What type of wire connects an SSB automatic tuner to an insulated backstay?

The correct type of wire that connects an SSB (Single Sideband) automatic tuner to an insulated backstay is GTO-15 high-voltage cable. This cable is specifically designed for use in RF (radio frequency) applications, which is essential for effectively transmitting signals between the tuner and the antenna, in this case, the backstay.

GTO-15 high-voltage cable is capable of handling high voltage and high-frequency signals, making it ideal for SSB operations where maintaining signal integrity is crucial. It's also well-suited for use in marine environments because of its durability and resistance to the elements, which can be particularly important when dealing with installation aboard boats.

The other options do not provide the necessary specifications for this kind of application. RG-58 coaxial cable, while commonly used for RF applications, may not be suitable for high-voltage connections in the same way that GTO-15 is. Standard copper wire lacks the insulation and dimensional characteristics needed for high-frequency transmission. Multi-strand HDMI cable is entirely inappropriate for radio frequency use, as it is designed for digital video and audio signals, not for RF transmission.