On 12/28/2011 2:42 PM, Jim Lux wrote:
> At some point, though, if you have enough wires, the cage will be
> identical to the tube.
> I'd say off the cuff that when the spacing between wires is smaller than
> the distance to the tree (or broomstick) inside the cylinder, you can
> start to ignore what's in the middle.
Jim -- one of the variables in this antenna is the current distribution
within the live tree, which will depend on the distribution of moisture
within the tree. The significance of this is the relationship between
the effective electrical diameter of the tree and this wire cage (that
is, the spacing between the wires and the "tree" as an electrical
element). The next question, of course, is what's that distribution and
what's the effective diameter?
As a sanity check for those who don't know what to believe in this
discussion, I would like to observe that Jim Lux is an EE working at JPL
(that is, Jet Propulsion Lab, our space program), and both he and I are
contributors to the ARRL Handbook. Notice also that Jim responded that
Dave, AB7E, had correctly and very clearly articulated the fundamentals
of this problem in his "three point" post. It's also worth re-reading
some of Jim's other posts in this thread, where he's citing some of the
research that has been published on this topic.
73, Jim K9YC
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