Does anyone know the conductivity of concrete?
Is it sufficiently low to use a concrete base as a base insulator
for a quarter wave vertical fed against ground based radials?
In an experiment conducted by NN4T/WA4CTA, he measured the
feed impedance of his 160M elevated GP with the tower base
connected to several ground rods.
Then he measured the feed impedance with the ground wires
removed. There was a noticable change.
Then he measured the feed impedance when the concrete was
wet and saw no difference from when it was dry (with ground wires
>From this data, I concluded that the concrete base was an adequate
With a quarter wave vertical, the base impedance is low (<35 ohms)
and voltages are below 250 VRMS. Presumably, a leakage path of
350 Ohms or greater will have little effect on efficiency.
Your thoughts and comments are solicited.
Thanks and 73, Tom - N4KG
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