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@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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