[TowerTalk] Orion 2800 Rotator Cable Replacement

[Jim Brown]

On 12/10/2019 2:41 PM, Bob Shohet, KQ2M wrote:
> My non-engineering understanding of wires and stretch is that a given wire after being subject to variable strength forces over a given period of time, will stretch only so far before it breaks.  Assuming that that is conceptually correct, let’s say that we have two wires – Wire A and Wire B.  Wire A has been pre-stretched before being put up and is now compared against Wire B which has just been put up without being pre-stretched
> 
> Now we subject both wires to the same forces over the same period of time.  I would expect that going forward Wire A will not stretch as far as Wire B, but is more likely to break and break sooner under significant force than Wire B because it has already been pre-stretched.  Wouldn’t this be correct?
> 
> If this is not correct, can you please explain why?

It all depends on what you define as a significant force. I use 100# 
weights at ground level on the ropes on one end of my high (125 ft) 
dipoles to maintain tension and allow for "give" with tree sway. That's 
a LOT less than the pulling tension applied by W6GJB's pickup to stretch 
and break them.

Hard drawing copper strengthens it significantly; NEC requirements for 
wire antennas call for either CCS or hard drawn copper for strength (so 
they won't break and create a potential shock or fire hazard). The 
stretching we're doing is a first approximation of hard drawing.

73, Jim K9YC