Radio station frequencies

[David H]

Why do radio stations change their frequence every 50 or so miles? As it would obviously be easier to keep one for each station nationally, there must be a technical problem if they tried to do this.

[darth vader]

I think its so the transmitters don't "bleed" over each other's signal and create a distortion

[phlapp]

Yes! as darth said, they can cross over into each others 'zones'. This is more of a problem on the FM wave band as it only has a short range when it is transmitted! However, new radio technologies are getting over this by automatically re-tuning to the strongest reception frequencies of the radio station being listened to as you travel through transmitter zones!