Triad: A Small-Footprint High Frequency Antenna System Design
Abstract
Marcus O. Durham, Pruitt R. Durham and Robert A. Durham
The objective is to develop high-frequency (HF) antenna systems that are small, unobtrusive, usable in limited space, indoor or portable, not exposed to lightning, easily configurable, requiring only simple tools, minimum install, without climbing, and inexpensive. Construction, tests, and measurements clearly illustrate an HF antenna system can be greatly reduced in size to a couple of meters.
Ten circuit design implementations condense HF antennas to a miniscule space, resulting in dramatically lessened environmental impact. A key consideration is changing every antenna element to a tunable inductor. Add inductor elements for wider bandwidth and multi-band. SWR, impedance, and frequency plots illustrate the fascinating performance.
Most contemporary antennas are variations of the balanced dipole used by Hertz in 1888 or the unbalanced monopole advocated by Marconi in 1895. Little has changed in high frequency antennas since those early two designs. This design is closely-coupled to the earth, more reminiscent of Tesla. Below 30 MHz, antennas are still largely long-wires with distributed electrical and magnetic properties. All antenna circuits have two electrical connections: 1) the radiator and 2) the electrical return, comprised of the monopole counterpoise or the dipole non-radiating side. More creativity options exist on the return side of the circuit than on the radiator. This article summarizes the NM0D Triad antenna system, which fits all the objectives.