What is the gain for a particular CB antenna – What antenna has the best gain?
Gain can be measured either against a 1/4-wave antenna or 1/2-wave. For most antennas, the old industry standard was to compare antenna gain to an isotropic antenna, which is a theoretical antenna that has the gain of a 1/2-wave antenna, but all emissions emanate from a pinpoint (that’s why it’s only theoretical). An isotropic antenna can be loosely defined as a single half-wave element. CB radio frequencies center around 27.2 MHz. By today’s standards, that’s a low frequency, even though back when it was named, it was called the “HF” or High Frequency band. The lower the frequency, the LONGER the wavelength. The longer the wavelength, the longer the antenna needs to be to have any gain. There is a commonly used formula to calculate the starting wire length for a 1/2 wavelength wire antenna: Length = 468/Freq Length is in feet, and Freq is in MHz. For CB, we solve this as follows: length = 468/27.2 = 17 feet, 2-1/2 inches. So, we now know that an antenna of about 17 feet will have the
