2110-2130 Mc/s and 2160-2180 Mc/s may be authorized for use by control and repeater stations functioning in conjunction with the Domestic Public Land Mobile Radio Service on the condition that the emission bandwidth is limited to the minimum necessary to serve the purpose required. Channel bandwidths in excess of 800 kc/s will not be authorized. In each of these bands, the highest frequency which will not cause harmful interference to any other station shall be assigned. Stations authorized prior to January 15, 1963, to operate on frequencies in the bands 2130-2160 Mc/s and 2180-2200 Mc/s may continue to operate on such frequencies until January 15, 1968.

(f) The frequencies listed in this paragraph are available for assignment to control and repeater stations functioning in conjunction with the Domestic Public Land Mobile Radio Service, on a shared basis with certain other radio services. A repeater station normally will not be authorized unless the land mobile radio system with which it is associated is continuously open for public correspondence and the emission of the repeater station are under the operational surveillance of the land mobile system's operating personnel.

72-76 Mc/s Band 1

(1) Wherever feasible, the frequencies 35.22 Mc/s and 35.58 Mc/s shall be assigned for use in any area prior to the assignment of the frequencies 43.22 Mc/s and 43.58 Mc/s.

(2) If an applicant for authorization to provide an exclusive one-way signaling service provides, or proposes also to provide, General or Dispatch service in accordance with paragraphs (a), (b) and (c) of this section, the application for a one-way facility should be supported with full information to show why the proposed signaling service could not be provided in connection with the base station facilities used for such General or Dispatch service.

(e) On a shared basis with fixed stations in the Point-to-Point Microwave Radio Service, frequencies in the bands

99-205-60– -4

1 Assignments made to stations on frequencies in this band are subject to the condition that no harmful interference will be caused to operational fixed stations or reception of television stations on channels 4 or 5. (See § 21.103.) Existing stations authorized in the 73 to 74.6 Mc/s band as of December 1, 1961, may continue to operate and shall not be required to afford protection to the radio astronomy service.

(g) New control and repeater stations will not be authorized in the 890-940 Mc/s band. However, stations which were authorized to operate on such frequencies on April 16, 1958, may be granted renewed licenses subject to the following conditions:

(1) Operations shall not be protected against any interference received from the emission of industrial, scientific, and medical equipment operating on 915 Mc/s or from the emission of radiolocation stations in the 890-942 Mc/s band.

(2) No harmful interference shall be caused to stations operating in the radiolocation service in the 890-942 Mc/s band.

(h) For assignment to base stations for use exclusively in providing a oneway signaling service to mobile receivers as follows:

(1) Communication common carriers engaged also in the business of affording public landline message telephone service:

geographical boundary of the nearest urbanized area having a population over 300,000 (as determined and defined in the most recent census reports of the U.S. Bureau of the Census).

(2) The repeater station, and the point to which its transmissions are directed, are located over 50 airline miles from the nearest geographical boundary of the nearest urbanized area having a population over 300,000 (as determined and defined in the most recent census reports of the U.S. Bureau of the Census).

(3) The effective radiated power of the control or repeater station does not exceed 150 watts.

(4) The use of the frequencies by a control or repeater station will not cause harmful interference to any other station authorized to use such frequencies and shall be on a secondary basis to the provision of mobile and rural radio service by other classes of stations.

(5) Series operation of more than one control or repeater station is not involved.

NOTE: The provisions of subparagraphs (1) and (2) of this paragraph may be waived by the Commission upon a factual showing, supported by such engineering proof as may be necessary, that all of the currently assignable pairs of 152-162 Mc/s band frequencies listed in paragraph (c) of this section are not assigned or applied for within interference range of existing or possible station assignments within the urbanized area having a population of over 300,000 and, upon a satisfactory showing, that in such area over a substantial period of years the growth of the public land mobile radio service has not been hampered and is not likely to be hampered by a shortage of frequencies allocated to such service in the 152 to 162 Mc/s band. Facilities authorized under the provisions of such waivers shall be on a secondary basis and subject to the condition that, in the event the frequencies are required for assignment to base and mobile stations in the area, operation thereon shall be terminated within 60 days after notice is received from the Commission.

[28 F.R. 13002, Dec. 5, 1963, as amended at 31 F.R. 10361, Aug. 2, 1966; 33 F.R. 4577, Mar. 15, 1968; 33 F.R. 7238, May 16, 1968]

§ 21.502 Classification of base stations.

Base stations in the Domestic Public Land Mobile Radio Service shall be classified, as set forth below, according to their transmitting antenna height above average terrain in any particular direction and according to their effective radiated power in the horizontal plane of the antennas in that direction.

(b) In any particular case, where it appears that unusual radio wave propagation conditions are involved, the Commission may require greater separation than indicated in the tables in paragraph (a) of this section, or make assignments at lesser station spacing. Reference may be made to § 73.611(d) of this chapter for methods of computing mileage separation between station locations. [32 F.R. 12041, Aug. 23, 1967]

§ 21.504 Service area of base station.

(a) The limits of reliable service area of a base station engaged in two-way communication service with mobile stations are considered to be described by a field strength contour of 31 decibels above one microvolt per meter for stations operating on frequencies in the 35-44 Mc/s band, 37 decibels above one microvolt per meter for stations operating on frequencies in the 152-162 Mc/s band, and 39 decibels above one microvolt per meter for stations operating on frequencies in the 450-460 Mc/s band. The limits of reliable service area of a base station engaged in one-way signaling service is considered to be 43 decibels above one microvolt per meter. Service within such areas is generally expected to have an average reliability of not less than 90 percent.

(b) The field strength contours described in paragraph (a) of this section shall be regarded as determining the limits of the reliable service area of the related base stations for the purpose of providing protection to such stations from co-channel electrical harmful interference and defining the area within which consideration will be accorded claims of economic competitive injury. The following F(50,50) radio wave propagation charts shall be used in connection with making such determinations, and shall be used in combination with the following F(50,10) radio wave propagation charts in the determination of areas of harmful interference between co-channel stations: