While this is a very interesting and useful antenna, it does not defy
physics. It only rivals a three element beam with a similar boom length. A
28' boom is pretty short for a 3 element 40m beam.
John KK9A
To: "Tony Brock-Fisher" <barockteer@aol.com>,<towertalk@contesting.com>
Subject: Re: [TowerTalk] W6NL 40-2CD => Moxon Conversion
From: "Bob Selbrede, K6ZZ" <k6zz@ccis.com>
Reply-to: k6zz@ccis.com
Date: Fri, 07 Dec 2007 17:53:31 -0800
List-post: <mailto:towertalk@contesting.com>
I concur. However, that wouldn't be as simple as it may
appear. The are three ways to approach the project from
what I can tell. The first is to biuld it from scratch
without benefit of having a 402-CD or XM-240 around as the
base antenna to start with. Then, depending on which CC
antenna you have on hand, the parts list will be different
primarily because the older 402-CD requires additional
beefing up already taken care of in the XM-240.
A little poking around on the Internet reveals that W6NL
initially published a design for a 2 element 40M Moxon at
Dayton in 2004. You can find this presentation and other FB
info on K3LR's web site (www.k3lr.com) as well as other
locations on the web. That antenna appears to have been
"built from the ground up" and has a slightly longer boom
than the 402-CD/XM-240. The 2007 variant is based on a
modified Cushcraft.
I started putting together a parts list for modifying an
XM-240. I didn't realize how long the Cross-Tee pieces were
until I put the tubing list together. Those buggers are
about 21' long and there's one on each element half! As a
result it's very important to truss and reinforce the
elements as shown in the design. I priced the tubing at one
source and it will run about $150 for the sizes and lengths
required. The balance of the parts consist of stainless
steel hardware, small aluminum plates, and the element truss
materials. I would estimate the entire cost to be around
$250 if purchased new. Not too bad for a shorty-forty which
rivals a full size three element mounted at the same height!
73, Bob K6ZZ
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