What kind of wire would be good for a 160m - 40m fan dipole?

Question

I want to know the best copper wire or tinned copper wire for a fan dipole for 160, 75, 40 meters. It would be coax fed and I would like it to handle 1500 watts or more. I would like 65/30 strands of tinned copper wire. Please let me know what to get. I would like the best wire.

Answer 1

The important things to consider when choosing wire for a wire antenna are mechanical strength, electrical resistance, power-handling capability, cost, and ease of handling.

As an unsupported horizontally-strung wire gets longer its tension increases, which makes mechanical strength more important. A dipole for 160m is quite a long wire antenna. One should also consider whether there may be additional mechanical loads, such as the weight of the feed line and balun, or weather-related loads such as wind and ice. (When I lived in the Midwest, winter ice storms periodically would coat everything in thick layers of ice, which is hard on wire antennas.) Adding mechanical support, such as using a strong bracket for the connections at the center of a dipole and then hanging the bracket from a strong rope, may be worth considering.

Unfortunately I don't have a source, but I read somewhere (a QST article maybe?) that copper wire may not be the best choice for long wire runs with additional mechanical loads. I also seem to remember reading that ordinary copper wire will stretch under strong tension, and that being drawn in that way makes the copper stronger. Copper has the advantage of being an excellent conductor, so if a wire antenna is made from thick copper wire, then one can rest assured that electrical resistance has been minimized. I would consider 14 AWG (2.08 mm²) copper wire to have low resistance and enough power handling capability for nearly any amateur radio wire antenna.

Alternating current at RF frequencies traveling through a conductor passes mainly through the surface, a phenomenon known as the skin effect. Since RF current doesn't flow through the center of an antenna wire, a type of wire that has a steel core for mechanical strength and an outer copper layer for low electrical resistance is popular for wire antennas. The brand "Copperweld" seems to be common.

Whether wire is solid or stranded doesn't make much of a difference once the antenna is in place, but it does affect how easy the wire is to work with. Stranded wire is more flexible than solid-core wire. Solid wire on a spool wants to stay coiled until it is laid out and put under tension, especially with steel-core wire. Raising an antenna made from solid-core wire is fairly straightforward, from what I've heard, but I also heard that taking down a wire antenna made from steel-core wire can be a pain.

The advantage of tinned-copper wire is slightly more convenient soldering, but this isn't much of an advantage for wire antennas because solder corrodes easily outdoors, so soldering should be used as little as possible. (Protect any soldered connections from the elements.)