What This BNC Barrel Adapter Covers
The Amphenol RF 31-219 is a straight BNC jack-to-jack adapter — two female BNC sockets back-to-back in a single nickel-plated brass body. The center contacts are female on both ends, silver-plated beryllium copper, with a PTFE dielectric holding the impedance steady across the band. The bayonet lock on each end mates with standard BNC plugs; the free-hanging inline body lets it float in a cable run without a panel cutout.
Impedance and Frequency — What 50 Ohm at 4 GHz Means
Rated to 4 GHz. This covers VHF, UHF, ISM bands, and cellular up through low microwave.
Temperature Range and Durability
The PTFE dielectric does not soften or shift impedance across that span. With 500 mating cycles on the silver-plated beryllium copper contacts, it survives repeated connects in test setups or field-service harnesses without wearing out the center socket.
Silver vs Gold — 31-219 and 31-219-RFX
The 31-219 uses silver-plated beryllium copper center contacts; the 31-219-RFX uses gold-plated phosphor bronze contacts. Both are straight BNC jack-to-jack adapters, same 50 Ohm / 4 GHz rating, same nickel brass body. Gold plating resists corrosion better in humid or chemical environments and holds lower contact resistance over more cycles — but silver gives lower insertion loss at RF frequencies and is standard for general-purpose RF work. If your application sees salt fog, high humidity, or frequent field reconnects, the gold-plated 31-219-RFX is the better call. For clean indoor bench use, silver is fine.