This document is saved at http://www.fcc.gov/mmb/asd/decdoc/letter/1987--08--11--tower.html

The Mobile Services Division of the Common Carrier Bureau is hereby reminding Part 22 licensees and permittees of their responsibility to protect existing licensees. The Commission's policy is clear. Whether by imposition of specific conditions or by operation of law, a licensee building a new facility is obligated to take all the necessary steps, including the financial burden, to correct interference problems caused by new or modified construction. See e.g., Sudbrink Broadcasting of Georgia, 65 F.C.C. 2d 691 [41 RR 2d 258] (1977); Athens Broadcasting Co., 68 F.C.C. 2d 920 [42 RR 2d 1659] (1978); Midnight Sun Broadcasting Co., 11 F.C.C. 2d 119 (1947); B&W Truck Service, 15 F.C.C. 2d 769 (1986).

Licensees and permittees planning to construct or modify a tower within 2 miles (3.2 km) of a directional AM array or within ½ (0.8 km) mile of a non-directional AM tower should take certain precautions.

If construction is planned within ½ mile (0.8 km) of a nondirectional tower the licensee should, prior to construction of the proposed tower, notify the AM station so that the station may commence operating power by the indirect method (see §73.51(e) & (f)). The common carrier shall be responsible for the installation and continued maintenance of any detuning apparatus necessary to prevent adverse effects upon the radiation pattern of the AM station. Measurements shall be taken both prior to construction of the tower and subsequent to the installation of all appurtenances thereon. Antenna impedance measurements of the AM station shall be made and sufficient field strength measurements taken at a minimum of 10 locations along each of 8 equally spaced radials to establish that the AM radiation pattern is essentially omnidirectional. The results of the field strength and impedance measurements should be reported to the Commission in an application for the AM station to return to direct method of power determination, using FCC Form 302-AM.

If construction is planned within 2 miles (3.2 km) of a directional AM array the licensee should notify the AM station so that, if necessary, the AM station may determine operating power by the indirect method and request special temporary authority (see §73.1635) from the Commission (Audio Services Division, Mass Media Bureau, FCC, Washington, DC 20554) in Washington, DC to operate with parameters at variance in order to maintain monitoring point field strengths within authorized limits (see §73.51(e) and (f)). The common carrier shall be responsible for the installation and continued maintenance of detuning apparatus necessary to prevent adverse effects upon the radiation pattern of the AM station. Both prior to construction of the tower and subsequent to the installation of all appurtenances thereon a partial proof, as defined by §73.154(a) of the Commission's Rules, shall be conducted to establish that the AM array has not bee adversely affected. Prior to or simultaneous with the filing of the FCC 489 notification, the results of the measurements must be submitted to the Commission on FCC Form 302-AM.

For further information contact Son Nguyen, snguyen@fcc.gov.

[See also Letter to Southwestern Bell Mobile Systems, dated October 2, 1997 . The AM Query may be used to locate AM stations within a specified radius if the NAD27 coordinates are known. ]

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