Why For a half-wave wire dipole the standard practical formula is length in feet = 468 divided by the frequency in MHz. That gives 468 / 14.250 = 32.8 feet, which rounds to about 33 feet. The 468 figure already includes the roughly 5 percent shortening from the velocity factor of wire and end effects, so it is a bit less than the 492/f free-space half wavelength.
Watch out About 16 feet is half that answer, which is a quarter-wave length, the size of one leg of the dipole or of a quarter-wave ground-plane vertical.
468 over f in MHz for a half-wave dipole; 234 over f for a quarter-wave vertical or one leg.