[Lowfer] re: GROUND RESISTANCE

[rick]

Thanks Ed,
 Appreciate the input! Thats alot of work .Even if I manage a decent ground 
system ,Im still stuck with the tree issue.I have lots of trees and the 
vertical would  end up too close to them.
 I just finished downloading Bill  Ashlocks loop articles and I think thats 
my best option.

                   Thanks Again
                           Rick  KA2PBO








----- Original Message ----- 
From: "Ed Phillips" <evp at pacbell.net>
To: "Discussion of the Lowfer (US, European, &amp; UK) and MedFer bands" 
<lowfer at mailman.qth.net>
Sent: Wednesday, December 31, 2008 2:52 PM
Subject: Re: [Lowfer] re: GROUND RESISTANCE


> Hi Rick ground resistance is frequency sensitive so needs to be measured 
> at
> the operating frequency at LF, using either a commercial RF bridge or you
> can construct a simple but effective unit....see
> http://www.alan.melia.btinternet.co.uk/aelossbr.htm
> There are also several articles on aerials for 136kHz that we used the
> bridge to measure."
>
> The simple method I've used here [very dry location sitting on an alluvial 
> fan from the San Gabriel mountains] is to tune up the transmitter, note 
> antenna current and power supply current, and then replace the antenna 
> with a series combination of a high-voltage variable capacitor and carbon 
> resistors.  I keep the circuit tuned with the capacitor and adjust the 
> resistors until I get the same antenna current at the same input current 
> from the PS.  I believe this gives me the equivalent series circuit for 
> the antenna and ground system alone and may include the effects of some 
> losses in tree limbs near the antenna.
>
> The antenna is a modified 50 foot Hygain "HiTower" and the effective 
> capacitance at the feed point is hughe - almost 450 uufd.  The ground 
> system is four 8' rods inserted into the dry soil with great effort [ended 
> up drilling a hole with a pipe and hose] and 6 feet apart.  Measured with 
> a DC ohmmeter the resistance between any pair is never less than about 500 
> ohms, even after one of our rare rains.  The rest of the ground system is 
> a strap to a 2" copper water line from the street to the house - total 
> length about 135 feet.  With this combination the effective antenna 
> circuit resistance [loading coil loss isn't part of the circuit] varies 
> from 30 to 60 ohms!!!!!  Very discouraging considering the infinitesimal 
> radiation resistance at 180 kHz.
>
> Ed
>
>
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