47 CFR § 22.625 - Transmitter locations.
(a) 928-960 MHz. In this frequency range, the required minimum distance separation between co-channel fixed transmitters is 113 kilometers (70 miles).
(b) 470-512 MHz. The purpose of the rule in paragraph (b)(1) of this section is to define the areas in which the 470-512 MHz channels are allocated for public mobile use. The purpose of the rules in paragraphs (b)(2) and (b)(3) of this section is to reduce the likelihood that interference to television reception from public mobile operations on these channels will occur.
(1) Control transmitter locations. Control transmitter locations must be within 80 kilometers (50 miles) of the designated locations in this paragraph.
|Urban area||N. latitude||W. longitude|
|Los Angeles, CA||34°03′15.0″||18°14′31.3″|
|New York, NY||40°45′6.4″||73°59′37.5″|
|San Francisco-Oakland, CA||37°46′38.7″||122°24′43.9″|
Note: Coordinates are referenced to North American Datum 1983 (NAD 83).
(2) Protection from intermodulation interference. Control transmitter locations must be at least 1.6 kilometers (1 mile) from the main transmitter locations of all TV stations transmitting on TV channels separated by 2, 3, 4, 5, 7, or 8 TV channels from the TV channel containing the frequencies on which the control station will transmit. This requirement is intended to reduce the likelihood of intermodulation interference.
(3) Co-channel protection from control transmitters with high antennas. This paragraph applies only to control transmitters that utilize an antenna height of more than 152 meters (500 feet) above average terrain. The distance between the location of such a control transmitter and the applicable protected TV station location specified in this paragraph must equal or exceed the sum of the distance from the control transmitter location to the radio horizon in the direction of the specified location and 89 kilometers (55 miles - representing the distance from the main transmitter location of the TV station to its Grade B contour in the direction of the control transmitter). The protected TV station locations in this paragraph are the locations of record as of September 1974, and these do not change even though the TV stations may have been subsequently relocated.
(i) The protected TV station locations are as follows:
|Control transmitter frequency range||Protected TV station location|
|470-476 MHz||Washington, DC 38°57′17″ 77°00′17″|
|476-482 MHz||Lancaster, PA 40°15′45″ 76°27′49″|
(ii) The distance to the radio horizon is calculated using the following formula: