§ 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;

   th 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 (uV/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 uV/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 (uV/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 uV/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 uV/m RMS; if analog recordings is
   used the peak values of the curves, when smoothed according to good
   engineering practices, shall not exceed 10 uV/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     uV/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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