Sec.  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.
   If the directional pattern has fewer than 4 monitored radials, the partial
   proof shall include measurements on those radials from the latest complete
   proof of performance which are adjacent to the monitored radials.

   (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]