[Antennaware] Simulating the W6NL 40M moxon variant

Billy Cox aa4nu at ix.netcom.com
Sun Feb 28 12:01:56 PST 2010

Hi Kevin,

You are on the right track with this ... and please
give this link a close review and note their findings
as to F/B, F/S and SWR with the W6NL Moxon design:


There are several challenges here, including which of
the antenna software 'engines' best models the manner
the Moxon elements are constructed. In comparing the
same antenna model here with say EZNEC and Antenna Model,
the results with the Moxon design are NOT the same.

I hope this helps, here I am doing the same thing with
an older Cushcraft 40-2CD, which uses different element
construction than the XM element that W6NL used.

73 de Billy, AA4NU

-----Original Message-----
>From: "knormoyle at surfnetusa.com" <knormoyle at surfnetusa.com>
>Sent: Feb 25, 2010 4:51 PM
>To: antennaware at contesting.com
>Subject: [Antennaware] Simulating the W6NL 40M moxon variant
>My problem: I'm working on a simulation for a M2 40M2L (shorty-forty, linear 
>loading) conversion to a moxon. I'm using the W6NL 40M moxon-like design as a 
>benchmark for SWR bw, and gain/fb. (trying to get similar results, but not the 
>same design)
>W6NL provided an AO .ant file so his can be easily simulated.
>(3 links there)
>I use 4nec2x, so I used it to convert the .ant to a .nec. There were some minor 
>issues that I hand-corrected. (for instance, using ' in a symbol name in the 
>The simulation of the W6NL moxon looks good in 4nec2x. The visual is right for 
>the antenna, the gain/fb and swr bandwidth is right (very wide swr bandwidth).
>BUT: the swr min is centered too low I think..it's around 6.8Mhz..I would have 
>expected it to be centered around 7.05 or 7.1, based on W6NL's presentation 
>I experimented a little. I played with different grounds. The simulation is at 
>70 ft. The taper schedule is done with explicit wires of different radiuses, but 
>it seems fine.
>I'd be surprised if nec-2 is simulating this wrong, compared to AO...
>So I'm assuming something is just wrong, but I can't figure out what.
>It's like it's shifted down in frequency for some reason. 
>If there was someone out there would could run the .ANT file exactly as W6NL 
>posted it above, and say what freq they see for a SWR min, that would be really 
>useful for me? I also could put my converted .nec somewhere if there was some 
>other simulator that could use the .nec? (or people can recommend something I 
>could use without retyping in a model?)
>I'm a little worried, because I have the design for my 40M2L conversion done, 
>and I think it's pretty good (got the wide bw I wanted).  nNot that much less 
>than the W6NL, but has just the typical moxon look (less aluminum) and on a 
>shorter boom (19-1/2') feet....But now I'm wondering if that simulation is 
>I don't know if there are other simulators that could use the .nec, but I could 
>provide that also (both the W6NL and mine) if anyone was interested in seeing 
>what they get for me.
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