[Antennas] insulated wire for open wire feedline or wire antennas...

[Chris BONDE]

IMHO Tom's comments have  merrit.

If we use a wire with insulative material there around, then the RF will 
flow in the outer part of the good conductor.
If we use a wire with semiconductor material there around, then the RF will 
flow in both the conductor and the semiconductor, giving somewhat a 
different flow.
Semiconductor material would be the copper oxides (2 forms that I know 
of).  Copper oxide can form a diode with other materials.  Another 
corrosion product is copper sulphides ( again a number of forms).  Again 
the sulphides of copper can form a diode with other materials.  In both of 
these cases the other materials is the copper (alloy) of the wire.

Stories of detection of AM Tx with copper compounds in phone cables, 
plumbing etc use to be prevalent.  Some of which were true!

So in real life I would rather use a wire with the insulator, dielectric 
rather than the semiconductor for the antenna part.

Chris opr VE7HCB


At 10:19 PM 2002-01-06 -0800, you wrote:
>Actually, there is a good case to be made that insulated wire is preferable
>to bare. (that ought to invite some disagreement!)
>
>Seriously, there was an excellent article in QEX maybe a year ago (I can dig
>up a pointer if anyone wants it), that tested the series loss resistance at
>frequency of various types of wire. It turns out that the corrosion that
>forms on bare wire after a short time causes more loss than good quality
>dielectric. What happens apparently is that the skin effect causes the
>current to flow in the surface of the wire, which if bare, will quickly
>become corroded and copper oxide is much lossier than clean copper, if the
>wire has good quality dielectric the wire will stay un-corroded for years.
>At least that's what the test results seemed to show.
>
>73
>
>- Tom Scott, Field Applications Engineering
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