> Gary-K9AY wrote:
> > You hit one of my "hot buttons" -- I have not seen any
convincing evidence
> > that equalizing currents in elevated radials is a valid
exercise.
Ford Wrote:
> My thinking has been that the characteristic null that is
supposed to occur at zenith is a good thing. If nearby QRN
arrives at a high angle, then the deep null at zenith should
be a good first line of defense against noise.
>
I go along with Gary on this so far as field strength
goes....and with you as far as pattern goes.
The problem with all of this Ford is none has any idea what
the earth is like under the radials. The model assumes it is
a homogeneous media with evenly distributed chracteristics.
Balancing current in the radials will not assure anything
in the real world, because almost never will you find a
perfectly balanced environment or evenly distributed soil
characteristics.
We can write a detailed 50 page analysis of what happens in
a model and it won't mean a thing in the real world 99% of
the time.
> I have been playing around with models of the system and
can see that even a slight change in electrical imbalance of
the various radials causes a somewhat insignificant skew to
the pattern at the horizon, but a significant skew at
zenith.
Imagine what other conductors near the radials, varying
conductivity in layers of soil below the antenna, and other
things do even when radial currents are equal. Why worry
about what we can't predict, measure, or control?
If you want a radial system that works reliably use 20 or
more radials as long as you can. They won't give you
radiation problems regardless of how they are tuned, losses
will always be reasonably low, they will work on multiple
bands.
If you want to save work by pretending less than a dozen
radials less than 1/10th wavelength high are "earth
independent", then you just have to take your chances with
the unpredictable hidden problems. No point in wasting a lot
of time balancing what is often over a radically unbalanced
media and 5 or 6 dB down from a good system.
73 Tom
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