On Wed, Aug 13, 2014 at 9:28 PM, Tom W8JI <w...@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 _________________ Topband Reflector Archives - http://www.contesting.com/_topband