Sec. 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:
[GRAPHIC] [TIFF OMITTED] TC01MR91.113

[GRAPHIC] [TIFF OMITTED] TC01MR91.114

where:
[GRAPHIC] [TIFF OMITTED] TC01MR91.115

ri is the distance (in meters) between the leakage source and 
          the center of the cable television system;
 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 
          (V/m) measured pursuant to Sec. 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 V/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 
(V/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 
V/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

[[Page 555]]

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 V/m RMS; if analog recordings is used the peak values 
of the curves, when smoothed according to good engineering practices, 
shall not exceed 10 V/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    V/m at 3 meters in 
accordance with Sec. 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 Sec. 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]