I did a lot of modeling a few years ago and found the tower interacts
with the vertical polarization. If the loop is about 5 ft out from the
tower then the pattern is improved. A feedpoint about 20% up (from
bottom) either leg yields a good low angle pattern and a near 1:1swr 70
ohm resonance Z (apex at 77', bottom 118' long at 26') There is about
4db front to side and about 1db lower gain on the tower side of the
loop. 2.33dbi peak gain at 20 deg which is pretty nice for a low no
radial single support antenna on 80m. However, with the apex up it is a
real cloud warmer on 40m. If you have two supports, and have the apex
down, the 40m performance is very good. I've not modeled perpendicular
loops but spent a lot of time modeling a phased pair, but gave that up
with the tower interaction issues. Others have built phased ones hung
on a tower and reported poor results.
Grant KZ1W
On 8/23/2015 12:11 PM, Robert Harmon wrote:
I would like to hear how your 80M Delta loop performs for you.
I had one strung form my tower at 80 feet fed as Dennis said 1/4 wave from the
apex. I could work any DX that I could hear but it picked up
much more noise (local electrical) than my inverted L I had up previously. I
was feeding with 450 ohm ladder line. I am thinking of stringing it
up again and this time feed with coax and see if it is better. I suspect the
ladder line was the culprit, not sure.
Bob
K6UJ
On Aug 23, 2015, at 11:34 AM, Dennis W0JX via TowerTalk
<towertalk@contesting.com> wrote:
Rich:
Check the patterns for an 80 meter Delta Loop hanging from a 78 foot tower. If
you feed it at the bottom center for horizontal polarization, you will have a
sensational cloud warmer and a poor DX antenna. This antenna should be feed 1/4
wave from the apex for vertical polarization.In that manner, the pattern is
almost circular with about 1 to 2 db favoring the plane of the wires,
You don't need the second delta loop.
Dennis W0JX
Milan, OH
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