[TowerTalk] Modeling the Moxon

[Grant Saviers]

My model is the W6NL scratch build 40m Moxon.  I obtained different 
results using EZNEC Pro4 with the bottom at 70' and top at 140' the peak 
gain of either alone is 10.5dbi and 11.0dbi respectively over average 
real ground.  As a stack the gain is 13.2dbi or 2.2db higher than the 
140' alone.  This is in line with other stack modeling I've done and in 
the range of many published results re stacking gains, practical and 
theoretical.

This model's AGT is 1.024 alone or stacked.

My QTH real-time A/B comparison is the Moxon at 91' vs a full size 3L 
48' boom at 140'.  The 3L most always wins, lower angle, lower noise 
with better F/S and F/B.  Not a fair comparison by any means.

Regarding stacking separation, for two high stacks in the modeling I've 
done, near 1/2 wl the gain is pretty much asymptotic to its max value.

Grant KZ1W

On 7/27/2017 4:53 AM, StellarCAT wrote:
> Dave's original statement was "can someone model 2 40 meter yagis 
> stacked?" .... at the time the discussion was about stacks - then got 
> in to the relative performance of 40 meter stacks ... my intent was/is 
> to do just that ... 2 x 2 element yagis will serve the purpose. If 
> modeling the interaction of the 40 on say a 15 (it won't interact 
> noticeably with a 20) then I can attempt a Moxon. Note I have modeled 
> a Moxon before with results that seem correct ...using NEC2.
>
> Regarding 40 meter stacks ... when I model 2 x 2 element yagis at 
> 140/70 the increase in gain is only about 1.4db ... which was my 
> original point that there isn't a great deal gained from stacking on 
> 40 meters other than the change in angle (which again the lowest one 
> will seldom be the better choice over the stack) and if available 
> having the ability to go 2 different directions... extending that to 2 
> 4 element antennas the increase in gain is even less - less than 1 db. 
> My original comment was you need to get 40's up higher and further 
> apart to start to get a bit more gain increase. (that stated even with 
> 20's stacked the increase in gain when stacked "properly" is 'only' 
> about 2.4 db or so).
>
> Gary
>
>
> -----Original Message----- From: Joe Subich, W4TV
> Sent: Wednesday, July 26, 2017 8:00 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Modeling the Moxon
>
>
> If you intend to model a Moxon, particularly the Leeson Moxon, you will
> need software that uses the NEC4 engine.
>
> NEC2, commonly used in amateur software because it is free, does not
> handle right angle connections and tapered elements correctly.
> Numerical corrections have been developed for the taper issues
> (primarily by Leeson) but NEC2 still does not handle elements that
> are not parallel very well.
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 7/26/2017 6:28 PM, Dave Sublette wrote:
>> I have spent a fair amount of time reading a few of the Moxon 
>> construction articles about the modified Moxon for 40 meters.  I have 
>> a spare 6 element 20 meter Telrex monobander for 20 meters in my 
>> barn.  Doing some scratching on paper, it looks like I could build 
>> two, two element Moxons for 40 using the material in that yagi.  I 
>> would need to buy the tubing necessary to build the Tee sections on 
>> the end.
>>
>> Since all of the element diameters and taper schedules would be 
>> different, I should model it.  I have the Antenna Model Software 
>> package.  I haven’t used it much.  I haven’t modeled antennas in over 
>> 15 years. I used to use K6STI software when I did and I loved it.  
>> Some of the articles I have read say good things about the Antenna 
>> Model program.  I am wondering if that would be good enough to use on 
>> the Moxon.
>>
>> Now I know the Moxon doesn’t model well. The W6NL version is the 
>> standard and the best advice is to build it like that.  But I have 
>> all this beautiful aluminum that I don’t want to waste. Plus, the 3 
>> 1/2 inch boom on the T-rex is really stout enough to handle this 
>> antenna.  At least one article says they wish they had used a larger 
>> boom diameter.
>>
>> I suppose a good plan would be to model the W6NL and then my version 
>> on the same software and adjust my version until the results matched 
>> those obtained with the W6NL.  The question is ..  Is the Antenna 
>> Model package adequate for the job?
>>
>> A really good answer would be that someone has already modeled the 
>> W6NL on Antenna Model and would share the file with me.  :-)
>>
>> Thanks,
>>
>> Dave, K4TO
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>>
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