User's Manual

Table 8-1: Availability and Outage
Availability Outage % Outage Time
99.9% 0.1% 9 hours/year
99.99% 0.01% 1 hour/yr
99.999% 0.001% 5 minutes/yr
The Availability is often referred to by the number of nines, e.g., 99.9% is Three
Nines Availability.
Typical cable industry targets
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are:
Downstream error rate of 1.e-9 or 1.e-10 for 64 QAM.
Upstream error rate of 1.e-5 to 1.e-7 for QPSK.
User Availability at least 99.7%
10.6 Antennas
Antennas come is many shapes and sizes, determined by the application.
The purpose of the antenna is to focus electromagnetic energy, just as a lens
focuses light, and to resonate at the desired frequency, just as a musical
instrument resonates, so that it performs best at the desired frequency.
We show the directionality of an antenna on polar graph paper, as in Figure 10-8.
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W. Ciciora, J. Farmer & D. Large, “Modem Cable Television Technology”, Morgan Kaufman,
1999, pp 644-649.
ARCXtend manual, August 2003 10-8