The delta loop antenna is one of the most capable yet misunderstood antenna designs in radio communications. Simple in appearance but rich in performance, it consists of a closed loop of wire arranged in a triangular shape. Despite its straightforward construction, the delta loop offers exceptional efficiency, flexible polarization, and remarkable noise performance across the HF spectrum. This book is a complete, focused exploration of the delta loop antenna, written for operators who want more than surface-level explanations. It connects electromagnetic theory with real-world results, showing not only how to build a delta loop, but why it behaves the way it does. Rather than treating the loop as just another wire antenna, this book explains how its closed geometry, circulating currents, and feedpoint options create radiation patterns and impedance characteristics that differ fundamentally from dipoles and verticals.