Capt. Paul Lee, Vertical Antenna Handbook, described using aluminum
irrigation tubing. It comes in 30' lengths and, while nowhere near as
strong as 6161, it is relatively inexpensive and works well for an 80 or
75 meter 1/4 wave. Capt. Lee describes a simple way of telescoping one
into another with wooden shims and bolts. I made aluminum collars, two
per joint. I dimensioned one to slide easily over the outside of the
inside tube and the other to slide easily into the inside of the outer
tube and fastened each to the tube with #8 machine screws. There are
screw holes only at the end of a tube and the integrity of the tube is
not affected at all. I've used as little as 2' overlap at a joint.
I've also telescoped tubing using nylon collars, available from
Grainger, and machining them as necessary. A step machined on the upper
collar serves to stop the upper tube, which is clamped with the set
screw of the collar, at the desired length. The electrical joint is
constructed with 3 or 4 (depending on the diameters of tubing to be
joined) pieces of 1/16" by 3/4" aluminum, formed to step from the OD of
one tube to the OD of the other, and clamped to each tube with a
stainless hose clamp. The material is soft enough to form to the
curvature of the tubes quite easily.
I buy the tubing at farm supply stores.
73 de WOØW
Roland Guidry - WA5CHX wrote:
>Trying to construct a full size 75 meter vertical with Aluminum tubing
>starting from the bottom with 4 inch tubing and tapering up. Does anyone
>know where I could locate a supplier of this tubing in the Tri-State area of
>Texas, Louisiana or Mississippi. I am looking for some thin wall tubing.
>Thanks in advance.
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