This is probably a silly question but...

[mattyw]

FM means frequency modulation, right. so how can you transmit on say 96.3MHz when your actually modulating the frequency?

 

[mattyw]

96.3MHz is purely an example od a defined frequency.

 

[#12]

The definition is that the 96.3 is the frequency that you are transmitting when no other signal information is included in the carrier wave. As soon as you add frequency modulation, the carrier frequency starts changing back and forth around the center frequency.

 

[mattyw]

ok thanks.

 

[mattyw]

What kind of change in frequency does a normal audio signal cause?

 

[Brevor]

The maximum allowed frequency deviation in the FM broadcast band is +/_ 75 Khz. 150 Khz total. The actual amount at any instant depends on the frequency of the audio at that instant. It is far less than 75 Khz, The actual audio bandwidth is about 15 Khz.

 

[crutschow]

The maximum allowed frequency deviation in the FM broadcast band is +/_ 75 Khz. 150 Khz total. The actual amount at any instant depends on the frequency of the audio at that instant

That's not quite correct. The amount of frequency deviation depends upon the modulating frequency amplitude (loudness), not it's frequency. How fast the deviation occurs is determined by the modulating frequency.

 

[Brevor]

Yes Crutshow is correct it should be amplitude of the audio.

 

[audioguru]

Maybe the OP doesn't understand how little the frequency changes with FM modulation.
When modulated as loud as possible, the frequency changes from 93.525MHz to 93.675MHz. Most of the time the frequency deviation is much less, maybe from 93.59MHz to 93.61MHz.