Free from Nexus Broadcast
FM and TV propagation curves calculator
The FCC's F(50,50), F(50,10) and F(50,90) curves: how far a contour reaches, how strong the signal is at a distance, or how much power you need to put a contour where you want it.
From curves to a full study
One contour is a start. RF Navigator draws every contour on real terrain, radial by radial, checks spacing and interference against every station in the FCC's database, and builds the exhibits. Or let Nexus Broadcast do the engineering for you.
About the curves
- Numbers come straight from the FCC's own curves calculation (geo.fcc.gov), which follows the FM charts of §73.333 and the TV charts of §73.699 for low VHF (2-6), high VHF (7-13) and UHF channels.
- F(50,50) is the field exceeded at 50% of locations 50% of the time, used for FM service contours. F(50,10) is exceeded 10% of the time, used for interfering contours. F(50,90) = F(50,50) - [F(50,10) - F(50,50)] is the TV service curve (§73.619(b)(1)).
- The curves are drawn for 1 kW ERP. Field strength rises 10 dB for every tenfold increase in ERP, which is how the ERP answer is found; the result is checked back against the FCC calculation.
- HAAT is the antenna's height above average terrain in the direction you care about. The curves run from 30 to 1,600 m: lower heights use 30 m and higher heights 1,600 m. Not sure of your HAAT? Use our HAAT calculator.
For planning. Not a product of the FCC; check the FCC's own tools and an engineer before you file.