§  73.154   AM directional antenna partial proof of performance measurements.

   (a) A partial proof of performance consists of at least 8 field
   strength measurements made on each of the radials that includes a
   monitoring point.

   (b) The measurements are to be made within 3 to 15 kilometers from the
   center of the antenna array. When a monitoring point as designated on
   the station authorization lies on a particular radial, one of the
   measurements must be made at that point. One of the following methods
   shall be used for the partial proof:

   (1) Measurement points shall be selected from the points measured in
   latest full proof of performance provided that the points can be
   identified with reasonable certainty, and that land development or
   other factors have not significantly altered propagation
   characteristics since the last full proof. At each point, the licensee
   shall measure directional field strength for comparison to either the
   directional or the nondirectional field strength measured at that point
   in the last full proof.

   (2) In the event that a meaningful comparison to full proof
   measurements cannot be made, the licensee shall measure both
   directional and nondirectional field strength at eight points on each
   radial. The points need not be limited to those measured in the last
   full proof of performance.

   (c) The results of the measurements are to be analyzed as follows.
   Either the arithmetic average or the logarithmic average of the ratios
   of the field strength at each measurement point to the corresponding
   field strength in the most recent complete proof of performance shall
   be used to establish the inverse distance fields. (The logarithmic
   average for each radial is the antilogarithm of the mean of the
   logarithms of the ratios of field strength (new to old) for each
   measurement location along a given radial). When new nondirectional
   measurements are used as the reference, as described in paragraph
   (b)(2) of this section, either the arithmetic or logarithmic averages
   of directional to nondirectional field strength on each radial shall be
   used in conjunction with the measured nondirectional field from the
   last proof to establish the inverse distance field.

   (d) The result of the most recent partial proof of performance
   measurements and analysis is to be retained in the station records
   available to the FCC upon request. Maps showing new measurement points,
   i.e., points not measured in the last full proof, shall be associated
   with the partial proof in the station's records, and shall be provided
   to the FCC upon request.

   [ 66 FR 20756 , Apr. 25, 2001, as amended at  82 FR 51165 , Nov. 3, 2017]