The fiberglass tubes lower the resonant frequency by an
uncontrolled amount, since they are just fishing poles
that do not have any exact permittivity value. It is
analogous to FR-4 PC boards where the impedance is
to some extent an accident of the characteristics of
the epoxy glass. SteppIR has sourced the tubes from
various vendors over the years which further complicates
the issue. Any correction factor you would use would
be specific to a particular run of tubes. SteppIR
seems to gloss over this issue. There is a parameter
you can set on the controller that scales all elements
by a fudge factor that can be determined experimentally
for the particular copy of the antenna that is being used.
Another issue is: what size round element is equivalent
to the copper tape?
Rick N6Rk
On 4/8/2015 1:05 PM, William Osborne wrote:
Does anyone have experience modelling an antenna in EZNEC and then loading
those elements into a SteppIR antenna (I am using 4E so that is of most
interest). If you have, how does your antenna perform with your new element
dimensions versus the factory default ones? Mine does not seem to resonate
at the same frequency as the model, so I think a correction factor is
required to the EZNEC model elements?
Bill--K5ZQ
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