T-adapter for splitting a BNC line — 50 Ohm, 4 GHz ceiling
The 31-208-RFX is a BNC to BNC T-adapter from the Dual BNC series, converting a single BNC plug input into two BNC jack outputs. It's a same-series adapter — no impedance or connector-family conversion — so it simply tee's off a 50 Ohm signal path. The T-shape body hangs free on the cable, with a bayonet lock on each of the three ports. Rated to 4 GHz, it covers the full BNC band through most of L-band and into S-band lower edge. The body is nickel-plated brass and zinc, with a POM acetal dielectric.
Gold vs silver — the real difference from the base 31-208
The 31-208-RFX and the base 31-208 are form-fit-function identical in every dimension and RF spec — same T-shape, same 50 Ohm impedance, same 4 GHz ceiling, same nickel body finish. The one meaningful difference is the center contact plating: the RFX uses gold, the 31-208 uses silver. Gold gives better corrosion resistance in humid or outdoor environments and maintains consistent contact resistance over the full 500-cycle life. Silver oxidizes over time, which can raise contact resistance in high-cycle or long-deployed applications. If the adapter lives indoors in a dry rack and cycle count stays low, the 31-208 is a cost-effective alternative. For field-service, outdoor, or high-reliability paths, the RFX's gold contacts are the safer call.