> I have a question about composite (CVBS) video and analog broadcast TV in
> NTSC land.  Going from a composite video source to an RF input on a TV
> usualy would be done with a "modulator'  but the real question is,  does the

The CVBS signal is 'air ready'. Simple modulators indeed take the CVBS input and
mix it in a RF mixer with a VHF or UHF carrier to yield a double side band
signal which is interpreted by any TV receiver as 'valid'. Sound modulation is
usually a separate issue, and a second FM carrier is generated for this. A
simple video only modulator consists of a single transistor oscillator and a
diode mixer. One with sound adds one more transistor (i.e. 2 total) and a few
more diodes. The signals produced by such modulators are not OK for transmission
over the air or in large cable systems. Modulators which generate the accurate
signals needed for professional use are significantly more complex (100 times
and more).

Component signal modulators (non-CVBS i.e. separate luma chroma and sync) are
much more complex.

Here is a very simple video only modulator (color but no sound) which uses a
special harmonics generator technique to cover all bands simultaneously:

http://petlibrary.tripod.com/rfmod.htm

-- Peter


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