R J Carpenter wrote:
Back considerably before the beginning of time, around 1940/1941, my uncle
bought a fancy Sears Silvertone console with multiple bandspread shortwave
bands and the lot. It came with instructions for using a substantial
center-fed dipole antenna with twisted-pair two-wire feedline. Back in
those days twisted-pair feedlines weren't much different from rubber
insulated two-wire AC cords - ZIP cord hadn't appeared yet. The impedance
probably wasn't far off from 75 ohms.

It's closer to 100 ohms, but the KEY phrase here is twisted.
Zip cord and or twin lead isn't twisted (unless you twist it)
and it's the twist that imparts the self sheilding.

Jeff

--
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." Benjamin Franklin
"A life lived in fear is a life half lived."
Tara Morice as Fran, from the movie "Strictly Ballroom"