Measuring Soil & Ground Conductivity

Submitted by Tom K1JJ

 

Here's another great  email I got from a helpful ham on the Top Band Reflector.  It's about measuring your ground conductivity. It's ideas are taken from the ARRL Handbook.  His personal experiences are included too

I've not heard of this handy procedure before and plan to try it out myself. It goes hand in hand with vertical antenna evaluation. If you have great soil conductivity, you can get away with few radials vs: poor ground.

IE, if the test bulb glows brightly, you may be fortunate enough to have the soil for a super performing  vertical antenna system.

73,

Tom, K1JJ
 


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Posted with permission -
As follows:

The "Ground Conductivity Test" is from the ARRL Antenna Handbook...

The book I have is from 1994....and it is on page 27-35 that's chapter 27 page 35........

Conductivity Soil, Measurement of....

It takes 4 rods.......9/16" diameter and 14 inches long these 4 rods are driven into the ground 18 inches apart in a straight line......drive them in 12 inches...

One side of the 120 AC line to a 100 watt light bulb...the other side of the bulb to a 14.6 ohm resistor.........they say to make up the resistor by paralleling 5 of them...3 of which are 68 ohm 1 watt....the other 2 are 82 ohm 1 watt......then the other end of the resistor goes to rod #1 .......the other side of the AC line goes to the farthest rod.....

You now have two AC voltage test points......V1 is across the resistor. V2 is voltage measured between rods #2 and #3.....

In general these two voltages they say should be from 2 to 10 volts......

Formula for calculation is......

C = 21 x V1/V2
 

This gives you the Millisiemens per meter

They do say that the measurements can vary considerably depending on moisture content of the round.......example given is a chart was someplace in New Jersey back in 1976.........the guy took measurements daily for 90 days......measurements varied from 15 to 30 Millisiemens per meter over that period of time.......

Anyway.....a big difference in my ground to George's.........and even better yet out at KD9SV Gary's house..........he is about 20 miles from me........and is in an area that has probably the best farm ground I have ever seen.........

Here at my place that light bulb lite up to maybe 1/3 brilliance at Gary's place you could read a newspaper with the bulb at midnight.........at George's place......he couldn't see the light bulb lite up at all at night..........same light bulb.....same rods.....they belong to George.....he sent them to Ft Wayne for Gary and I to check ground here as he wanted the reference information..........

Anyway......that's how it goes........

John k9uwa


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