How Narrow is "Narrow-Bandwidth"?

Forum for discussion of narrow-bandwidth mechanical television

Moderators: Steve Anderson, Dave Moll, Andrew Davie

What do you regard as a bandwidth limitation for NBTV?

Less than 10 kHz.
1
8%
Less than 15 kHz.
0
No votes
Less than 20 kHz.
9
69%
Less than 50 kHz.
1
8%
50 kHz or more.
1
8%
I do not care because I have switched to non-electric TV.
1
8%
 
Total votes : 13

100th anniversary.

Postby Steve Anderson » Fri May 11, 2007 4:58 pm

This is my 100th post on this board, so I have decided to change my Avatar which is an example of what SSTV can achieve. Sorry, but the pic is of me, I'll change it in due course....

It's done to the original (almost) Copthorne McDonald specs, 128 x 128 pixels, 8 bit greyscale.

Steve A.
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Postby DrZarkov » Fri May 11, 2007 5:05 pm

I have a small collection of old black and white TVs (with the "boring" 625 lines system which is in use since 1952 in Germany), but that is a complete different hobby, the technologie in CRT-monitors is completely different. And here we come back to the problem: A modern DLP-video projector is mechanical TV, too, but it does not fit here. On the other hand I would like to have a CRT monitor like the "von Ardenne" type, but compatible with the NBTV-standard. It would look more modern than a Televisor, but technically it is easy technology compared to a modern TV, and indeed narrow bandwidth.

So narrow bandwidth was the technical limitation of that time, which makes it a better description than mechanical TV which would include DLP-projectors or VCRs, but exclude early CRT experiments. If we want to include non electric television (until now nobody saw a working TV-set), maybe "Low Definition TV" would be the better term.
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Signal compatability.

Postby Steve Anderson » Fri May 11, 2007 5:16 pm

On the other hand I would like to have a CRT monitor like the "von Ardenne" type, but compatible with the NBTV-standard.


That is indeed the area of interest to me, keeping the signal waveform the same and using different systems for capture and display. In theory being able to display a mechanically derived signal on a non-mechanical display, and vice-versa.

There's a mention (all to briefly) of von Ardenne here..

http://www.radarworld.org/hans5.html

"Low Definition TV" would be the better term.


I believe that in the early days of the NBTVA it was called LDTV (working from my rather pathetic memory)....can others fill in the history here?...

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Postby Viewmaster » Fri May 11, 2007 6:38 pm

Many terms use the names of the famous people who discovered them.
Such as Volt, Decibel and Hertz etc.
So why not NTV....Nipkow Television? At least that will cover every type of mech scanning and altered slightly maybe much more.
I throw this into the pot. :)
Albert.
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Postby Andrew Davie » Fri May 11, 2007 9:33 pm

Viewmaster wrote:Many terms use the names of the famous people who discovered them.
Such as Volt, Decibel and Hertz etc.
So why not NTV....Nipkow Television? At least that will cover every type of mech scanning and altered slightly maybe much more.
I throw this into the pot. :)
Albert.


Personally I see no need for a name change!

"'Tis but thy name that is my enemy;
Thou art thyself, though not a Montague.
What's Montague? it is nor hand, nor foot,
Nor arm, nor face, nor any other part
Belonging to a man. O, be some other name!
What's in a name? that which we call a rose
By any other name would smell as sweet;
So Romeo would, were he not Romeo call'd,
Retain that dear perfection which he owes
Without that title. Romeo, doff thy name,
And for that name which is no part of thee
Take all myself."
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Postby DrZarkov » Fri May 11, 2007 9:43 pm

Goethe had the same opinion: "Namen sind Schall und Rauch" (names are sound and smoke). :lol:

Indeed I see no need for changing the name,
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The not the name change...

Postby Steve Anderson » Fri May 11, 2007 10:06 pm

I feel somewhat responsible for even generating this train of thought. I'm not, as I have mentioned before even suggesting a name change of NBTV(A). I was just trying to unify and encapsulate our varied interests into a short phrase or saying that in an instant is understood by Joe Public.

Steve A.

I feel that this should be the end of this discussion...let's move on...and show some pictures...
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Postby Stephen » Sat May 12, 2007 1:24 am

AncientBrit wrote:One I have not yet seen proposed would be a version of MAC, multiplexed analogue component, where 3 signals are time compressed to fit within a single NBTV line.

It would make sense for the channels to carry Y and two colour difference signals, with the Y signal occupying 0.5 of the NBTV line time, and the difference signals occupying 0.25 line time each.
A scheme that I came up with inspired by one of John Logie Baird's patents sort of approaches this. See http://www.taswegian.com/NBTV/images/SDS.pdf . An optical system projects four images of the televised picture within a 30 by 70 pixel scanning area. One is large and the other three are smaller, lining up along the top of the scanning area, and image-reversed. In Figure 5, the three small images may be red, green and blue, as indicated by the notations R, G and B. The large one is achromatic (monochrome). The large image provides detail and serves as the luminance information. The smaller images provide low detail chrominance information.

Each scanning line provides a single line of luminance detail for a single frame and a single line for one of three chrominance frames. Since the smaller images are image-reversed, the chrominance information scans in the opposite direction from the luminance information, from left to right instead of right to left. Due to the smaller size of the chrominance frames, the chrominance information is limited to one third the horizontal and vertical resolution. The luminance frame provides the detail.

The bandwidth for this scheme is exactly the same as the regular 30 line achromatic format. The sacrifice is a slight decrease in vertical resolution. The resulting picture has a resolution of 30 by 51 pixels instead of 30 by 70, changing the aspect ratio from 3:7 to 3:5. This is still respectable. Theoretically an optical converter to do this could be added to any 30 line camera or display.
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Postby Stephen » Thu May 17, 2007 9:00 am

Viewmaster wrote:Many terms use the names of the famous people who discovered them.
Such as Volt, Decibel and Hertz etc.
So why not NTV....Nipkow Television? At least that will cover every type of mech scanning and altered slightly maybe much more.
I throw this into the pot. :)
Albert.
Yes, it is about time that we honoured John Logie Baird and Paul Nipkow with some standard unit of measure. I was just thinking...why not adopt a unit of measure for television scanning lines? Why not Baird or Nipkow? The club standard would then be a 3.2 decabaird (daB) or decanipkow (daN) system. Standard definition television would be 5.25 or 6.25 hectobaird (hB) or hectonipkow (hN). I am sure that the general public would catch on and quickly embrace this. :lol:
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Postby DrZarkov » Thu May 17, 2007 4:57 pm

Steven, I was drinking coffee while reading this! Now I have to clean my keyboard! :lol:
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