A TV signal carries a lot more information that a standard radio signal does ...
it has to give the receiver enough information to draw a picture and color it,
in addition to just making sound.
In order to carry more information, the TV signal has to spread over wider band
of frequency, or a wider 'channel' that a radio signal occupies.
Example: The AM radio band, between 550 and 1700 on your dial, accommodates
many radio stations in a band of roughly 1.2 MHz. And the FM radio band, between
88 and 108 on your dial, accommodates many FM stations in a band of 20 MHz.
But each and every TV channel is given a space of 6 MHz to operate in.
Partly related to this reasoning is the fact that all broadcast TV operation takes place
at frequencies higher than any commercial AM radio, and most TV is at frequencies
that are also higher than all FM radio.
