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Re: [TenTec] Aeolian Vibration

To: tentec@contesting.com
Subject: Re: [TenTec] Aeolian Vibration
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Reply-to: geraldj@weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 10 Jan 2011 23:19:42 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Power and open phone wires (not used much anymore) sound the loudest 
with just a 2 or 3 mph wind. Any stronger wind and the wind noise hides 
the sound on the ground. Those wires are generally strung at a fairly 
high tension to minimize the need for tall poles. One way of checking 
the tension is to strike the line and measure the time it takes that 
wave to propagate the span out and back.

No doubt your poly rope was trying to shrink with the cold too and had 
plenty of tension.

So you left a twig leaning on the poly to upset that resonance?

73, Jerry, K0CQ

73, Jerry, K0CQ

On 1/10/2011 10:03 PM, Neal Laugman wrote:
> Jerry and the group:
>> The wire elements in the Hex Beam and Spideream surely vibrate in the
>> wind, on power and phone wires its called Aeolian vibrations, most
>> prominent at light winds. http://www.uh.edu/engines/epi1653.htm
>> describes it in more detail.
> I wondered if there was a name for that effect. Polyrope was indeed my
> enemy one 30 below moonlit night out in the Alaskan Bush. I had a
> 20-foot spruce pole mast attached to a cabin's perlin with a polyrope
> halyard running the length of the mast. I thought I was loosing it as I
> the entire cabin seemed to resonate with this chilling sound. After I
> had been outside a couple of times checking for flying saucers, I
> finally figured out the mystery whilst reclining in my bunk. I went
> back outside, put the flashlight to the eighth-inch line, touched it -
> and the sound stopped! It was the temperature and an ever-so-slight
> breeze off the river.
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