Roy Lewallen wrote:
I've also seen "messenger line" or more often "messenger wire" used to
describe the steel wire that supports such things as telephone cables
between poles and mains power service drops from the pole to a building.

I got a bunch of free 75 ohm coax from the TV cable
company that has a messenger wire. It seems to me to
be for strain relief to keep the coax from breaking
from wind or ice.
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73, Cecil http://www.w5dxp.com