BNC connectors

Summary

BNC connectors are professional-grade radio frequency (RF) and coaxial connectors that serve a critical role in precision timing applications. In the episode "GPS Has a Secret Job," these connectors become a central component of the PPS Watch Project being built by Sean Hodgins and Jeff Geerling. The connectors are included on the GPS PPS Watch design specifically to enable timing comparison between different GPS sources—when two watches are connected via BNC cable, a third LED on the watch only lights when the two timing signals are out of sync. Beyond their functional importance, BNC connectors present a significant soldering challenge due to their large metal construction, which acts as a massive heat sink and makes them notoriously difficult to work with during assembly.

Details

During the build session featured in "GPS Has a Secret Job," BNC connectors emerge as both a technical necessity and a practical challenge. The connectors enable the core functionality of the timing comparison system, as Sean Hodgins explains: "And you can sync them up with like a BNC cable". This synchronization capability is what allows users to verify the accuracy of their GPS timing sources.

The soldering difficulty is a major point of discussion. As Sean notes, "because this whole connector is metal, you pretty much have to heat up this whole bottom part before it'll start flowing solder. It's a huge pain." He advises cranking up the soldering iron temperature since, unlike sensitive integrated circuits, the metal connectors can handle high heat. The connectors must be hand-soldered after the reflow process because they are through-hole components rather than surface-mount parts.

The conversation also reveals practical considerations about BNC connector use. Sean shares an anecdote about over-tightening: "Sometimes with my dad, he'll always crank it another half turn. It's like you crank it a half turn, pop, comes right off the board." This warning highlights the delicate balance between ensuring a secure connection and avoiding mechanical damage to the circuit board.

Jeff Geerling contributes his own experience with BNC cables in precision timing setups. When building his clock rack, he invested in a comprehensive BNC cable collection: "I bought a whole set of like 40 BNC cables from 6 in to 6 ft. So, I have enough for any little run perfectly." This collection, ranging from six inches to six feet, ensures he always has the appropriate cable length for any connection in his timing equipment setup.

History

GPS Has a Secret Job

BNC connectors are featured as essential components of the GPS PPS Watch that Sean and Jeff assemble during this episode. The connectors enable the watch's timing comparison functionality, allowing two watches to be synchronized and compared for accuracy verification. Sean walks Jeff through the challenges of soldering these particularly difficult components, explaining the heat sink problem and offering practical advice about temperature settings. The episode also includes discussion of proper connector handling to avoid board damage and Jeff's extensive BNC cable collection for his home clock rack setup.