§ 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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