Two remarks to Graham's inputs:
It is true that in the early TV broadcast transmitters the vision and sound signals were transmitted by separate RF transmitters. However, I'm pretty sure that later the vision and sound intercarrier were first combined and then in one step modulated a single transmitter.
The same was essentially true for the VCR UHF modulators, see e.g.
https://www.maximus-randd.com/tv-tun...tml#vcrmodules. Otherwise a modulator module should contain two UHF oscillators.
Due to this method indeed a double sided RF signal was generated, occupying roughly 2 RF channels. When tuning the TV to these signals only one would give correct picture and sound, the other one only a distorted picture or sound-only.
Pieter