[asdefghyk]

The photo shows a cable ( with insulation ) that looks at least 4 inches thick ... (from a distance )

[tedd4u]

Probably something like this:

HJ9HP-50 Heliax High-Power Air-Dielectric Coax

https://www.alldataresource.com/Commscope-HJ9HP-50-HJ9-50-HE...