Question
What is the approximate physical length of an air-insulated, parallel conductor transmission line that is electrically 1/2 wavelength long at 14.10 MHz?
Answer Options
- A) 7.0 meters
- B) 8.5 meters
- C) 10.6 meters
- D) 13.3 meters
Correct Answer: C
Explanation
The physical length of a half-wavelength transmission line required for a specific electrical length is calculated using one of the formulas L_{Feet} = \frac{492 \times VF}{f_{MHz}} or L_{Meters} = \frac{150 \times VF}{f_{MHz}}, where VF is the velocity factor, and f is the frequency. Since the line is air-insulated (such as ladder line), the velocity factor (VF) is very high, approximately 0.95 to 0.98. Therefore, we use the speed of light approximation, VF \approx 1 for a simple calculation.
\frac{150}{14.1} \approx 10.6m
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