Question
How does parallel conductor transmission line compare to coaxial cable with a plastic dielectric?
Answer Options
- A) Lower loss
- B) Higher SWR
- C) Smaller reflection coefficient
- D) Lower velocity factor
Correct Answer: A
Explanation
Parallel conductor line (ladder line or open-wire line) is typically air-insulated with plastic spacers, while coaxial cable (coax) often uses a solid or foamed plastic dielectric. The type of dielectric material used has a direct impact on the line’s characteristic losses and velocity factor.
Compared to coax with a solid plastic dielectric, the parallel conductor line is mostly air-insulated. Since air is a very low-loss dielectric, the main advantage is Lower loss, especially at HF frequencies. This low loss makes open-wire line superior to coaxial cable for feeding high-SWR loads or for applications where line loss must be minimized.
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