Some of the pull-pull systems use plastic coated cable....not easily solderable by any means. That type of cable is meant to have swaged or crimped cable fittings. (The cable supplied is actually fishing leader material, or similar) Have you ever seen a soldered cable fishing leader? They use small "Nicopress" style cable splice sleeves.

Full scale aircraft control cables require swaged end fittings. I have swaged and installed lots of them over the years.

Harley Condra
BVM REP
JetCat REP