For this OnAllBands blog post, we’ve changed our traditional Word of the Day entry to a Question of the Day:
What is the best solution available for creating an optimized directional antenna using two identical ground-mounted, quarter-wave verticals?
To narrow our search for the ideal answer, we need to pose several more questions: Is the system easy to install? Is it within the budget of the average Ham? Is it well-designed and manufactured? How does it perform compared to past systems? Will it draw too much attention from my non-Ham neighbors?
Here’s what we concluded:
For those who are still relying on the legacy COMTEK PVS-2 to accomplish the above, you’ll want to write this down: Designed, manufactured, and tested by DX Engineering, its DVA Dual Vertical Array Systems set a new standard of performance for two-element HF vertical arrays. The system comes with a compact DVA Phasing Relay Unit made for a single band (160 through 10 meters), and an EC-DVA Directional Control Console.
Let’s look at what makes this system better. For starters, DX Engineering’s Dual Vertical Array Systems have been designed for improved efficiency by eliminating the wasteful dump load common with older hybrid-style units. This means that all power goes to the antenna elements. The installed system produces two opposite end-fire cardioid patterns and one broadside-omni pattern, as shown below.
The system also provides:
- A stable, clean, and low-angle radiation pattern
- Great signal-to-noise ratio
- Directivity over a wide frequency range in the band selected
- Heavy-duty relay unit components that can handle over 2 kW continuous RF power for enhanced performance at low SWR over a wide bandwidth
- End-fire directional patterns that achieve a real front-to-back over 20 dB with typical array forward gain up to 3 dB over a single vertical
- Excellent bandwidth under 2:1 SWR, with solid mono-band coverage (depending on the verticals installed)
Why choose a Dual Vertical Array over other directional options?
A main advantage is that this system lets Hams enjoy the transmitting and
receiving benefits of a directional antenna without the tower and rotator
needed for a large Yagi. If you have neighbors who may not appreciate the sight
of your Yagi, a ground-mounted phased array has less visual impact. Plus, mono-band
arrays are easier to install than a tower and beam, are more fiscally practical
for many operators, and achieve patterns and performance that multi-band
systems cannot duplicate.
What’s available?
Generally, DX Engineering has systems specifically for 160M (DXE-DVA 160B-P), 80M (DXE-DVA-80B-P), and 40M (DXE-DVA-40B-P) in stock. Other packages for 60M, 30M, 20M, 17M, 15M, 12M, and 10M are available by special order.
About the Relay Unit and Control Console
The weatherproof DVA Phasing Relay Unit includes a chassis bracket, with stainless steel clamp and hardware, for mounting on a 1 to 2 inch O.D. pipe or post. When mounted, the black UV-resistant cover protects the chassis and downward facing connectors. Each relay unit has three SO-239 connectors, two for the array element 75-ohm quarter-wave phasing feedlines and one 50-ohm feedline to the station. A removable connector is provided for the user-supplied four-conductor control cable with field-serviceable compression screw wire connections.
The companion DXE-EC-DVA Directional Control Console has a three-position rotary switch to select opposite end-fire or broadside patterns, and features direction selection LED indicators with two erasable labeling pads.
The DVA Relay Phasing Unit is typically placed directly between two ground-mounted, full-size, quarter-wave resonant vertical elements that must be base insulated (shunt-fed towers cannot be used). Vertical element spacing must be one-quarter wavelength free space at the array target frequency, and each element should be installed with 40 or more ground radials. DX Engineering offers tower sections and aluminum tubing to create your elements and vertical antenna accessories to build your array with top-quality components.
DVA systems require 75-ohm antenna feed cables, electrically tuned to one-quarter wavelength at the target center frequency of the array. Offered by DX Engineering as an option, the custom-built quarter-wave tuned cable assemblies use a direct-burial DXE-11U low-loss 75-ohm foam coax, terminated with PL-259s with a waterproof polyethylene jacket. These are frequency specific, electronically tuned cables that connect from the DVA Phasing Relay Unit to each vertical element feedpoint.
For many more details, check out DX Engineering’s instruction manual, which includes information on additional parts you will need, choosing a site for your dual array, topographical considerations, recommended full-size quarter-wave vertical antennas, details on installing a radial system, installing the DVA Phasing Relay Unit to a mounting pipe or post, connecting the Dual Vertical Array Control Console, installing station and vertical element feedlines, lightning protection, radiation pattern samples, and troubleshooting.
