Topband: Modeling the proverbial "vertical on a beach"

[Guy Olinger K2AV]

On Wed, Aug 13, 2014 at 9:28 PM, Tom W8JI <w8ji at w8ji.com> wrote:
>>> One would think if there was a 10-20 db penalty, it would show on
>>> skimmers and that W2GD would be unbeatable being on the water.
>>>  I'm sure I'm missing something. What is it I am missing?

>> A contest certainly is not only about transmit signal strength, nor is
>> the lowest angle propagation always the most productive. There is
>> always the 27 dB gain between the operator's ears (or lack of it) to
>> be reckoned with.

> But skimmer, which displays a relative level, does not show the level
> difference.

I quite agree, and from what I have personally observed, I WOULD NOT
EXPECT peak levels on RBN to show the difference, except in very
special circumstances.

The Core Banks N4A test was walking backward FROM WATER'S EDGE up onto
the sand beach, and then over the low dunes to about 400-500 feet from
water's edge.  MSL 0 feet to about MSL 5 or 6 feet.

The signals showing the most change were not the loudest. They were
the ones on the edge of the developing band opening. The stronger or
peak signals from these stations would occur later as (presumably) the
angle of arrival moved up. The advantage to the water's edge I was
hearing would only last from first hearing to full band opening. To
the extent that the opening was very marginal, the advantage could
persist.

I need to make some phone calls, but both W2GD and K3ZM appear to be
well away from water's edge to NE, possibly over 1000 feet for W2GD,
and depending on where and how ZM's 4 square is constructed, nearly a
half mile from water's edge at bearing 45 degrees. Given these
yet-to-be-verified distances both these stations will enjoy the
excellent advantages of EFFICIENCY from those locations, and lack of
intervening clutter, but not the water's edge change.  I have only
seen the large change from water's edge, not from water's vicinity.

Therefore I must apologize for including W2GD and K3ZM in the
discussion, and retract that aspect in my prior comments.  My
observations are strictly water's edge vs. the walk back 400 or 500
feet.

In deliberately construing an on-purpose experiment with skimmer/RBN,
I would need to put a pair of skimmers on the beach. One with a
vertical at water's edge or over water, and the other back 100 or 200
meters from water's edge. This would need to be done in a contest with
a large population of competing stations in directions both over the
water and elsewhere. Then table up all the readings before the data
reduction part of the program is employed.

My intuitive understanding of what is going on, is that the difference
is not an amplification of the signal at the lower angles so much as
it is opening up the lowest angles for use at all, or possibly
something looking like a reverse ground wave or "formed ground wave"
which loses gas as it gets away from the salt water surface. As soon
as the higher angles are employed on the path, the difference
disappears. This is why peak levels on RBN would not show the
phenomena.

The more I dig into this the more I am convinced that this phenomena
observed by multitudes for decades is very poorly understood, and
maybe now we have some stuff to investigate it properly.

73, Guy K2AV