Why are there no even numbered radio frequencies? I think of the stations around here, 88.7, 93.1, 93.9, 94.7, 95.5, 96.3, 99.5 so on and so on. What is on the even numbered stations? Or are there even numbered stations?
Are the even numbered stations like the 13 floor of old buildings? Or is this where the subliminal messages come from?!!
http://ask.yahoo.com/20050817.html
Why do all radio stations end in odd numbers?
Doug
Saratoga, California
Dear Doug:
In the United States, FM radio stations end in odd numbers, but AM stations do not. We are grieved to report there is absolutely no reason for this. A long time ago somebody at the FCC made the call, and that’s the way it’s been ever since.
The FCC is responsible for divvying up the radio spectrum for commercial use. It has assigned spectrums for cell phones, baby monitors, radio-controlled cars, air traffic controllers, and even the Mir space station. At this point, much of the process of assigning bandwidths simply depends on what’s still available.
As HowStuffWorks explains, FM radio operates between 88 and 108 megahertz, or millions of cycles per second. Individual stations are allotted 200 kilohertz (thousands of cycles) “slices” between odd number fractions: 90.1, 90.3, 90.5, etc.
AM radio, however, operates between 535 kilohertz and 1,700 kilohertz (note: that’s kilohertz, not megahertz), and the stations have even-numbered call signs: 610, 620, etc. FM operates at a higher frequency than AM simply because it came later: AM radio started in the '20s, but FM didn’t become popular until much later.
My very basic understanding from 20 years ago.
All radio waves travel in sign waves.
AM Radio: Operates at one frequency, but modulates(changes) the amplitute (AM) of the sign wave to transfer the data. a.k.a different wave heights are different data.
FM Radio: Operates around a base frequency, but modulates the frequency (FM) of the sign wave (constant height) to transfer the data. a.k.a. different frequency is differnet data. So they need the even numbers for the modulation around the odd numbers to embed the data and prevent cross talk of channels.
All radio waves travel in sign waves
Sign waves? ;->
yeah you know sign waves. It’s what protesters do with their signs.
The answer is that each radio station is assigned a piece of the spectrum .2 MHz wide not a single frequency. The spacing is to minimize cross talk between the stations. Think of the power versus frequency as a bell shaped curve with little curves on either side. If the curves overlap, you get interference between stations. Those spaces between the stations is where HD radio lives or will live. HD radio occupies a much narrower slice of the spectrum.