On Fri, 08 Jun 2007 20:58:04 +0000, Radium wrote:

Why not carry the luminance-signal on FM and the audio-signal on AM?

Because it would be abysmally stupid to try to do so. You'd need about
10 times as much bandwidth if you used FM for the video, and using AM
for the audio would make it susceptible to all manner of noise.

Hope This Helps!
Rich