Why do radio frequencies always end in odd numbers?

101.1, 98.7, 93.1.

You never see any 98.4 or 97.2.
Why not?

I should have clarified....in the USA the frequencies always and in an odd number. It is interesting it is not like that in the rest of the world!

In Europe and in Asia it's seems random but it isn't.

It's back in the days of early radio the FCC set it that way to protect other stations one channel away from each other (basically less interference..that and most stations use up to that one number higher to deliver a signal pre HD radio (in other words , a normal radio station has a signal that goes from say 98.4 to 98.6 but the signal is centered at 98.5)

There are reports that HD stations however make for a signal wider than that and reports of the signals killing out of town stations are becoming normal occurance in the the trades I read.

http://en.wikipedia.org/wiki/FM_broadcas...
http://en.wikipedia.org/wiki/FM_broadcas...
http://en.wikipedia.org/wiki/FM_broadcas...

Even numbers are the work of Satan, Ned. 666!

well i've seen 91.20 in india!!

because even numbers suck.
ha
just kidding...interesting question though, I have no idea.

In the UK, where I'm based, you do see even numbers. It depends on how your country manages the allocation of frequences, and how much space it demands between each allocated frequency in order to prevent interference.

I always thought it was because FM means frequency Modulation and if there were even numbered stations their would be some overlapping "modulation" if you know what i mean.

I dont think they intentionally end in strange numbers, the stations probably buy the air time for a specific frequency (eg 101) and then depending on where you are when you tune in to the station, depends on the exact frequency that you see.

Its probably a lot more complicated than that but hey, thats the simplest answer

I believe the FCC requires it. The government site is impenetrable, but I believe the FCC assigns the frequencies on which you can transmit radio and television. some times they auction off unused frequencies, like cell phone transmissions.

those frequencies are used by private organizations on a different band. Police, Fire, EMS

The even numbers are sidebands and to give plenty of separation between the actual frequencies available for commercial use. As pointed out, there would be interference issues if we were to use them all.

There's a lot more to it and one of our more technologically astute members will pipe up about it.
-a guy named duh