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Re: [TowerTalk] Vertical in the swamp

To: Jim Lux <>
Subject: Re: [TowerTalk] Vertical in the swamp
From: Jack Brindle <>
Date: Tue, 13 May 2008 14:05:21 -0700
List-post: <">>
This depends largely on the QTH. Everglades water tends to be  
brackish, while water in the Louisiana swamps more fresh. My  
experience with a HyGain 14AVQ in Miami in the 70s was very good, no  
matter how many radials (or none). The water table (very brackish)  
was just three feet down, the QTH two miles from the Atlantic. I saw  
no difference in signal strength/quality from the northeast or EU  
whether it had radials or not. On the other hand, moving the exact  
same antenna to Southwest Louisiana (Lake Charles) made the antenna  
somewhat useless. The QTH was at 14 ft elevation, and the antenna  
performed equally poorly whether it had 16 or 60 radials. A long (200  
ft) open-wire fed dipole at 30 feet was the big winner there.

I came to the conclusion that vertical antennas close to the beach  
with lots of salt water between the station and the "other" guy meant  
far more than having lots of radials. Of course this was in the 70s  
and physics may have changed since then... ;-)

On May 13, 2008, at 12:46 PM, Jim Lux wrote:

> Carrington, Walter wrote:
>> Is swamp water conductive?
>> Fresh water swamps have a lot of stuff suspended or dissolved in  
>> the water. The conductivity might be much higher than pure water.
>> A quick google:
>> Great Salt Lake = 158,000 uS/cm
>> Salt water is about 50,000 microSiemen/cm  (uS/cm)
>> Atlantic Ocean = 43000 uS/cm
>> Drinkable water -- less than 3000 uS/cm  (and you'd prefer <1000 )
>> Irrigation water -- 3000 to 6000 for  salt tolerant plants.
>> Lake Mead = 850 uS/cm
>> Lake Superior = 97 uS/cm
>> Soil conductivity in New England = 10 to 20 uS/cm  (Map ARRL  
>> Antenna Handbook).
>> Deionized water = .05 uS/cm
>> "Fresh" water swamps =  250 to 37000 by one Australian study,  but  
>> conditions were strange there (the 37000 was almost dry,  all were  
>> drying out).
>> My guess for swamps = 250 to 3000
> For the area right in the neighborhood of the antenna (say, within one
> antenna height), the conductivity is important.  Farther away, it's  
> the
> relative permittivity (dielectric constant) that's more important, and
> water, fresh or salt, is HUGE (e.g. 80ish) compared to almost  
> anything else.
>>> From what I can find online,  your conductivity ought to be 10 to  
>>> 100 times mine.
>> It ought to be more conductive than Lake Superior for sure, i.e.,  
>> substantially better than a clean lake.
>> If your swamp gets drier seasonally the conductivity should go up  
>> when it's drier but still liquid.
>> These numbers make it look like a fresh water swamp will be better  
>> for radio than almost all soils and most fresh water lakes but not  
>> as good as salt water.
>> I wonder if the swamp at the bottom of my hill helps on 2 meters.
>> --Walter, K1CMF
>> _______________________________________________
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- Jack Brindle, W6FB


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