As with any standard three element design, this three
element direct connect antenna utilizes a reflector and a director to achieve
gain. As in the case of the 'Tiny 2', the front-to-back was sacrificed in order
to squeeze as much gain as possible from the antenna. I managed to obtain 6.52
dB over a dipole in free space while still retaining a direct connect antenna.
Right up front you might ask, "Why build this antenna rather than some other
design?". The first reason is the very fact that it IS a direct connect antenna.
The design allows you to hook your cable directly to the antenna without the
time consuming process of matching, yet the SWR is just 1.18 to 1. The 6 1/2 dBd
gain is of course a nice side bonus. Another nice feature of this design is the
element diameter. Each of the elements is made from 1 inch diameter aluminum
tubing. I like the fact that you don't have to play around sliding elements in
and out trying to get to the proper lengths. You simply cut each to the lengths
shown in the side bar and position the elements on the boom. It is also easy to
find 1 inch furniture tips at local hardware stores which give the antenna a
nice professional look!
| Element name |
Relative position on the boom |
Element length |
Center point of element |
| Reflector |
0 |
3' 1" |
1' 6-1/2" |
| Driven |
2' |
1' 5" |
N/A |
| Director |
4' |
2' 9" |
1' 4-1/2" |
Things to keep in mind:
You will need a boom length of
about 4 feet 2 inches even though the distance between the reflector and the
director is only 4 feet. The extra space is needed to allow for the use of
mounting brackets to hold each element to the boom. Center each of the elements
by using the center point column in the chart above. When mounting the driven
element, remember that it is split at the center and must be insulated from the
boom, you can use PVC pipe to accomplish this. It not only helps insulate the
elements, but also supports them at the same time.
The proper location for connecting the mast is exactly
center, either between the driven element and the director, or between the
driven element and the reflector. Connecting a metallic mast any closer to the
elements will detune the antenna causing a higher SWR.
To Build Or Not To Build, That Is The Question
There are so many antenna designs out there that it is
sometimes difficult to decide which one is worth while building. The simplicity
of this antenna makes it perfect for clubs and organizations that are looking
for a "First Time" antenna project.
Copyright © 1996-2006 Ed Oros and Bob Cocco All Rights Reserved.
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