Speaker cables: Go to the dollar store and buy two 9 foot 18 AWG extension cords for $2 each and cut off the ends.
Ok, I'll admit that I like to put banana plugs or spade lugs on the ends.
Also heatshrink the cables where the "zipping" ends.
MHz? I don't worry. There should be losses at those frequencies.
https://en.wikipedia.org/wiki/Boucherot_cell