# Twisting copper wire for a less-flexible DIY antenna

I am making DIY antenna for a home project. The antenna is going to be "V-dipole" with leg length about 53cm.

Unfortunately, I didn't find a thick copper wire, but I have a lot of thin core from tv antenna cable.
I am attending to twist a few thin wires together (without isolation, of course) in order to get a less-bendy leg. Something like this:

So, does the twist make any changes in physical antenna characteristic? Skin effect? I guess it is the same conductor, which probably will have less resistance than a single thin wire.

Thank you.

• Another thing you can do is stretch the wires. Clamp one end in a vice and grab the other end in a pair of heavy pliers; rotate the pliers a couple of times so that the wire is wrapped around them (otherwise the next step will pull the wire out of your grip). Then pull the wire fairly taught, and hit the pliers firmly with a hammer a couple of times, swinging the hammer along the wire so that the impact stretches the wire further. Sounds weird, I know, but it stiffens the wire. Commented Aug 29, 2018 at 12:10
• @PeteNU9W Thank you, I should try. Commented Aug 30, 2018 at 5:44

Your thought processes are on track - the primary electrical impact is on the RF resistance of the wire.

Twisting the wires effectively creates a larger wire diameter with more surface area. The additional surface area reduces the RF resistance attributable to skin effect. Depending on the frequencies involved, this may be of minimal benefit. Based on the geometry of your antenna, it appears that you are in the 130 MHz range. If so, the radiation resistance of the antenna is around 70 ohms which means it would take at least of couple of ohms to have a significant effect on efficiency. The formula for antenna efficiency is:

$$Efficiency=\frac{R_r}{R_r+R_l} \tag 1$$

where Rr is the radiation resistance of the antenna and Rl is the resistive losses in the antenna.

Efficiency is multiplied times directivity to specify the gain of the antenna.

One thing to consider is that corrosion between the individual strands can offset the increased surface area. We often see this when a coaxial cable gets water inside the jacket. The braided outer conductor becomes corroded and it no longer makes an effective shield. But since mechanical strength is your primary reason for twisting the wires, this will probably have negligible impact on the performance of your antenna.

• Would capacitance between the strands (particularly as corrosion sets in) be an issue? Commented Aug 29, 2018 at 14:28
• @Duston That is an interesting question. When pure copper corrodes "naturally", the primary result is two forms of copper oxide - cuprous oxide and cupric oxide. Cuprous oxide is a semiconductor material that was used to make diodes before silicon took over this role. Cupric oxide is also a semiconductor material and is commonly used in dry cell battery construction. Since both materials are characterized as semiconductors, I doubt that there would be any significant change in inter-strand capacitance as these materials form. Commented Aug 29, 2018 at 14:58
• The millions of twisted copper wire dipoles that hams have been using since forever ago is further evidence that corrosion between the strands is a non-issue. Commented Aug 30, 2018 at 11:20
• @PhilFrost-W8II That is true but in many cases, the gauge of the wire is large for mechanical reasons so some increase in RF resistance may not even matter for the application - so it could go undetected. Commented Aug 30, 2018 at 11:36