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1-3 of 3 messages
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delta loop question
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by ON8WW on October 6, 2009
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Hi i'am usin a delta loop for 40m but i take my feedpoint at the right bottom corner of the triangle.
The signals are much stronger then with my inverted V but only dx usa, etc are so strong. I receive a email form a france station he says the follow :
My Delta Loop is feeded at the top corner (because of my tower).
I have never played with feeding at bottom corners or top to see if a real difference exists or not.
I work North Amercia, Pacific or Europe without any issue and without any amplifier.
For me, feeding at the top corner is the best solution and results are perfect for me.
I have more than 230 DXCC barefoot with my Delta Loop for last years.
SO If anyway that can tell me when I change the feedpoint to the top of the triangle works that better for dx or not???
73's Dave
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RE: delta loop question
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by WB6BYU on October 7, 2009
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Does your delta loop have one corner pointing down and
two pointing up, or one up and two at the bottom?
How high off the ground is your loop?
With a square loop, feeding it in the middle of the bottom
or top wires gives horizontal polarization, while feeding
it in the middle of one of the side wires gives vertical
polarization. At low heights with reasonable soil conditions,
vertical polarization may be better for DX. A the height
increases you will get more low angle radiation from
horizontal polarization.
We can apply the same principle to a delta loop: if fed
in the middle of the bottom or the top wire (which may be
the top or bottom corner, depending on the orientation of
the delta loop) we get horizontal polarization. For
vertical polarization we feed it in one of the sloping
side wires about 1/4 wave from the vertex (whether it
is pointing up or down.) This is not exactly at one of
the corners.
Feeding at one of the side corners (whether at the top
or the bottom) gives mostly vertical polarization, but
not entirely.
Note also that the average height of a delta loop depends
on the orientation: for the same top and bottom heights,
a delta with a flat top and point down will have a higher
average height above ground than one with a point up.
So there are many variables that affect the performance
of a delta loop, as well as differences in ground
conductivity and terrain. (Ground slope affects the
angle of radiation from a horizontal antenna.) Without
more details it is difficult to compare two antennas
even if both are "delta loops."
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RE: delta loop question
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by WX7G on October 9, 2009
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For vertical polarization a 1-wavelength symmetrical delta loop (apex at the top) should be fed 1/3 up from the bottom. Moving the fedpoint from the bottom corner will give you about 2 dB more gain at low angles (<30 deg take-off).
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