AdvancedA-007-002-011
The velocity factor of a transmission line is the:
A
Answer
Interference, EMC, and safety
Type
A
ratio of the velocity of propagation in the transmission line to the velocity of propagation in free space
B
impedance of the line, e.g. 50 ohm, 75 ohm, etc.
C
speed at which the signal travels in free space
D
speed to which the standing waves are reflected back to the transmitter
Answer Notes
The velocity factor of a transmission line is a fractional number, usually expressed as a decimal or percentage (like 0.66 or 66%), that compares how fast a signal travels within the cable to how fast it travels in a vacuum.
Because the dielectric material in the cable slows the electromagnetic wave down, the velocity in the line is always less than the speed of light. Thus, velocity factor is defined strictly as the ratio of the velocity of propagation in the line to the velocity of propagation in free space.
Options describing the absolute speed in free space or VSWR-related wave reflections are incorrect because velocity factor is fundamentally a comparative measurement of signal speed.
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The reciprocal of the square root of the dielectric constant of the material used to separate the conductors in a transmission line gives the ____________ of the line:
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What term describes a method used to match a high-impedance transmission line to a lower impedance antenna by connecting the line to the driven element in two places, spaced a fraction of a wavelength on each side of the driven element centre?