Question
What is a characteristic of a random-wire HF antenna connected directly to the transmitter?
Answer Options
- A) It must be longer than 1 wavelength
- B) Station equipment may carry significant RF current
- C) It produces only vertically polarized radiation
- D) It is more effective on the lower HF bands than on the higher bands
Correct Answer: B
Explanation
A ‘random-wire’ antenna is typically a long wire whose length is not carefully related to the operating wavelength. When this type of antenna is fed directly by an unbalanced output (like a coaxial cable center conductor) without a matching network or counterpoise, it often presents a poor impedance match.
Crucially, this setup creates high common-mode current that flows on the shield of the coaxial cable, which then flows onto all conductors connected to the transmitter, including the station equipment grounds and power cords. This means station equipment may carry significant RF current, leading to RF burns, RFI, or erratic equipment behavior.
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