FCC 74.796 Revised as of October 1, 2007
Goto Year:2006 |
2008
Sec. 74.796 Modification of digital transmission systems and analog transmission
systems for digital operation.
(a) The provisions of Sec. 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 operation.
(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 Sec. 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
transmitter; and
(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 following
manner:
(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
Sec. 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 kilowatts;
and
(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]
Subpart H—Low Power Auxiliary Stations
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