After originally being somewaht satisfied with my K8UR style 40 meter 1/2
dipole 4SQR, I was becoming disillusioned and having trouble..the F/B seemed
inconsistent and gain was not much over my Butternut HF2V. Sometimes it
worked ok, sometimes it seemed like a lot of work for nothing-
For reference: the tower it hangs off of is 60 feet, with insulated guy
wires, using a Comtek coupler (www.comteksystems.com).
After a few modifications suggested by W1XE and K0RF, the antenna system is
now working with some great comparison results working long haul (over
3,500km) DX:
Antenna measured F/B to HF2V measured gain to HF2V
Butternut HF2V na na
K8UR 4SQR 5-15dB 0-2dB
Modified
W1XE/K0RF
design 25-30dB 3-5dB
The modifications made were simple. All we did was move about 2/3rds of the
top half of the dipoles vertically over the feed points vs having none of the
top half of the dipole over the feedpoints on the K8UR design. (None of the
top or bottom portion of the dipole sits above or below the feed point on a
K8UR style 4SQR because the dipoles are in a V shape pattern, with the ends
tied closely to the tower.
The tops of the dipoles on the modified 4SQR were tied 13 feet from the top
of the tower. We then pulled the dipole down towards the ground with a rope
tied to the feed point baluns at about a 45 degree angle.
Then using some very long bailing twine, we tied to the twine to the wire
with a knot 10 feet from the top of the dipole. Then, pulling out on the
twine some 200 feet to a support post, we created an angle in the wire so
that the rest of the antenna's top portion, about 2/3rds of it, was sitting
directly over the feed point. (On a 40 meter 4 SQR, The feedpoint was pulled
just about 25 feet from the center of the tower.)
Our dipoles went from a side ways V shape (K8UR style) to a sort of sideways
square C pattern-
To complete this square C shape, we took the bottom portion of each dipole
and pulled it directly below the feedpoint, until it was about 6 feet from
the ground. Then using ropes, we pulled the remaining end of the dipole
(about 1/2 of it) back to the tower. With an opposing rope, we pulled the
bent angle in the dipole out so that it made a right angle when pulled
towards the tower.
Now, about 2/3rds of the top half of the dipoles sat directly above the
feedpoints while around 1/2 of the bottom of the dipole was directly below
the feed points.
Some basic notes..........On the K8UR design, on a 60 foot tower, the tops
and bottoms of the dipoles are tied much closer to the tower it self with
about 5 feet of diagonal spacing between ends.....On the W1XE/K0RF design,
the diagonal distance between the top ends of the dipoles is around 20 feet
and around 6 feet on the bottom.
The bottom of the dipoles on the K8UR antenna were about 4 feet off of the
ground while on the W1XE/K0RF design, they were at least 6 feet off the
ground.
What was really cool was that my K8UR array had minimal resonance jump
compared to where the individual dipoles were tuned. But there was a huge
140Khz jump experienced with the W1XE/K0RF design. Now thats a system acting
like an array! (K0RF had even more of a jump on his, but his dipoles are
hanging a lot higher then mine-)
The K8UR had little if any F/B on stateside signals compared to the Butternut
HF2V. While the W1XE/K0RF designed had on average 15-20dB F/B stateside.
On stateside DX, the K8UR had little if any gain over the Butternut HF2V
while the W1XE/K0RF had around 3-5dB's, even with stations as close as Texas
and California.
(refer to the table at the beginning of this posting for long haul DX
results)
Not a scientific study, but a good amount of time was spent testing these two
styles of 1/2 wave dipole 4SQR's. What seemed like minor modifications had
huge results.
If you have about an acre of land available, and you don't like having to put
up huge towers, this modified W1XE/K0RF design will play well.
If your short on space, the V shape 1/2 wave dipole version of the K8UR style
works ok but you might be better off with a 40 shorty on a decent tower--
With a tall enough tower, you can suspend the tops of the dipoles directly
above the feedpoints. But I think you still need to fold back the bottom of
the dipoles towards the tower to help eliminate unwanted high angle radiation
.......I've never tried this so I don't really know what would happen but
ON4UN talks about this in his 3rd edition of "Low Band DX'ing" Chapter 11,
page 78.
I played around with this array for about a year. I got the idea on the
modifications when W1XE and K0RF strung one up at K0RF's contest station. I
was told that the computer model showed this wider spaced version would blow
away the K8UR design, with it's sideway V shape dipoles, and it was
right......
""""""""""Increasing the average spacing between the tops of the dipoles had
huge results here!!!""""""""""""""
If anyone has a computer modeling program, and would like to better explain
what is happening here, please let me know- Also, if any past results were
published by K8UR or by anyone else, on the effects of increasing spacing
between the tops of dipoles in a 1/2 wave dipole 4SQR, I'd like to read up on
it-
E-mail photos of the K8UR style I built, and/or the modified W1XE/K0RF
version, are available- I'll be glad to send it-
Of note, I wrote about this last year, but since making more accurate spacing
between feed points on both versions, and taking more time to better align
the dipoles for 4SQR spacing, the differences between the two styles was even
more dramatic than originally tested last year.
73 Paul N0AH
Carpenter, WY
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