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 <staupe@gmail.com>
>To: towertalk@contesting.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
>results.
>
>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 <grants2@pacbell.net>
>Subject: Re: [TowerTalk] 2 el 40m beams
>To: lkeller73@roadrunner.com
>Cc: towertalk@contesting.com
>Message-ID: <4FBF0A73.3050904@pacbell.net>
>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
>months.
>
>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
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|