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Re: LF: RE: Soil Conductivity Measurement

To: [email protected]
Subject: Re: LF: RE: Soil Conductivity Measurement
From: Dick Rollema <[email protected]>
Date: Mon, 01 Aug 2005 14:50:04 +0200
Delivery-date: Mon, 01 Aug 2005 13:50:31 +0100
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To All from PA0SE

Mike, G3LHZ, wrote:
Has anyone on the list experience in measuring ground conductivity at such frequencies?

I do it by first resonating the aerial system at 137kHz. Then I measure the total resistance of the aerial-earth system by connecting a measuring bridge between the bottom  end of the coil and earth. The bridge can be a simple one because it only has to measure a pure resistance. Loss resistance of the coil can be found from its inductance and Q. Subtracting this from the total resistance yields the earth resistance. Radiation resistance and loss resistance of the aerial itself are negligible contributions to the total.

It is indeed important to measure the resistance at the actual working frequency as it is frequency dependent. See ON7YD's website
http://www.qsl.net/on7yd/136khz.htm.

In my station the only earth electrode is the gas mains. Earth resistance varies with season and humidity of the ground but usually is of the order of 22 ohms or so. But we live in a polder almost with our feet in the water.

73, Dick, PA0SE
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