Sunspots and solar radiation, ionospheric disturbances, propagation forecasting, and indices

Amateur radio communications are subject to the whims of nature. Many different phenomena affect the propagation of signals, and it behooves you to know a little something about the phenomena. Doing so will make you a more effective amateur radio communicator.

Directional antennas

To make their signals more effective, some amateurs use directional antennas. Directional antennas, such as Yagis and quads, direct most of the power output in a particular direction, making the signal seem more powerful. They are also more sensitive to receiving signals from a particular direction. This feature makes them useful for reducing interference. All you have to do is turn the antenna away from the source of interference.

Feed lines are the cables used to connect antennas to receivers and transmitters. The most important characteristic of a feedline is its characteristic impedance. Many different factors affect the characteristic impedance of a feedline, including the distance between the center of the conductors and the radius of the conductors.