Amongst all available wire-antenna options, the vertical full-wave loop (vFWL) has established itself as an excellent performer in terms of efficiency, gain, and take-off angle (TOA). However, full realization of these considerable advantages are accompanied by size, geometry, and height requirements that become increasingly daunting as we progress to lower frequencies. Accordingly, in hopes of extending the vFWL concept to 160-meters, we consider a loaded-loop design (vFWLL) of a size amenable to a standard suburban or even city lot deployment. As will be seen, this antenna has proven a quite effective DX performer.
The described antenna is a culmination of some four years of work involving a series of loop antenna designs that have proven both compact and DX-capable. My work with electrically ‘large’ loops began at 20m and progressed incrementally to longer wavelengths; 30m, 40m, and 60m, all without need for loading-coils or resonators of any type. These antennas were very effective, resulting in several DXCC awards, all of which were obtained while running 50 Watts or less. However, at the point I envisioned extending these results to 80-meters or even 160meters, it was immediately apparent I simply didn’t have the real estate. This is what has motivated consideration of so-called ‘loaded-loop’ designs.
In this presentation, we consider application of inductive loading to a specific full-wave loop structure, and in doing so, we discover degrees of freedom enabling design trade-offs whereby efficiency and gain may be exchanged for a DX-favorable TOA. A previous design for 80m has already proven quite effective, resulting in successful completion of DXCC and well beyond. Here, we push the concept to a substantially more difficult objective – design, simulation, and test of a vFWLL design for 160-meters. Despite a reduced efficiency due to what is essentially a 1/16-sized physical footprint, we discover this antenna to be quite DX-capable. We then take a close look at the less-than-obvious roles of polarization cancellation and ground-reflection in realization of what is an extraordinary performance level for a reduced-size antenna.