Why is a 19-inch-long vertical antenna often used on 2 meters?

To understand why a 19-inch antenna is used for the 2-meter band, you can calculate the physical length of a radio wave at that frequency. The 2-meter band covers roughly 144 to 148 MHz. Using the standard formula for a quarter-wavelength antenna in inches (234 divided by the frequency in MHz), 234 / 146 MHz equals approximately 1.6 feet, which is just over 19 inches. Because 19 inches corresponds to a quarter-wavelength, an antenna of this length is naturally resonant on the 2-meter band. This makes it highly efficient and very popular for mobile and handheld transceivers. It is not a half-wave antenna, which would be about 39 inches long, nor does a simple quarter-wave whip provide high gain compared to larger directional antenna designs.