Determining a radio signal's range If I know the:


*

*Frequency

*Effective Radiated Power

*Height Above Average Terrain

*Radiation Center Above Mean Sea Level

*Radiation Center Above Ground Level


of a radio signal / tower, is there a way to determine the rough range of the radio signal?
 A: There is, but it takes a lot of data. Further, depending on the frequency, the signal can bounce around. Commercial radio stations are required by the relevant regulating agencies to have a survey done. This survey produces a report explaining exactly what you are looking for. However, this is usually done by a consultant who specializes in this kind of survey.
That being said, you can make guesstimates. These are very rough. ~100mW, a few houses, maybe a block. Five watts I'd say a couple miles, give or take. I can hit the local repeater on 145.37 on five watts and a good antenna from roughly a 30 minute drive away. 100 watts is good enough for DX work, can go quite far. Under the right conditions, you can go across country on five watts.
Commercial radio stations use a lot more power, upwards of a kilowatt. This is chiefly because radios for the FM and AM broadcast bands lack an RF pre-amplifier. Ham radio equipment and the like has an RF pre-amp, and as such can pick up much weaker signals. Further, remember that the intensity of the signal drops off with the square of the distance. It's not uncommon to have the antenna having only a few picowatts to work with when receiving.
