A dipole antenna uses two conductors of the same length to detect radio waves and transmit the corresponding variable electrical current to a receiver. Each conductor represents one-quarter of a wavelength, and when combined, the dipole can detect a half-wavelength signal. The length of the two conductors determines the operational frequency.
Dipole antenna conductors can be wires or metal rods, depending on the design. One conductor provides the feeder while the other provides a second signal path, balancing each of the one-quarter wavelengths. Some receivers use the feeder signal and ground the other signal, but many designs use a coaxial connection to feed both signals. With coaxial connections, an additional device called a balun helps balance both signals and reduce potential radio frequency noise. Dipole antenna designs range from simple two-wire units to complex folded dipoles mounted on a mast. Folded designs allow for longer conductor lengths without additional space and are typically used by professionals.
Before cable television, most households had some kind of dipole antenna. Early televisions used “rabbit ears,” a dipole antenna with telescoping conductors at an angle. Adjusting the length of the conductors and the corresponding angle usually produced a strong signal for some channels. Later televisions and radio receivers used the coaxial design, and most came with a balun as part of the packaging.