Sat, 11 Apr 1998 18:17:04 -0400
As a prelude to the eventual testing of the "earth dipole"
approach to LF transmitting antennas, I ran today the
1). two galvanized 1/2 inch diameter water pipes, 6 feet
long, were driven 5 ft into the ground at the end of my
garden. They are 50 feet apart.
2). these rods are connected back to my shack with 12 gauge
3). using a good digital VOM, I obtained a DC reading of 489
4) using an isolation transformer, I then connected in
series with the two rods a 120 volt, 40 watt lamp.
The current flowing through the circuit was 200 mA. The
output voltage of the isolation transformer was 130 volts,
the voltage across the lamp was 45 volts and the voltage
between the two "ground" rods was 85 volts. Hence the
calculated AC impedance between the two ground rods was 425
ohms, which is fairly close to that originally measured with
Conclusion #1: my next experiment will consist in applying
the same technique, but with an audio generator, and making
measurements at 100 KHz, 130 KHz and 180 KHz.
Conclusion #2: for a current of 200 mA, 85 volts AC between
two points supposedly grounded ! That could be enough to
give someone a nasty shock (if not worse). Hence, watch for
those "grounds" in your own shack.
Andre Kesteloot N4ICK