Jim,
I mentioned "one antenna that does work well even over poor ground", not
the best antenna overall. And it does work very well - enough to let me
work 39 zones and 300+ countries on 80 not to mention being a very
effective antenna in DX contests when the K index is below 5.
I elevated the radials specifically to reduce the impact of lossy
"earth" that my 4-square would otherwise suffer and due to the fact that
there is very little actual "ground" where I have my 4-square - it
resides above ledge, jagged uneven ledge, and a few inches of "dirt" so
devoid of nutrients that it can't grow anything but weeds, thorn bushes
and poison ivy. That's what hilltops are like in Western Central CT.
Great for beverages but not so much for vertically polarized antennas.
Sure, a 4-square of full-size aluminum verticals with 32 radials per leg
would be an improvement but that is not an option at my qth. So it was
either a 4-square or an Inv L or Inv V at a low height, both of which
were far worse. You have to do the best that you can with what you have
and the 4-square works best here.
73
Bob, KQ2M
On 2024-07-24 14:41, Jim Brown 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
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