Foundations Of Amateur Radio

Foundations of Amateur Radio Recently I was asked about finding the best antenna calculator. It's a tool that helps you determine what the length of an antenna should be for a particular frequency. Picture a dipole antenna, two wires, end to end, strung out horizontally, joined in the middle by a feed point. A dipole is most effective if its total length is half of the wavelength of the frequency it's intended for. To calculate what that is, you divide the speed of light by the frequency. So, for argument sake, the wavelength for 28.5 MHz is roughly 10 m, which makes sense, since 28.5 MHz is in the 10 m band. If you use your favourite search engine to find a dipole calculator, you'll find many different ones. If you try a few, you'll find that the answers that each calculator gives is slightly different. For a half-wave dipole on 28.5 MHz, you'll find that there is a half meter variation among the calculated answers. If you do this for a dipole for 3.5 MHz, you'll find the variation is just over 4 m betw