Nominal Velocity Of Propagation (Nvp) - Fluke DSP-4100 User Manual

Nominal Velocity of Propagation (NVP)

NVP is the speed of a signal through a cable relative to the speed of light. In a
vacuum, electrical signals travel at the speed of light. In a cable, signals travel
slower than the speed of light. Typically, the speed of an electrical signal in a cable
is between 60 % and 80 % of the speed of light. Figure 7-12 shows how the NVP
percentage is calculated.
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NVP values affect the limits on cabling length for Ethernet systems because
Ethernet operation depends on the system's ability to detect collisions in a
specified amount of time. If a cable's NVP is too low or the cabling is too long,
signals are delayed and the system cannot detect collisions soon enough to prevent
serious problems in the network.
Signal Speed
in Cable
CABLE ANALYZER ADAPTER
DSP-658 CABLE ANALYZER
Speed Pulse Travels in Cable
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Figure 7-12. How NVP is Calculated
Nominal Velocity of Propagation (NVP)
300,000,000 NVP m/s
=
300,000,000 m/s
Speed of Light
Basic Cabling Testing
X 100%
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