General exam question G9D08
Subelement G9, ANTENNAS AND FEED LINES· Group G9D
How does a “screwdriver” mobile antenna adjust its feed point impedance?
- A.By varying its body capacitance
- B.By varying the base loading inductance (correct answer)
- C.By extending and retracting the whip
- D.By deploying a capacitance hat
WhyA screwdriver mobile antenna adjusts its feed point impedance by varying the base loading inductance. A screwdriver antenna adjusts its resonant frequency and feed point impedance by using a small motor to move a tap or slider along a base-loading coil, changing how much loading inductance is in the circuit, answer B. It doesn't work by varying body capacitance, mechanically extending/retracting the whip (that describes a manual travel antenna instead), or deploying a capacitance hat, so A, C, and D are wrong.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2023-2027 NCVEC Element 3 pool (public domain); the explanation above is original writing, see our methodology.
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