In message , Clive
writes:
[]
I think nearly all interference was caused by car ignition systems
which would have been positive going, but modern cars don't use
distributors any more so the biggest source of interference has gone
anyway.

(Won't _all_ interference be positive going, if by that you mean
stronger?)

Isn't it that interference causes ringing in overloaded circuits (or
something that rings gets amplified beyond the intended range), so that
any interference has some black and some white edges, no matter what
modulation is in use?
--
J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf

Times are bad. Children no longer obey their parents, and everyone is writing a
book. -Marcus Tullius Cicero, statesman, orator and writer (106-43 BCE)