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Old February 6th 05, 11:29 PM
Roy Lewallen
 
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Buck wrote:

If I read this correctly, the more above ground radials (to a point),
the better. Until one gets to 8 radials, there is a significant drop
in antenna loss.


Nope, you didn't. My analysis was for buried, not above ground, radials.
And the loss increases, rather than drops, as the number increases. This
has been well known since at least 1937.

How do the gains/losses change when the radials are disproportionate?
i.e., you have been working with essentially a 40 meter vertical with
40 meter radials. What if I were to place a 20 meter vertical (16
foot for example) on that 33 foot radial system vs placing a 20 meter
vertical on the same 8 radials 16 foot long?


There are an infinite number of such questions, each with its own
answer. But a little research will show that the difference between 16
and 33 foot radials will make little difference on either 40 or 20
meters. There's been a lot posted on this newsgroup in the past about
ground radial systems -- you'll find the answers to many of your
questions by using groups.google.com for a search.


One of the things I would like to have for a multiband vertical is the
separate elements using GAP technology or just using a common feed
point as seen in some of the handbooks.


You really want to use a lossy piece of coax to load your antenna as the
GAP does instead of a more efficient method? Why? Fanned wires with a
common feed point will be more efficient. If you bury the radials, you
need only one ground system -- 8 or so radials will get you within a
couple of dB of a perfect system.


Thanks for all the info. I have a eznic and the ARRL version, but
there is something that isn't registering with me when using it.
Sometimes there are things I just can't seem to learn unless someone
shows me what i am doing wrong or missing.


I've heard many good comments about the ARRL on-line course in antenna
modeling. You might consider it.

Roy Lewallen, W7EL
 
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