Radio Amateur Quiz Canadian License

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Question B-006-011-003

Approximately how long is the director element of a Yagi antenna for 21.1 MHz?

Correct Answer

6.4 metres (21 feet)

Explanation

Directors are shorter than the driven element (which is ~1/2 wavelength). Half-wavelength at 21.1 MHz is ≈ 150/21.1 ≈ 7.1m or 468/21.1 ≈ 22.2 ft. Directors are typically 5-10% shorter. 6.4m / 21 ft seems reasonable.

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