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Re: [TowerTalk] 2 el 40m beams

Subject: Re: [TowerTalk] 2 el 40m beams
From: Grant Saviers <>
Date: Thu, 24 May 2012 21:28:35 -0700
List-post: <">>
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

On 5/24/2012 6:51 AM, wrote:
> Hello out there.
> I'm at a loss as to what to replace a snow-damaged 2 el 40m beam with.
> Everything I've found on-line doesn't really call out how strong the antenna 
> is.
> Ideally, since most "gain" figures would be nebulous anyway, I want the 
> out there since it's going on Bertha at 100 feet.
> Any suggestions?
> Lonnie
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