What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?

To find the approximate physical length of a quarter-wave antenna in inches, you can use a modified version of the standard dipole formula. First, calculate a half-wavelength in feet using 468 / Frequency (MHz). For 146 MHz, 468 / 146 is about 3.2 feet. Since you need a quarter-wavelength, divide that in half to get 1.6 feet. Finally, multiply by 12 inches per foot to get 19.2 inches. Rounding this down gives the correct answer of 19 inches, which is the standard size for a 2-meter quarter-wave whip.