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FM and TV Propagation Curves Calculations

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 http://www.fcc.gov/fcc-bin/audio/fmclasses.html.

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.


NTSC (analog) Television

For NTSC TV stations, the service contours are as follows (from Section 73.683 and Section 73.685):

Channels Grade B
Service Contour
Grade A
Service Contour
City Grade
Service Contour
Channels 2 through 6 47 dBu 68 dBu 74 dBu
Channels 7 through 13 56 dBu 71 dBu 77 dBu
Channels 14 through 69 64 dBu 74 dBu 80 dBu
Frequencies corresponding to TV channels are available from Section 73.603.


Digital Television (DTV)

For DTV TV stations, service is defined to exist where the received signal strength exceeds the limit shown in the following table, using the F(50,90) propagation curves. These field strength values are defined in Section 73.622 and Section 73.625).

Channels DTV Noise-Limited Service Minimum Field Strength over Community of License
Channels 2 through 6 28 dBu 35 dBu
Channels 7 through 13 36 dBu 43 dBu
Channels 14 through 69 41 dBu 48 dBu

Note: Using ERP and HAAT to define the F(50,90) contour may not give identical results to the more complex methods of noise-limited coverage prediction used for DTV allocations work.

Default values are already checked but may be changed:

Metric units [ meters, km ]
English units [feet, miles ]




Kilowatts (kW)
dBk [ dBk=10 * log10 (KW) ]




dBu [ dB above 1 microvolt per meter for 1 kW ERP ]
mV/m [ millivolts per meter ]




FM and NTSC TV Channels 2 through 6
NTSC TV Channels 7 through 13
NTSC TV Channels 14 through 69
Digital TV Channels 2 through 6 [ F(50,90) only ]
Digital TV Channels 7 through 13 [ F(50,90) only ]
Digital TV Channels 14 through 69 [ F(50,90) only ]




F(50,50) curves for Service Contours (FM & NTSC TV)
F(50,10) for Interfering Contours
F(50,90) for DTV (Digital Television) Service

NOTE: 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.




Field Strength, given a Distance
Distance, given a Field Strength
ERP, given an HAAT and a Distance [ FM and F(50,50) service contours only ]





The original CURVES program was written by Gary Kalagian and John Boursy.
Adapted for Internet use by Dale Bickel in July 1998.
Modified June 2003 to include F(50,90) Digital TV curves.


     


Please send comments via standard mail to the Federal Communications Commission, Consumer and Governmental Affairs Bureau, 445 12th Street, S.W., Washington, D.C., 20554. Questions can also be answered by calling the FCC's National Call Center, toll free, at 1-888-Call FCC (1-888-225-5322).

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