Specifications

[
StarServe Installers Guide
]
page 33
Ghosting
There are three common causes of ghosting:-
• Pickup of reflected signals by the antenna.
• Direct pickup of a signal by the TV or TV lead.
• Poor installation techniques.
Not all signals reach an antenna directly. They can be
reflected by buildings, mountains, or bodies of water. These
reflected signals arrive at the antenna microseconds after
the direct signal. This causes a second, fainter image to
appear on the TV screen, just to the right of the main image.
This is called a trailing ghost.
A trailing ghost can usually be eliminated by using a highly
directional antenna or by stacking antennas. Changing the
orientation of the antenna slightly may also eliminate the
reception of the reflected signal.
A second image appearing to the left of the main image is
called a leading ghost. This is the result of the direct pickup
of signal by the TV lead (when using 300-Ohm twin lead), by
the TV tuner itself or by the down lead from the antenna.
A leading ghost sometimes occurs in strong signal areas
when signal is picked up directly and displayed microseconds
before the image picked up by the antenna. Since 300-Ohm
twin lead is unshielded and can act like an antenna, it should
be removed and replaced with 75-Ohm coaxial cable. A balun
should be placed as close as possible to the antenna terminals
and the coaxial cable connected to the TV set with a matching
transformer. Overpowering the unwanted signal can also
eliminate this type of ghosting.
Poor installation techniques can cause ghosting. If the
distribution line installations are improperly terminated, the
signal can bounce up and down the line, causing multiple
images. Proper use of terminators can eliminate this problem
at the time of installation.
Poor crimping of “F” fittings can cause an impedance
mismatch, and can result in reflected signals in the line. Using
a good crimping tool and making sure that all fittings and
splices are correctly executed will help ensure trouble free
operation of a system.
Cable
StarServe video cabling should be cabled with RG-6, quad
shield, 75-Ohm coaxial cable. Coaxial cable is a concentric
transmission line. It consists of a central conductor, a
dielectric medium (such as polyethylene) which fixes the
spacing between the central conductor and an outer shield
(such as copper braid or aluminum foil) and a weatherproof
outer jacket (usually vinyl).
All StarServe coaxial cable connections use standard
F-Type connectors for faster, easier installation.
Losses in coaxial cable are specified as attenuation per metre
of cable.