[Hi-zreceivingarraydiscussions] Grounds for 4 square

[John Kaufmann]

I have measured RF ground resistance for a short receiving vertical (about
15 ft tall) with just a 4-foot ground rod.  I used the AIM-4170, which is a
pretty accurate instrument, although I won't claim it's perfect.  On 160m
the resistance is about 60 ohms.  As expected, the measurement also shows a
large amount of capacitive reactance, equivalent to a series capacitor of
about 50 pF.

 

Actually I measured the resistance across a span of 1 to 10 MHz.  The trend
is for the resistance to decrease with increasing frequency, although it
reaches a floor of 25-30 ohms around 4 MHz and higher.  The equivalent
series capacitance is pretty constant across frequency.

 

I would have expect the resistance to be higher with just a simple ground
rod and it's possible there is some measurement error here.  On the other
hand the vertical is installed in an area that is surrounded by wetlands, so
the soil conductivity is probably above average.

 

73, John W1FV