Steel wire?

[iXod]

When shopping for electrical wire and cable, the tool I take along with me is a strong neo magnet.

But I now find that most coax cables are unabashedly using copper-clad steel center conductors.

Two questions:
1. Does steel cu-clad have any impact on signals of any type? Is steel contraindicated for any application?

2. What’s the reason for going to steel from copper? Last I looked the USA isn’t sucking up all copper for use as bullet cladding (a la Vietnam war era, resulting in the introduction of aluminum mains wiring). Is it to simply keep shareholders happy (A.K.A. greed)?

Thanks.

[TimFox]

Copper-clad steel (“Copperweld” TM) has been common in coaxial cable with solid conductor since at least WW II.  The copper is sufficiently thick for skin depth at the radio frequencies for which the coax was intended.  Of course, the Copperweld is mechanically stronger than copper.

[Conrad Hoffman]

Many resistor leads are steel. Audio people are against it but I've never found any difference nor any measurement that suggests it's a problem. Ever wonder what they use for scope probes? Hint- it's not copper or steel!

[bob91343]

The main problem with different materials is thermal voltages that can impair sensitive measurements.

[TimFox]

During my days with MRI work at RF frequencies, we had to choose our cables carefully to avoid ferromagnetic material.  For thermoelectric problems, the surface material should dominate, but pure copper is a better choice.

[m3vuv]

Ive used copper plated mig welding wire to make hf dipoles lots of times,seem to work well due to the skin efect at hf,a smear of grease on the wire and its cheap strong works well and lasts!

[richard.cs]

The copper clad steel is cheaper and stronger, and the strength is good for things like F connectors where the coax inner is the centre pin. For RF, there's little downside to having the steel core, them main time it would matter is when DC bias is applied to a coax to power some remote RF amplifier, and then the increased DC resistance may be important.

[Terry Bites]

Cheap nasty and profit driven. Like DT. I've even found this junk in mainds leads. I wonder who dominates the market? https://www.statista.com/statistics/693466/distribution-of-global-refined-copper-consumption-by-region/ 

[edpalmer42]

I had to run a link to a satellite antenna on the roof through 10 floors (maybe 30 meters).  It didn't work right because the copper-coated steel center conductor had too much DC resistance.  This wasn't a matter of signal loss, it was related to the inline power and switching requirements.  I had to replace the cable with one that had a pure copper center conductor.  Problem solved!  Note that a pure copper cable is much weaker than one with a steel core so it needs to be well supported.

Ed

[TimFox]

Copperweld (TM) brand wire, depending on model, has 30% or 40% the conductivity of copper.  20 AWG solid wire is approximately 100 ohms/km = 0.03 ohms/ft.  Real mil-spec RG coaxes use this type of copper-clad steel—check the spec sheet (sarcasm) for cheap copper-plated wires used elsewhere.  See ASTM B-910 for annealed copper-clad steel wire.

[David Hess]

1. Does steel cu-clad have any impact on signals of any type? Is steel contraindicated for any application?

The resistance is higher at DC and low frequencies.  At high frequencies, the skin effect limits conduction to the copper cladding anyway.

Some demanding applications preclude iron or nickel wiring to prevent magnetic distortion.

2. What’s the reason for going to steel from copper? Last I looked the USA isn’t sucking up all copper for use as bullet cladding (a la Vietnam war era, resulting in the introduction of aluminum mains wiring). Is it to simply keep shareholders happy (A.K.A. greed)?

Steel is cheaper and stronger.  I think all of the RG-174 coaxial cable I have seen uses copper clad steel because otherwise it would be too fragile.  Cheap coaxial cable may use copper clad aluminum.

Many resistor leads are steel. Audio people are against it but I've never found any difference nor any measurement that suggests it's a problem. Ever wonder what they use for scope probes? Hint- it's not copper or steel!

I have seen steel component leads but more often something like Kovar is used, but it is still magnetic.

Power diodes use pure copper for its higher thermal conductivity but larger glass packaged small signal diodes, like DO-7 packaged 1N270 and 1N34A, use Kovar.  Smaller glass DO-35 diodes like the 1N4148 use copper but this might reflect DO-35 diodes being available for currents up to 400 milliamps.

I often save resistor leads after cutting them off because they are useful when something stronger than soft copper wire is needed for a short connection.

[TheMG]

1. Does steel cu-clad have any impact on signals of any type? Is steel contraindicated for any application?

2. What’s the reason for going to steel from copper? Last I looked the USA isn’t sucking up all copper for use as bullet cladding (a la Vietnam war era, resulting in the introduction of aluminum mains wiring). Is it to simply keep shareholders happy (A.K.A. greed)?

The primary purpose of coax being to carry high frequency RF signals, due to the skin effect there would be little impact on the signal. Of course, the added DC resistance could be an issue in situations where in addition to the RF you also need to carry DC power at a significant current and/or distance.

Always refer to the cable datasheets to determine suitability for a particular application.

Several other types of coax even have copper-clad aluminum (LMR400, LDF4-50 for example), or even a hollow core for some larger coax (LDF5-50).
Steel is of course cheaper but also stronger, a benefit especially for the types of coax used for CATV distribution, which often ends up being subjected to all kinds of abuse and even hung in the air over large spans.

[Nassau Cable]

Modern aluminum cables are to use in homes. The standard aluminum alloy of today expands less than fifty years ago. Moreover, all outlets and connections are made to fit aluminum cables, and these cables pass safety standards before being allowed into modern homes.

With copper prices on the rise again, many turn to aluminum wiring at home with no issues. If you take the time, you can find high-quality aluminum and copper wire.

Edited by moderator: Removed hyperlink from first-time poster. Probably spam.

[jpanhalt]

Modern aluminum cables are to use in homes.

Years ago when aluminium house wiring proved to be a disaster, who had to pay for the fix?  Who will have to pay for the next fix?  Copper is in my house and will stay there for any additions.

[Kokoriantz]

See the discussion how the magnetic field effects the current limit.
https://www.eevblog.com/forum/projects/what-limits-the-current-in-wires/

[coppercone2]

I think that BNC cables are incredibly fragile when they don't have the steel center. But usually the braid rips out. Be careful with coaxial cables near HV applications when the cable separates from the connector... I saw this happen and I wished there was a extra steel braid in there for strain relief, the center pin pulls out and the braid rips and you are left with a hot poker

I recommend buying the correct adhesive heat shrink tubing and putting it over coaxial cables. The adhesive is essential to keep it together, I have seen it slip out of heat shrink regular before. I have seen it pull out of a factory crimp too, and the non-crimp ones are the worst (the ones you tighten on the shield braid) for durability.

[David Hess]

I think that BNC cables are incredibly fragile when they don't have the steel center. But usually the braid rips out.

I like double shielded cables now because the braid is so much less likely to rip at the connector.

[coppercone2]

yeah that is a improvement but deformation over a foam core is always suspect IMO. Solid teflon is better but its not exactly a real crimp. I need to mod my cables with sticky heat shrink. The better manufacturers do it for high grade cables.

[james_s]

Modern aluminum cables are to use in homes. The standard aluminum alloy of today expands less than fifty years ago. Moreover, all outlets and connections are made to fit aluminum cables, and these cables pass safety standards before being allowed into modern homes.

With copper prices on the rise again, many turn to aluminum wiring at home with no issues. If you take the time, you can find high-quality aluminum and copper wire.

Huh? As far as I know, solid conductor aluminum wiring has been illegal to use in homes for years. The vast majority of outlets, switches and light fixtures clearly state copper conductors only. I know two people that live in early 70s houses wired with aluminum and it has been a nightmare, one of them has had 5 or 6 receptacles burn up and I keep telling her this is seriously dangerous and needs to be dealt with. The other lives near me and I've just about finished going through and pigtailing everything with AlumiConn splices. From what I can find, these are reliable when properly installed but it's a pain in the butt.

It'll be a cold day in hell before I ever even consider installing aluminum wire, I don't care how much cheaper it is or what the manufactures say, I don't trust it. The early aluminum wiring was an absolute disaster and the "new and improved" alloys in the 70s still didn't really solve the problem. It might be fine for 20-30  years, maybe more, but houses typically last a lot longer than that and it's a ticking time bomb that someone is going to have to deal with eventually. No, just no.

[Haenk]

Years ago when aluminium house wiring proved to be a disaster, who had to pay for the fix?  Who will have to pay for the next fix?  Copper is in my house and will stay there for any additions.

I really think that the somewhat higher costs of copper cables are worth every cent. Don't use crap for something that needs to last decades.
(Good thing: I still have a dozen or so rolls of NYM 3x2,5 left from wiring our company building. 20 years ago, those did cost pretty exactly 1/10th of todays price.)