[TowerTalk] Impact of high water table levels on antennas
r_bakalov at yahoo.com
Sun Nov 3 14:02:40 EST 2013
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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