Goto Section: 76.611 | 76.613 | Table of Contents
Revised as of May 23, 2019
Goto Year:2018 |
§ 76.612 Cable television frequency separation standards.
All cable television systems which operate analog NTSC or similar
channels in the frequency bands 108-137 MHZ and 225-400 MHz shall
comply with the following frequency separation standards for each NTSC
or similar channel:
(a) In the aeronautical radiocommunication bands 118-137, 225-328.6 and
335.4-400 MHz, the frequency of all carrier signals or signal
components carried at an average power level equal to or greater than
10−4 watts in a 25 kHz bandwidth in any 160 microsecond period must
operate at frequencies offset from certain frequencies which may be
used by aeronautical radio services operated by Commission licensees or
by the United States Government or its Agencies. The aeronautical
frequencies from which offsets must be maintained are those frequencies
which are within one of the aeronautical bands defined in this
subparagraph, and when expressed in MHz and divided by 0.025 yield an
integer. The offset must meet one of the following two criteria:
(1) All such cable carriers or signal components shall be offset by
12.5 kHz with a frequency tolerance of ±5 kHz; or
(2) The fundamental frequency from which the visual carrier frequencies
are derived by multiplication by an integer number which shall be
6.0003 MHz with a tolerance of ±1 Hz (Harmonically Related Carrier
(HRC) comb generators only).
(b) In the aeronautical radionavigation bands 108-118 and 328.6-335.4
MHz, the frequency of all carrier signals or signal components carrier
at an average power level equal to or greater than 10−4 watts in a 25
kHz bandwidth in any 160 microsecond period shall be offset by 25 kHz
with a tolerance of ±5 kHz. The aeronautical radionavigation
frequencies from which offsets must be maintained are defined as
(1) Within the aeronautical band 108-118 MHz when expressed in MHz and
divided by 0.025 yield an even integer.
(2) Within the band 328.6-335.4 MHz, the radionavigation glide path
channels are listed in Section 87.501 of the Rules.
Note: The HRC system, as described above, will meet this requirement in
the 328.6-335.4 MHz navigation glide path band. Those Incrementally
Related Carriers (IRC) systems, with comb generator reference
frequencies set at certain odd multiples equal to or greater than 3
times the 0.0125 MHz aeronautical communications band offset, e.g. (6n
+ 1.250 ±0.0375) MHz, may also meet the 25 kHz offset requirement in
the navigation glide path band.
[ 50 FR 29400 , July 19, 1985, as amended at 83 FR 7630 , Feb. 22, 2018]
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Goto Section: 76.611 | 76.613
Goto Year: 2018 |
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