How does a “screwdriver” mobile antenna adjust its feed point impedance?
By varying its body capacitance
By varying the base loading inductance✓Bonne réponse
By extending and retracting the whip
By deploying a capacitance hat
Explication
A screwdriver antenna uses a small motor to move the loading coil relative to a fixed contact, changing the effective base loading inductance so the short whip is brought to resonance on different frequencies. The whip itself does not extend or retract.