Coaxial Connectors: PL-259, N-Type, BNC, and SMA Compared

Pick the wrong connector for your feedline and you'll be chasing problems for months. I've seen hams lose 2+ dB at a single connection point because they used a PL-259 at 440 MHz where an N-type was the right call. That's power you paid for with your amplifier just getting wasted as heat in a connector body.

This guide covers the four connectors you'll encounter most in amateur radio, their actual performance specs, and where each one belongs in your station.

The PL-259 (UHF Connector)

The Basics

The PL-259 is the male connector; it mates with the SO-239 (female). Together they're called the "UHF connector family," which is one of ham radio's great naming jokes since they perform poorly at actual UHF frequencies. They were designed in the 1930s for frequencies that were considered ultra-high at the time — around 30 MHz.

Impedance: Not constant (non-constant impedance design) Frequency range: Usable to about 150 MHz; performance degrades above that Power handling: 500W at 30 MHz, decreasing with frequency Weatherproof: No (requires tape or sealant outdoors) Cost: $2-5 per connector

Where PL-259s Belong

HF operations. Period. Well, and 6 meters. At 50 MHz and below, the PL-259/SO-239 combination works fine. The impedance mismatch is negligible at these frequencies, they're cheap, widely available, and every HF radio manufactured since the 1960s has an SO-239 on the back.

For most HF stations running 100W on RG-213 or LMR-400, the PL-259 introduces maybe 0.1 dB of loss per connection at 30 MHz. Not worth losing sleep over.

Where They Don't Belong

Above 150 MHz, the PL-259 becomes a measurable problem. The non-constant impedance creates a discontinuity that shows up as added VSWR and signal loss. At 440 MHz, you can easily see 0.5 dB or more of loss at each connector. On a run with multiple connections (patch panels, lightning arrestors, switches), that adds up fast.

Also not great outdoors without weatherproofing. The gap between the connector body and the shell isn't sealed. Water gets in, corrosion starts, and your 1.5:1 SWR becomes 2.5:1 over a winter.

Installation Notes

Soldering a PL-259 onto RG-213 is a skill that takes practice. The center pin needs a clean solder joint with no cold solder, and the braid must make solid contact through the connector body's solder holes. For RG-58 or thinner cables, you'll need a UG-175 or UG-176 reducer sleeve.

Here's the thing. A bad PL-259 installation is worse than no connector at all. If you can't solder cleanly, spend the extra money on crimp-style PL-259s from manufacturers like Amphenol or Times Microwave. They're more forgiving.

The N-Type Connector

The Basics

Designed by Paul Neill at Bell Labs in the 1940s, the N-type is what happens when engineers actually care about impedance consistency through a connector.

Impedance: 50 ohms (constant) Frequency range: DC to 11 GHz (standard), up to 18 GHz for precision versions Power handling: 300W average at 1 GHz; 2kW at lower frequencies Weatherproof: Yes (when properly torqued) Cost: $5-15 per connector

Where N-Type Connectors Belong

Anything above 2 meters (144 MHz). For 220 MHz, 440 MHz, 902 MHz, and 1296 MHz operations, the N-type is the standard. Its constant impedance means minimal reflection loss across its entire frequency range.

Most quality VHF/UHF base station antennas (Diamond, Comet, Cushcraft) come with N-type female connectors. Commercial repeater equipment uses N-type almost exclusively. There's a reason for that.

Real-World Performance

At 440 MHz on LMR-400 cable, an N-type connector adds about 0.05 dB of loss per connection. Compare that to the 0.5 dB you'd lose with a PL-259 at the same frequency. Over a typical station setup with 4-6 connections (radio to patch panel, patch panel to lightning arrestor, arrestor to feedline, feedline to antenna), that difference is significant.

I switched my entire 70cm station from PL-259s to N-type connectors three years ago. My receive noise floor dropped by about 1.5 dB — partly the better connectors, partly the LMR-400 replacing old RG-8X. But the connectors mattered.

Installation

N-type connectors are more complex to install than PL-259s. The center pin must be soldered or crimped precisely, and the cable preparation dimensions are critical. A cable strip tool specific to your cable type (LMR-400, RG-213, etc.) makes a huge difference.

For LMR-400, Times Microwave sells pre-made jumpers in standard lengths. If you're not confident in your connector installation skills, these are worth the premium.

The BNC Connector

The Basics

BNC stands for Bayonet Neill-Concelman (yes, the same Neill from the N-type). It's a quick-connect/disconnect bayonet-style connector common in test equipment and portable operations.

Impedance: 50 ohms (constant) Frequency range: DC to 4 GHz Power handling: 80W at 1 GHz; 500W at HF Weatherproof: Somewhat (better than PL-259, not as good as N-type) Cost: $3-8 per connector

Where BNC Connectors Belong

Portable and QRP operations. The quick-connect bayonet mechanism makes them perfect for field use where you're assembling and disassembling stations quickly. POTA and SOTA operators love them for this reason.

Test equipment connections. Your oscilloscope, signal generator, and antenna analyzer likely have BNC ports. The Rigol DSA815 spectrum analyzer, NanoVNA, and most bench instruments use BNC.

Scanner and receiver connections. Many wideband receivers (RTL-SDR dongles with their SMA ports aside) use BNC as the antenna connection.

Limitations

Power handling. At 80W maximum at UHF, BNC connectors aren't suitable for high-power transmitting applications above VHF. They're fine for QRP (5W or less) anywhere in the spectrum.

The bayonet mechanism, while convenient, isn't as mechanically robust as a threaded connector. In permanent installations, the slight mechanical movement over time (from wind vibration on antenna connections, for instance) can cause intermittent connections.

Not ideal for permanent outdoor installations.

The SMA Connector

The Basics

SubMiniature version A. These tiny threaded connectors are everywhere in modern radio equipment, especially handhelds and SDRs.

Impedance: 50 ohms (constant) Frequency range: DC to 18 GHz (standard), up to 26.5 GHz for precision) Power handling: 10W at 1 GHz (standard size); varies by manufacturer Weatherproof: No (too small for effective O-ring seals in standard versions) Cost: $2-6 per connector

The SMA vs. SMA-Female Confusion

This trips people up constantly. SMA has gendered connectors that don't follow the usual convention:

• SMA Male: Has a center pin AND external threads
• SMA Female: Has a center socket AND internal threads

Then there's RP-SMA (Reverse Polarity SMA): The threading is the same, but the pin/socket is swapped. RP-SMA was designed for WiFi equipment. Your Baofeng UV-5R uses SMA-Female on the radio body (which is unusual — most handhelds use SMA-Male on the radio). The Yaesu FT-60 and Kenwood TH-D74A use SMA-Male on the radio body.

Seriously. Check your specific radio before buying adapters or antennas.

Where SMA Belongs

Handheld radios, SDR dongles (RTL-SDR, HackRF, Airspy), GPS receivers, and internal RF connections. Anywhere size and weight matter more than power handling.

For connecting an RTL-SDR to a discone antenna or a handheld to a better external antenna, SMA pigtails and adapters are the way to go.

Where SMA Doesn't Belong

High-power anything. The small contact surfaces and thin center conductor limit current handling. Running 50W through an SMA connector is asking for failure, even if it doesn't fail immediately.

Also, the small size makes them fragile. I've broken SMA connectors by being careless with coax strain. If there's any side-load or tension on the cable, use strain relief or switch to a larger connector.

Quick Comparison Table

Feature PL-259/SO-239 N-Type BNC SMA Impedance Non-constant 50Ω 50Ω 50Ω Max Freq (practical) 150 MHz 11 GHz 4 GHz 18 GHz Power Handling 500W (HF) 2kW (HF) 500W (HF) 10W Weatherproof No Yes Partial No Quick Connect No (threaded) No (threaded) Yes (bayonet) No (threaded) Typical Cost $2-5 $5-15 $3-8 $2-6 Best For HF base station VHF/UHF, repeaters Portable, test equip Handhelds, SDR

My Recommendations by Use Case

HF base station (100W): PL-259 on RG-213 or LMR-400. Don't overthink it. The connector loss at HF is trivial.

VHF/UHF base station: N-type everywhere. Yes, it costs more. Yes, you'll need adapters for radios with SO-239 outputs (most desktop VHF/UHF rigs still use SO-239 — looking at you, Icom IC-2730). The performance difference at 440 MHz justifies the adapter.

Portable/QRP operations: BNC for fast setup and teardown. Most QRP rigs (Elecraft KX2, IC-705) use BNC antenna connectors for exactly this reason.

Handheld to external antenna: SMA pigtail to whatever connector your external antenna uses. Keep the pigtail short — SMA cable assemblies use thin coax (RG-316 typically) with high loss.

Repeater installations: N-type. Full stop. This is commercial-grade infrastructure. Use commercial-grade connectors.

Adapters: The Necessary Evil

You'll end up with adapters. Everyone does. A few guidelines:

• Every adapter adds loss and a potential failure point
• Quality matters more with adapters than with connectors (cheap adapters often have poor internal contact)
• Buy from Amphenol, Pomona, or Pasternack — not the cheapest eBay listing
• An N-Female to SO-239 adapter (sometimes called a UG-146) is probably the most common adapter in any ham's junk box
• Barrel connectors (female-to-female of the same type) are useful for extending cables but add two connection points of loss

Keep your adapter collection small. If you find yourself chaining two or three adapters to make a connection, stop and buy the right cable with the right connectors on each end.

Weatherproofing Outdoor Connections

Even weatherproof connectors benefit from additional protection outdoors. Here's what works:

• Self-amalgamating tape (also called self-vulcanizing or rescue tape): Wrap the connection, stretching as you go. It fuses to itself and creates a waterproof seal. Scotch 2228 and ProSeal are popular brands.
• Coax Seal (butyl rubber putty): Press it around the connection before taping. Belt and suspenders approach.
• Don't use electrical tape alone. It degrades in UV and loses adhesion within a year.

I reweatherproof my outdoor connections annually. Takes thirty minutes and prevents the corrosion that ruins connectors over time.

Key Takeaways

• PL-259/SO-239 for HF (below 150 MHz) — cheap, ubiquitous, adequate at these frequencies
• N-type for VHF/UHF and above — worth the cost for the performance improvement
• BNC for portable ops and test equipment — fast connect/disconnect, moderate power
• SMA for handhelds and SDR — tiny, fragile, low power only
• Match your connector to your frequency and power level, not to what's cheapest or easiest
• Weatherproof every outdoor connection regardless of connector type