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Fig. 5-4. Twinlead inserted into a standout (standoff).
Next, pass the twinlead through a standout or
standoff (Figure 5-4). Install the standout on either
the mast or the antenna boom as recommended by
the antenna manufacturer. Leave just enough slack to
relieve tension on the antenna connections. Crimp
the standout firmly enough to securely hold the twin-
lead but not so firmly that it deforms the twinlead.
Thoroughly spray the antenna connections with an
acrylic insulator such as Krylon.
This will retard corrosion and rust. Also, seal the end
of the twinlead if foam is used as part of the twinlead
insulating material. This will prevent moisture
absorption.
Twinlead must not be run close to metal. Metal
interacts with the twinlead conductors. This causes
signal mismatch, resulting in inefficient signal
transmission through the line.
Horizontal runs of twinlead also act as an antenna.
This causes two or more sets of identical signals to
reach the receiver at different times producing ghosts
on the TV screen. It may also cause "suck out," or loss
of signal.
Some types of twinlead also develop high attenuation
(increased impedance) in wet or humid weather. This
causes severe signal loss.
If an antenna rotor is used, never run the twinlead
and rotor wire through the same standout. The wires
and signals will interact, and the quality of the TV
picture will be decreased. Use two evenly spaced
mast standouts for the top 5 feet of mast or in-line
double standouts designed to carry both rotor and
transmission line. Use additional standouts as
necessary to keep the twinlead away from the mast.
Standouts should be at least three inches long. Twist
the twinlead once every three feet to prevent wind
lashing (Figure 5-5).
Use additional standouts at ends and turns to keep
the twinlead away from eaves, gutters, drainpipes
and any other metal surfaces. When running twinlead
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indoors, drive staples or tacks only in the center
portion of the insulation between the conductors. Do
not use any staples or tacks large enough to "bridge"
the conductors. This will short the conductors. Run
twinlead directly to the back of the set from the wall,
floor, or baseboard. Don't leave more twinlead than
absolutely needed. Extra twinlead will coil up and act
as additional antennas. This causes ghosting and
signal loss.
Fig. 5-5. The twinlead should be twisted to prevent windlash.
L
INE
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