3 x #14 gauge wires run from the top of the aluminum tube up to the base of the coil and are silver soldered to the coil. 3 x #14 gauge wires run from the top of the coil to the top of the mast and are soldered together at the top. The wires are spaced more or less evenly around the perimeter of the mast. They are held to the mast with vinyl tape. No special care was taken to make the wire extremely tight, as I wanted some play available when the mast bends in the wind. The wire was fixed to the mast with a spiral of tape on each section. Thus far this has proven to be a good compromise between holding power and flexibility.
The base is fed with a 1" piece of aluminum clamped around the diameter of the 2.125 tubing, and the wires are connected to a similar clamp at the top. The hardware is stainless to avoid the oxidation problem of copper on aluminum. Pentrox is used liberally on all aluminum joints.
The top connects to the wires with this bracket. The detail of this picture is interesting. It shows the 1.875 tube with a hose clamp the supports the 2" tube. The next 2 clamps are the compression clamps around 2" tube which compressed the cross cut in the 2" tube. They also act to support the Spiderpole. The next clamp goes around the Spiderpole, and keeps the pole from turning as well as reinforces the pole to keep it from splitting. Wrapped around the 2" tube is a layer of aluminum tape which acts to give the Spiderpole a nice press fit and something to snug down against.
The bolts are 1/4" stainless steel with washers on both sides of the copper and a lock washer and a stainless nut. .
I experimented with different form factors and found a diameter of 4" to 6" was best, with a length between 1:1 to 2:1. I found for 1/4" tubing I could easily sweat solder 1/4" lugs into the ends of the tubing using silver solder. The 3 wires that make up the element were also soldered into a 1/4" lug and the lugs were joined to each other using 1/4" stainless hardware. I measured the value of this coil at 15 micro-henries. A shot of the 6" coil can be seen here. It has ten turns and is 6" long for a 1:1 form factor. 4" coil is closer to a 2:1 form factor being about 7" long.
To wind the coil I used PVC couplings to give the desired diameter. The 1/4" tubing holds its form well once it is clamped to the fiberglass pole.
