Delta loop Antenna

The delta loop antenna, like the Greek uppercase letter “delta” (∆) from which it draws its name, is triangle-shaped (Fig. 14-8). The delta loop is a full wavelength, with elements approximately 2 percent longer than the natural wavelength (like the quad). The actual length will be a function of the proximity and nature of the underlying ground, so some experimentation is necessary. The approximate preadjustment lengths of the sides are found from:

The delta loop antenna is fed from 52-Ωcoaxial cable through a 4:1 balun transformer. The delta loop can be built in a fixed location, and will offer a bidirectional pattern.

Reference : Practical Antenna Handbook - by Joseph J. Carr