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Date: Wed, 31 Jul 2002 09:15:27 +0200

FM Station Classes and Service Contours
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The following table lists the various classes of FM stations, the reference
facilities for each station class, and the protected and city grade contours
for each station class. A contour may be visualized by imagining a rough
circle surrounding a transmitter site at some distance, where the circle
represents a certain field strength value, with greater radio field
strengths inside, and lesser radio field strengths outside. The distances to
the contours herein were derived using the maximum effective radiated power
(ERP) and antenna height above average terrain (HAAT) combination permitted
for each station class (see Section 73.211), and assumes uniform (flat)
terrain in all directions. In practice, the distances to a specified contour
for a given FM station in a given direction will vary from the listed value
depending on the effects of terrain in that direction.

The listed values are for commercial FM stations. This data also holds true
for noncommercial educational stations, except that the 70 dBu city grade
requirement of 47 CFR Section 73.315(a) does not apply to noncommercial
educational stations in the portion of the FM band reserved for
noncommercial educational use (88.1 to 91.9 MHz). Please note, however, that
the 60 dBu contour must encompass at least a portion of the community of
license. In addition, please note that the distances to reserved band
noncommercial educational stations' protected contours for Class B and Class
B1 stations are the same as the distances listed for Class C2 and Class C3
stations, respectively, since the protected contour for all reserved band
stations is 60 dBu ( 1.0 mV/m ).

For different combinations of ERP and HAAT, you may determine the applicable
FM station class by using our FM propagation curves calculations program and
comparing the result with the table below. Be sure to use the 60 dBu
F(50,50) contour, since it is on the basis of that contour (not the 70 or 54
or 57 dBu contour) that equivalence between facilities is determined.

[ For FM minimum separation requirements, especially for commercial FM
stations, please see our document FM Radio Station Spacing Standards. ]
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Reference (Maximum) FM Proteced Distance to Distance to
Facilities for Station or Primary Protected or 70 dBu or
Class (see 47 CFR Service Primary Service 3.16 mV/m City
Section 73.211) Contour Contour Grade or
FM Station ERP in kW / HAAT in Principal
Class meters dBu mV/m Community Con.
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Class A 6.0 kW / 100 meters 60 1.0 28.3 km 16.2 km

Class B1 25.0 kW / 100 meters 57 0.71 44.7 km 23.2 km

Class B 50.0 kW / 150 meters 54 0.50 65.1 km 32.6 km

Class C3 25.0 kW / 100 meters 60 1.0 39.1 km 23.2 km

Class C2 50.0 kW / 150 meters 60 1.0 52.2 km 32.6 km

Class C1 100.0 kW / 299 meters 60 1.0 72.3 km 50.0 km

Class C 100.0 kW / 600 meters 60 1.0 91.8 km 67.7 km

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km/1.609 = miles
feet = 3.281 x meters
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Notes: Class B and B1 stations are authorized only in Zones I and I-A, which
include the following states and areas: CA (south of 40° latitude), CT, DC,
DE, IL, IN, MA, MD, coastal ME, MI (south of 43.5° latitude), NJ, NH (south
of 43.5° latitude), NY (south of 43.5° latitude), OH, PA, PR, RI, northern &
eastern VA, VI, VT (south of 43.5° latitude), southeastern WI, WV. Class C,
C1, C2, and C3 stations are not authorized in Zones I or I-A, but may be
authorized elsewhere. See Section 73.205 for the exact zone boundaries.