[TowerTalk] Impact of high water table levels on antennas
glhuber at msn.com
Sun Nov 3 14:42:53 EST 2013
I have a similar situation. My QTH is on a glacial moraine about a tenth of
a mile from the crest. There is water bearing clay less than thirty inches
down and the soil is the black muck left by the glacial ponding. To top it
off, I've mounted my HV-2 w/160m mod and umbrella capacitance hat over two
dozen 66 foot radials all over the septic leach field. A friend who has
operated from ZF2 and C6 numerous times says I am very strong using the HV-2
on 40..... I've worked a lot of DX with the HV-2 over the septic field over
the past 27 years including ZL9CI, KH1, KH6, etc.
I believe the high water table helps me and will help you.... but the
advantage works also for the 4SQ or any antenna. Probably about 3 dB from
the Fresnel reflection.
From: Rudy Bakalov
Sent: Sunday, November 03, 2013 1:02 PM
To: towertalk at contesting.com
Subject: [TowerTalk] Impact of high water table levels on antennas
Ever since I have put up two inv-Vs, one for 80m and one for 160m, with
their apexes at roughly 90', I have been puzzled by their exceptional
performance. Ditto for my vertical on 40m. I have done tons of comparisons
using skimmer data and my signal seems to be pretty darn close to the big
stations I am using as my benchmark. The performance is so good that I have
been wondering if I should bother with building 4SQs. I have read tons of
books on antennas and the performance of these two antennas simply does not
match what the books describe.
I shared my thoughts with a friend of mine (a WRTC2014 participant) and he
shared a similar experience with his station. He recently relocated to a new
place, about 30 miles from his old place, and his antennas at the new place
perform significantly better than the old location. Same antennas, tower,
feed line, and FLAT terrain. His only explanation is that the new place had
a very high water table that somehow impacted antenna performance.
This is when I realized that I also have a very high water table. Even in
the driest months of summer, the area around my tower is damp and the grass
is very green, growing like crazy. This was the obvious common element
between his and my situations.
I have not seen anything on high water tables in my antenna books. The soil
itself is mostly sandy. The impact I believe I am seeing is mostly on the
lower bands, but I am not sure if this is also the case on the upper bands
as at 105' my antennas are a bit too high.
Is there any rationale in our thinking? Can high water table explain better
than expected performance from low band antennas? If so, what is the theory
behind it and how do I take advantage of it? If not, any other suggestions
for why the antennas work so well?
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