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
|