At 02:40 AM 7/12/2006, you 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.
I think the advantage of strap, pricewise, is that it can be a LOT thinner
than the wall on tubing. At 1 MHz, skin depth in copper is around 2.5
mils. This implies that you could use sheet around 20-25 mils thick
(0.020" - 0.025") giving you 5 skin depths on each side. (that's 22 to 24
ga sheet, btw).
As a comparison Type L 1/2" copper tubing is 0.625 OD and 0.545 ID, so the
wall thickness is 0.040". As pointed out elsewhere, the current would tend
to flow only on the outside. Type M is slightly thinner wall. As you get
bigger with tubing, the wall thickness gets larger too.
To a first order, the dominant cost is the cost of the metal, so, for a
given amount of useful conductor, the copper flashing is a better choice,
but even ignoring this, tubing costs more to make than rolling a strip out.
Tubing IS more convenient to handle. You're not as likely to slash
yourself open working with it, an almost certainty if you're rassling many
feet of thin sheet metal. You might also be able to find a small quantity
of tubing that is cheaper than an (electrically) equivalent amount of
strip, just because of transportation, marketing, etc. costs.
>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?
There's no reason why you couldn't propagate current on the inside of the
pipe without slitting it. That's what happens in coax.
>Just some thoughts.
>73 - JC, K0HPS
>[mailto:email@example.com]On Behalf Of Gary Schafer
>Sent: Tuesday, July 11, 2006 7:25 PM
>To: 'Robert Chudek - K0RC'; firstname.lastname@example.org
>Subject: Re: [TowerTalk] TT SHUTDOWN (was: 4 awg copper wire and Amp locks)
> > One interesting idea that did came out of this thread (so far) is the use
> > of copper tubing instead of solid wire. I'd like to hear more comments
> > pro/con about this. I would expect tubing would be more cost effective and
> > equal in the capability to dissipate the energy in a strike.
>Copper tubing is a waste of money. Buy copper strap instead. You get much
>more surface area for your money. Copper tubing has one whole side (the
>inside) that is wasted. Copper strap makes use of both sides.
>Copper pipe used as ground rods is expensive also compared to a regular
>ground rod. Driving copper pipe you risk that it will bend or fold up as it
>is being driven. In anything but sand it is almost impossible to drive a
>copper pipe to a useful depth. It is the length and depth of a ground rod
>that counts not the surface area. And no you don't want to wash it in with a
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