Section 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: View Image
[THETA] 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;
Ei is the electric field strength in microvolts per meter ([MICRO]V/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 [MICRO]V/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 ([MICRO]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 [MICRO]V/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 [MICRO]V/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 [MICRO]V/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 [MICRO]V/m at 3 meters in accordance with § 76.609 for analog signals or 17.4 [MICRO]V/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