Goto Section: 74.737 | 74.751 | Table of Contents
Revised as of January 19, 2021
Goto Year:2020 |
§ 74.750 Transmission system facilities.
(a) A low power TV, TV translator, or TV booster station shall operate
with a transmitter that is either certificated for licensing under the
provisions of this subpart or type notified for use under part 73 of
(b) Transmitting antennas, antennas used to receive the signals to be
rebroadcast, and transmission lines are not certificated by the FCC.
External preamplifiers also may be used provided that they do not cause
improper operation of the transmitting equipment, and use of such
preamplifiers is not necessary to meet the provisions of paragraph (c)
of this section.
(c) The following requirements must be met before low power TV and TV
translator transmitters will be certificated by the FCC:
(1) The equipment shall be so designed that the electrical
characteristics of a standard television signal introduced into the
input terminals will be maintained at the output. The overall response
of the apparatus within its assigned channel, when operating at its
rated power output and measured at the output terminals, shall provide
a smooth curve, varying within limits separated by no more than 4 dB:
Provided, however, That means may be provided to reduce the amplitude
of the aural carrier below those limits, if necessary to prevent
intermodulation which would mar the quality of the retransmitted
picture or result in emissions outside of the assigned channel.
(2) Radio frequency harmonics of the visual and aural carriers,
measured at the output terminals of the transmitter, shall be
attenuated no less than 60 dB below the peak visual output power within
the assigned channel. All other emissions appearing on frequencies more
than 3 megacycles above or below the upper and lower edges,
respectively, of the assigned channel shall be attenuated no less than:
(i) 30 dB for transmitters rated at no more than 1 watt power output.
(ii) 50 dB for transmitters rated at more than 1 watt power output.
(iii) 60 dB for transmitters rated at more than 100 watts power output.
(3) When subjected to variations in ambient temperature between minus
30 degrees and plus 50 degrees Centigrade and variations in power main
voltage between 85 percent and 115 percent of rated power supply
voltage, the local oscillator frequency stability shall maintain the
operating frequency within:
(i) 0.02 percent of its rated frequency for transmitters rated at no
more than 100 watts peak visual power.
(ii) 0.002 percent of the rated frequency for transmitters rated at
more than 100 watts peak visual power.
(iii) Plus or minus 1 kHz of its rated frequency for transmitters to be
used at stations employing offset carrier frequency operation.
(4) The apparatus shall contain automatic circuits which will maintain
the peak visual power output constant within 2 dB when the strength of
the input signal is varied over a range of 30 dB and which will not
permit the peak visual power output to exceed the maximum rated power
output under any condition. If a manual adjustment is provided to
compensate for different average signal strengths, provision shall be
made for determining the proper setting for the control, and if
improper adjustment of the control could result in improper operation,
a label shall be affixed at the adjustment control bearing a suitable
(5) The apparatus must be equipped with automatic controls that will
place it in a non-radiating condition when no signal is being received
on the input channel, either due to absence of a transmitted signal or
failure of the receiving portion of the facilities used for
rebroadcasting the signal of another station. The automatic control may
include a time delay feature to prevent interruptions caused by fading
or other momentary failures of the incoming signal.
(6) The tube or tubes employed in the final radio frequency amplifier
shall be of the appropriate power rating to provide the rated power
output of the translator. The normal operating constants for operation
at the rated power output shall be specified. The apparatus shall be
equipped with suitable meters or meter jacks so that appropriate
voltage and current measurements may be made while the apparatus is in
(7) The transmitters of over 0.001 kW peak visual power (0.002 kW when
circularly polarized antennas are used) shall be equipped with an
automatic keying device that will transmit the call sign of the
station, in International Morse Code, at least once each hour during
the time the station is in operation when operating in the translator
mode retransmitting the programming of a TV broadcast station. However,
the identification by Morse Code is not required if the licensee of the
low power TV or TV translator station has an agreement with the TV
broadcast station being rebroadcast to transmit aurally or visually the
low power TV or TV translator station call as provided for in § 74.783.
Transmission of the call sign can be accomplished by:
(i) Frequency shift keying; the aural and visual carrier shift shall
not be less than 5 kHz or greater than 25 kHz.
(ii) Amplitude modulation of the aural carrier of at least 30%
modulation. The audio frequency tone used shall not be within 200 hertz
of the Emergency Broadcast System Attention Signal alerting
(8) Wiring, shielding, and construction shall be in accordance with
accepted principles of good engineering practice.
(d) Low power TV, TV translator and transmitting equipment using a
modulation process for either program origination or rebroadcasting TV
booster transmitting equipment using a modulation process must meet the
(1) The equipment shall meet the requirements of paragraphs (a)(1) and
(b)(3) of § 73.687.
(2) The stability of the equipment shall be sufficient to maintain the
operating frequency of the aural carrier to 4.5 MHz Â±1kHz above the
visual carrier when subjected to variations in ambient temperature
between 30Â° and + 50Â° centigrade and variations in power main voltage
between 85 and 115 percent of rated power supply voltage.
(e) Certification will be granted only upon a satisfactory showing that
the apparatus is capable of meeting the requirements of paragraphs (c)
and (d) of this section. The following procedures shall apply:
(1) Any manufacturer of apparatus intended for use at low power TV, TV
translator, or TV booster stations may request certification by
following the procedures set forth in part 2, subpart J, of this
(2) Low power TV, TV translator, and TV booster transmitting apparatus
that has been certificated by the FCC will normally be authorized
without additional measurements from the applicant or licensee.
(3) Applications for certification of modulators to be used with
existing certificated TV translator apparatus must include the
specifications electrical and mechanical interconnecting requirements
for the apparatus with which it is designed to be used.
(4) Other rules concerning certification, including information
regarding withdrawal of type acceptance, modification of certificated
equipment and limitations on the findings upon which certification is
based, are set forth in part 2, subpart J, of this chapter.
(f) The transmitting antenna system may be designed to produce
horizontal, vertical, or circular polarization.
(g) Low power TV, TV translator, or TV booster stations installing new
certificated transmitting apparatus incorporating modulating equipment
need not make equipment performance measurements and shall so indicate
on the station license application. Stations adding new or replacing
modulating equipment in existing low power TV, TV translator, or TV
booster station transmitting apparatus must have a qualified person
examine the transmitting system after installation. This person must
certify in the application for the station license that the
transmitting equipment meets the requirements of paragraph (d)(1) of
this section. A report of the methods, measurements, and results must
be kept in the station records. However, stations installing modulating
equipment solely for the limited local origination of signals permitted
by § 74.731 need not comply with the requirements of this paragraph.
[ 28 FR 13722 , Dec. 14, 1963, as amended at 33 FR 8677 , June 13, 1968;
36 FR 19592 , Oct. 8, 1971; 37 FR 25844 , Dec. 5, 1972; 41 FR 17552 , Apr.
27, 1976; 43 FR 1951 , Jan. 13, 1978; 46 FR 35465 , July 8, 1981; 47 FR 21500 , May 18, 1982; 47 FR 30496 , July 14, 1982; 52 FR 31404 , Aug. 20,
1987; 60 FR 55483 , Nov. 1, 1995; 62 FR 26722 , May 14, 1997; 63 FR 36605 , July 7, 1998]
Goto Section: 74.737 | 74.751
Goto Year: 2020 |
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