New Antenna Design: E-Z-O
A Successful Alternative to the Cubical Quad
The most fascinating part of a ham radio station, for me, has always been the antenna system. I have installed sophisticated antennas for clubs I belong to, but my personal station has only used some type of wire. That changed last summer.
While trying to reduce the cost of my longtime favorite, the cubical quad, I created the antenna you see pictured. It is a radical break from convention designs. (Patent Pending)
I wanted to save money. Spreader arms and "spiders" that attach them to the boom are expensive. I recalled the way camping tents have changed, with flexible tubes replacing ridged poles. I imagined that fiberglass tubes could support the wire elements of a quad more cheaply. I was right. I saved money with this design.
But I discovered several other advantages. The antenna weighs much less than a quad. It has less surface area for wind and ice loading. Stresses from wind gusts are relieved because the elements are not rigidly fixed to the boom. The lower stresses
allow for a smaller and cheaper (2") boom. Further, one person can install this
antenna with no need for a crew of helpers. And to top all that, it even performs better than a quad! The square loops of a quad admit to being only approximations to their theoretical ideal: circles!
Another surprise was the positive response from my neighbors. People smile and ask what it is. When I tell them it's a ham radio antenna, they congratulate me. Other antennas, with sharp protruding angles hoisted above the boom, have elicited fear and skepticism. Evidently these thin circles suspended below the boom are not threatening.
This antenna shares the positive characteristics of a quad. For example, radiated
signals do not couple with the tower. That is because when fed from the top, the
E-Z-O Antenna is horizontally polarized. And since quad antennas
characteristically propagate at low angles even at heights below L/4, suspending the E-Z-O
below the boom is inconsequential for most tower heights.
I am primarily a DXer. My biggest concern is being heard over the pileup. For that, I need gain. The 3 element E-Z-O gives 15 dB over my G5RV, which is no
slouch itself having earned me 235 DXCC's during this sunspot minimum.
Fiberglass tubes worked as I hoped they would as wire supports, but I was surprised at the magnitude of the imposed "dielectric effect". The driven element wound up being much shorter than I had expected. The reduction was greater still for the parasitic elements, since signals transverse their boundaries twice: coming and going. Happily, the smaller elements produce less surface loading and a lighter antenna.
Multiple Dacron radii are precut and their ends are terminated, making for very quick and easy assembly. They connect at the center with a single fastener. The 17, 15, 12, and 10-meter band elements are held in place by preinstalled fasteners. Since more supports are used than the four with a cubical quad, there is less stress and strain on the wire. A smaller gage wire can be used, which translates to reduced weight, wind loading, and cost.
I hoisted the elements up (and down) with a rope thrown over the boom. Notice how flexible they are. The ease and simplicity of placing elements on the boom will be appreciated by anyone who has installed a cubical quad. Imagine trying to do that job alone!
I fed all five bands with the same coax. Performance would improve with separate feed lines or a remote switch, and a matching system at the feed points, but I just rely on my automatic tuner at the transceiver. Transmission line loss is small at these frequencies, and I am very pleased with the results, even with the antenna fed in this less than optimum way. Of course, others who want to try this antenna are free to feed it any way they like.
These are the parasitic elements. They are pulled into position with Dacron lines, which thread through eyebolts at each boom end. Other lines connect the elements together, in order to restrict their movement. Since they are not rigidly fastened to the boom, stress from wind gusts are regulated. Like riding in a car with springs to keep the frame from shaking, the element's relative freedom of motion reduces peak forces on the boom. Totally absent are the torques that are considerable with
the quad design.
Trial and error with every detail of this antenna design became my full-time summer job. I spent weeks experimenting with the driven element alone. The result is a coherent and sensible antenna system.
After my success, I'm sure that other hams will want to try this antenna design. For convenience, I have detailed plans and antenna kits available from this site's
The plans eliminate much of the guesswork involving the magnitude of the dielectric effect, element length, and spacing. Complete pre-fabricated and pre-tuned antennas are also
available here. The packaged antennas are essentially "snap-together" and assemble