Wire Antenna

Many amateur radio antenna systems use a simple wire to carry the RF current in such a way as to radiate. One of the simplest is the dipole. When a dipole oscillates current, in sync with the radio's RF output during a transmission, the magnetic field generated around the wire expands and contracts very quickly, in most cases millions of times per second. It is the outer most part on the field that is radiated away.

The shape of a dipole resembles the letter "T". The middle leg connects the radio to the center of the upper, horizontal legs. There are several ways to make the connection. The simplest has the coax shield connected to one side and the center conductor connected to the other side. This works but there are losses at the connection due to impedance mismatch. A better way is to make or purchase a "balun". A balun matches the impedance of the radio to the impedance of the dipole more closely. This increases the power actually transferred to the upper legs of the dipole. (Balun stands for BALanced to UNbalanced.)