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Guy Olinger, K2AV
olinger at bellsouth.net
Sun Dec 3 11:57:22 EST 2006
Since you didn't mention switching each element, what occurs to me,
given your two dips in resonance, is that you have in effect a pair of
two element beams, a reflector beam on the low end and a director beam
on the high end. (Or perhaps the reverse?) This would be a compromise
to allow it to work on two frequencies that are too far apart
octave-wise to use anything except the driven element in common.
In such a situation, the driving impedance may not be "traditional".
Also, it is entirely possible that the SWR points may not be the
optimal forward gain points.
If you forward the dimensions off-list (lengths and diameters by
tubing section on each element) it would be quite interesting to model
and see what kind of pattern it has against the height you describe.
Would also be interested in the model and the year of the design, the
question being whether the design was done before the current modeling
tools were available.
On the fixed 80m 4 element 220 foot wire beam in use at N4AF, it
simply could not be used at 3799, nor anywhere close, becoming
unusable at 3575. Also it's effective height is more like 100-110
feet. It regularly puts an s-unit or two over Howie's 4 square in the
US sunset, EU sunrise periods. The 4 square will best the 4e mildly
from time to time when the band is really long.
PS, excellent CQWWCW score posted from down there this year.
----- Original Message -----
From: "Rick Dougherty NQ4I" <nq4i at contesting.com>
... I plan to make another trip to the top of the tower next week to
plot x and y values from 3.2 mhz to 4.2 mhz to see if I have
overlooked something....the antenna as it is now has a W shaped
resonance curve...its 1.2:1 at 3523 and goes slightly up to approx 2:1
and then dips back down to 1.1:1 at 3799 mhz...so it has a very
The actual performance is far less than I would expect though....there
are many times at sunset that the 4 square I have will beat this yagi
into EU....there have only been a few times that the yagi has beaten
the 4 square in EU or JA....but it sometimes does occur.....the yagi
shows approx 20-25 db f/b.....
Are 80m conditions so flaky that the yagi will at times not equal the
4-square?? I am puzzled by the 100 ohm feedpoint impedance also??
Any comments either here or offline would be appreciated...
thanks de Rick nq4i
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