RadioBanter - View Single Post

August 18th 04, 04:58 AM

(Clay Denski) wrote in message . com...
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.
......snip........................................ ...................
It is quite easy to build a receiver that will give you all the
stations in your area all mixed together. It is called a crystal
detector. The thing it needs to start separating the stations is to
add a tuned circuit composed of a coil and a variable condenser. When
the tuned circuit is added to the crystal detector, the stations that
were on top of each other will appear at different points as the
condenser is turned. Some sound from adjacent stations will still be
heard as this arrangement is not very selective. When good coils,
filters, and digital filters are used in a radio, it is very selective
and you only hear the station you are tuned to. Actually, there is
much more to this topic, but a good place to start is "The Radio
Amateur's Handbook" found at any library. "Resonant Circuits" will
probably tell you more than you want to know.....ken.....