2007-04-06 14:46:48 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
FM station bandwidth is 30Hz - 15kHz maximum. This doesn't mean that every station uses all that bandwidth all the time, but that is what is alloted to each station by the FCC.
NOTE: in response to other answers: bandwidth and channel spacing are not the same. Channel spacing is much greater than bandwidth in FM, since unlike AM, FM sidebands extend beyond the bandwidth of the modulation. Channel spacing is designed to minimize inter-station interference.
EDIT: Final comment. The question isn't clear what "bandwidth" refers to. There is the bandwidth of the transmitter carrier plus sidebands, for which 150kHz IS ALLOWED. However, in communications systems, bandwidth is used to indicate information-carrying capacity, and for FM transmission, that is the permitted bandwidth of the MODULATION, which is 15kHz. So it depends on which bandwidth you are talking about. From a listening standpoint, the station's carriers could be 2MHz apart, but you would only receive 15kHz of information.
2007-04-06 14:56:41 · answer #1 · answered by gp4rts 7 · 1⤊ 0⤋
The bandwidth or the channel spacing for audio FM is 100 kHz. Channels are assigned with a guard channel between transmitters. This prevents adjacent channels from interfering with one another. This is the same with TV stations, i.e. 7, 9, 11, 13 (in the continue VHF band).
The audio signal is limited to less than 20 kHz with a modulation factor of 5 times (or modulation index of 5). This means you need 5 times the bandwidth to send the baseband signal, thus 5 x 20 kHz = 100 kHz. In real practice the baseband audio signal is limited to 15 kHz, thus the modulated FM signal is within 150 kHz. By using more bandwidth, you effectively trade that for 5 times reduction in noise. This is why FM has less static noise than AM. This is for analog signal transmission.
Transmitting a digital signal can employ other signal processing gains and compression techniques to reduce the required bandwidth and/or reduce noise.
2007-04-06 15:12:32 · answer #2 · answered by ? 6 · 1⤊ 0⤋
What gp4rts was talking about is the modulation range for audio. That has something to do with the bandwidth, but doesn't quite get it. The signal bandwidth is allowed to be 150KHz. This with a guard band of 25 KHz on each end gives the 200KHz spacing between channels in the FM commercial band.
2007-04-06 17:28:50 · answer #3 · answered by Anonymous · 0⤊ 0⤋
No that's not right. FM bandwidth is 200 kHz, that is why stations are 0.2 MHz apart.
2007-04-06 15:01:54 · answer #4 · answered by rondoggnuts 3 · 0⤊ 1⤋