§  76.611   Cable television basic signal leakage performance criteria.

   (a) No cable television system shall commence or provide service in the
   frequency bands 108-137 and 225-400 MHz unless such systems is in
   compliance with one of the following cable television basic signal
   leakage performance criteria:

   (1) Prior to carriage of signals in the aeronautical radio bands and at
   least once each calendar year, with no more than 12 months between
   successive tests thereafter, based on a sampling of at least 75% of the
   cable strand, and including any portion of the cable system which are
   known to have or can reasonably be expected to have less leakage
   integrity than the average of the system, the cable operator
   demonstrates compliance with a cumulative signal leakage index by
   showing that 10 log I∞ is equal to or less than 64 using the following
   formula:
   eCFR graphic er22fe18.000.gif

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   θis the fraction of the system cable length actually examined for
   leakage sources and is equal to the strand kilometers (strand miles) of
   plant tested divided by the total strand kilometers (strand miles) in
   the plant;

   Ei is the electric field strength in microvolts per meter (µV/m)
   measured 3 meters from the leak i; and

   n is the number of leaks found of field strength equal to or greater
   than 50 µV/m measured pursuant to § 76.609(h).

   The sum is carried over all leaks i detected in the cable examined; or

   (2) Prior to carriage of signals in the aeronautical radio bands and at
   least once each calendar year, with no more than 12 months between
   successive tests thereafter, the cable operator demonstrates by
   measurement in the airspace that at no point does the field strength
   generated by the cable system exceed 10 microvolts per meter (µV/m) RMS
   at an altitude of 450 meters above the average terrain of the cable
   system. The measurement system (including the receiving antenna) shall
   be calibrated against a known field of 10 µV/m RMS produced by a well
   characterized antenna consisting of orthogonal resonant dipoles, both
   parallel to and one quarter wavelength above the ground plane of a
   diameter of two meters or more at ground level. The dipoles shall have
   centers collocated and be excited 90 degrees apart. The half-power
   bandwidth of the detector shall be 25 kHz. If an aeronautical receiver
   is used for this purpose it shall meet the standards of the Radio
   Technical Commission for Aeronautics (RCTA) for aeronautical
   communications receivers. The aircraft antenna shall be horizontally
   polarized. Calibration shall be made in the community unit or, if more
   than one, in any of the community units of the physical system within a
   reasonable time period to performing the measurements. If data is
   recorded digitally the 90th percentile level of points recorded over
   the cable system shall not exceed 10 µV/m RMS as indicated above; if
   analog recordings is used the peak values of the curves, when smoothed
   according to good engineering practices, shall not exceed 10 µV/m RMS.

   (b) In paragraphs (a)(1) and (2) of this section the unmodulated test
   signal used for analog leakage measurements on the cable plant shall—

   (1) Be within the VHF aeronautical band 108-137 MHz or any other
   frequency for which the results can be correlated to the VHF
   aeronautical band; and

   (2) Have an average power level equal to the greater of:

   (i) The peak envelope power level of the strongest NTSC or similar
   analog cable television signal on the system, or

   (ii) 1.2 dB greater than the average power level of the strongest QAM
   or similar digital cable television signal on the system.

   (c) In paragraphs (a)(1) and (2) of this section, if a modulated test
   signal is used for analog leakage measurements, the test signal and
   detector technique must, when considered together, yield the same
   result as though an unmodulated test signal were used in conjunction
   with a detection technique which would yield the RMS value of said
   unmodulated carrier.

   (d) If a sampling of at least 75% of the cable strand (and including
   any portions of the cable system which are known to have or can
   reasonably be expected to have less leakage integrity than the average
   of the system) as described in paragraph (a)(1) of this section cannot
   be obtained by the cable operator or is otherwise not reasonably
   feasible, the cable operator shall perform the airspace measurements
   described in paragraph (a)(2) of this section.

   (e) Prior to providing service to any subscriber on a new section of
   cable plant, the operator shall show compliance with either:

   (1) The basic signal leakage criteria in accordance with paragraphs
   (a)(1) or (2) of this section for the entire plant in operation or

   (2) a showing shall be made indicating that no individual leak in the
   new section of the plant exceeds 20 µV/m at 3 meters in accordance with
   § 76.609 for analog signals or 17.4 µV/m at 3 meters for digital
   signals.

   (f) Notwithstanding paragraph (a) of this section, a cable operator
   shall be permitted to operate on any frequency which is offset pursuant
   to § 76.612 in the frequency band 108-137 MHz for the purpose of
   demonstrating compliance with the cable television basic signal leakage
   performance criteria.

   [ 83 FR 7629 , Feb. 22, 2018]