Ideal tuner for experiments with magnetic loop antennas. Simply wind a wire around a frame or hang it between two trees and connect both ends to the MFJ-935B antenna tuner - and you have an efficient Magnetic Loop!
The MFJ-935B uses a large butterfly capacitor to tune a self-built loop antenna. Depending on the wire length you can cover the frequency range from 3.5 to 30 MHz, but not with the same wire length. The tuner is designed for a maximum power of 150W PEP.
Magnetic loop antennas are known for their very good efficiency in relation to the size of the antenna. They achieve a low radiation angle and are therefore well suited for DX. When receiving, such antenna types prove to be very quiet, QRM and QRN are reduced due to the narrow bandwidth. Even simple receivers benefit because the loop antenna acts like a pre-selector. The actual frequency range results from the wire length, the shape of the loop, the environment and the height above ground. Ideal would be λ/4 for the main operating band, usually a loop of fixed length will reach a frequency range with a ratio of 1:1.5, e.g. from 3.5 to 5.25 MHz, or 5 to 7.5 MHz, or 10 to 15 MHz etc. The shape of the loop does not matter, but a larger enclosed area would be ideal. The best ratio of circumference to area is of course a circle, if possible. Horizontally and not too high above ground, such loops form excellent skywave radiators for local traffic (NVIS). The connection to the radio is a PL socket, the antenna loop is connected with large screw terminals. Size 152 x 127 x 228 mm, weight approx. 1.5 kg.