[GreenKeys] What type of wire for loop?

[Jordan Spencer Cunningham]

I've actually wondered this same thing. Technically a 22 or 24 AWG wire (typical for telephone/ethernet UTP cable) could carry the 60ma typical of a high voltage current loop as long as there was adequate insulation. According to my rudimentary understanding of the physics behind this (and some handy voltage drop calculators), technically you'd only be facing a drop of around 10 volts on 22 AWG wire at 60ma/120VDC over a mile's length. Voltage could be bumped up a bit if you needed it, though I think in many cases people have been able to get away with a nominal selector voltage of ~90VDC if I recall. Maybe even less.

Not that you were planning to do this, but I've put some thought into it, and I've come to the conclusion that I'd probably avoid using RJ11/RJ45 connectors as I worry about arcing, though they would come in handy for some applications.

I've always used 16 or 18 AWG wire since that's what my machines originally came with, though I did use 20 AWG wire in a pinch once. This was for only for a very small patch (a couple inches) until I replaced the full cable that had a cut in it. That being said, I've been wanting to do some real-life tests with modern twisted pair rather than calculations. I just haven't had the chance to do it yet.

-
Jordan Spencer Cunningham
teletype.net


On Fri, Jun 14, 2019, at 1:17 PM, Joe Herdler via GreenKeys wrote:
> Hi All (again)
> 
> What type of wire would be best for field use to connect Teletypes together over several miles? 
> 
> Would field telephone wire work? I am assuming that the wire should be twisted. 
> 
> I am thinking as if I would someday have to use these wonderful white elephants in an actual situation.
> 
> 
> 
> Thank you very much, (again)
> 
> Best,
> 
> Joe H
> 
> 
> 
> 
> 
> Consciousness affects the medium. Think happy, be happy, and happiness will follow you.
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