§ 73.155   Periodic directional antenna performance recertification.

   A station licensed with a directional antenna pattern pursuant to a proof of
   performance using moment method modeling and internal array parameters as
   described in § 73.151(c) shall recertify the performance of that directional
   antenna pattern at least once within every 24 month period.

   (a) Measurements shall be made to verify the continuing integrity of the
   antenna monitor sampling system.

   (1) For towers using base current or base voltage sampling derived at the
   output of the antenna coupling and matching equipment, the sampling devices
   shall be disconnected and calibrated by measuring their outputs with a
   common reference signal (a current through them or a voltage across them, as
   appropriate)  and  the  calibration must agree with the manufacturer's
   specifications.

   (2) For towers using base current or base voltage sampling derived at the
   output  of  the antenna coupling and matching equipment, sampling line
   measurements shall be made to verify the open-circuit resonant frequency
   closest to carrier frequency, to establish length, and also at frequencies
   corresponding to odd multiples of 1⁄8 wavelength immediately above and below
   the open-circuit resonant frequency closest to carrier frequency, while open
   circuited,  to  verify their characteristic impedance. The frequencies
   measured must be the same as were measured in the most recent proof of
   performance and must demonstrate that the sampling lines continue to meet
   the  requirements  of  § 73.151(c)  with  regard  to  their  length and
   characteristic impedance.

   (3) For towers having sampling loops, measurements shall be made at carrier
   frequency or, if necessary, at nearby frequencies where the magnitude of the
   measured impedance is no greater than 200 ohms with the sampling loops
   connected. The frequencies measured must be the same as were measured in the
   most recent proof of performance and the measured impedances must agree
   within ±2 ohms and ±4 percent resistance and reactance of the proof values.

   (b)  Field  strength measurements shall be made at the reference field
   strength measurement locations that were established by the most recent
   proof  of  performance. If locations have become inaccessible or their
   readings contaminated by localized electromagnetic environmental changes,
   new locations that meet the requirements of the moment method proof of
   performance rules in § 73.151(c)(3) shall be established to replace them.

   (c)  The  results  of  the  periodic  directional  antenna performance
   recertification measurements shall be retained in the station's public
   inspection file.

   [ 73 FR 64562 , Oct. 30, 2008]

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