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3. Calculate the physical length of the cable by dividing the above speed by the
resonant frequency (in Hz) and multiplying the result by the number which
corresponds to the location of this resonant frequency (1/4, 1/2, 3/4, 1, 5/4, etc.)
Example:
197,863,022 / 9,400,000 · (1/4) = 5.26 meters
- or -
649,156,897 / 9,400,000 · (1/4) = 17.26 feet
5.2.3. Velocity factor measurement
F
or a known resonant frequency and physical length of a cable, the actual value of the
velocity factor can be easily measured:
1. Locate a resonant frequency as described above.
Example:
5 meters (16.4 feet) of open-circuited cable.
Resonant frequency is 9400 kHz at the 1/4-wave point.
2. Calculate the speed of electromagnetic wave in this cable. Divide the length by
1/4, 1/2, 3/4, etc. (depending on the location of the resonant frequency), then
multiply by the resonant frequency (in Hz).
Example:
5 / (1/4) · 9,400,000 = 188,000,000 meters per second
- or –
16.4 / (1/4) · 9,400,000 = 616,640,000 feet per second
3. Finally, find the velocity factor. Just divide the above speed by the
electromagnetic constant.
Example:
188,000,000 / 299,792,458 = 0.63
- or –
616,640,000 / 983,571,056 = 0.63
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