Small Loop Antennas

Small Loop Antennas
Joseph J. Carr
Small loop antennas are defined as loops that have a total wire length of less than 0.15 wavelength (0.15l). These antennas perform quite differently than large loop antennas such as the bisquare or quad loop. Small loops are used in radio direction finding, and in ordinary DXing for receiving weaker stations in the presence of strong interfering stations. The performance of the small loop is less than that of other antennas (e.g. the half wavelength dipole), but its extremely sharp nulls and broad maxima frequently make it the antenna of choice on very crowded bands. In those cases you are swapping gain for signalto- QRM ratio.

Small loop antennas are used mostly on the lower frequencies. Although designs exist for the upper end of the high frequency shortwave band (and some for VHF bands), the principal uses are in the VLF through mid-HF spectrum (roughly 10 KHz to 8,000 KHz). Loop antennas can have a circular, square, rectangular, hexagonal or octagonal shape. In this paper we will take a look at the square form because they are relatively easy to build compared with the other forms (including circular). The square loop is not only mechanically easier to build, it performs very nearly the same as circular loop antennas of similar size. read more >>