I have been looking everywhere for a simple, easy-to-understand explanation of antenna dimensions/properties. I am referring to omni-directional that are basically just a piece of wire that stands perpendicular to the ground, like Wi-Fi antennas. I've read that the length of the antenna has something to do with the frequency that the antenna works best at. I've read stuff mentioning the quarter-wavelength as being an important value. I've read that a coil can be a part of the antenna to split the antenna into two antennas, each for a different frequency; I've also read that a coil at one end or the middle of an antenna can improve the signal somehow. My questions are: Which of the above things I've read are true, and which are not? What is the formula used to calculate the length for a given frequency? What is the formula used to determine the number of turns, diameter, and spacing between turns of a coil described above for a given frequency? What is so important about the quarter-wavelength? I mean, why would the full-wavelength be less important/not work as well?