Go to K3LR's site and check the mods to make that antenna a Moxon. the
performance is quite a bit better.
The original 40-2 you could easily crush the ends of the boom when
tightening down the elements. I would add an insert to the ends to that
does not happen. They also had metal overheads. I replaced them with
Philystran. In addition to the worm clamps I would pin the elements
with a #10 or so SS bolt and nylock nut. I would change all the nuts
There are number of good articles about beefing up this antenna.
W0MU-1 CC Cluster w0mu.net:23 or w0mu-1.dnsdynamic.com
On 5/25/2012 10:24 AM, Roger Cooke wrote:
> 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<firstname.lastname@example.org>
>> To: email@example.com
>> 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<firstname.lastname@example.org>
>> Subject: Re: [TowerTalk] 2 el 40m beams
>> To: email@example.com
>> Cc: firstname.lastname@example.org
>> 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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