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Copper Tubing Weight

Aug 13th 2011, 01:32

KG6SYX

Joined: Nov 7th 2003, 10:54
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I’m ramping up to build my first J-Pole antenna and reading through a few of the J-Pole designs they all recommend rigid copper tubing. There are three weight of rigid copper tubing (1) K - the heaviest weight, (2) L - medium weight, and (3) M - lightest weight. Should I assume the references to rigid copper tubing is reference to “M” the lightest weight tubing?
Aug 13th 2011, 06:10

KE8DO

Joined: Apr 4th 1998, 00:00
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I would think that because of skin effect there would be little differance in the type of copper tubing that you use.
73 Don KE8DO
Aug 13th 2011, 10:55

w1rfi

Super Moderator

Joined: Apr 4th 1998, 00:00
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I agree with Don. From an electrical perspective, they would all perform about the same. In a copper J-pole antenna, ohmic losses are going to be insignificant.

Mechanical considerations would be more important. While the type M should be strong enough for a small J pole mounted permanently somewhere, or even leaned up against a wall in an apartment, if I were putting up a J pole outside, or building any antenna I would be taking portable, I'd go for the type L pipe. Both are available at the big box building supply stores. (I don't recall seeing type K pipe at my local Home Depot or Lowes, but I may be mistaken.)

The reason I suggest that is that sooner or later, the J pole will be packed in a car and something heavy will end up on top of it, possibly bending the antenna. Even with the price of copper being quite high right now, the difference in cost for a single pipe will be relatively small, and I'd like the peace of mind of knowing I had an antenna that could take a bit more abuse.

Don't be tempted to carry that one step farther and use pipe with a larger outder diameter, however, as the resonance of any antenna is dependent on both its length and the diamater of the conductors. One could design a 3/4-inch pipe J pole, but it would be a few percent shorter than one designed with 1/2-inch. The thickness of the wall of the pipe won't affect the resonance.

Speaking of the price of copper, when I had to rebuild most of my house due to storm damage and a complete gutting when we found asbestos in all the joint compound, I ran all new PEX plumbing (love that stuff!!), except for the pipes very near our wood-burning furnace, which we kept as copper. When I was done, I cut up all the old copper pipe and took two boxes to the scrap yard. They totaled about 100 pounds and I walked away with $337 cash. That is about what the PEX pipe, manifolds and shutoffs cost, so my old copper paid for my all new plumbing. If you have old copper pipe laying around and you aren't going to turn it into antennas, this is a great time to sell it!

73, Ed Hare, W1RFI
ARRL Lab
Technical forums moderator
Aug 15th 2011, 21:29

KG6SYX

Joined: Nov 7th 2003, 10:54
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Total Posts: 0
Thanks for the feedback.
Cheers Beers All

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