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Two Loops 80-10 Meters
One of the most unique home brew HF antennas is the Skelton Cone. This antenna will operate on 10M - 80M and is reported to show gain above 40 meters. The antenna is almost never used now.
There is a lot of literature on the Cone. It first appeared in in the RSGB Handbook ( 3rd edition, pp 387), and again in 73 Magazine ( Aug. 1969, pp 133 ) and was deeply researched by the late K6LV, in many different configurations.
The antenna looks very much like two G5RV antennas on one feed line. Basically it is. It's just a G5RV that has been broad banded by adding additional legs and spreading them apart.
The feed point can be set 38-48 feet high, with the legs sloping down to about 18 feet at the ends. The 33 degree angle between the leg pairs works out to be about 28 feet. Also, the feed point separation should be set at 4 inches wide. These configurations are not absolute. The Cone is very forgiving in different configurations of installation.
Feed the cone with 38 feet of 300 to 600 ohm twin lead connected to the balanced output of a good tuner. Note. Add 33 foot increments of feed line if more is needed above the basic 38 feet.
Performance reports are unique. Computer models show the highest gain of the cone towards the 10M end of the scale, but the antenna really shines on 40 and 80 meters. In addition, the antenna exhibits the best points of both horizontal and vertical omnidirectional antennas, with none of the apparent drawbacks.
As you probably know a G5RV was not designed to be an "ALL-BAND" antenna. G5RV
designed it to be an antenna with gain on 20 meters. The fact that it works on the
other bands is incidental. Also, the G5RV was not intended to be installed in a
configuration other than a flat top. With a big enough tuner, it can be made to show
a low SWR in any configuration, but this more a function of the tuner's ability to
force current into the feed line rather than the antenna's resonance at any certain
frequency. Still, the major problem will be with the radiation patterns this antenna
displays when it is installed as an inverted vee.
At 1 1/2 wave lengths on 20 meters, it does have gain, but when the ends are
lowered down into a vee configuration the lobes change shape and the angle of
radiation changes in the direction of lost efficiency. On the bands above 20 meters
the lobes of radiation are shaped more like those of a long wire than a dipole, and
when this antenna is erected as an inverted vee, the pattern worsens and the gain diminishes.
To be continued...