Topband: Grounded Tower

[Tom Rauch]

> Jim Jarvis writes:
>
>> I disagree.  There is data to the contrary...that is, 
>> that a
>> few elevated radials work better than an insufficient 
>> on/in
>> ground system.  I am sure this depends on the 
>> conductivity of
>> the earth involved, to some degree.
>
> Jim, you've opened a real can of worms.
>
> You can't say there is "data" to the contrary ... there 
> may be
> legend, anecdote or even model studies but there are no 
> validly
> conducted field strength studies that show elevated 
> radials to
> outperform a reasonable (16 - 32 radials) in ground system 
> when
> the length of the in ground radials are "sufficient" 
> (e.g.,

W7EL and myself just finished measuring radials (we stopped 
at 32 radials for now) and ground conductivity using a 
single probe measurement method on 7 MHz. The entire 
exercise will be an article. There is a lot to learn from 
what we saw. We included base impedance measurements with 
precision test gear (my HP impedance test set) and FS 
measurements with a  Rohde and Schwartz field strength meter 
and did some radial current and dipole impedance 
measurements.

As many recall, I measured 80 meters at two different 
locations, here and near Conyers, GA. My earlier tests 
showed about 12-16 buried radials were about equal to 4 
elevated radial system that was carefully tuned and used a 
feedline choke

In the meantime, three thoughts to keep in mind:

1.) Don't depend on base impedance to tell you if your 
antenna's ground system is good. Forget that idea!

2.) If you have a choice between 16 buried radials and a 
good system of four elevated radials with good feedline 
isolation, pick whichever you find easiest to maintain and 
install.

3.) I'd be very cautious about using the simple Internet 
program from a G4's web site to predict vertical efficiency, 
at least for the moment.

I hope within the next week or two to pull a full ground of 
60 or more radials in that system, but the dirt is pretty 
hard and the weather is near 100 degrees in the daytime.

73 Tom