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The
shielding effectiveness of a coaxial cable
depends on the construction of its outer
conductors. Generally, the shielding efficiency
is measured by the relative level of the
signal leaking from the outer conductor
in decibels per one foot of the length.
The effectiveness of shielding on microwave
cables usually diminishes with increased
frequency. In practice, the shielding efficiency
of semi-rigid (solid sheath) cables is limited
by the leakage of the connectors and the
cable/connector junction. Some factors which
influence the shielding effectiveness of
flexible cable assemblies are:
-
Number of shields: (flat braid, round
braid and helical wrap).
- Braid
style and coverage: (a flat braid is usually
better than a round braid and a higher
percentage of braid coverage normally
provides better shielding).
- Thickness
of shield materials and plating of the
conductor: (cable outer conductors are
typically silver plated).
- Connector
and style of attachment: (the best shielded
connector typically uses a threaded coupling
nut with a slotless outer conductor attached
to the cable by clamping, soldering or
crimping with minimal amount of outer
conductor junctions).
Engineering
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