In truth, that doesn't mean we have a good ground, but the point is, we do have a DC connection to earth where a half wave dipole antenna will have both legs isolated from earth ground. Even though the shield of the coax will generally be connected to one leg of the antenna and at the other end of the coax the shield will be connected to a ground inside the station, the antenna will be above ground on both sides.

The Butternet in its original configuration had the radials at ground potential. In addition to the radials, the shield side of the coax feed line and the bottom of the 80 and 40 meters matching coil were at ground potential as well. The lug intended for attaching the radial system was located on the lowest tube section which is isolated from the upper system by an insulator. The lower tube section is meant to mount either in the ground (if the antenna is ground mounted) or to a supporting mast which is assumed to be grounded if the antenna is to be elevated. That is the same point the shield side of the coax attaches to as well as the bottom of the 80/40 meter matching coil.

I wanted to isolate the lower part of the antenna with the radials from earth ground. The only way to do that would be to isolate the area from the lower tube which is going to be grounded when it is mounted. I fabricated the assembly seen in the picture below. Basically just a plate with a PVC pipe sleeve fitted in the center through which the antenna lower mount passes through and insulates the two assemblies. The radials are attached to the plate at the four corners. The shield side of the coax is also attached to this plate as is the bottom of the 80/40 meter matching coil. This makes it the equivalent of the coax shield being attached to one side of a dipole antenna.

Before I continue, I must explain the purpose of the blue nylon line tied to one of the radial tie points. The HF9V has two wire elements. One for 15 meters and one for 6 meters. These wires run parallel to the main center element and are supported at each end by standoffs from the main element. One end of each wire is "fed" by having it in direct electrical contact with the main element. The other end of the wire is dead ended but supported by an insulated standoff so that it remains straight and ideally rigid.

Initially the wire which was supplied with the antenna assembly for these two elements was insulated, stranded wire. That did not seem rigid enough and with movement in the breeze, the wire seemed to flex too much and thus affect the tuning of those two bands. I replaced the stranded wire with solid aluminum wire which was much more rigid and did not move as much. That worked pretty well but over the course of several years the standoffs themselves are going to weaken a little and tend to be pulled by the tension placed on the wires. The wires should be somewhat tense so that they do not "flop around" in the breeze. We always have a breeze here in North Texas where the idea of a dead, calm day is almost unheard of. So the antenna is always going to be swaying a little.

I found that I could not keep proper tension on my 6 meter element and thus the wire tended to flex a bit. The flexing did not affect the tuning of the 15 meter element but it sure did the 6 meter one. Now perhaps my perceived "good idea" to go with the more rigid wire for these elements was not as good as it appeared to be, but on the other hand, it may not have mattered. The fact is, as the antenna flexed in the direction of the element which is mounted on the side of it, that caused the element wire to flex and bend a little and resulted in it bowing just a little. When it did, it was a little closer to the main element and the band tuning was affected. As I work the lower portion of the 6 meter band I liked to have the tuning bandwidth run from 50 MHz to close to 51 MHz. Something like that. When the element became detuned, it lowered the resonant frequency so that it was somewhat below 50 and much closer to 49 MHz.

There were probably a number of schemes I could have applied to correct this problem but I elected to take the simple approach for now. I detached the lower end of the 6 meter element wire and tied the nylon line to it and ran it down through the center of the 30 meter coil form and down to where I could tie it to the radial base plate. The idea was to allow me to access it if need be to adjust the tension. So far I have not had to do that and there is just enough tension on that wire to keep it straight and thus the tuning on the 6 meter band is constant.

So how well does the antenna work? Performance and Specs.

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