[TowerTalk] Copper clad telephone wire

[Patrick Greenlee]

There is an exponential extinction coefficient that governs penetration 
of RF currents below the surface of conductors.  Lower freq means 
greater depth of penetration or in other words how thick is the skin of 
the skin effect? The lower the freq the greater the depth of 
penetration.  In the limit as freq goes to zero (DC) the entire wire 
conducts.

If you have access to a micro ohm meter or miliohm meter if you use a  L 
O O N G  piece of wire you can compare the DC resistance of your 
candidate antenna material to the published specs for steel or copper of 
that gauge.

Making DC measurements you can treat the wire as two resistors in 
parallel, one is the copper resister and the other is the steel 
resister. With a measurement of your wire's resistance per unit length 
you will be able to assign a cross sectional area to the copper and to 
the steel.  A little arithmetic later... and you should be able to 
calculate the thickness of the copper cladding.

Properly instrumented you would be able to measure the change of 
resistance per unit length as it varies with freq and get the same 
answer more easily.

Patrick  NJ5G

On 8/8/2014 3:54 PM, Gary Schafer wrote:
> I have lots of old copper clad telephone wire that I want to use for radials
> and antenna wire. This is the stuff that is bare and went from pole to pole
> for old telephone lines. It is not the insulated drop wire.
>
> When you cut it, it looks like copper all the way thru but it will attract a
> magnet.
> I want to use this stuff on the low bands (160, 80, and 40).
>
> Is there a way to measure/determine how thick the copper layer is?
> Measure the resistance, wind a small coil and measure Q?
>
> Thanks,
> Gary K4FMX
>
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