75 Ohm BNC for video and broadcast — the 112740-20
75 Ohm variant of the standard BNC — the centre conductor and dielectric are sized to hold the 75 Ohm line impedance across the mated pair. A 50 Ohm BNC on a 75 Ohm cable or vice versa creates a reflection at the junction that degrades return loss — noticeable as ghosting in analog video or bit errors in HD-SDI. This jack is built for the 75 Ohm ecosystem: RG59, RG6, and Belden 1855A cable assemblies. Frequency range runs to 4 GHz. The insertion loss is specified at 0.2 dB.
Mounting and termination — what arrives in the bag
The 112740-20 is a bulkhead-mount jack with front-side nut retention. The package includes three pieces: the connector body with the centre contact pre-installed, a lockwasher to prevent the nut from backing off under vibration, and a hex nut. The user supplies the panel cutout and the cable. Termination is solder-only — the centre contact has a solder cup for the signal wire, and the shield termination is a solder bucket that accepts the braid. No crimp tooling required, but the installer needs a soldering iron rated for the brass body's thermal mass. The board-edge, end-launch mounting option allows the jack to sit flush with the PCB edge for a clean RF launch. The bayonet lock (BNC standard) gives a quarter-turn mate with positive engagement. The locking studs on the jack body engage the slots in the mating plug; the spring-loaded sleeve snaps the pair together. No tools needed for mating or unmating.
The 112740-20 is listed as Active on the manufacturer's lifecycle record.