Goto Section: 76.610 | 76.612 | Table of Contents
FCC 76.611
Revised as of October 1, 2008
Goto Year:2007 |
2009
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 I[3000]is
equal to or less than −7 or (ii) 10 log I[00]is equal to or less than 64,
using one of the following formula:
[MATH:
:MATH]
[MATH:
:MATH]
where:
[MATH:
:MATH]
r[i]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;
R[i]is the slant height distance (in meters) from leakage source i to a
point 3000 meters above the center of the cable television system;
E[i]is the electric field strength in microvolts per meter ( µV/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
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 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]
Goto Section: 76.610 | 76.612
Goto Year: 2007 |
2009
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