Destructor: FM works better.

You see, max power output with AM is about 40%. FM is always 100% since the amplitude is always the same; only the frequency changes.

If you like to know more, find your local ham radio club.

Some serve hotdogs.

I hereby demand that I be given a Fark account: Ivo Shandor: Sounds like AM is 60% more power-efficient. Why waste the energy?

AM is actually really bad...you have two side bands, each carries the same information so one is redundant. Two thirds of the broadcast power goes into the carrier, so really, one sixth - 16% - of the power is being used to carry signal. It does have the advantage that it is easy to tune - you have the carrier to lock onto.

Single Side Band with Suppressed Carrier dumps the carrier and one of the sidebands, and puts all the energy into the other. Good - much more signal power from the transmit power, and since you only have one sideband, the bandwidth required is much less. You can do clear voice with less than 3KHz worth of bandwidth - Broadcast AM in the US uses 10KHz channels, broadcast FM uses 200KHz channels. Bad - harder to tune and you need to be able to create the carrier in the receiver to properly demodulate the signal, and of course if you're squeezing down the bandwidth, you're going to lose frequency response, but voice is often filtered to 300-3KHz.

This is also why FM radio sounds better for music. You've got barely 5KHz of bandwidth on the audio signal on standard AM, FM can handle 20-18KHz, and there's a VERY sharp filter at 18.1KHz, because to indicate the broadcast is FM Stereo, there's a pilot tone at 19KHz. If your radio "hears" that, it knows there's another signal higher up (23-53KHz) that has the information needed to turn the mono signal at 0-18KHz into two stereo channels. Plus, since it's always broadcasting at full power (unlike AM) it's much more resistant to noise.