“Wire Antennas 160 meters to 70 cm: Concepts, Construction and On the Air”
Bob Glorioso, W1IS and Bob Rose, KC1DSQ
Many modern transceivers have built-in tuners that can tune out SWRs of 3:1 or less. The goal of the antennas in this book is to achieve a 3:1 or less SWR across the full width of as many bands as possible. Much of this work is motivated by antennas for Field Day. All of the antennas used by our local club for Field Day are included in this book.
We start by building an understanding of how dipoles work. This is followed by a build project aimed at new Technician licensees to build a simple to deploy 6m dipole. Another build follows: a 2 m / 70 cm roll-up J-Pole. That may be of interest to the new Technician as well as those interested in Emergency Services and remote operation.
The next two chapters expose more antenna theory to help the reader get the most out of the following chapters. This imparts the understanding needed for building multi-band wire antennas. Detailed instructions for building baluns and capacitive loads follow.
Next we show how to make 40-15-meter antenna or modify an existing 40m dipole into a 40-15-meter dipole that achieves low SWR on both bands. We introduce the concept of deploying a capacitive load to selectively raise the frequency of resonance for 40-meters without changing the 15-meter resonance.
The following three Chapters apply the concepts in all the previous chapters to Off Center Fed Multi-Band Antennas and End Fed Multi-Band Antennas. These antennas cover 160m to 6m. The capacitive loading principle is applied to these designs to achieve low SWRs. A unique C-Pole design is included for space-constrained deployments.
Beams for HF can be awkward and this chapter boils them down to a configuration that can be carried by one person and installed from ropes hanging from trees. The first, a 40m beam uses a Driven Element – Director configuration to deliver good forward gain from this wood and wire beam. The second, two-phased dipoles also made of wire and wood that delivers good forward gain and an outstanding front to back ratio. The front/back direction can be reversed by flipping a relay. These are mono-band antennas that can be built for 20, 17, 15. 12, 10 or 6-meters. We close with a novel and effective 70 cm reflector beam.
This is followed by an introduction to Vertical antenna theory coupled with practical wire verticals for 160m, 80m and 40m. These antennas have low take-off angles useful for working DX on the lower bands.
The last construction effort includes an introduction to the basics of Loop antennas for lower bands and a simple wood and wire loop design for 20m, 15m, 10m and 6m to fill in holes in coverage when using multi-band lower band antennas on harmonics that have nulls in signal strength in some directions.
The final Chapter is a collection of simple “Rules of Thumb” that boils down complex concepts to some simple definitions that may be both helpful and amusing.
The authors have built and put on the air most of the antennas described in this book and, in many cases, use them daily.