Endfed

Endfed refers to end-fed antennas, a class of radio antenna configurations in which the radiating element is connected to the feedline at one end. The conductor is usually a single wire or a small number of parallel wires that are supported or elevated away from the ground. End-fed designs are commonly used on HF bands, with the radiator length typically chosen to be roughly a half-wavelength at the target frequencies. Because the end of a half-wave radiator presents a relatively high impedance to the feedline, a matching device is normally required to connect to standard 50-ohm coax.

A typical end-fed half-wave antenna uses a matching network at the feedpoint, such as an impedance transformer or unun, to transform the high antenna impedance to a suitable level for the coax and transmitter. This network may be mounted at the feedpoint or nearby. A counterpoise or ground connection is usually provided to furnish a current path for the antenna; in some installations the coax shield or the matching network itself serves part of this path.

Advantages of end-fed antennas include a simple and compact physical footprint, suitability for restricted spaces, and the ability to install them on rooftops, balconies, or portable setups. They can offer multi-band operation with a single wire, though performance depends on height above ground, overall length, and the effectiveness of the counterpoise.

Limitations include reliance on a good matching network, potential RF exposure near the feedpoint, and varying efficiency depending on installation details. End-fed antennas are widely used by amateur radio operators and are discussed in the context of antenna design and tuning.