Sec. 76.612  Cable television frequency separation standards.

    All cable television systems which operate in the frequency bands 
108-137 and 225-400 MHz shall comply with the following frequency 
separation standards:
    (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 &177;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 &177;1 Hz (Harmonically 
Related Carrier (HRC) comb generators only).

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    (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 &177;5 kHz. 
The aeronautical radionavigation frequencies from which offsets must be 
maintained are defined as follows:
    (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 &177; 0.0375) MHz, may also meet the 25 kHz offset 
requirement in the navigation glide path band.


[ 50 FR 29400 , July 19, 1985]