Goto Section: 73.258 | 73.277 | Table of Contents
FCC 73.267
Revised as of October 1, 2008
Goto Year:2007 |
2009
Sec. 73.267 Determining operating power.
(a) The operating power of each FM station is to be determined by either the
direct or indirect method.
(b) Direct method. The direct method of power determination for an FM
station uses the indications of a calibrated transmission line meter
(responsive to relative voltage, current, or power) located at the RF output
terminals of the transmitter. This meter must be calibrated whenever there
is any indication that the calibration is inaccurate or whenever any
component of the metering circuit is repaired or replaced. The calibration
must cover, as a minimum, the range from 90% to 105% of authorized power.
The meter calibration may be checked by measuring the power at the
transmitter terminals while either:
(1) Operating the transmitter into the transmitting antenna, and determining
actual operating power by the indirect method described in Sec. 73.267(c); or
(2) Operating the transmitter into a load (of substantially zero reactance
and a resistance equal to the transmission line characteristic impedance)
and using an electrical device (within ±5% accuracy) or temperature and
coolant flow indicator (within ±4% accuracy) to determine the power.
(3) The calibration must cover, as a minimum, the range from 90% to 105% of
authorized power and the meter must provide clear indications which will
permit maintaining the operating power within the prescribed tolerance or
the meter shall be calibrated to read directly in power units.
(c) Indirect method. The operating power is determined by the indirect
method by applying an appropriate factor to the input power to the last
radio-frequency power amplifier stage of the transmitter, using the
following formula:
Transmitter output power=Ep × Ip × F
Where:
Ep=DC input voltage of final radio stage.
Ip=Total DC input current of final radio stage.
F =Efficiency factor.
(1) If the above formula is not appropriate for the design of the
transmitter final amplifier, use a formula specified by the transmitter
manufacturer with other appropriate operating parameters.
(2) The value of the efficiency factor, F, established for the authorized
transmitter output power is to be used for maintaining the operating power,
even though there may be some variation in F over the power operating range
of the transmitter.
(3) The value of F is to be determined and a record kept thereof by one of
the following procedures listed in order of preference:
(i) Using the most recent measurement data for calibration of the
transmission line meter according to the procedures described in paragraph
(b) of this section or the most recent measurements made by the licensee
establishing the value of F. In the case of composite transmitters or those
in which the final amplifier stages have been modified pursuant to FCC
approval, the licensee must furnish the FCC and also retain with the station
records the measurement data used as a basis for determining the value of F.
(ii) Using measurement data shown on the transmitter manufacturer's test
data supplied to the licensee; Provided, That measurements were made at the
authorized frequency and transmitter output power.
(iii) Using the transmitter manufacturer's measurement data submitted to the
FCC for type acceptance and as shown in the instruction book supplied to the
licensee.
(Secs. 4, 5, 303, 48 Stat., as amended, 1066, 1068, 1082 (47 U.S.C. 154,
155, 303))
[ 44 FR 58731 , Oct. 11, 1979, as amended at 45 FR 28141 , Apr. 28, 1980; 48 FR 38479 , Aug. 24, 1983; 49 FR 4210 , Feb. 3, 1984; 49 FR 49851 , Dec. 24, 1984]
Goto Section: 73.258 | 73.277
Goto Year: 2007 |
2009
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