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[TowerTalk] upper yagi noise--a reason?

Subject: [TowerTalk] upper yagi noise--a reason?
Date: Tue, 31 Aug 2004 21:57:55 +0000
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I have a theory....
w8ji wrote:
Snow would have an entirely different noise than heavy rain
drops, and dust in wind would be an almost perfectly smooth
white-noise hiss. It would all tie directly in to the
particles per second hitting the antenna if it was charge
movement between the antenna and the media striking the
antenna. If I had 60 large drops per second hitting the
antenna it would be a strong 60 Hz pulse. If I had 5000
gentle snowflakes, it would be a 5000Hz low level pulse.

The frequency would NOT change unless the contact rate
changed since the pulse rate would very clearly be synced to
the rate of the media contacting the antenna. Only the
intensity (level) would change as charge gradient  varied.
Yesterday, I observed what a 40 story building did in the backwash of tropical 
storm Chuba, typhoon # 16, as it blew across Tokyo yesterday.   On the 21st 
floor, the building creaked like a sailboat, with about a 4 second resonance 
period.  First the window wall, then the hallway door frame..back and forth...
When I went out, it was blowing a good 35-40kts on the ground.   At up at the 
tops of the buildings?  
The answer is, airflow is less affected by friction with objects, trees, etc. 
up high, than it is down low.   The upper antenna sees more wind,  intercepts 
more particles of snow, rain, sand, etc.  and thus builds more charge.
I remember taking down a 100' rohn 25 at 2000' in the poconos, some years ago.  
At 50', it felt breezy.  At 100', my tag line blew out horizontal and stayed 
there.   I had to add 10 lbs to the bucket, to keep it where the ground crew 
could reach it.   
So that's my builds on Tom's physics discussion, and makes 
intuitive sense.   

See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

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