Sec.  27.63   Disturbance of AM broadcast station antenna patterns.

   AWS and WCS licensees that construct or modify towers in the immediate
   vicinity of AM broadcast stations are responsible for measures necessary to
   correct disturbance of the AM station antenna pattern which causes operation
   outside of the radiation parameters specified by the FCC for the AM station,
   if the disturbance occurred as a result of such construction or
   modification.

   (a) Non-directional AM stations. If tower construction or modification is
   planned within 1 kilometer (0.6 mile) of a non-directional AM broadcast
   station tower, the AWS or WCS licensee must notify the licensee of the AM
   broadcast station in advance of the planned construction or modification.
   Measurements must be made to determine whether the construction or
   modification would affect the AM station antenna pattern. The AWS or WCS
   licensee is responsible for the installation and continued maintenance of
   any detuning apparatus necessary to restore proper non-directional
   performance of the AM station tower.

   (b) Directional AM stations. If tower construction or modification is
   planned within 3 kilometers (1.9 miles) of a directional AM broadcast
   station array, the AWS or WCS licensee must notify the licensee of the AM
   broadcast station in advance of the planned construction or modification.
   Measurements must be made to determine whether the construction or
   modification would affect the AM station antenna pattern. The AWS or WCS
   licensee is responsible for the installation and continued maintenance of
   any detuning apparatus necessary to restore proper performance of the AM
   station array.

   [ 69 FR 5715 , Feb. 6, 2004]