Is steel or aluminum structurally a better material for catenaries?

Question

I understand that steel is not a good material for antenna wire, but let's consider that I'm using the wire for purely structural support, or I am cladding it with copper to address the RF conductivity issues.

Then, which material is more suited to being strung between two supports? It seems to me there is a balance between at least two main concerns:

• the wire should be strong, so it doesn't break
• the wire should be light, so it has to support less of its own weight

To a lesser extent, cost may be a factor, although both steel and aluminum are affordable enough that it may not be an issue.

What material properties are relevant to this application? (Remember: purely structural concerns, not electrical.) Can we put some numbers and proper engineering to it?

Answer 1

Power cables typically have Aluminium conductors enclosing a steel core. 'nuf said? The Aluminium stretches with time, thus changing the tuning, work hardens and can crack, as does steel but at a greater rate, expands more with change in temperature, and although I have no experience with this, becomes brittle at higher temperatures (Read that as 'less cold') than steel. Copper antenna wires need to be pre-stretched to harden the copper, but I don't believe that works for Aluminium.

Another concern is the cross-section, or outer diameter of the conductor as this effects the band-width of the tuning. Thicker conductors have a greater bandwidth.

Light Aluminium power conductors with a steel core be good if a suitable size is available.

Check your local electrical cable supplier for catenary rated cables.

I have known of hams using discarded coax used in television stations for the copper plated steel core, but mostly for the outer sheath as a thick conductor, and low weight. (NB: the impedance doesn't matter, we're using the sheath.)

Answer 2

This might help : Type M® Guy Wire - Alumoweld Aluminum-Clad Steel