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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