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That means the signal is entirely in the tin layer, if one is present. Not a good thing, as tin is not a very good conductor. Tin has about seven times the resistance of copper). So anything at 1MHz or higher should not have a tin layer. It needs to be bare copper. That means video cable, digital audio cable, RF coax or Category data cables all need to be bare copper. No tinned copper.
Tin is a chemical element with the symbol Sn (for Latin: stannum) and atomic number 50, is a post-transition metal in group 14 of the periodic table. It is obtained chiefly from the mineral cassiterite, which contains tin dioxide, SnO2. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4.