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Re: [TowerTalk] TT SHUTDOWN (was: 4 awg copper wire and Amp locks)

Subject: Re: [TowerTalk] TT SHUTDOWN (was: 4 awg copper wire and Amp locks)
From: Jim Lux <>
Date: Wed, 12 Jul 2006 09:43:46 -0700
List-post: <>
At 08:20 AM 7/12/2006, Martin Ewing wrote:

>JC Smith wrote:
>>Gary's right although copper strap can be overpriced depending on where you
>>find it.  Copper tubing is such a common commodity it's hard to overprice
>>it.  One other advantage tubing has is it's easy to protect from
>>weedwackers, lawnmowers (not the blades), etc.  Just run it inside a length
>>of thick hose.
>If you are running strap in order to make a ground, you don't want to 
>insulate it -- at least when it's running underground.  Maybe you are 
>referring to runs above ground.
>>I wonder... if you roll (the long way) copper strap you could put it inside
>>hose.  As long as the inside circumference of the hose was greater than the
>>width of the strap you wouldn't be forming a tube with the strap.  What if
>>you slit the copper tube before using it, would that be enough to allow both
>>the inside and outside to conduct high frequency current?
>You get minimum impedance when the strap is flat.  If you roll it up, it 
>is no better than thin wall tubing - i.e., there is no current on the 
>inside.  Impedance per foot is roughly doubled.  A narrow slit on tubing 
>won't change things at all, since all the current flow is 
>longitudinal.  Pound for pound of copper, you get the best ground with a 
>wide flat strap, maybe 10 skin depths thick.  You get the least effective 
>ground by compressing it into a circular rod (wire).  Hollow tubing is a 
>little better.
>Basically all the interior copper (below the skin depth) is wasted for AC 
>current flow.  Of course, it does give you better physical strength and 
>thermal mass.  (A low impedance ground isn't much help if it gets 
>vaporized.  Has anyone done a thermal analysis for very thin strap in a 
>lightning surge?)

Wouldn't it be better than a round wire?  greater surface area to volume 
ratio and all that.

>>Just some thoughts.
>>73 - JC, K0HPS
>73 Martin AA6E
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