[TowerTalk] DX Engineering 20DX-5 modeling

[Paul Playford]

I suspect that the lobe that goes straight up is a function of your models
ground.  Try the model in free space and see what happens.

When I scaled the 4 element W2PV 12 meter design to 20 meters (41 foot boom)
I adjusted only the driven element length and beta match for best SWR, and
it has a terrific pattern.

If you would like me to play with it just email me your EZNEC model file.
Better yet, how about emailing the original DX Engineering dimensions along
with the height of the antenna above ground?

I assume your QTH is Parker, CO.

de Paul, W8AEF

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ZF2TA  FO8DX  FO0PLA  8Q7AA  XZ0A
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----- Original Message ----- 
From: "W0YG Charlie Summers" <w0yg at plusten.net>
To: "TowerTalk" <towertalk at contesting.com>
Sent: Monday, August 04, 2003 10:13 PM
Subject: [TowerTalk] DX Engineering 20DX-5 modeling


> Has anyone modeled the old DX Engineering 20DX-5 antenna?  This was a 5
> element 20M yagi on a 43.75 foot boom.  The reason I asked is I just spent
a
> whole morning trying to tune one by yanking it in the air after every
> adjustment and it just never came into what I considered acceptable
> parameters.  So, I modeled it in EZNEC and find that it has some problems
> the way it is factory set.  For one thing, the forward gain and f/b are
not
> what I would expect.  For another, there is a strong lobe straight up, a
> cloud buster.  For another it is hard to move the frequency down.
>
> Let me explain.  If you set it the way DX Engineering said, then it
> resonates at 14.280.  By playing with the driven element, the first
director
> and the reflector, one can get it to move down to about 14.200 where it
> plays but still I am not quite satisfied.
>
> I asked in the first paragraph above if anyone has ever modeled this
> antenna.  Perhaps I should have stated has anyone ever run YO or some
other
> yagi optimizing program on it.  That is what I would like to see the
results
> of.
>
> 73,
>
> Charlie, W0YG..>>