This map is drawn using engineering data from the FCC. The coverage pattern for an FM station is calculated using the effective radiated power (ERP) of the station and the antenna height above average terrain (HAAT). The HAAT is calculated in all directions based upon the average ground elevation between 1.5 and 10 miles from the station in each direction.
The red, purple, and blue lines correspond to the “local”, “distant”, and “fringe” predicted coverage areas of each radio station:
- Local Coverage: Within this area, you should be able to receive the radio station on almost any radio with moderately good to very good reception.
- Distant Coverage: Within this area, the signal of the radio station may be weak unless you have a good car radio or a good stereo with a good antenna. You may not be able to receive the station at all on inexpensive radios or radios with poor antennas.
- Fringe Coverage: Within this area, the station’s signal will be very weak. You may be able to receive this station if you have a very good radio with a good antenna, but it’s possible that interference from other stations may prevent you from picking up these stations at all.
The “local”, “distant” and “fringe” lines on the FM maps correspond to the predicted 60, 50, and 40 dBμ signal strength contours respectively.
These maps are generated using the same data and most of the same algorithms that the FCC uses when trying to predict coverage of radio stations and interference with other nearby radio stations.
However, there are many factors that contribute to radio reception. One of the biggest factors is your radio; some radios will perform much better than others in trying to pick up distant radio stations. Other factors include interference from radio signals bouncing off nearby buildings (multipath interference), interference from other stations on nearby frequencies, or interference from nearby electrical equipment in your area.
Very mountainous terrain or very non-typical geology can also affect radio signals. If you’re on a mountain, you may be able to pick up radio signals much farther than indicated on our maps. Likewise, if you're in a valley, you may have trouble receiving many stations.
For more information check out our Reception FAQs.