Commscope Drop Cable User Manual download pdf (Page 8)

Braid Shielding and Coaxial Cable Performance

A coaxial cable must have, at minimum, a dual shield of aluminum foil tape overlaid with a woven braid of alumi-

num. This braid shield greatly improves the electrical and mechanical performance of the coax;

in fact, a braid shield can vastly increase the installed life of the cable. All CommScope subscriber access coaxial

cables use a combination of foil and braid shields.

Braid Shielding Provides Low Frequency Protection

Foil shielding is usually a layer of aluminum bonded to a polyester tape. It provides

100% coverage over the dielectric and is best at preventing ingress and leakage of

high frequency signals; however, it is not that effective with lower frequency signals.

Aluminum braid shielding complements foil by containing and preventing interference

from those lower frequencies.

Braid Shielding Helps Maintain DC Resistance

Foil shielding is very flexible but lacking in mechanical strength. Stress caused by installation or by twisting and

flexing over time (like in an aerial installation) will cause microscopic gaps to open in the foil. These ‘microcracks’

degrade the electrical integrity of the foil and cause the DC resistance of the cable to rise. Resistivity gets worse as

the cable twists.

Strong, flexible braid shielding supports the foil and helps fight the formation of microcracks. The braid wires do

not microcrack; they bridge the gaps in the foil. Braid shielding keeps its integrity and delivers low and constant

resistivity numbers even when twisting and flexing.

Braid Shielding Keeps Attenuation Low

Attenuation performance goes hand in hand with DC resistivity; high resistivity caused by microcracks in the foil will

result in higher attenuation. A history of 15,000 flexures can degrade a foil shield to the point where the calculated

attenuation could worsen by 400% or more. However, the robust nature of the additional braid shield keeps at-

tenuation low.

Braid Shielding Keeps Connectors Connected

The additional strength provided by braid shielding gives connectors something to hold onto. In terms of pulloff

force, both compression and crimp-fitted connectors hold much tighter to cables with braid shields.

Braid shields

increase cable

performance

and can

greatly extend

the useful life

of the cable

2.2 Cable Descriptions

The Importance of Braid Shielding

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Commscope Drop Cable User Manual Page 8