Question
What Yagi driven element feed point impedance is required to use a beta or hairpin matching system?
Answer Options
- A) Capacitive (driven element electrically shorter than 1/2 wavelength)
- B) Inductive (driven element electrically longer than 1/2 wavelength)
- C) Purely resistive
- D) Purely reactive
Correct Answer: A
Explanation
The Beta or hairpin match is an inductive element (a shunt inductor) placed across the center of the driven element. Its purpose is to cancel out an existing capacitive reactance in the element and bring the total impedance back to a purely resistive value, which is usually or .
Since the hairpin is inductive, it must be used to cancel an existing capacitive component. Therefore, the driven element feed point impedance required to use a Beta or hairpin matching system must be Capacitive. Capacitive impedance is created by making the driven element slightly electrically shorter than wavelength.
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