This program uses the FM or TV television propagation curves to compute distances to contours or a field strength at a given distance. This program below gives results identical to the FCC’s CURVES and F(50,90) programs. Printable graphs of the F(50,50), F(50,10), and F(50,90) curves may be obtained on the FM and TV Propagation Graphs page.

HAAT values for a particular FM or TV station may be retrieved from the FM Query or TV Query, or may be calculated. The class of an FM station may be retrieved from the FM Query. Reference values for FM station classes are available at

FM Broadcast Radio

F(50,50) protected service contours for FM stations are the 54 dBu for commercial Class B stations, the 57 dBu for commercial Class B1 stations, and 60 dBu (1 mV/m) for commercial Class A, C3, C2, C1, and C stations, as well as 60 dBu for all classes of noncommercial educational stations (including low power FM (LPFM) stations). Please be aware that stations can often be heard in locations beyond the protected service contour, but that service is not protected from interference caused by other stations.

City coverage for commercial FM stations is defined by the F(50,50) 70 dBu contour, per Section 73.315. For noncommercial educational stations (except LPFM), coverage over the community of license is defined by the 60 dBu contour (see Section 73.515).

For the appropriate FM interfering contour, please consult Section 73.509 for noncommercial educational stations (88.1 MHz to 91.9 MHz) or Section 73.215 for commercial FM stations (92.1 MHz to 107.9 MHz).

If you already know the FM station class and the HAAT, you may find it helpful to use the FMpower program. The FMpower program will compute the effective radiated power (ERP) needed to achieve coverage equivalent to the reference (maximum) facilities for the station class.