FW: [TowerTalk] KLM 20M 6 el Beam

[Dick Weber]

Hello again Dennis,
	
	The answer to your question is, "Yes, this problem has been addressed." You could add to the boom to make is symmetric. There's a simpler way that was shown in an article in Commumications Quarterly, Summer 94 on pages 70-73. This uses a square piece of aluminum sheet U-bolted to the short side of the boom. The plate is 14.16 inch square. It is mounted 23ft  7inch from the mast to the center of the plate. This puts the plate between the reflector and first driven element. This plate is sized to counter act the imbalance due to the boom asymmetry. The sizing of this plates takes into account the amount of boom hidden by the plate and uses the correct drag coefficient for a square plate. I say these two last things because there is published elswhere a discription of this method. Unfortuantely the author did not use the correct drag coefficient for a square plate and did not acount for the portion of boom hidden by the plate. If you have any questions about doing this let me know.

73-Dick, PE, K5IU 

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I have a KLM 20M, 6 el Beam up on Rohn 45 at 135 feet.

If you are familiar with this beam, you know it is not geometrically
centered, one end of the boom is 4 feet longer than the other.

It turns in the wind.

Has anyone done the calculations to add something to the short side of
the boom to balance the wind? Add an extra 3" piece to the short end?

I am looking for the best solution.   Does anyone have one they have
used before on this antenna?

73's
-- 
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Have a Nice Day,

W5KU ex-K2UA
Dennis Jay Alexander
1964 FM 1094
Sealy, Texas 77474

(713) 646-6174 (work) e-mail at work: dalexan@enron.com
(409) 885-4838 (home) e-mail at home: w5ku@iamerica.net
(409) 885-0438 (24 hr. FAX)
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