On 5/24/11 5:14 AM, Eddy Swynar wrote:
> Hi Guys,
>
> IMHO, most of the mystique surrounding radials is deliberately
> concocted black magic propagated by a handful of self-serving gurus
> desperate to somehow stand alone above us masses of great unwashed,
> as beacons of excellence...
>
well I don't know that it's deliberately concocted..
It's definitely an area where one can draw not entirely correct
conclusions based on applications data from other uses (e.g. AM
broadcast) or a simplified theory that seems reasonable, and then, in
good conscience propagate it as good advice.
It also points up the difference between craft and engineering. The
former does things "because we've done it that way in the past and it
worked"; the latter does things "because we understand the theory and it
predicts that it will work"
> Poppycock.
I'll buy that for a lot of the published material (particularly the
older), but not for "most", at least
>
> Don't be intimidated into believing that your miniscule radial field
> will serve only to keep the earthworms below your feet warm. There
> are several sources on-line that actually QUANTIFY the net effects of
> specific types of artificial grounds, as opposed to simply
> admonishing , "Put in as many radial wires as you can (OR ELSE!)."
but but,but, the earthworms in my yard do much better when snuggly
warm<grin>
>
> Even the stalwart ARRL ANTENNA HANDBOOK summarized the effects of
> using "X" number of radials "X" wavelength long, compared to the BC
> industry standard. If anyone is interested, I'd be more than happy to
> share that info, off-reflector.
One problem with a lot of the "how many radials" or "what's the optimum
number of radials" is that (for a variety of reasons), they tend to hold
a number of parameters constant and vary just one. Good experimental
technique, but the results need interpretation for specific applications.
An example is the work where it was assumed you had a certain number of
feet of wire, and wanted to know whether few long radials is better than
lots of short ones.
In reality, there's other trades on top of that: diameter of the wire,
forking radials, etc. It also depends on whether you are worried about
copper cost or labor cost (labor to install a foot of radial doesn't
change much between AWG6 and AWG20, but the copper cost is a lot different)
I think the overall complexity of the whole "it depends" aspect is what
leads to "put in as many radials as you can" kind of advice. At least
you'll know you did as well as you could, and while there might be other
crippling problems with your setup, at least the radials are as good as
they can be.
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