NBTV on HAM

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NBTV on HAM

Postby DrZarkov » Sat Mar 24, 2007 7:01 pm

As I understood, there are transmission every saturday at 8.00 pm english time at about 3700 kHz. Is this just "chat", or are there any NBTV-transmission? If yes, in which standard? I think 12,5 frames/sec is too much for a HAM-frequency on shortwave? What is the club standard on shortwave, if there is any?
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Postby Klaas Robers » Fri Mar 30, 2007 5:26 am

It is chat. The bandwidth of SSB is far too small to carry NBTV. As well the SSB-system without reference carrier is unsuitable for waveform sensitive signals.
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Postby DrZarkov » Fri Mar 30, 2007 7:10 pm

Thank you, I've expected that answer, it would have been too nice... Are there any NBTV transmissions on any frequencies? SSB is too small, of course, using AM would be strange, but not illegal. There is software, using lower framerates than 12.5, beginning with about 2 frames/sec.

(I'm not a radio amateur, I'm an "only-listener", but my shortwave-radio is connected to a PC in order to receive SSTV and weather-fax. )
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Ham NBTV

Postby Stephen » Sat Mar 31, 2007 12:03 am

According to the NBTVA Handbook, the ham radio transmission standards for NBTV signals are as follows:

AM
Polarity: negative, sync is the largest HF amplitude, white the smallest.
Mod. depth: 90%, white HF amplitude is 10% of max. HF amplitude.
Bandwidth: 20 kHz.

FM
Polarity: positive, white is the highest frequency, sync the lowest.
Deviation: 15 kHz peak to peak.
Bandwidth: 35 kHz, occupies 3 channels in the 12½ kHz grid.

As far as I know, these are permissible on any of bands that permit these modes. However, with respect to AM it would be more desireable to have an AM transmitter with a VSB modulator to achieve less bandwidth and better signal to noise ratio. It is my understanding that the 2003 75th anniversary transatlantic transmissions on 15 metres used AM transmitters with VSB modulators and a 12 kHz bandwidth.
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Postby DrZarkov » Sat Mar 31, 2007 6:03 am

But currently nobody is using it on a more or less regular basis?
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Ham NBTV

Postby Stephen » Sat Mar 31, 2007 6:10 am

I do not know the answer to that. I let my ham license expire a number of years ago and I have no equipment or aerials set up at present for lack of time. Perhaps someone else out there has an answer.

Certainly if I had more time I would get my license back and get on the air with NBTV using the VSB AM mode.
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Postby DrZarkov » Sat Mar 31, 2007 6:43 am

Time... always a big problem, for me too... :wink: But I saw how many "HAM-people" are member of the club, so I thought there must be more activity "on air". So I have no excuse to make my own licence.
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