![]() While having BNC on one end will help from a technical standpoint, really for digital audio like this, the bandwidth is pretty low and the theoretical signal benefit is negligible, and in any case won't make a difference to the actual 'reception' of the signal at the receiving end (what you end up hearing). The BNC connector is the correct choice as 75ohm BNC jacks and plugs are actually 75ohm (FYI: there are BNC connectors at other impedances as well, so do check you're not mistakenly buying antenna-style BNC connectors which can be like 50 and other things). You cannot make a 75ohm RCA connector, so the use of RCA is a compromise (fundamentalists might say it's simply wrong, but that's going overboard IMO) for the common consumer. That being said, you did hear correctly that BNC is superior for this application that requires 75ohm. I would not spend an exorbitant amount of time or money on an RCA-BNC cable, if a good quality 75ohm RCA-RCA cable is easily attainable. Strain-relieving them could be tricky.For SPDIF, it really should be okay either way. But, obviously, they’re not watertight, and are unsuitable for use outdoors. ![]() RCA connectors, on the other hand, are probably electrically adequate for HF QRP. I’ve been burned by Chinese BNCs in my 10Base2 network. Many of these parts from unknown sources, especially sources where the metric system prevails, are made to the nearest metric dimension and are out of tolerance mechanically, resulting in intermittents that are hard to locate. Obviously, these connectors aren’t watertight, so they’re suitable only for a dry environment such as the shack.Ĭoax connectors of any kind should only be bought from a reputable manufacturer qualified for MIL-spec products. Use ONLY the exact tool part number specified by the manufacturer.) Also, there is no strain relief in most crimp versions, so shrink tubing should be added to prevent a stress concentration during flexing. (And it’s absolutely intolerant of incorrect crimp tools. ![]() A lot of commercial BNCs use a hex crimp sleeve, which is electrically secure and less dependent on the assembler’s skill, but doesn’t control the dimensional transition from the line to the connector body well, and can have an inductive discontinuity in the outer conductor that varies as the cable bends. The MIL-spec versions connect to the cable outer conductor with an axial clamp and a rear peripheral seal, which gives some strain relief. If the installation will be outdoors, especially where salt spray is possible, such as the seaside or the bottom of a road vehicle, TNC or Type N would be a better choice, according to what an Amphenol applications engineer told me when I ran into trouble. That causes corrosion of the coax braid, and high RF losses. The BNC family has an interfacial seal, but I learned the hard way that the coupling mechanism can rock laterally and let water leak in past the gasket. The former type can develop an inductive discontinuity at UHF, or if it backs out far enough, an open circuit. There are two basic constructions of MIL-spec BNCs: the older ones in which the axial location of the center pin is determined only by the center conductor of the coax, and the newer captivated-contact types in which the contact is accurately positioned between a pair of dielectric parts. The impedance is pretty flat up to 1 GHz, at least for well-made MIL-spec versions. However, there are a lot of BNC product families, whose characteristics, capabilities, and general quality vary greatly. It’s a more complicated issue than either/or.įor QRP, BNC is certainly adequate from an electrical standpoint. (Of course, any cables that are up over the ground, or any guy lines, should be marked with flagging tape - available from any hardware store - to prevent someone from tripping.) This can be an annoyance if you lose your connection when someone trips over the cable, or it can be a feature in that the antenna won’t get pulled over when someone trips over the cable RCA connectors are inexpensive but can become unplugged. The commercial version of the Buddipole uses them. Wikipedia has a side-by-side picture comparing the two types. My picture above seems to be of the 50 Ω type. What I didn’t realize until recently is that they come in both 75 Ω and 50 Ω types. RF cables with BNC connectors seem to be more available. Maybe you can help me out: Which is the “best” (most common, most useful, works best) for a QRP Antenna Connector: BNC (which stands for “Bayonet Neill-Concelman” according to Wikipedia ) or RCA “phono” connectors (they were used for connecting a turntable to an audio amplifier for something like a half a century)? 50 Ω Female BNC Connectors (Photo by W1AKI)īNC connectors cost more but won’t come loose. Which is best for QRP Antenna Connectors: BNC or RCA? I’ve seen both on the web, so I’m trying to decide which connector to use for a QRP antenna.
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