NBTV in general and CB radio in particular

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NBTV in general and CB radio in particular

Postby Harry Dalek » Sat Mar 24, 2018 10:05 pm

Link here to Narrow band NBTV experiments .
https://translate.google.com/translate? ... edit-text=
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV in general and CB radio in particular

Postby DrZarkov » Sun Apr 29, 2018 2:24 am

Interesting discussion. I wonder why he had so bad results. Well, I tried to transmit NBTV via a common FM radio transmitter (legal here in Germany) on the normal FM band inside my living-room. The result was also not sufficient.
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Re: NBTV in general and CB radio in particular

Postby Harry Dalek » Sun Apr 29, 2018 9:30 pm

DrZarkov wrote:Interesting discussion. I wonder why he had so bad results. Well, I tried to transmit NBTV via a common FM radio transmitter (legal here in Germany) on the normal FM band inside my living-room. The result was also not sufficient.


Reading old magazines Slow scan was very much used in your part of the world on CB ,NBTV that was the first i heard any one trying it should be fine ? i am not sure why the FM try was a problem.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV in general and CB radio in particular

Postby DrZarkov » Tue May 01, 2018 4:11 am

I blame it to the poor quality of my FM transmitter and to the full FM-band here in the area between the Netherlands, Belgium and Germany.
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Re: NBTV in general and CB radio in particular

Postby Klaas Robers » Sun May 06, 2018 10:06 pm

The problem of NBTV over CB-funk is absolutely the bad low frequency response. For NBTV you need at least a low frequency cut off lower than 12 Hz, better is 1 Hz. The CB-funk does not go lower than 300 Hz and is far from linear in the speech bandwidth. It is optimised for speech recognition an not at all for video signals.

SSTV overcame this problem by using audio FM, a tone, frequency modulated between 1200 Hz and 2300 Hz. Then the demodulated band is straight form 0 (!!) to 1 kHz. That is why SSTV works over radio and telephone links.
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Re: NBTV in general and CB radio in particular

Postby DrZarkov » Wed May 30, 2018 11:14 pm

That is very likely the problem with the FM-transmitters, too. As CB-radio (at least in Europe) today is usually in FM, too, wouldn't it be possible to modulate the NBTV-signal in AM on a lets say 1000 Hz signal?
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Re: NBTV in general and CB radio in particular

Postby Klaas Robers » Thu May 31, 2018 7:22 pm

In fact that was what Cop Mac Donald used first. But amplitude disturbances then give visible distortions of the picture. So they switched to FM modulation of an audio tone.
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