Thanks to Greg for this thorough analysis.
I'm still absorbing it all but one thing that struck me was this in the
consideration of optimizing:
"The one thing that can’t be changed is the location of the parasitic elements.
They are located over extensive radial systems with miles of wire that can’t be
moved."
I think moving the elements in one of several ways could provide an increase in
gain. Certainly achievable if one were starting to build this from scratch.
In my own case I added a second director toward Europe for a theoretical extra
0.9 db gain.
But what got me thinking of modifying the other elements was an article by K0HA
(Bill in Nebraska) that described his 5-element parasitic arrays made of BX
tower in the 1970's or '80s. I believe he found 80-foot spacing to be the
optimum.
In another vertical array I have, a broadside-endfire for 80 meters, I nested
it inside a 160m broadside-endfire array and simply tapped into a single radial
of the 160m array radial field for each 80-meter feedpoint. Impedance
measurements were similar to what I would expect from having the radials all
terminating at the 80m feedpoints. Performance has been good.
So could we simply move move the K3LR array feedpoints outward without moving
the radial field, tying into a single radial?
I started building my 160-meter version of the K3LR array in 1998, after
reading about it in ON4UN's book and some earlier articles on sloping 2-element
reflectors or directors hung off a driven tower. Initially the parasitics used
the sloping "T" top.
But after I added three other towers in strategic positions these held up the
end of the ropes and the top of these T elements became horizontal. The NW
element remains a sloping T. I have pondered shifting the T tops outward from
the tower if this could produce more gain, with the vertical wire sloping away
from the tower.
Another option I've thought about is pulling the vertical portion of the wire
outward from the tower, perhaps 20-30 feet up from the feedpoint.
Next summer I'm planning a re-do of my array and may experiment with some of
these.
73/Jon
Jon P. Zaimes, AA1K
Tower climber for hire
Felton, Delaware
http://www.aa1k.us/
Cell: 302-632-2353
Reviews of AA1K tower work on eham website:
http://www.eham.net/reviews/detail/12922
Hug your favorite tower every day, and always stay connected to it.
On Sunday, November 10, 2024 at 11:18:49 AM EST, Tim Duffy <k3lr@k3lr.com>
wrote:
The 160 meter three element vertical parasitic array that we use at K3LR has
been published (details on how to build) in the last three editions of the
ON4UN Low Band DXing book. Since I have used this antenna for 30 years,
several stations such as K9CT, VE3EJ, AA1K, W5ZN and NR5M now use this
antenna. Greg, W8WWV recently did some investigative modeling work about the
antenna - which is presented here:
<http://www.k3lr.com/engineering/160m/K3LR160m2024Revisit.pdf>
K3LR160m2024Revisit
73
Tim K3LR
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|