Choosing the right RF connector matters more than it looks. The wrong choice can add loss, raise SWR, let water into your feedline, or simply fail to mate with your gear. This guide compares two of the most common coaxial connectors in amateur and commercial radio — the PL-259 (UHF) and the N Type — and then summarises the other connectors you are most likely to meet: SMA, SMB, MMCX, MCX, TNC and BNC.
PL-259 vs. N Type at a glance
| Property | PL-259 (UHF) | N Type |
|---|---|---|
| Coupling | Threaded (5/8″-24) | Threaded (5/8″-24), precision interface |
| Impedance | Not a true constant-impedance design (nominally 50Ω) | Constant 50Ω (75Ω version also made) |
| Practical frequency range | HF/VHF, generally to ~300 MHz | DC to 11 GHz (precision versions to 18 GHz) |
| Weatherproofing | Not weatherproof on its own | Weatherproof when correctly mated (gasket/O-ring) |
| Power handling | High at HF/VHF; robust body | High, with better consistency at UHF and above |
| Cost & assembly | Cheap, easy to solder, very forgiving | Dearer, more parts, needs careful assembly |
| Typical use | HF/VHF ham rigs, CB, antenna tuners | UHF/microwave antennas, Wi-Fi, cellular, test gear |
PL-259 (the “UHF” connector)
Despite the name, the PL-259 is best thought of as an HF and VHF connector. It dates from the 1930s, when “UHF” meant anything above about 30 MHz. The plug is the PL-259 and the matching socket is the SO-239 (the “PL” and “SO” come from old Signal Corps nomenclature for plug and socket). It is not a true constant-impedance connector — there is a noticeable impedance discontinuity through the joint — so performance falls away as you climb in frequency. Its strengths are that it is inexpensive, mechanically tough, easy to solder onto thick coax like RG-8 or RG-213, and almost universal on HF and VHF amateur equipment.
Rule of thumb: fine to about 300 MHz; above that, expect rising SWR and use something better.
N Type
The N Type was developed at Bell Labs in the 1940s by Paul Neill (the “N” is for Neill). Unlike the PL-259 it is a genuine 50Ω constant-impedance connector, which makes it well behaved all the way up to 11 GHz, and to 18 GHz in precision versions. Properly mated it is weatherproof, which is why it is the default choice for mast-mounted antennas, Wi-Fi and cellular systems, and microwave links. The trade-offs are cost, a few more parts to assemble, and the need for more care during termination. A 75Ω variant also exists for broadcast and CATV work — note that 50Ω and 75Ω N connectors should not be mated, as the differing pin diameters can damage them.
Which should I use? For HF and VHF on a budget, or to match existing ham gear, the PL-259 is hard to beat. For anything outdoors, anything above ~300 MHz, or where low loss and a clean match matter, choose N Type.
Other common RF connectors
Beyond these two, a handful of smaller connectors turn up constantly in modern radios, antennas, modules and test equipment. The table below summarises the essentials; brief notes follow.
| Connector | Coupling | Impedance | Typical max frequency | Where you’ll see it |
|---|---|---|---|---|
| BNC | Bayonet (quarter-turn) | 50Ω & 75Ω | ~4 GHz (50Ω) | Test gear, oscilloscopes, video/SDI, older networking |
| TNC | Threaded | 50Ω (75Ω made) | ~11 GHz | Threaded “BNC” for vibration/microwave environments |
| SMA | Threaded (1/4″-36) | 50Ω (75Ω rare) | 18 GHz (to 26.5 GHz) | Wi-Fi, GPS, handheld antennas, RF modules, test gear |
| SMB | Snap-on (push) | 50Ω & 75Ω | ~4 GHz | Tight spaces needing quick, repeated connections |
| MCX | Snap-on (push) | 50Ω (75Ω made) | ~6 GHz | GPS, cellular, compact devices (~30% smaller than SMB) |
| MMCX | Snap-on (push) | 50Ω | ~6 GHz | Wi-Fi/M.2 cards, tiny antennas, IEMs — smaller than MCX |
Quick notes
- BNC — a fast bayonet lock that is the workhorse of the test bench. The 50Ω type is for RF; the 75Ω type for video. Convenient but not for high microwave frequencies.
- TNC — essentially a threaded BNC. The screw coupling makes it far more reliable under vibration and pushes the usable range up to around 11 GHz.
- SMA — the small threaded connector you find on most Wi-Fi and GPS antennas and on countless RF modules. Excellent to 18 GHz, but the threads have a limited number of mating cycles, so don’t treat it as a frequent connect/disconnect joint. Watch out for RP-SMA (reverse-polarity), which is common on consumer Wi-Fi gear and will not mate with standard SMA.
- SMB — a push-on snap fit that is quicker than SMA in cramped assemblies, at the cost of a lower frequency ceiling.
- MCX / MMCX — progressively smaller snap-on connectors for space-constrained devices such as GPS modules, laptop wireless cards and compact antennas. MMCX adds a little rotational freedom, handy for routing thin cables.
A note on the names: several of these share a heritage. N is for Neill, BNC is Bayonet Neill–Concelman, and TNC is Threaded Neill–Concelman — so the B and T simply tell you how the connector locks.