What is the broadcasting range of a typical FM radio station?

Question

My guess is that the range is related to the amount of power the transmitter receives, so theoretically if given enough power a radio station in L.A. can interfere with one in New York using the same frequency, but at some point it becomes too expensive to supply that much power, so what is the typical broadcasting range?

Answer 1

The limitation is not power or earth curvature but mutual interference with another station using the same or adjacent frequencies. Most commercial FM stations fall under Class A or Class C0 limitations. A Class A station has its ERP and HAAT adjusted so the it will cover 28.3 km distance at a signal level of 60 dBu. This is the protected service area. The Class C0 stations has its ERP and HAAT adjusted to cover 83 km distance at the 60 dBu protection contour. In situations where there is no limiting interference (like Wyoming eg), a station can be heard with the typical car FM receiver out to the 40 dBu contour or about 139 km.  The FCC uses spacing criteria based on the station class of operation to assure that stations do not overlap their respective protected coverage (60 dBu) contours.

Answer 2

The FCC will mandate the ERP (effective rated power) for the broadcast station and the freq it can operate on. The ERP of the station will usually not allow it to broadcast more than 50 miles or so.There are other factors that come into play as well, like elevation, and terrain. Other than that the curvature of the earth starts to come into effect and the transmitter will not be heard.

Answer 3

FM is limited to line of sight, so you will not receive signals over the horizon. And this depends on how high the transmitting antenna is.

Power of the transmitter is also part of the equation.

Typical ranges are 50 miles.

Answer 4

Just as billrussell42 say, its usually limited by line of sight of the horizon (upwards of 50 miles). The more complicated answer would deal with the inverse cube time transmitting power times distance unit away from the transmitter

There are times when due to the atmosphere, FM signals (and TV signals) tend to go further. This is called tropospheric ducting.

Answer 5

Actually the frequencies that US FM stations operate at are mostly line of sight - there is little reflection or 'skip' for FM stations or TV stations for that matter - the antenna has to be pretty high to reach out very far - typically ranges are 100 miles or less depending on the topography of the surrounding area.  If you were in orbit, you might experience the interference between stations as there is still a detectable signal at 1000 miles out,  but because it is line-of-sight for the most part, LA station won't interfere with NY stations (unless there is a solar flare 'aiding' in reflecting signals back to earth...

Answer 6

In general, the aim when setting up a transmitter is to reach the target audience. An initial installation would consider just how far the station would need to reach before designing the antenna and selecting the power. For exactly the reason you have mentioned, the power is kept to the lowest that would accomplish the job. Not because interference would be much of an issue (FM has what is known as "Capture" which means the strongest signal is the one received. As well, the signal does not normally go beyond the horizon) but because on occasions, the signal could be boosted (under "Freak conditions") and then it might cause trouble.

Major costs when running a commercial station is the power. There is no incentive to use more than the bare minimum.

Answer 7

i would say state limits but like (90 miles)