Hi All,
The base loading coil was designed to resonate with the copper pipe antenna at the high end of the band. To give repeatable results, all dimensions should be adhered to fairly strictly. The critical dimensions are: antenna pipe length, coil form diameter (3" PVC has an OD of 3.5"), wire type and size, number of turns and turn spacing. 16 gauge magnet wire is specified primarily for the repeatability of turn spacing when tightly wound. There are no specifications for the insulation thickness of common plastic insulated "hookup" wire, whether stranded or solid. The insulation thickness will determine the spacing of the wires when tightly wound. A coil wound with plastic insulated wire will work if you play around with it. The turns will be spaced farther apart due to the unspecified insulation thickness, so a coil of 87 turns will have less inductance than required to resonate with the antenna pipe in the intended range of frequencies (1500-1700 kHz).
Magnet wire, with its thin enamel insulation coating, is the only wire that will give repeatable results. That's why it's specified in the plans. If you want to experiment with common hookup wire, then I recommend winding more than 87 turns. I can't say how many more turns, it depends on the particular wire. Maybe 110 or so turns would be a good place to start. The taps can be placed every 2 turns from the bottom of the coil as in the plans. If the experimental coil resonates at a lower frequency than desired, you can remove a few turns at a time from the high end of the coil until you can tune the antenna at a higher frequency. If it resonates at a higher frequency than desired, you will need to add turns at the top side. That's a little more difficult than removing turns, but you can do it by splicing wire to the top of the coil.
For plastic hookup wire, I don't think it matters if you use stranded or solid wire. The strands in stranded wire are all shorted together, so they act like a solid wire. Litz wire is like stranded wire except each strand is insulated with an enamel coating, so they don't short together. The result is that the skin effect resistance is reduced vs. solid wire of the same gauge. It's like having a whole bunch of wires in parallel, so the skin effect resistance is reduced by the parallel combination of resistances. Litz wire is expensive and hard to come by. It is the best, but not practical for the average builder.
Phil B
First, thanks so much for being here ...
On the antenna guy's site, the coil wire spec says it's #12 magnet wire. Is that an error? The article says SStran antennas he builds are to spec, but the spec calls for #16 magnet wire.
This is confusing ... which one is it?
magnet wire? can this be bought at home depot or lowes?