A Truly SIMPLE GROUNDPLANE ANTENNA

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simple groundplane

By George Christakes, K9MDE Contributed by Michael D. Bolton N5RLR

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A SIMPLE GROUNDPLANE ANTENNA

For VHF and/or UHF, a groundplane antenna capable of handling a full kilowatt can be constructed inexpensively using stiff wire or 3/32″ (2.38mm) brazing rod. The secret lies in the use of the familiar SO-239 coaxial chassis connector. As shown in the image, turn the connector upside down (the center terminal pointing up) and solder the vertical element to the terminal. The four ground radials are soldered to the four holes in the connector and the feedline with a mating PL-259 connector is plugged into the SO-239.

The antenna can be made self-supporting and can be mounted by attaching the PL-259 connector to a supporting mast with a worm-drive hose clamp. The radials should be angled at about 45º from horizontal in order to obtain a reasonable 50W match. The lengths of the elements can be found from the formulas:

Vertical Element in Inches: 2808/f
Vertical Element in Centimeters: 7132/f

Ground Radials in Inches: 2880/f
Ground Radials in Centimeters: 7315/f

…where f is the frequency in MHz.


(Text Credit: Edited from original article by George Christakes, K9MDE in the December 1961 issue of QST.)

The Unedited Version Follows

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Simple ground plane
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A ground-plane antenna capable of handling a full kilowatt can be constructed, using wire elements, for less than five dollars. The secret lies in the use of the familiar type SO-239
coaxial connector. Simply turn the connector upside down (the center terminal pointing up) and solder the vertical element to the terminal. See the sketch in Fig. 1. The four radial
wires are soldered to the four holes in the connector and the feed line with a mating connector is plugged into the SO-239.

Fig. 1. Ground-plane antenna made from an SO-239 connector.
For v.h.f. ground planes, the antenna can be made self-supporting and can be mounted by attaching the feed line to a supporting mast. Low-frequency models will require an insulator
at the top of the vertical element. The antenna is then suspended from a tree. The radials will also require insulators and guy wires. The radials should “droop” at about 45 degrees in
order to obtain a reasonably good 50-ohm match. The lengths of the elements can be found from the formulas:
George Christakes, K9MDE

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Glossary - See Glossary for terms used on the show.

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About the Author

Richard KB5JBV has been an Amateur radio operator since 1988. He has held positions with the America Radio Relay League including but not limited to Assistant Section Manager, Official Observer, Official Relay Station, Official Emergency Station, ARES Emergency Coordinator for Resonant Frequency: The Amateur Radio Podcast was created to help get information on amateur radio out to the new ham and the ham that wants to find out more about different aspects of the hobby they are thinking about getting into. So sit back have a drink and enjoy.

Richard KB5JBV has been an Amateur radio operator since 1988. He held positions with the America Radio Relay League including but not limited to Assistant Section Manager, Official Observer, Official Relay Station, Official Emergency Station, ARES Emergency Coordinator for Kaufman County Texas, Volunteer Examiner and Technical Specialist in the North Texas section.

Richard has also served as RACES assistant radio officer for the city of Mesquite, Tx. and among numerous other duties Including club president for the HAM Association of Mesquite Texas.

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