RG142 coaxial cable is serious stuff, and yes it's a bit expensive - it's the same diameter as RG58 (5mm) but, due to its PTFE material, is capable of handling lots of power! Features a double-screen and is perfect for QRO baluns and internal hook-ups in legal-limit amplifiers. 8-12 turns of this on an FT240-31 or FT240-43 Ferrite Toroid make an ideal HF Balun.
Sold in multiples of 1 metre. eg: Order 3 for a 3m length - a single 1m length is ample for any type of Balun/Choke.