate, exactly one quarter of the audio CD sampling frequency of 44.1kHz.
I wonder if there's some historical linkage here? I know the 44.1kHz is derived from standard 625 frequencies, but it all seems rather more than
somewhat coincidental.

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Postby dominicbeesley » Thu Oct 16, 2008 11:05 am

And 441 * sqrt(2) almost equals 625, I wonder if there's a reason for that too....

Sometimes these things just come about because engineers and physicists tend to do all their workings using handy constants like that before finessing them to the real figures....Something like we'll double the band width = roughly sqrt(2) more horizontal pixels and sqrt(2) more lines?.... Then adjust for the fact that it was difficult to make frequency dividers to give even numbers so pick a close odd number...

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Postby AncientBrit » Thu Oct 16, 2008 5:14 pm

see :


http://www.madsci.org/posts/archives/2005-10/1130678537.Cs.r.html


for one possible reason for the choice of 44.1kHz sampling,

Regards,



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Postby Panrock » Fri Oct 17, 2008 3:35 am

After seeing that beautiful 1934 Tekade 180-line mirror-screw
receiver ... I must have one!

But the only way I'll ever be able to have one is to make one.
Not to be lightly undertaken! But once the aperture correction
has been added to my present rig I'll move on. I think a high
definition mirror screw really will have to be the next project... :P

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