Sec. 73.69  Antenna monitors.

    (a) Each station using a directional antenna must have in operation 
at the transmitter site an FCC authorized antenna monitor. However, if 
the station authorization sets specific tolerances within which the 
phase and amplitude relationships must be maintained, or requires the 
use of a monitor of specified repeatability, resolution or accuracy, the 
antenna monitor used will be authorized on an individual basis.
    (1) Normally, the antenna monitor is to be installed immediately 
adjacent to the transmitter and antenna phasing equipment. However, the 
monitor may be located elsewhere provided that its environment is 
maintained at all times within those limits under which the monitor was 
type-approved.
    (2) The antenna monitor installed at a station operating a 
directional antenna by remote control or when the monitor is installed 
in the antenna field at a distance from the transmitter, must be 
designed and authorized for such use in accordance with the provisions 
of Sec. 73.53(b)(9).
    (b) In the event that the antenna monitor sampling system is 
temporarily out of service for repair or replacement, the station may be 
operated, pending completion of repairs or replacement, for a period not 
exceeding 120 days without further authority from the FCC if all other 
operating parameters, and the field monitoring point values are within 
the limits specified on the station authorization.
    (c) If conditions beyond the control of the licensee prevent the 
restoration of the monitor to service within the allowed period, 
informal request in accordance with Sec. 73.3549 of the Commission's 
rules must be filed with the Engineer in Charge of the radio district in 
which the station is located for such additional time as may be required 
to complete repairs of the defective instrument.
    (d) If an authorized antenna monitor is replaced by another antenna 
monitor, the following procedure shall be followed:
    (1) Temporary authority shall be requested and obtained from the 
Commission in Washington to operate with parameters at variance with 
licensed values, pending issuance of a modified license specifying new 
parameters.
    (2) Immediately prior to the replacement of the antenna monitor, 
after a verification that all monitoring point

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values and base current ratios are within the limits or tolerances 
specified in the instrument of authorization or the pertinent rules, the 
following indications must be read for each radiation pattern: Final 
plate current and plate voltage, common point current, base currents, 
antenna monitor phase and current indications, and the field strength at 
each monitoring point.
    (3) With the new monitor substituted for the old, all indications 
specified in paragraph (d)(2) of this section, again must be read. If no 
change has occurred in the indication for any parameter other than the 
indications of the antenna monitor, the new antenna monitor indications 
must be deemed to be those reflecting correct array adjustments.
    (4) If it cannot be established by the observations required in 
paragraph (d)(2) of this section that base current ratios and monitoring 
point values are within the tolerances or limits prescribed by the rules 
and the instrument of authorization, or if the substitution of the new 
antenna monitor for the old results in changes in these parameters, a 
partial proof of performance shall be executed and analyzed in 
accordance with Sec. 73.154.
    (5) An informal request for modification of license shall be 
submitted to the Commission in Washington, DC, within 30 days of the 
date of monitor replacement. Such request shall specify the make, type, 
and serial number of the replacement monitor, phase and sample current 
indications, and other data obtained pursuant to this paragraph (d) of 
this section.
    (e) The antenna monitor must be calibrated according to the 
manufacturer's instructions as often as necessary to ensure its proper 
operation.

(Secs. 4, 5, 303, 48 Stat., as amended, 1066, 1068, as amended, 1082, as 
amended; 47 U.S.C. 154, 303. Interpret or apply secs. 301, 303, 307, 48 
Stat. 1081, 1082, as amended, 1083, as amended, 47 U.S.C. 301, 303, )

[38 307 FR 1918 , Jan. 19, 1973, as amended at  40 FR 15884 , Apr. 8, 1975;  40 FR 25459 , June 16, 1975;  40 FR 27939 , July 2, 1975;  41 FR 22942 , June 8, 
1976;  41 FR 32892 , Aug. 6, 1976;  43 FR 4022 , Jan. 31, 1978;  45 FR 26062 , 
Apr. 17, 1980;  48 FR 38478 , Aug. 24, 1983;  49 FR 3999 , Feb. 1, 1984;  50 FR 47054 , Nov. 14, 1985;  51 FR 9965 , Mar. 24, 1986;  56 FR 64859 , Dec. 
12, 1991;  60 FR 55480 , Nov. 1, 1995]