FM and NTSC TV Propagation Curves Calculations

This program uses the FM or NTSC (analog) television propagation curves to compute distances to contours or a field strength at a given distance. (Digital television uses a different set of curves and is not included here.) This program gives results identical to the FCC's CURVES program.

HAAT values for a particular FM or TV station may be retrieved from the FM Query or TV Query. 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.

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 Classes A,C3, C2, C1,C, as well as 60 dBu for all classes of noncommercial educational stations on Channels 201 through 220. 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 the appropriate FM interfering contour, please consult Section 73.509 for noncommercial educational stations (88.1 MHz to 91.9 MHz) and 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.

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.

Default values are already checked but may be changed:

Metric or English Units:

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

Power in kW or dBk:

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

Field strength units:

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

Select Service being considered:

FM and NTSC TV Channels 2 through 6
NTSC TV Channels 7 through 13
NTSC TV Channels 14 through 83

Protected F(50,50) or Interfering F(50,10) field strength curves:

F(50,50) curves for Service Contours

(View the F(50,50) curves (592 KB) for FM and NTSC TV Channels 2 through 6)

F(50,10) for Interfering Contours

(View the F(50,10) curves (653 KB) for FM and NTSC TV Channels 2 through 6)

Output:

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.