two other things to remember also.
1- the antenna will probably cost more because everywhere i know of
square tubing is more costly than roung, but if you have a sourse OK,
2- the wind load will be much larger, 30% roughly larger, the wind load
of a 1 inch round tube is 0.6 the amount of a flat surface IE: square
Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 8/14/2013 8:24 PM, i8cvs wrote:
Hi Mike, N6IMF
Russ, K0WFS
and All on the list
Generally speaking, if the elements of a yagi antenna are mechanically
mounted insulated over a metallic boom like a round or square aluminum
boom than the effect of the boom is to SHORT the lenght of the elements.
The same shortening effect affect the element lenght if the elements are
mounted directly in contact over or inside the metallic boom.
No matter if the boom is round or square the lenght of the elements
will be shortened in comparison to mount the elements over a plastic
insulated boom.
The plastic material as used for the boom do not affect the elements lenght.
BTW in your case if you mount the elements over the boom in the same
manner as designed for 1/4 inch round elements than to change the size
elements from round 1/4 inch to about 3/8 inch square will affect only
a small amount the center resonance of the antenna at the working center
frequency and hence his change in VSWR and performance will be
very small.
Please read the following references on this matter:
1)P. Viezbicke, "Yagi Antenna Designe" NBS Technical Note 688,
1976, page. 6
2) Guenter Hoch, DL6WU, "Extremely Long Yagi Antennas ,VHF
Communications 3/82, pag.130
3) J.E. Pearson ,KF4JU, Element Lenght Disturbancies Due to End
Chamfering and Insulated Metal Boom" Proceedings of the 22nd
Conference of the Central States VHF Society.
4) J. Lawson,"Yagi Antenna Designe" ARRL 1° Edition 1986 ,
pages. 7-11
5) The ARRL UHF/Microwave Experimenter's Manual,ARRL
1990 pages. 9-5
6) R. Bertelsmeier, DJ9BV, "Yagi Antennas for 144 MHz DUBUS
1/1990 pag. 23
Have fun
73" de
i8CVS Domenico
----- Original Message -----
From: "Russ Ramirez" <russ.rami...@gmail.com>
To: <amsat-bb@amsat.org>
Sent: Wednesday, August 14, 2013 6:46 PM
Subject: [amsat-bb] Re: Antenna element and Boom material
I am wondering about going from 1/4 inch tound elements to about 3/8 inch
square
would effect the performance of this antenna.
Mike Hoblinski
N6IMF
It definitely will Mike, but not in a positive/negative way per se. Let me
explain.
If you follow an optimized design that called for 1/4 inch round elements
and substitute 3/8 in square tubing, the impedance and SWR bandwidth
characteristics will change in the general sense, and these changes may or
may not be desirable. I do not have the experience with LP antenna
implementations that I do with Yagi or wire antennas, so perhaps there are
other issues to consider. I would suspect that the low SWR points across
the bands would simply shift. Changes in element diameters generally
affects the electrical length, and in your example only a small amount.
Russ
K0WFS
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