Or read the Trompeter connector catalog.
Most folks who gold-plate connectors use a nickel strike under the gold. Ni, being ferromagnetic, causes problems with IMD on extremely low-level signal lines. Trompeter took great pains to develop a pulse plating process to put down gold on their contacts *without* the Ni strike, to avoid this problem.
I found this out when I was trying to locate connectors with very low remanent magnetization.
I also don't thing that plain copper tubing would work well for an antenna, the skin effect will cause most of the rf currents to flow along the tanished exterior. Solution might be to paint the outside.
Jim