BTW - The difference in optimum antenna lengths from one end of the 72MHz band we use to the other end of the band is probably in the order of a few milli-meters.
The actual quarter wavelength for channel 11 (72.01 MHz) is approximately 40.91431746 inches, and for channel 60 (72.99 MHz) 40.3649815 inches (very approximately!)
So the very approximate difference in antenna length for a quarter wave one is (very approximately) 0.549335952 inches.
(approximately)
Incidentally, that calculation can easily be done by taking the speed of light (and radio waves ) at 186,000 miles per second, expressing it in inches per second (times 63360) and dividing it by the frequency to get the wavelength of approx 163 inches, then dividing by 4 to get a quarter wave length.
(approximately)
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-David C.