On Thu, 19 Feb 2009 07:32:55 +0100
"Wolf Ostwald" <df2py@t-online.de> wrote:
> examples from EU: FK,FW and ZL7 . all are
> some ten thousand miles away copied in eastern EU and
> not in western EU....more ERP needs to be launched..
Wolf,
The problem is probably, as you suggest, attenuation
around the gray-line. To launch more ERP one needs to
increase power or build a better antenna, or do both.
Increasing power is often not practical (or legal).
Improving the antenna, on the other hand, is often easy.
In the case of the recent FW operation, I believe that the
antenna would have worked better if it was standing in
the water -- perhaps as much as 3 dB better. That could
have made the difference for you!
My experience, both from DXpeditions and my home QTH,
which is next to the sea, is that the antenna should be
mounted either in the water or right on the edge of it!
The general consensus is that as long as the antenna is
within 1/10th wavelength of the water, it will work
equally well. I do not agree! If there is water under the
sand, not more than 30 cm down, that maybe true, but
otherwise the antenna will perform better standing in the
water! I have numerous examples when I moved an antenna
and the performance changed noticeably. Think of it this
way: if half of your yard was covered with a copper sheet,
while the other half was just sand, which side would you
put your vertical on? On 160 any vertical on a DXpedition
is likely to be a compromise antenna, with corresponding
low radiation resistance. Perfect ground will help to
offset that. A little less perfect ground, like what you
get 10 - 15 meters from the water, will likely add
significant losses, even with a lot of radials! The
difference can easily be 3 dB and a few hundred extra
miles!
CU and 73,
George
AA7JV
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