E. V
p
of Common Cables
E.1. Cable Types
Commonly encountered cable designations, along with their associated characteristic
impedances and typical Vp values, are listed below. A more complete listing is stored in the
CT100B’s internal memory. Note that the actual Vp of a given cable can vary by manufacturer,
manufactured lot, cable age and condition, whether it is flat or coiled on a roll, and other
variables. The most accurate way to test a cable is to determine the Vp of the cable using the
CT100B and a known length of the cable you wish to test. See Section 3.10.3 for more
information on determining the Vp of a cable.
E.2. Dielectric Material
Table E.1.
Vp of Common Dielectric Materials
Type
Probable Vp
Jelly-filled
0.64
Polyethylene
0.66
PTFE / TFE
0.70
Pulp
0.72
Foam / cellular PE
0.78
Semisolid PE
0.84
Air
0.98
CT100B TDR Cable Analyzers Operator’s Manual
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