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Re: [TowerTalk] 2 el 40m beams

To: Paul Staupe <>, "" <>
Subject: Re: [TowerTalk] 2 el 40m beams
From: Roger Cooke <>
Reply-to: Roger Cooke <>
Date: Fri, 25 May 2012 17:24:09 +0100 (BST)
List-post: <">>
I have the Cushcraft 40-2CD which I am about to put up this summer. It has 
never been assembled, much
less put on a tower.  Has anybody modified one of these beams?


Regards from Roger, G3LDI
Swardeston, Norfolk.

> From: Paul Staupe <>
>Sent: Friday, 25 May 2012, 16:20
>Subject: Re: [TowerTalk] 2 el 40m beams
>Last summer I joined a group of YCCC club members in a project to rebuild
>my XM-240 into a Moxon (Grant's V2).  Several of us built this version, and
>Tony, K1KP decided to build the V3. We've all been very pleased with the
>It took a lot of time, a lot of SS nuts and bolts and a good drill press to
>get the job done, but I finally was able to get the antenna up in the air
>in January, thanks to a mild winter here in Minnesota.  Since I had too
>many trees near the base of the tower, I had to assemble the Moxon piece by
>piece on the tower so it went up without testing.  I was shocked that it
>worked perfectly, had the published SWR and real gain.
>The Moxon sits 18' above a 4L SteppIR which is at 77' so it's totally
>exposed. We've had some severe winter gales and recent straight line winds
>combined with thunderstorms here that I no longer worry about.... the Moxon
>is rock solid, and sheds the wind "gracefully."  I can't say enough good
>things about this antenna.
>Best regards,
>Paul W0AD
>Date: Thu, 24 May 2012 21:28:35 -0700
>From: Grant Saviers <>
>Subject: Re: [TowerTalk] 2 el 40m beams
>Message-ID: <>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>The W6NL 40M  Moxon has several design iterations.  As far as I know
>there are 4 versions, in time sequence I think they are
>V1 - 2006 original Cushcraft modified XM-240
>V2 - 2007 center of element strengthening of V1, also known as the
>"K3LR" version
>V3 - 2010? the "120 MPH" design, a scratch build from raw stock, no
>antenna is modified
>V4 - 2012 "100 MPH" design for W2SC, modified from the XM-240
>K6KR and I opted to parallel build two V3's in my garage.  I cannot
>attest to any relative comparisons since I haven't owned the other
>Moxons or commercial 2L alternatives.  However, I've done some basic
>mechanical analysis of the V3 and can confirm it is in the strength
>ballpark as specified.  One reason we decided on the scratch build is we
>could buy known alloys whereas starting with the now MFJ built Cushcraft
>has some unknowns, and neither of us had one.  Also, as the build
>progressed, we became convinced that Dave's element segment connections
>are superior.  In rebuilding and strengthening a used F12  EF120C to use
>a Tornado variable center coil I found many loose or missing rivets and
>changed to the V3 bolting technique.  YagiMech predicted structural
>failures at about 70MPH and it had damage where predicted.
>Performance wise, the V3 Moxon was exactly as expected, testing at 92'
>with an AIM4170.  Observed pattern seems about right.  Measuring gain
>and elevation pattern is not feasible for me (who can? :-( ).  I've had
>some 1/2" icing and all was ok, but it has been on the tower for only 7
>There is nothing particularly difficult about building this antenna, but
>there are many parts and it does take considerable time and
>concentration to build it (we made a little scrap).  Getting all the
>tubing sizes is a bit of a challenge.  The ballpark material costs for
>us, going first class with all DXE element saddle clamps and SS hardware
>was around $1700 per antenna.  W3TX emailed me that he may be interested
>in commercially building it.
>I doubt there is anything commercial that is stronger.  Dave in a recent
>QSO (Moxon to Moxon) said "it is the largest antenna I can keep together
>at my QTH"  I think he has recorded 160MPH gusts.  At my Redmond, WA QTH
>the wind so far has been negligible, I'm back from the ridge edge and
>100'+ trees all around make a huge difference.
>Grant KZ1W
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