Directional Delta Loop Antennas

Delta loop antenna is a full wave length antenna in the shape of the Greek alphabet Delta (Δ). A single delta loop antenna has a gain of about 3 dB over a center fed half wave dipole. It is a good transmitting antenna as well as a low noise receiving antenna. In general, closed loop antennas are not affected by electrostatic noise or QRN. That is why Delta loop antenna is useful in locations where other antennas are not useful due to electrostatic noise.

Radiation pattern of the delta loop antenna is along its broad side. Instead of using a 4:1 balun at feedpoint, a quarter wave length matching section of 75 Ohms coax can be used. The matching section is needed as the impedance of Delta loop antenna is around 100 Ohms. Directional gain of the delta loop antenna can be increased by adding elements just as in Yagi-Uda antenna. They have higher gain than a Yagi antenna with the same number of elements, up to 5-6 elements.

Recently I saw a Twitter post of two element 10 m Delta loop antenna. The reflector element was bigger than the driven element and the boom length was 2 m. It was fed at the bottom corner. If a side corner is fed, Delta loop antennas can be made with only a single high support. Otherwise it needs two tall supports in the usual pattern. Low take off angle of the main lobe of radiation makes it a good antenna for long distance or DX contacts. Signals with low angle are bounced back by the ionosphere at a larger distance. Another advantage cited for multi-element Delta loop antenna is that, compared to a Yagi antenna of same gain, it has a wider beam width. This could be an important advantage for working DX as well as contests.