Sec. 101.145  Interference to geostationary-satellites.

    These limitations are necessary to minimize the probability of 
harmful interference to reception in the bands 2655-2690 MHz, 5925-6875 
MHz, and 12.7-12.75 GHz on board geostationary-space stations in the 
fixed-satellite service.
    (a) Stations authorized prior to July 1, 1976 in the band 2655-2690 
MHz, which exceed the power levels in paragraphs (a) and (b) of this 
section are permitted to operate indefinitely, provided that the 
operations of such stations does not result in harmful interference to 
reception in these band on board geostationary space stations.
    (b) 2655 to 2690 MHz and 5925 to 6875 MHz. No directional 
transmitting antenna utilized by a fixed station operating in these 
bands may 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.
    (c) 12.7 to 12.75 GHz. No directional transmitting antenna utilized 
by a fixed station operating in this band may be aimed within 1.5 
degrees of the geostationary-satellite orbit, taking into account 
atmospheric refraction.

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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 +45 dBW for any antenna beam directed within 1.5 degrees of the 
stationary satellite orbit.
    (d) 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-211 501).