50-ohm through-line, panel-ready
The Hirose BNC-PA-JJ(40) is a straight BNC female-to-female adapter, a same-series barrel that passes a 50 Ohm transmission line through a bulkhead. It is built for the RF engineer who needs a clean, repeatable interconnect at the panel face — the impedance is 50 Ohm, not 75 Ohm, so it belongs in a 50-ohm system (test gear, radio equipment, telecom infrastructure) and will cause a mismatch in a 75-ohm video path.
4 GHz ceiling, 10000-cycle floor
Rated to 4 GHz, this adapter covers the full BNC practical band — VHF/UHF, ISM, cellular backhaul up to L-band, and most lab instrumentation. The 10000 mating cycles tell you the interface is built for frequent connect/disconnect duty: patch panels, test jigs, or field-deployed equipment where the cable gets swapped regularly. Silver plating on the centre contact and body (beryllium copper centre pin, brass shell) keeps contact resistance low and resists corrosion over those cycles.
Flange-mount bulkhead fit
Panel mount with a flange — the adapter bolts to the outside of an enclosure, presenting two BNC jacks: one inside for the internal cable, one outside for the field run. The straight body keeps the signal path axial; no right-angle bend to introduce a parasitic reactance. The PTFE dielectric maintains consistent impedance through the barrel.