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There are some people selling steel wire plated with copper for making wire antennas.

Perhaps the most well-known brand of this product, Copperweld, makes at least two kinds of copper-clad wire, copper-clad steel (CCS), and copper-clad aluminum (CCA). On Copperweld's applications page, they write:

CCA is a natural for antennas in a variety of applications such as large ground-based arrays or even ham radios or mobile phones. CCA is applicable to most localized RF transmitters and is being used near radio towers to shield other structures from creating interference.

(note: CCA, the A for aluminum)

Wikipedia on copper-clad aluminum lists applications:

The primary applications of this conductor revolve around weight reduction requirements. These applications include high-quality coils, such as the voice coils in headphones, portable loudspeakers or mobile coils; high frequency coaxial applications; such as RF antennas; CATV distribution cables; and power cables.

The article on copper-clad steel lists nothing about RF applications:

Grounding, union of ground rods to metallic structures, meshes, substations, power installations and lightning arrestors.

To be fair, most of the amateur radio sites I've seen selling anything similar call it simply "copper-clad wire", and don't specify if the core is steel, aluminum, or gold.

It seems to be understood that steel is not a good antenna wire. So, is copper-clad steel a good antenna wire, or no? Why?

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  • $\begingroup$ The Wireman likes it. They seem to know what they're talking about. $\endgroup$ – Pete NU9W Feb 6 '14 at 22:53
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Depending on the RF frequency and wire diameter, skin effect may dominate the effective resistance at that frequency. If so, since copper has a lower resistance, any resistive losses of a copper skin might be lower. Silver or gold plating would be even better, but a little too expensive except in exotic applications.

However, pure copper also has a lower tensile strength that steel, so would be more likely to fail under load (wind, etc.) without a stronger core. Copper is usually more expensive than steel as well. Steel is cheaper and stronger. And AL is lighter, if weight is an important issue.

If corrosion or oxidation is likely to affect reliability, than gold plating might increase contact reliability, or wire lifetime in unusual chemical environments.

Thus, a blend may be the best trade-off, depending on all the constraints and requirements.

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  • $\begingroup$ I'd think gold plating would be worse, as it's less conductive than copper. Also, I'm not sure that simply saying that skin effect exists is sufficient to demonstrate that there aren't losses associated with the steel core. We must also consider the mechanism by which the current got to be flowing in the skin, and we must demonstrate the fields associated with the skin current don't couple to the core in a way that is lossy. $\endgroup$ – Phil Frost - W8II Feb 10 '14 at 20:49
  • $\begingroup$ Agree regarding the gold plating, which would only help if and where the antenna wire required contact connectors after possible oxidation. So the answer has been edited. $\endgroup$ – hotpaw2 Feb 10 '14 at 21:28
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Copper clad steel is a good antenna wire. It's not the best for every application, but it's good for most applications.

The advantages it has are:

  • Doesn't stretch as much as copper and other good conductors (which changes the resonant frequency)
  • Stronger than other wires, so when you don't need a large gauge for electrical reasons, you can save on weight and size and still have sufficient strength for self support
  • Less expensive than copper wire of a similar gauge, strength, and electrical capacity at RF frequencies
  • More conductive than steel

It does have a few disadvantages:

  • More expensive than steel wire of a similar gauge and strength
  • Have to correctly seal the ends to avoid oxidation of the center steel conductor

Keep in mind that at frequencies between 3.5MHz and 30MHz the conductor's skin depth, the depth at which 63% of the electrical current flows, is between 35uM and 12uM for copper wire. The link you gave has 30% or more copper, which provides a total copper skin depth much greater than 35uM, so the majority of the current will be carried in the copper cladding at the frequencies we are interested in for HF and higher frequency antennas.

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  • $\begingroup$ That's the skin depth for copper wire. Are you sure that the skin depth for copper clad steel wire is the same? Can you cite references or show some math? $\endgroup$ – Phil Frost - W8II Feb 10 '14 at 18:23
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    $\begingroup$ "Skin depth also varies as the inverse square root of the permeability of the conductor. In the case of iron, its conductivity is about 1/7 that of copper. However being ferromagnetic its permeability is about 10,000 times greater. This reduces the skin depth for iron to about 1/38 that of copper" (source) In effect, the steel wire's additional permeability pushes the electrons further away from the center of the wire, actually forcing most of the current onto the copper cladding. $\endgroup$ – Adam Davis Feb 10 '14 at 19:59
  • $\begingroup$ You're right to consider this, and it's worth further investigation, but when you're talking about,say, 18awg wire, 30% of which is copper, you have plenty of copper on the outside - over 10x the copper's skin depth, and 30-50x the steel's skin depth (depending on its permeability). At worst it can't handle the current an 18awg copper wire can, but its effective resistance will not be greater since the majority of the current at frequency will travel in the copper. Overall you'll actually find the AC resistance of the wire is lower than the DC resistance. $\endgroup$ – Adam Davis Feb 10 '14 at 20:02
  • $\begingroup$ So the only case you'd need to worry about it is if you're trying to transmit significant power, and then you'd need to worry about antenna heating. Anything up to 100W can be handled by 18awg 30% copper clad steel wire without question. It will handle much higher power, but you'd have to do the math (or testing) to verify the actual power handling capability. $\endgroup$ – Adam Davis Feb 10 '14 at 20:05
  • $\begingroup$ What about hysteresis losses in the iron? While I don't doubt that most of the current will flow in the copper, we must consider the mechanism by which it got there before we can say it's not without loss. As we demonstrate with radios every time we use them, a moving electric charge can affect and be affected by its surroundings. $\endgroup$ – Phil Frost - W8II Feb 10 '14 at 20:25

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