Hi.
What would be the minimum radio frequency that NTSC video can modulate for a 'decent' quality real time video ?

What parameters are involved in calculation ? Corresponding bandwidth, ...

And for black-and-white video ?

 

The general rule of thumb is 10:1 ratio of the carrier and modulating signals for AM.

This is mainly because of demodulation. With simple filters it's very hard not to have detectable carrier ripple in the demodulated signal at 10:1 with an envelope detector.

 

Hello,

With the @nsaspook theory, you can understand why the TV channels start at about 50 Mhz:
https://en.wikipedia.org/wiki/Television_channel_frequencies

Bertus