§ 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 either that (i) 10 log I3000 is
   equal to or less than −7 or (ii) 10 log I00 is equal to or less than 64,
   using one of the following formula:
   eCFR graphic ec01mr91.113.gif

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   eCFR graphic ec01mr91.114.gif

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   where:
   eCFR graphic ec01mr91.115.gif

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   ri is the distance (in meters) between the leakage source and the center of
   the cable television system;

   θ is 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;

   Ri is the slant height distance (in meters) from leakage source i to a point
   3000 meters above the center of the cable television system;

   Ei is the electric field strength in microvolts per meter (µV/m) measured
   pursuant to § 76.609(h) 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 pursuant to Section 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 reasonant 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; 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 (a)(2) of this section the unmodulated test
   signal used on the cable plant shall: (1) Be within the VHF aeronautical
   band  108-137  MHz  or any other frequency in which the results can be
   correlated to the VHF aeronautical band and (2) have an average power level
   equal to the average power level of the strongest cable television carrier
   on the system.

   (c) In paragraph (a)(1) and (2) of this section, if a modulated test signal
   is  used, 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) 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).

   (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 paragraph (a)(1) or (a)(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 fo the Rules.

   (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.

   [ 50 FR 29399 , July 19, 1985, as amended at  53 FR 2499 , Jan. 28, 1988;  53 FR 5684 , Feb. 25, 1988;  58 FR 44952 , Aug. 25, 1993]

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