I have a wire 4-sq with elevated feed points around a 80? tower. The feed
points are about 10? above ground. I have 5 radials on each vertical. The
radials are 41?. There are two coils between the radials which are tied
together at each feed point and the coax shield. One coil is fixed and
tunes the array at 3780. I have a relay that switches in the other coil to
drop the resonance to 3540. Shortening the elevated radials to less than a ¼
wave significantly improved F/B and F/S. The vertical #12 wires go vertical
for about 20? then are pulled to the top of the 80? tower.
The spacing of the 4 posts is for 3650.
The feedlines are ¼ wave RG6 55? 9? with 100 ferrite beads at the feed
points. I believe they are #31 material.
I want to bury the feed lines so I made some ¾ wave lines with 8 turns
through a #31 big clamp-on core.
I did a test where I measured the power in at the Comtek box and the power
out of the dumped power port comparing the ¼ wave to the ¾ wave feed lines.
SWR was 1.1:1 on all the tests as I would expect. And the shape of the graph
is as I would expect.
There is not much difference in dumped power between the ¼ and ¾ wave lines.
Check the graph.
<https://drive.google.com/file/d/1E0Wi6s5PhFx3_acUvbWm5-O1OFbYWMjo/view?usp=
sharing>
https://drive.google.com/file/d/1E0Wi6s5PhFx3_acUvbWm5-O1OFbYWMjo/view?usp=s
haring
<https://drive.google.com/file/d/1ynbz_zle6ORo51eWkUPd5jEGTQz-WZAT/view?usp=
sharing>
https://drive.google.com/file/d/1ynbz_zle6ORo51eWkUPd5jEGTQz-WZAT/view?usp=s
haring
Questions and comments:
Does this graph seem normal and is it what I should expect?
It would seem the difference in feed lines would not make a noticeable
difference on pattern and efficiency, correct?
Has anyone added a 100 pf cap across Z2 in the Comtek box to move up the F/B
peak to better align with the minimum dumped power point?
And a question for those that are good at modeling. If I moved the feed
points to 2? above ground and removed the elevated radials and added 16
buried radials 32? long at each feed point would I see a loss of pattern or
efficiency?
Tnx for any feedback. Figured the WX is getting cold enough here in NY to do
some antenna projects.
N2TK, Tony
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