Precisely, and the bandwidth of that match with the ground rod will be
much wider than with a radial system.
10 ohms is a very good ground rod, and one driven into basement fill is
likely to be considerably higher in resistance at RF and at DC. Dirt is
a poor conductor, just for AC and DC there's so much of it in parallel
that the impedance over a distance is low, but locally its rotten stuff
for conductivity unless its a salt marsh swamp.
73, Jerry, K0CQ
On 12/3/2010 1:01 AM, Ken Brown wrote:
A quarter wavelength monopole with a really good counterpoise/ ground
radial system has a feed point radiation resistance of around 37 ohms
and very little loss resistance. That will give you an SWR of about
1.4:1. If you use just a ground rod and have about 13 ohms of resistive
loss in the ground system, the series equivalent feed point impedance
will be about 50 ohms, and the SWR will be very near 1:1. Some people
think this is better. It does "tend to make the matching easier."
I don't know what kind of ground you have, or whether your ground system
resistance would be 13 ohms with just a ground rod. The point I am
trying to make is that a really efficient vertical is likely to have a
higher SWR than a partially radiating dummy load. Many hams do choose a
lower SWR over a more efficient radiator.
The ground rod will work, but it will introduce more resistance to the
antenna feed than radials. It will tend to make the matching easier, but
the efficiency poorer.
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