thanks for your contribution... your figures come very close to my empirical
data when analysing dipoles (of exactly the same length in exactly the same
place on the same day in bright sunshine all day) for 14 MHz using different
kinds of materials, insulations, thicknesses, diameters etc....
obviously there is a flaw in Roys formula as well... some people erroneously
think that he employs NEC/4 with EZNEC 4.0 when taking wire insulation into
----- Original Message -----
Sent: Wednesday, June 23, 2004 10:59 AM
Subject: [Antennaware] Follow Up - Velocity factor of insulated wire
> first of all thanks for the trigger about the insulated wires.
> This started me to do some experiments with my 4nec2 package
> in which a few months ago included the possibility to specify
> radius- and material info for insulated wires.
> Unfortional this showed up there was bug in the internal formula to
> create the LD2 card for specifying the distributed L resulting from
> the insulation layer. (thanks to RA9MB/UA3AVR and L.B.Cebik for the
> additional info about the subject).
> After this version 5.3.9 bug was fixed I modelled a 40 meter dipole
> above average ground using 2.5 mm sq. copper wire (radius 0.892 mm)
> with a 0.5 mm thick layer of hard PVC (diel-const about 4.5).
> This showed up a resonant length of 10.419 meter for the bare copper
> wire and a resonant length of 10.158 meter for the insulated wire,
> in shortening factor of about 0.975
> Maybe this is of interest.... :-)
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