Note: Fly-overs are generally con-
ducted by specialized engineering
contractors who have an equipped air-
craft with the appropriate measuring
instruments already installed.
~ Cumulative Leakage Index
(CLI)
In March 1985, new regulations gov-
erning frequency offsets, signal leak-
age and the cumulative leakage index
(CLI) were approved. All of the new
regulations went into effect on July 19,
1985 except for the CLI measurement
and reporting requirements, which
became effective on July 1, 1990.
The CATV system has the option of
selecting either of two methods of cal-
culating the CLI.
1. The Iinfinity (commonly called “I
of infinity”) is easier to compute
because it entails less data col-
lection; however, this method
penalizes large systems.
2. The I
3000
method is a bit more
complex because it factors in the
distance of the leak with an imagi-
nary point 3000 meters above the
geographic center of the system.
For large systems, plan to gather
the distance data during ride-outs.
The FCC allows CATV systems to use
both methods to calculate CLI and
will accept the most favorable result.
For instance, the FCC considers a sys-
tem acceptable that passes I
3000
but
fails Infinity. In other words, if a sys-
tem passes either test, it qualifies!
Computer Software
Most technicians will probably not be
called upon to compute the CLI without
the help of a personal computer and
specialized software. Computers can
calculate the CLI quickly and accurately.
5-3
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