Sec. 73.58  Indicating instruments.

    (a) Each AM broadcast station must be equipped with indicating 
instruments which conform with the specifications described in 
Sec. 73.1215 for determining power by the direct and indirect methods, 
and with such other instruments as are necessary for the proper 
adjustment, operation, and maintenance of the transmitting system. 
However, auxiliary transmitters with a nominal power rating of 100 watts 
or less are not required to be equipped with instruments to determine 
power by the indirect method provided that the licensee can determine 
the antenna input power at all times.
    (b) A thermocouple type ammeter or other device capable of providing 
an indication of radio frequency current, meeting the requirements of 
Sec. 73.1215, shall be installed at the base of each antenna element. A 
suitable jack and plug arrangement may be used to permit removal of the 
meter from the antenna circuit thereby protecting it from damage by 
lighting.
    (c) Since it is usually impractical to measure the actual antenna 
current of a shunt excited antenna system, the current measured at the 
input of the excitation circuit feed line is accepted as the antenna 
current.
    (d) The function of each instrument shall be clearly and permanently 
shown on the instrument itself or on the panel immediately adjacent 
thereto.
    (e) In the event that any one of these indicating instruments 
becomes defective when no substitute which conforms with the required 
specifications

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is available, the station may be operated without the defective 
instrument pending its repair or replacement for a period not in excess 
of 60 days without further authority of the Commission: Provided, That:
    (1) If the defective instrument is an antenna base current ammeter 
of a directional antenna system, the indications may be obtained from 
the antenna monitor pending the return to service of the regular meter, 
provided other parameters are maintained at their normal values.
    (2) If the defective instrument is the antenna current meter of a 
non-directional station which does not employ a remote antenna ammeter, 
or if the defective instrument is the common point meter of a station 
which employs a directional antenna and does not employ a remote common 
point meter, the operating power shall be determined by a method 
described in Sec. 73.51(a)(1) or (d) during the entire time the station 
is operated without the antenna current meter or common point meter. 
However, if a remote meter is employed and the antenna current ammeter 
or common point meter becomes defective, the remote meter can be used to 
determine operating power pending the return to service of the regular 
meter.
    (f) If conditions beyond the control of the licensee prevent the 
restoration of the meter to service within the above allowed period, 
information requested in accordance with Sec. 73.3549 may 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.

[ 41 FR 36817 , Sept. 1, 1976, as amended at  48 FR 38477 , Aug. 24, 1983; 
 49 FR 49850 , Dec. 24, 1984;  50 FR 32416 , Aug. 12, 1985;  51 FR 2707 , Jan. 
21, 1986;  53 FR 2498 , Jan. 28, 1988]