Re: LF: RE: Soil Conductivity Measurement

[Dick Rollema <dickrollema@casema.nl>]

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