Reg Edwards wrote:

Let's start a parallel thread on the effect of coating a 14-gauge
antenna wire with a thick layer of ferrite. Say 1mm thick,
permeability = 100.

Would this have any effect on velocity factor? If so, by how much?

Something easier for me to do was to take the 20m dipole,
DIPTL.EZ, that came with EZNEC+ 4.0, remove the transmission
line, and determine the resonant frequency for uninsulated
wire and for wire insulated with 0.1 inch of neoprene with
a dielectric constant of 6.7 (deliberately chosen to emphasize
the differences).

The resonant frequency for uninsulated wire was 14.42 MHz.
The resonant frequency for neoprene insulated wire was 13.3 MHz.
That is an abundant amount of insulation with a high dielectric
constant and it lowered the resonant frequency by 7.8% according
to EZNEC.

Adding the insulation increased the feedpoint impedance from
57 ohms to 65 ohms which means the forward and reflected
waves on the standing-wave antenna were attenuated more
using insulated wire and sure enough, using that particular
insulation reduced the EZNEC maximum gain by 0.12 dB.

Many people have noticed shifts in resonant frequency when
their antenna gets wet. Water has a dielectric constant
around 80.
--
73, Cecil http://www.qsl.net/w5dxp

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