I’ve written about magnetic loops for tight spaces, but full-size wire loops are a completely different animal and they deserve their own writeup. A full-wave loop is simply a wire, roughly one wavelength long on your target band, formed into a closed shape and fed at one point. No magic, just a different geometry than a dipole with some real advantages.
Delta Loop vs Horizontal (Rectangular) Loop
A delta loop is a triangular full-wave loop, usually fed at a bottom corner, and it’s popular because it only needs one high support point with the other two corners anchored near ground level. A horizontal loop is flatter and more rectangular, strung between four supports (or however many corners you can manage), and behaves more like a big, quiet receiving and transmitting antenna for the bands it’s cut for.
Why Bother Over a Dipole
A full-wave loop typically shows a small gain advantage over a simple dipole on its design frequency, and loops tend to run quieter on receive, which matters a lot on crowded bands. They also present a different impedance and pattern than a dipole, so if you already have a good dipole and want a genuinely different signal on the same band, a loop is a legitimate second antenna rather than a redundant one.
Space and Support Requirements
This is the real tradeoff. A full-wave 40m loop needs roughly 140 feet of wire, which is a lot more real estate than a 40m dipole needs in a straight line, though a loop’s shape gives you more flexibility to bend around trees and property lines than a dipole does. If your property can’t fit one, this isn’t the antenna for you, full stop.
Feeding a Loop
Full-wave loops present a relatively high impedance at resonance, so most people feed them with ladder line into a tuner rather than trying to force a direct 50 ohm coax match. That adds a little complexity and cost over a coax-fed dipole, but it also means the loop can be worked reasonably well across multiple bands rather than just the one it’s cut for.
Who Should Actually Build One
If you’ve got the property and you already have a working dipole or vertical, a full-size loop is a great next antenna project rather than a first one. It rewards people who already understand feedline and tuner basics and want to hear the difference for themselves.
Related reading: The G5RV and Windom · Hex Beams and Cubical Quads · Fan Dipoles