4 GHz Ceiling and the 50 Ohm Match
The 031-5329-52RFX: The gold center contact keeps the signal path corrosion-free over those 500 mates, which matters more for consistent VSWR than for raw contact resistance.
Through-Hole Mounting and Solder Termination
The center contact terminates with a solder cup or through-hole pin — the datasheet will show the exact tail geometry — and the shield is soldered directly to the ground plane on the PCB. This gives a mechanically rigid joint that handles the torque of bayonet mating without stressing the board traces. The dielectric is PBT/polyester, which handles the 500 V rating without breakdown at the 50 Ohm impedance.
The 031-5329-51RFX is electrically identical — same 50 Ohm, 4 GHz, 500 V rating, same brass body and nickel finish — but swaps the center contact plating from gold to silver. For a clean lab bench at 25 °C, silver works. For a coastal site, a plating line, or any environment where the connector sees humidity or airborne corrosives, the gold on the 031-5329-52RFX is the safer call. The price delta between the two is small; the corrosion margin is not.