Sec. 73.53  Requirements for authorization of antenna monitors.

    (a) General requirements. (1) Antenna monitors shall be type 
approved or notifed by the FCC. Effective March 5, 1984, only grants of 
notification will be issued for antenna monitors.
    (2) Notification can be obtained by following the procedures 
specified in subpart J of part 2 of the FCC's Rules.
    (b) An antenna monitor eligible for authorization by the FCC 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 deg..
    (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 deg., or less. If a 
digital indicator is provided, the smallest increment shall be 0.5 deg., 
or less.
    (5) The device used to indicate relative amplitudes shall be 
graudated 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

[[Page 22]]

meeting the specifications of the monitor manufacturer shall not affect 
adversely the performance of the monitor in any respect.
    (10) The monitor must be accompanied by complete and correct 
schematic diagrams and operating instructions when submitted for type 
approval. When approved under notification, these materials shall be 
retained by the applicant and not submitted unless otherwise requested 
by the FCC. For the purpose of the 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 plus-minus1 deg.,or 
better, for signal amplitude ratios of from 2:1 to 1:1, and 
plus-minus2 deg.,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 plus-minus1 deg., 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 plus-minus2 
percent of the amplitude ratio, or better, and for amplitude ratios in 
excess of 2:1 and up to 5:1, plus-minus5 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 plus-minus2 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 
plus-minus0.5 deg..
    (12) The performance specifications set forth in paragraph (c)(13) 
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 deg.C; external meters 
furnished by the manufacturer will be subjected to variations between 15 
and 30 deg.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.
    (c) A station determined to have a critical directional antenna must 
use an antenna monitor having high tolerance characteristics determined 
on an individual basis, and specified on the station authorization. Such 
monitors are not subject to the authorization of paragraph (a), however 
they may be used only at the station for which they were specified.

    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

[[Page 23]]

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, ))

[38 303 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]