§ 73.53   Requirements for authorization of antenna monitors.

   (a) Antenna monitors shall be verified for compliance with the
   technical requirements in this section. The procedure for verification
   is specified in subpart J of part 2 of the FCC's rules.

   (b) An antenna monitor shall meet the following specifications:

   (1) The monitor shall be designed to operate in the 535-1705 kHz band.

   (2) The monitor shall be capable of indicating any phase difference
   between two RF voltages of the same frequency over a range of from 0 to
   360°.

   (3) The monitor shall be capable of indicating the relative amplitude
   of two RF voltages.

   (4) The device used to indicate phase differences shall indicate in
   degrees, and shall be graduated in increments of 2°, or less. If a
   digital indicator is provided, the smallest increment shall be 0.5°, or
   less.

   (5) The device used to indicate relative amplitudes shall be graduated
   in increments which are 1 percent, or less, of the full scale value. If
   a digital indicator is provided, the smallest increment shall be 0.1
   percent, or less, of the full scale value.

   (6) The monitor shall be equipped with means, if necessary, to resolve
   ambiguities in indication.

   (7) If the monitor is provided with more than one RF input terminal in
   addition to a reference input terminal, appropriate switching shall be
   provided in the monitor so that the signal at each of these RF inputs
   may be selected separately for comparison with the reference input
   signal.

   (8) Each RF input of the monitor shall provide a termination of such
   characteristics that, when connected to a sampling line of an impedance
   specified by the manufacturer the voltage reflection coefficient shall
   be 3 percent or less.

   (9) The monitor, if intended for use by stations operating directional
   antenna systems by remote control, shall be designed so that the
   switching functions required by paragraph (b)(7) of this section may be
   performed from a point external to the monitor, and phase and amplitude
   indications be provided by external meters. The indications of external
   meters furnished by the manufacturer shall meet the specifications for
   accuracy and repeatability of the monitor itself, and the connection of
   these meters to the monitor, or of other indicating instruments with
   electrical characteristics meeting the specifications of the monitor
   manufacturer shall not affect adversely the performance of the monitor
   in any respect.

   (10) Complete and correct schematic diagrams and operating instructions
   shall be retained by the party responsible for verification of the
   equipment and submitted to the FCC upon request. For the purpose of
   equipment authorization, these diagrams and instructions shall be
   considered as part of the monitor.

   (11) When an RF signal of an amplitude within a range specified by the
   manufacturer is applied to the reference RF input terminal of the
   monitor, and another RF signal of the same frequency and of equal or
   lower amplitude is applied to any other selected RF input terminal,
   indications shall be provided meeting the following specifications.

   (i) The accuracy with which any difference in the phases of the applied
   signals is indicated shall be ±1°, or better, for signal amplitude
   ratios of from 2:1 to 1:1, and ±2°, or better, for signal amplitude
   ratios in excess of 2:1 and up to 5:1.

   (ii) The repeatability of indication of any difference in the phases of
   the applied signals shall be ±1°, or better.

   (iii) The accuracy with which the relative amplitudes of the applied
   signals is indicated, over a range in which the ratio of these
   amplitudes is between 2:1 and 1:1, shall be ±2 percent of the amplitude
   ratio, or better, and for amplitude ratios in excess of 2:1 and up to
   5:1, ±5 percent of the ratio, or better.

   (iv) The repeatability of indication of the relative amplitudes of the
   applied signals, over a range where the ratio of these amplitudes is
   between 5:1 and 1:1, shall be ±2 percent of the amplitude ratio, or
   better.

   (v) The modulation of the RF signals by a sinusoidal wave of any
   frequency between 100 and 10,000 Hz, at any amplitude up to 90 percent
   shall cause no deviation in an indicated phase difference from its
   value, as determined without modulation, greater than ±0.5°.

   (12) The performance specifications set forth in paragraph (b)(11) of
   this section, shall be met when the monitor is operated and tested
   under the following conditions.

   (i) After continuous operation for 1 hour, the monitor shall be
   calibrated and adjusted in accordance with the manufacturer's
   instructions.

   (ii) The monitor shall be subjected to variations in ambient
   temperature between the limits of 10 and 40 °C; external meters
   furnished by the manufacturer will be subjected to variations between
   15 and 30 °C.

   (iii) Powerline supply voltage shall be varied over a range of from 10
   percent below to 10 percent above the rated supply voltage.

   (iv) The amplitude of the reference signal shall be varied over the
   operating range specified by the manufacturer, and in any case over a
   range of maximum to minimum values of 3 to 1.

   (v) The amplitude of the comparison signal shall be varied from a value
   which is 0.2 of the amplitude of the reference signal to a value which
   is equal in amplitude to the reference signal.

   (vi) Accuracy shall be determined for the most adverse combination of
   conditions set forth above.

   (vii) Repeatability shall be determined as that which may be achieved
   under the specified test conditions over a period of 7 days, during
   which no calibration or adjustment of the instrument, subsequent to the
   initial calibration, shall be made.

   (viii) The effects of modulation of the RF signal shall be separately
   determined, and shall not be included in establishing values for
   accuracy and repeatability.

   Note: In paragraph (b)(1) of this section, the requirement that
   monitors be capable of operation in the 535-1705 kHz band shall apply
   only to equipment manufactured after July 1, 1992. Use of a monitor in
   the 1605-1705 kHz band which is not approved for such operation will be
   permitted pending the general availability of 535-1705 kHz band
   monitors if a manufacturer can demonstrate, in the interim, that its
   monitor performs in accordance with the standards in this section on
   these 10 channels.

   (Secs. 4, 5, 303, 48 Stat., as amended, 1066, 1068, 1082 (47 U.S.C.
   154, 155, 303))

   [ 38 FR 1917 , Jan. 19, 1973, as amended at  49 FR 3999 , Feb. 1, 1984;  49 FR 29069 , July 18, 1984;  50 FR 32416 , Aug. 12, 1985;  50 FR 47054 , Nov.
   14, 1985;  51 FR 2707 , Jan. 21, 1986;  56 FR 64859 , Dec. 12, 1991;  57 FR 43290 , Sept. 18, 1992;  60 FR 55480 , Nov. 1, 1995;  63 FR 36604 , July 7,
   1998;  66 FR 20755 , Apr. 25, 2001]

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