§  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 of1/8wavelength
   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]