Goto Section: 74.795 | 74.797 | Table of Contents
Revised as of September 1, 2021
Goto Year:2020 |
§ 74.796 Modification of digital transmission systems and analog
transmission systems for digital operation.
(a) The provisions of § 74.751 shall apply to the modification of
digital low power TV and TV translator transmission systems and the
modification of existing analog transmission systems for digital
(b) The following additional provisions shall apply to the modification
of existing analog transmissions systems for digital operation,
including installation of manufacturers' certificated equipment (“field
modification kits”) and custom modifications.
(1) The modifications and related performance-testing shall be
undertaken by a person or persons qualified to perform such work.
(2) The final amplifier stage of an analog transmitter modified for
digital operation shall not have an “average digital power” output
greater than 25 percent of its previous NTSC peak sync power output,
unless the amplifier has been specifically refitted or replaced to
operate at a higher power.
(3) Analog heterodyne translators, when modified for digital operation,
will produce a power output (digital average power over the 6 MHz
channel) not exceeding 30 watts for transmitters operating on channels
14-69 and 3 watts for transmitters operating on channels 2-13.
(4) After completion of the modification, suitable tests and
measurements shall be made to demonstrate compliance with the
applicable requirements in this section including those in § 74.795.
Upon installation of a field modification kit, the transmitter shall be
performance-tested in accordance with the manufacturer's instructions.
(5) The station licensee shall notify the Commission upon completion of
the transmitter modifications. In the case of custom modifications
(those not related to installation of manufacturer-supplied and
FCC-certificated equipment), the licensee shall certify compliance with
all applicable transmission system requirements.
(6) The licensee shall maintain with the station's records for a period
of not less than two years the following information and make this
information to the Commission upon request:
(i) A description of the modifications performed and performance tests
or, in the case of installation of a manufacturer-supplied modification
kit, a description of the nature of the modifications, installation and
test instructions and other material provided by the manufacturer;
(ii) Results of performance-tests and measurements on the modified
(iii) Copies of related correspondence with the Commission.
(c) In connection with the on-channel conversion of existing analog
transmitters for digital operation, a limited allowance is made for
transmitters with final amplifiers that do not meet the attenuation of
the Simple emission mask at the channel edges. Station licensees may
obtain equivalent compliance with this attenuation requirement in the
(1) Measure the level of attenuation of emissions below the average
digital power output at the channel edges in a 500 kHz bandwidth;
measurements made over a different measurement bandwidth should be
corrected to the equivalent attenuation level for a 500 kHz bandwidth
using the formula given in § 74.794;
(2) Calculate the difference in dB between the 46 dB channel-edge
attenuation requirement of the Simple mask;
(3) Subtract the value determined in the previous step from the
authorized effective radiated power (“ERP”) of the analog station being
converted to digital operation. Then subtract an additional 6 dB to
account for the approximate difference between analog peak and digital
average power. For this purpose, the ERP must be expressed in decibels
above one kilowatt: ERP(dBk) = 10 log ERP(kW);
(4) Convert the ERP calculated in the previous step to units of
(5) The ERP value determined through the above procedure will produce
equivalent compliance with the attenuation requirement of the simple
emission mask at the channel edges and should be specified as the
digital ERP in the minor change application for an on-channel digital
conversion. The transmitter may not be operated to produce a higher
digital ERP than this value.
[ 69 FR 69336 , Nov. 29, 2004]
Goto Section: 74.795 | 74.797
Goto Year: 2020 |
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