Sec. 21.904  Transmitter power.

    (a) The maximum equivalent isotropically radiated power (EIRP) of a 
transmitter station in this service shall not exceed 2000 watts (33 dBW) 
except as provided in paragraph (b) of this section.
    (b) If a station uses a transmitting antenna with a non-
omnidirectional horizontal plane radiation pattern, the maximum 
equivalent isotropically radiated power (EIRP) in dBW in a given 
direction shall be determined by the following formula:

EIRP=33 dBW+10 log (360/beamwidth) [where 10 log (360/beamwidth) 
          6 dB].


Beamwidth is the total horizontal plane beamwidth of the transmitting 
antenna system in degrees, measured at the half-power points.
    (c) An increase in station transmitter power, above currently-
authorized or previously proposed values, to the maximum values provided 
in paragraphs (a) and (b) of this section, may be authorized, if the 
requested power increase would not cause harmful interference to any 
authorized or previously proposed co-channel or adjacent-channel station 
with a transmitter site within 80.5 kilometers (50 miles) of the 
applicant's transmitter site, or if an applicant demonstrates that:
    (1) A station, that must be protected from interference, potentially 
could suffer interference that would be eliminated by increasing the 
power of the interfered-with station; and
    (2) The interfered-with stations may increase it own power 
consistent with the rules; and
    (3) The applicant requesting authorization of a power increase 
agrees to pay all expenses associated with the increase in power to the 
interfered-with station.
    (d) For television transmission if the authorized bandwidth is 4.0 
MHz or more for the visual and accompanying aural signal, the peak power 
of the accompanying aural signal must not exceed 10 percent of the peak 
visual

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power of the transmitter. The Commission may order a reduction in aural 
signal power to diminish the potential for harmful interference.
[ 55 FR 46010 , Oct. 31, 1990, as amended at  58 FR 44896 , Aug. 25, 1993; 
 60 FR 36554 , July 17, 1995;  60 FR 57367 , Nov. 15, 1995]