Frequency Modulation

If FM radios work by modulating the frequency, how is it that we can tune into a specific channel, and hear a song or station? Wouldn't the channel need to be modulated along with the varying frequency?

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That is the work of Band-Pass Filter . en.wikipedia.org/wiki/Band-pass_filter –  Mr.ØØ7 May 9 '13 at 2:56
The details of how FM works are a deeper question than just how signals can be selectively filtered, so I don't see this as a duplicate of 13599. –  dmckee May 9 '13 at 3:05

The frequency of the signal is modulated in a relatively narrow band, and drives the audio circuit in proportion to the resonant power between the signal and a resonating circuit tuned to almost the range where the signal resides.

The result is that the power in the audio circuit varies with the frequency of the driving signal

Other signals are far from the resonant frequency of the tuner and do not drive it to an appreciable degree. Further regulatory steps are taken in most place to reduce insure a minimum difference between nearby stations.

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When you say other signals are far from the resonant frequency, do you mean that FM stations are fairly spaced out? –  Anthony May 9 '13 at 3:12
When you drive a resonator (within some limits in the power of the driver and the $Q$ of the resonator) the response is strongly dependent on the difference between the driving frequency and the natural frequency of the resonator divided by a width figure that is proportional to $1/Q$. The next station over differs in frequency by many times that width so there is negligible response from the resonator. –  dmckee May 9 '13 at 3:15
This is why FM radio stations in the US use the odd points only. 98.1, 98.3, 95.5, 98.7, 98.9, etc. (all in MHz). There are no .{0,2,4,6,8} FM stations. They are spaced out by 200 KHz even though each station is only about 25 - 50 KHz wide which gives about 75 KHz of padding on each side. –  Brandon Enright May 9 '13 at 23:48