Towertalk
[Top] [All Lists]

Re: [TowerTalk] 80 Meter Delta Loop

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 80 Meter Delta Loop
From: David Gilbert <ab7echo@gmail.com>
Date: Wed, 24 Jul 2024 13:32:51 -0700
List-post: <mailto:towertalk@contesting.com>

A vertical on a slope (or cliff) means that the dirt in the far field isn't actually all there.  Air is a lot less lossy than dirt. It's the takeoff angle that gets the benefit.

Dave   AB7E


On 7/24/2024 1:00 PM, Wes Stewart via TowerTalk wrote:
  I'm confused, First you say, "Poor soil degrades the efficiency of vertically 
polarized antennas both
under the antenna AND in the far field..." I think we agree so far.

But then you say that according to N6BT, a vertical on a cliff mitigates the soil 
characteristics in the far field.  Doesn't the dirt in the far field behave the 
same regardless of the height of the antenna?
I live in AZ but I'm not familiar with any cliffs overlooking saltwater.  Of course if 
the "Big One" happens....



     On Wednesday, July 24, 2024 at 12:08:02 PM MST, Jim Brown 
<jim@audiosystemsgroup.com> wrote:
On 7/24/2024 11:31 AM, kq2m@kq2m.com wrote:
One antenna that does work well even over poor ground is a 4-square with
elevated radials, preferably above .05 wavelength in height.
Poor soil degrades the efficiency of vertically polarized antennas both
under the antenna AND in the far field, where the ground reflection that
reinforces the direct wave is created. Radial systems affect ONLY what
happens under the radials -- they screen the direct field of the antenna
from the lossy earth, and give the antenna a low resistance path for its
return current. That's ALL that they do. They cannot compensate for
lossy ground in the far field.

But ground characteristics DO vary with location, even with lousy ground
under the antenna, good ground in the far field can support the needed
reflection, making the antenna work well. That's the classic case of a
vertical near salt water. And N6BT, well-known for his "Team Vertical"
setups, has recently done field measurements with a drone to show that a
vertical very close to a drop-off (his testing was on a mesa in AZ)
produces a very strong signal in the direction of the dropoff. He first
showed this work as part of the Pacificon Antenna Forum about five years
ago, to which we both often contributed.

73, Jim K9YC



_______________________________________________



_______________________________________________
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


_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
<Prev in Thread] Current Thread [Next in Thread>