Topband: Modeling the proverbial "vertical on a beach"

[k1zm--- via Topband]

Hi Guys


K3ZM is my brother - and his 160m antenna is located in a salt marsh just to the West of Chesapeake Bay in Matthews, Va as I recall. Indeed he is located inland a bit (eg: not directly at water's edge) - perhaps 1000 feet distant (although this is only a guess on my part from photos I have seen).  But the intervening land is also primarily salt marsh.  At certain times of the year this land floods with salt water and it is necessary to wear very tall boots in order to walk out to the base of the towers Peter owns.  I am sure Peter could add more specifics.


From conversations I have had with Peter over the years - and from listening to his signal over at 7O6T, I can tell you that he is very competitive when compared to his peers.  Additionally, his ability to hear for a location so far South (eg - not in New England) - especially in winter is quite remarkable  His contest results in 160M contests speak for themselves.


Other observations - perhaps relevant, perhaps not.


W1WEF and I often get together for lunch in Orleans on Cape Cod.  Jack works the HF bands from his mobile CW rig in his car - and when he drives out to the peninsula where I live (just off Pleasant bay which is salt water) - dead 15m and 20M bands magically go from NO European signals to a full band of signals as he comes up the road that runs along the Bay.  He describes it as going from a DEAD BAND to a wide open band as he nears my home.  This is in the daytime in summer as I recall.


Personally here at VY2ZM - I am sure by co-locating my vertical systems at or near the water's edge has helped me - to what degree I am not sure - but it is rare to be outheard looking NE or East on the lowbands.


During this thread I am pretty sure I read a post that co-location near Salt water is additive also for horizontal yagis.  I do not believe this to be correct.  My good friend Don Toman has several times told me the effect we are seeing here is primarily limited to verticals - and not to horizontal yagis - which according to Don, rely principally on their height above ground as the key variable impacting their performance.


On the other hand, shooting out over open ocean from a slightly elevated position with HF yagis is a pretty good takeoff to be sure.  Especially when compared to looking uphill over land in other directions - which I find causes performance to suffer by comparison.


FWIW


Salt water is good stuff.  Especially for verticals placed at or near the ocean - with additional ocean out in front of the antenna for hundreds of miles.  I too have never fully understood the phenomena but I know it is magical in terms of lowband DX'ing performance.


73 JEFF  K1ZM/VY2ZM














---- Original Message ----
From: Guy Olinger K2AV <k2av.guy at gmail.com>
To: Tom W8JI <w8ji at w8ji.com>
Cc: TopBand List <topband at contesting.com>; Guy Olinger K2AV <k2av.guy at gmail.com>
Sent: Fri, Aug 15, 2014 7:20 am
Subject: Re: Topband: Modeling the proverbial "vertical on a beach"


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
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