| This antenna is designed to exploit some
of the positive aspects of a vertical radiating element
e.g. low-angle radiation, while minimizing some of the
negative properties e.g. the need to bury many radials in
the ground. It is inexpensive and easy to construct. The
antenna at KI7T is a 14 gauge enameled copper wire
supported by a branch of a fir tree. Since it is a
half-wave in length (height), the current loop which
actually does the radiating is located about 16 feet
above ground, rather than at ground level as you would
have with a more conventional quarter-wave vertical.
Also, the antenna is fed at a voltage loop, or
high-impedance point. This drastically reduces the amount
of current flowing in the ground. A much smaller ground
system can be used. In fact, I use nothing but some 1/2
inch copper pipe at a depth of about 18 inches. A diagram of an antenna for the 20-meter band is shown at the right. The LC circuit matches the low impedance of the coaxial feedline to the high impedance of the antenna. L and C are chosen to resonate at the operating frequency. The L/C ratio can be adjusted for a low s.w.r. at resonance. |
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To the right is a picture of the ground element I made for this antenna. It is nothing but some 1/2 inch copper pipe soldered together. It is about 18 inches in length, and about 5 inches across. The cross pieces are to help resist being pulled out of the ground. |
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