ComSonics CyberTek QUALIFIER User Manual page 42

Appendix - Qualifier System
Exhibit C
Local Tap
Drop Cable
Antenna
Inside Cables
Transmitter
Service Vehicle
Ground Block
The CATV cabling inside a home is usually hidden in areas such as craw spaces, behind
walls, attics, and basements. The effects of aging on the cable (especially metal connectors),
rodent damage, and possibly improper installation reduce the shielding integrity of the
system within the home. Poor shielding integrity allows the inside cabling to become a
receiving antenna for interfering signals. A signal or noise entering (ingress) the internal
cabling has the possibility of traveling to the upstream path and causing problems.
Since all homes have the potential to cause problems in the upstream path, a test is needed to
qualify each individual home. If the internal cabling is susceptible to ingress from devices
within the home, then it will also have ingress from a known signal source. The known
signal source is a mobile transmitter operating on a frequency in the 5 to 50 MHz range. The
mobile transmitter is installed in a service vehicle and is powered from the vehicle. An
omni-directional antenna is connected to the transmitter and mounted on the vehicle. The
antenna is best mounted on the vehicle roof in an area clear of other metallic objects such as
other antennas, ladders, and lifting apparatus. The vehicle is parked adjacent to the home
(usually between 30 and 150 feet) and the transmitter is powered on. The home is radiated
with the test signal. A test signal frequency is chosen as not to cause interference with
known upstream communications.
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