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Re: natural frequency of an antenna mounted on a 5 foot pole

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Here is a starting point
The frequency of the periodic exciting force caused by the flow (Vortex shedding  - von Karman Vortices) can be found by solving the following equation
n*d/V = C
where n is the exciting frequency in cycle per second
          d is the dimension of the body normal to the flow
          V is the Velocity
           C = 0.207 (dimensionless) for cycular cyclinders
           C = 0.18 (dimensionless) for rectangular plates
Reference : Den Hartog, "Mechanical Vibration," copyright 1940 page 343 

Richard M. Beldyk, PE, CPEng, NSPE, MIEAust, CWEng, CPE
Professional Engineer - Delaware, Maine, Maryland, Michigan, Ohio, Oklahoma,  Pennsylvania, Virginia, West Virginia
Chartered Professional Engineer - MIEAust, NPER
Registered Member - International Registry of Professional Engineers (USCIEP)
AWS Certified Welding Engineer
AFE Certified Plant Engineer
----- Original Message -----
From: Tom Mabry
Sent: Friday, February 07, 2003 1:07 PM
Subject: natural frequency of an antenna mounted on a 5 foot pole

How do I determine what is safe in terms of natural frequency for equipment mounted on poles.

I just did the calculations for an antenna mounted on a 6 foot pole( mounted on roof), the natural frequency is about 4 Hz, and how do I determine if this is ok at 90mph wind speed.



Tom Mabry

Senior Mechanical Engineer

SkyPilot Networks

1301 Shoreway Road # 211

Belmont, Ca. 94002