The tube section shown above displays the first of four pinstripes made of black ABS glue, each at a 90 degree interval. The edges of the stripes hold the coil wire even on hot, sunny days. When the pipe is free-standing, it will bend slightly in the wind. The wire will move a finite distance on the coil form! The black adhesive will keep the wire secure.
Be sure to have lots of ventilation if you use this stuff !! Most hardware stores
sell Oatey ABS cement in several flavors. Be sure to get the black version.
The data sheet from Oatey is recommended reading;
Blue painter's tape defines the black channel. Allow the cement to harden for a day before winding wire on the form.
PVC electrical conduit is inexpensive and available everywhere. It's ideal for Tesla coil projects and RF coil forms.
A 10' piece of Cantex 4 inch schedule 40 electrical conduit, part number A52EA12, ready for coiling, is shown below. A plastic scouring pad and windshield washer fluid are used to clean the section prior to winding.
Electrical conduit is designed for above-ground and below ground service, and is stable over a wide temperature range. The Cantex formulation is consistent from lot to lot. The tube does not exhibit "chalking", or surface weathering.
References;
All kinds of useful data here.
Here are two sites that outline the dielectric properties of different plastics, including PVC.
Cantex pipe data sources;
A thoroughly developed web site; easy to navigate and packed with information.
A copy of the Cantex catalog; http://www.cantexinc.com/resources/product-catalog
My local source for all things Cantex. The company has several stocking facilities in northeast Ohio. Call 800 288 6277 for more information.
Here is an all-band vertical dipole antenna for my ham station. The stand is a discarded safety sign base, and brings new meaning to the term "portable". The wire is 309 stainless steel, .045" diameter.
Above, a re-wound single wind on the same 4" coil form as was used for the dipole.
The wire spacing is determined by the tool shown below.
Several readers have asked for more specifics on the winding guide. The tool shown above is a 3" piece of 1/4" Teflon(R) PTFE tubing with a 1/16" inside diameter. I buy this from McMaster-Carr in Ohio. The part number is 8547K22. It's sold by the foot and is not very expensive.
Two sets of cuts are made on the tubing with a razor blade. The first set is made for the tubing to conform to the coil form as it rotates under the operator's hand.
I use 2 cuts, each at 30 degrees with respect to the tool end, on opposite sides of the tool. Configured this way, the tool rests on the coil form surface without twisting or turning.
The second set of cuts is made on the right and left sides of the tool. These determine the distance between the wire on the coil form and the wire exiting the tool, in other words, the coil spacing.
As shown above, I'm experimenting with a 1.5 times wire diameter spacing for a trade off between the amount of wire on the form and the capacitance between the turns.
http://www.w8ji.com/loading_inductors.htm presents some interesting data on the subject.
http://www.kennethkuhn.com-students-crystal_radios-designing_inductors.pdf has compiled an insightful primer here.
http://www.g3ynh.info/zdocs/magnetics/appendix/self_res/gallery.html has a fascinating article on coil phenomena.
http://www.crystalradio.net/professorcoyle/professorcoylecyl.shtml has a calculator that every Coil Builder will find useful.
As to the type and size of wire shown on theses pages, the best wire is the wire you can get your hands on at the right price.
Adhesive tape is wound on the Teflon(R) tool as a grip pad for the operator. Five or six layers of tape should be sufficient for the operator to hold the tool between the thumb and index finger of one hand without interfering with the winding process.
The Teflon(R) tool material has a very low wear rate. I've used the one you see on six 10' coils and have yet to see any appreciable wear.
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