[Antennas] Vibrating hollow elements

Wed Sep 21 22:49:14 EDT 2005

Ed, those were excellent comments - thank you for sharing this.
On the damping side, attaching a plain u-bolt (or two) along the supporting
mast might also tame the sympathetic oscillations. This could be tried
without taking down the whole antenna. String wound in a spiral on parts of
the antenna sound like a good plan if easier to accomplish efforts don't
solve it.
Jack
>From: DJED1 at aol.com
>>Tho I'm an electrical engineer I ran across this problem years ago
>in one of
>my antenna designs. The mechanical engineers identified the vibration
>problem as one induced by vortex shedding when air flows over the
>element. While
>one solution is to damp the vibration, another is to break up the
>vortex. I
>was reminded of the problem when I got my new car a few years ago- the
>antenna had a spiral filament wound on the cylindrical antenna
>shaft. I've seen it
>on several car antennas, so it must be effective in eliminating
>the vortices
>that cause vibration. While getting the antenna down may not be easy,
>wrapping some twine or wire along the elements may solve the problem.
>Ed WB2LHI