Signal is the emission of interest, however it occurs. Noise is the other stuff. In common use though people mentally (and literally) drop the first word from "modulated signal" and seize upon signal. It's normal and writers should make an effort to use unmodulated or, probably better, natural in such descriptions. Emission isn't a bad word for this context, but it's still all encompassing and easy to mentally go the wrong direction when reading it.
Probably, but I think the post you are responding to is talking about the sort of modulation that artificially alters a radio carrier wave in order to encode information.
