Full Wave Loop Antenna

Full wave loop antenna is also known as self-resonant loop antenna and large loop antenna. Other loop antennas are halo antenna and small loop antenna. Perimeter of the full wave loop antenna is slightly more than a full wavelength of the operating frequency. It is quite efficient and can be used for transmission and reception. Small loop antenna is mostly used as a receiving antenna. Shape of the loop can be a circle, triangle, square, rectangle or any closed polygon.

A popular form of full wave loop antenna is quad antenna with a square shape constructed with a wire strung on an X shaped supporting frame. Additional parasiting elements can be used as director and reflector. Such an antenna array will have unidirectional gain which increases with each additional parasitic element, like a Yagi-Uda antenna. The antenna gets a diamond shape if mounted on a ‘+’ shaped support. A triangular full wave loop antenna is another form of a vertical loop which it requires only one elevated support.

In a special case of full wave loop antenna, a rectangle which is twice as high as its width gives a better gain and can match 50 Ohms directly if used as a single element. Different shapes of loop antennas will have different gains and impedances. Gain and impedance also changes with the location of the feed point on the loop. My Twitter contact G6AD uses a full wave loop of wire at 30 feet for 80 m. It is coax fed to a 2:1 transformer. With that set up he is able to work DX on 80 m with 100 W.
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