Sec. 74.643  Interference to geostationary-satellites.

    These limitations are necessary to minimize the probability of 
harmful interference to reception in the bands 6425-6525 MHz, 6875-7075 
MHz and 12.7-12.75 GHz on board geostationary space stations in the 
fixed-satellite service (Part 25).
    (a) 6425 to 6525 and 6875 to 7075 MHz. No directional transmitting 
antenna utilized by a fixed station operating in these bands shall be 
aimed within 2 degrees of the geostationary-satellite orbit, taking into 
account atmospheric refraction. However, exception may be made in 
unusual circumstances upon a showing that there is no reasonable 
alternative to the transmission path proposed. If there is no evidence 
that such exception would cause possible harmful interference to an 
authorized satellite system, said transmission path may be authorized on 
waiver basis where the maximum value of the equivalent isotropically 
radiated power (EIRP) does not exceed:
    (1) +47 dBW for any antenna beam directed within 0.5 degrees of the 
stationary satellite orbit or
    (2) +47 to +55 dBW, on a linear decibel scale (8 dB per degree) for 
any antenna beam directed between 0.5 degrees and 1.5 degrees of the 
stationary orbit.
    (b) 12.7 to 12.75 GHz. No directional transmitting antenna utilized 
by a fixed station operating in this band shall be aimed within 1.5 
degrees of the geostationary-satellite orbit, taking into account 
atmospheric refraction. However, exception may be made in unusual 
circumstances upon a showing that there is no reasonable alternative to 
the transmission path proposed. If there is no evidence that such 
exception would cause possible harmful interference to an authorized 
satellite system, said transmission path may be

[[Page 424]]

authorized on waiver basis where the maximum value of the equivalent 
isotropically radiated power (EIRP) does not exceed +45 dBW for any 
antenna beam directed within 1.5 degrees of the stationary satellite 
orbit.
    (c) Methods for calculating the azimuths to be avoided may be found 
in: CCIR Report No. 393 (Green Books), New Delhi, 1970; in ``Radio-Relay 
Antenna Pointing for controlled Interference With Geostationary-
Satellites'' by C. W. Lundgren and A. S. May, Bell System Technical 
Journal, Vol. 48, No. 10, pp. 3387-3422, December 1969; and in 
``Geostationary Orbit Avoidance Computer Program'' by Richard G. Gould, 
Common Carrier Bureau Report CC-7201, FCC, Washington, DC, 1972. This 
latter report is available through the National Technical Information 
Service, U.S. Department of Commerce, Springfield, VA 22151, in printed 
form (PB-211 500) or source card deck (PB-211 ).

[52 501 FR 7143 , Mar. 9, 1987]