What is the approximate length of the driven element of a quad antenna designed for 21.4 MHz?

The driven element of a quad antenna is a closed wire loop with a total perimeter of exactly one full wavelength. To find this length in metres, amateur radio operators use the practical formula of 306 divided by the frequency in MHz (derived from the imperial equivalent of 1005 divided by frequency in MHz). Plugging the target frequency into this formula gives: 306 ÷ 21.4 MHz = 14.299 metres. Rounding this result gives 14.30 metres, which represents the total circumference of the four-sided loop. The other options represent incorrect formulas for this antenna type. For instance, roughly 7 metres would be the length of a half-wave straight dipole, which is only half the length needed for a full-wave quad loop.