"Clay Denski" wrote in message
om...
I have a very technical fundamental question about how radio works.
And no, I'm not ignorant of physics or the basics (I don't think,
anyway).. Here goes:

Say you have for simplicity two radio stations (AM for simplicity).
One is talk radio and the other plays Led Zeppelin all day. I
understand that "Talk" uses a different carrier frequency than
"Zeppelin" and that this allows my radio to tune in and detect one
without the other interfering. I also understand how a carrier wave
is modulated in AM and FM..

BUT, what I don't get is why the two do not interfere. Let me
explain.. Take a timeslice of EM radiation hitting my recieving
antenna at some moment. Some electrons in the antenna move up in
response to experiencing some energy from "Talk" station that
corresponds to a high point in the sine-wave. The same electron,
though, is pulled down a bit in response to some EM hitting it from
"Zeppelin". How does "Talk" not affect "Zeppelin" if both are shoving
the same electron in my antenna? How does my radio figure out that an
effect at the antenna is NOT an ordinary modulation of the "Talk"
carrier wave but rather of some other one and therefore to be ignored?

Thanks for answers folks!

You are thinking in the time domain where the signals are combined and hard
to separate. If you think in the frequency domain the signals are easy to
separate because of the difference in the carrier frequencies.

The filters in your radio act in the frequency domain. Their behaviour is
independant of time, but not frequency. Signals at one frequency are allowed
to pass while at another they are attenuated.

craigm