Definition of a Dipole Antenna

Antenna Components

• The typical wire dipole antenna is made up of two predetermined lengths of wire, a central insulator that isolates the two wires from each other, and two end insulators that allow the antenna to be hung between two supports.

Antenna Formula

• The accepted construction formula for a dipole antenna is L=468/MHz where L is the length of the antenna in feet and MHz is the desired frequency in megahertz.

Versatility

• Although a dipole antenna's length is calculated according to a preferred frequency, it also works well on multiples of its frequency on other radio bands. It is therefore common for a dipole antenna that was designed for 80 meters to also work on 40, 20 and 10 meters.

Connection

• The dipole is connected to the radio by a feedline that can be coax cable, twin lead or "window" line. Depending on the type of dipole antenna, the connection can be center-fed, end-fed or off-center-fed.

Orientation

• The dipole antenna's maximum efficiency is perpendicular to its axis. Its primary radiation nodes radiate more prominently in that direction than in any other.

Antenna Tuning

• The dipole antenna works best when its length has been carefully trimmed to its maximum efficiency. Alternatively, an antenna tuner can be used to change the electrical length of the antenna for optimum use.