Years ago I also did model this and did tha same findings,
i e it seems low in frequency.
I remember speaking with someone about it, actually I
think it was W6NL himself, he claimed it was "dead on".
73 Jim SM2EKM
------------------
On 2010-02-28 21:01, Billy Cox wrote:
> 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:
>
> http://www.kkn.net/dayton2008/Real%20vs%20Theoretical%20Antenna%20Mesurementsv5.pdf
>
> 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@surfnetusa.com"<knormoyle@surfnetusa.com>
>> Sent: Feb 25, 2010 4:51 PM
>> To: antennaware@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.
>>
>> here:
>> http://www.kkn.net/dayton2004/
>> (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
>> .ant)
>>
>> 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
>> curves.
>>
>> 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
>> accurate..
>>
>> 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.
>>
>> thoughts?
>>
>> thanks
>> kevin
>> AD6Z
>>
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