Intuitively, without actually modeling the array you converted to, the
heavy radiation is near the dipole feedpoint. In the sideways V
configuration the horizontal placement of the radiation was "fuzzy", and
on average probably suboptimal. The trick you used "focused" the
radiation (apparently to some considerable degree) at the design points,
which allowed "sharper" cancellation for the f/b.
Certainly worth checking out on the program when I get some time. Wonder
what the difference would be for the minimum vertical run possible. That
might make an 80 meter version scalable.
73
-----------------
Guy Olinger
Apex, NC, USA
----- Original Message -----
From: <Dinsterdog@aol.com>
To: <towertalk@contesting.com>
Sent: Thursday, March 15, 2001 12:40 AM
Subject: [TowerTalk] K8UR 4SQR modifications
> 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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