Clay Denski wrote:
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!

Tuned circuits. The stations transmit on different frequencies, the
radio wave from "Talk" induces a current (vibrates the electrons)at
whatever carrier frequency the station transmits on, and likewise the
station transmitting "Zeppelin", but at a different frequency. The tuned
circuits in the receiver are selective and will pass the frequency they
are tuned to and reject the other frequencies. In the case of a parallel
tuned circuit, (coil and capacitor connected in parallel), the circuit
presents a high impedance at the resonant frequency (the frequency it is
tuned to) and a low impedance to other frequencies. A series tuned
circuit (coil and capacitor in series) is just the opposite, low
impedance to the resonant frequency and high impedance to other frequencies.