[TowerTalk] 80 Meter Delta Loop

[Joe Subich, W4TV]

On 7/24/2024 4:00 PM, Wes Stewart via TowerTalk wrote:

> Doesn't the dirt in the far field behave the same regardless of the 
 > height of the antenna?

No, field intensity decreases at the square of the distance.  Thus,
if one is a wavelength (or significant fraction of a wavelength)
away from the dirt, the field intensity and therefor losses are
reduced significantly.

This is the same mechanism that results in the reduced near field
losses in elevated radial systems - more than ~ 0.05 - 0.1 wavelength 
(e.g., ~10 - 25 feet on 160 meters) high.

> I live in AZ but I'm not familiar with any cliffs overlooking
> saltwater.

The cliff doesn't need to be over saltwater ... one of your 200
foot high mesas would work nicely.

73,

    ... Joe, W4TV

On 7/24/2024 4:00 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 at audiosystemsgroup.com> wrote:
>   
>   On 7/24/2024 11:31 AM, kq2m at 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
>