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Author Topic: Round Aluminum Tubing vs Square Aluminum for Yagi Elements  (Read 2136 times)
K3VAT
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Posts: 763




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« on: February 03, 2013, 08:12:32 AM »

We're building a two-element yagi for 20M.

We have dozens of 6', 8', and 12' aluminum square tubing pieces - most are 0.065 or 0.125 wall thickness and most are between 1" and 2" on a side; Al grade looks to be 6061 extruded.  There are no round sections in this collection.

QUESTION: for HF operation such as 20M and disregarding windload, is there any disadvantage (RF wise) to using this square tubing in place of round tubing for the elements?

thanks, 73, Rich, K3VAT
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AD4U
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Posts: 2186




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« Reply #1 on: February 03, 2013, 08:20:24 AM »

Assuming same diameter I do not think there will be any electrical difference.  As you alluded to, windload with square tubing will probably be significantly greater.  Round tubing is more aero-dynamic.

Dick  AD4U
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WB6BYU
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« Reply #2 on: February 03, 2013, 09:03:28 AM »

W9CF has a handy calculator to determine the equivalent round diameter of a rectangular
element here:

http://fermi.la.asu.edu/w9cf/equiv/index.html

That's the diameter you would use in a modeling program.
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W9FIB
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Posts: 971




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« Reply #3 on: February 03, 2013, 09:21:20 AM »

My only question is, is there hardware for square tubing to saddle the elements to the boom like they have for round tubing? I would think just tubing to tubing would allow slippage for the wind to twist the joints if there is no added support. I am thinking in the lines of the saddles for round tubing being made to grip the boom and the element sits in curved part of the saddle to prevent slippage. Just a question since I have not seen it done.

73,

Stan
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K3VAT
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Posts: 763




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« Reply #4 on: February 04, 2013, 04:34:52 AM »

WB6BYU: Thanks Dale for the calculator!

W9FIB: We have access to a TIG welder.  The aluminum boom will have two plates welded to it: one for the reflector, one for the driven element that makes mounting a snap.  The driven element plate is actually a 2 piece (one for each side of the driven element).  Here's an interesting manual on TIG welding with mention on techniques for 6061 aluminum:
http://igor.chudov.com/manuals/Miller/Miller-TIG-Handbook.pdf.

thanks all, 73, Rich, K3VAT
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W9FIB
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« Reply #5 on: February 04, 2013, 06:46:36 AM »

Cool stuff Rich! Like the saying goes...The right tool for the right job!

73,

Stan
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