I'm experimenting with antennas, and I'm going to model some on my
computer, but I need to know the ground conductivity at my QTH.

How may I measure this without special-purpose instruments?

TIA.

73, Bill W1AC


--
Bill Horne

(Remove QRM from my address for direct replies.)

On Tue, 30 Sep 2008 16:14:22 EDT, Bill Horne wrote:

I'm experimenting with antennas, and I'm going to model some on my
computer, but I need to know the ground conductivity at my QTH.

How may I measure this without special-purpose instruments?

TIA.

73, Bill W1AC

You can get estimated ground conductivity at
http://www.fcc.gov/mb/audio/m3/index.html

73 de Dick, AC7EL

Bill Horne wrote:
I'm experimenting with antennas, and I'm going to model some on my
computer, but I need to know the ground conductivity at my QTH.

How may I measure this without special-purpose instruments?

TIA.

73, Bill W1AC



If you want a real value you will have to do a four pole fall of
potential measurement using a Ground Resistance Tester. That is the
only way to get a real value that will hold up to later scrutiny of the
antennas you have modeled.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison

Bill Horne wrote:
I'm experimenting with antennas, and I'm going to model some on my
computer, but I need to know the ground conductivity at my QTH.

How may I measure this without special-purpose instruments?


From an ARRL Handbook

You drive 4 rods into the ground 18 inches apart in a straight line.

You have a 100 watt bulb in series with a resistor that goes to the near
rod, the other side of the bulb goes to one half of a 120 volt line.
The other side of the 120 volt line goes to the farthest rod.

If the bulb lights brightly, then rejoice! You have great ground.


Here is the more detailed link

http://amfone.net/ECSound/K1JJ12.htm


Needless to say, you're operating with some voltage here, so care is the
watchword. Keep in mind that conductivity is constantly changing, so the
best we can hope for is a rough idea anyhow.

Now a simpler way to do all this, and much less dangerous, is to use
maps like the one at:

http://www.fcc.gov/mb/audio/m3/index.html



- 73 de Mike N3LI -

On Thu, 2 Oct 2008 16:44:22 EDT, Michael Coslo wrote:

Now a simpler way to do all this, and much less dangerous, is to use
maps like the one at:

http://www.fcc.gov/mb/audio/m3/index.html

Ah yes, the venerable M3 map. It is only an approximation, and for
real-life stuff it isn't used any more, supplanted by real ground
conductivity measurements.
--

73 de K2ASP - Phil Kane

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon

e-mail: k2asp [at] arrl [dot] net

Phil Kane writes:

On Thu, 2 Oct 2008 16:44:22 EDT, Michael Coslo wrote:

Now a simpler way to do all this, and much less dangerous, is to use
maps like the one at:

http://www.fcc.gov/mb/audio/m3/index.html

Ah yes, the venerable M3 map. It is only an approximation, and for
real-life stuff it isn't used any more, supplanted by real ground
conductivity measurements.

How much would you get out of plotting how impedance changes as you
lower the antenna?

Jon LA4RT