Fall 2005 Issue

Connecting the Radio to the Sky

 By Kent Britain, WA5VJB

Painting antennas was first recommended to me by WB6NMT. Louie ran Lunar Electronics and sold a fine line of antennas. He also lived near the Pacific coast, and thus his antennas were subjected to a lot of salt spray. If paint helps antennas last a few more years in salt spray on the coast, then it will help them last decades longer here in inland Texas. My 432-MHz and 222-MHz Yagis were painted in 1979 and they are still up in the air (with a few touch-ups over the years).

Painting antennas has several advantages (photo A). First, the paint tends to “glue” the hardware together. Not as many screws and nuts seem to work their way loose with some paint in the threads. Next, the paint protects plastic parts from ultraviolet light exposure and air pollution. Therefore, the antenna holds together longer and fewer bits fall off if it is painted.

I had several reservations about how the paint might detune the antenna. I built a 3.45-GHz loop Yagi and measured its gain. Then I gave it several coats of spray Zynolite‚ epoxy paint. I let the paint set and then measured the gain again. There was no measurable difference. If I can’t measure any loss at 3.45 GHz, I’m not going to worry about paint losses with my 2-meter beam.

Next I used a light-gray -paint. It used to be called “Battleship Gray,” but Machinery Gray is a common color among the better spray paints, and when the sky is just a little overcast, the antennas virtually disappear. Louie painted his antenna white, but I like to keep mine somewhat lower profile.

Photo A. Painting an antenna protects the plastic parts from ultraviolet light and pollution and also tends to “glue” the hardware together.

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