piclist 1998\11\04\122356a >
Thread: CMOS video camera modules
picon face BY : Peter L. Peres email (remove spam text)

On Wed, 4 Nov 1998, Sean Breheny wrote:

> >TV carriers use a vestigial side band.  Only the center + the uppper side
> band
> >are transmitted.  There is a small lower side band where the FM audio
> hangs out.
> Dan, are you sure?

He is very right.

> I thought I had seen Amateur TV transmitters which use full double side
> band video. In fact, I believe that the reason why vestigial side band is

Yes, because it's a royal pain to remove the other sideband at high
frequency. Broadcast TV uses very elaborate schemes to do this.

> used instead of SSB is that some vestige of the other sideband(and the full
> carrier) is required for downward compatibility with DSB receivers (not
> sure of this last assertion).

The carrier isn't there at all. In fact, it is there, but this is
deliberate. A 10% RF power corresponds to the sync tips and this is there
to allow the sound intercarrier demodulation to function during sync tips.

> In my case, I don't care about the audio, I only need video. Will it make a
> difference in this case?

No. A SSB TV receiver will receive a DSB transmission fine. The other way
around it won't work. The video game/VCR modulators are DSB for the
reasons explained above.



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See also: www.piclist.com/techref/displays.htm?key=video
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