Which connector does SMA to BNC RF Coax Patch Cable, 50 Ohm RG-58 use?

It is built around SMA male, straight or right angle, 50 ohm.

What lengths does SMA to BNC RF Coax Patch Cable, 50 Ohm RG-58 come in?

0.3 to 5 m typical, OEM build to order.

SMA to BNC Coax Cable, 50 Ohm RG-58

Last updated: 13 September 2026

Overview

An sma to bnc coax cable is the adapter cord every lab owns six of and can never find: instrument side is BNC, device side is SMA. Building it as one cable instead of stacking a barrel adapter on a BNC lead removes two mechanical joints, and every joint is a reflection you pay for at frequency. We build it on 50 ohm RG-58, in the length you actually need, with crimp or solder terminations to the connector maker’s strip geometry.

Key Specifications

Connector A	SMA male, straight or right angle, 50 ohm
Connector B	BNC male, straight, 50 ohm
Cable	RG-58 class, 50 ohm, braided shield
Termination	Crimp or solder, to connector maker geometry
Length	0.3 to 5 m typical, OEM build to order
Impedance	50 ohm nominal, stated per order
Marking	Heat-shrink labels with your part number

50 ohm or 75 ohm: the decision that comes first

Characteristic impedance is set by the ratio of inner conductor diameter to the inner diameter of the shield, so it is fixed by the cable geometry, not by the connector. Mixing the two is the single most common way to lose margin on a bench: every impedance step reflects part of the signal back toward the source.

	50 ohm	75 ohm
Optimized for	Power handling and low loss across RF	Lowest signal attenuation
Typical use	Radio, test instruments, antenna feeds	Video, SDI, broadcast, CATV
Common cables	RG-58, RG-316, LMR-195	RG-59, RG-6
Connectors	SMA, N, TNC, BNC 50	BNC 75, F, SMB
What happens if mixed	Reflection, standing waves, measurement error	Same — the mismatch is the problem

The 50 ohm figure is an industry-general compromise: coaxial line has its lowest attenuation near 77 ohm and its highest power handling near 30 ohm, and 50 ohm sits between them. The coaxial cable family is defined around that value. What your assembly is built and verified to — return loss, insertion loss, velocity — is stated per order, measured on your build.

SMA and BNC: what each interface is built for

These two are not interchangeable in spirit even when you can screw an adapter between them. One is a precision threaded RF interface, the other is a quick bayonet that was never meant for 18 GHz.

	SMA	BNC
Coupling	Threaded, 1/4-36	Bayonet, quarter turn
Impedance versions	50 ohm as standard	50 ohm and 75 ohm versions exist
Usable frequency	Into the tens of GHz for precision grades	Low GHz; the bayonet limits repeatability
Mating cycles	Hundreds, thread dependent	Hundreds, quick to connect
Best at	Device and module ports, small form factor	Instruments, scopes, generators, patch panels
Watch out for	Thread wear, overtightening	Worn bayonet slots losing contact pressure

Because the two ends are doing different jobs, the weak point is almost always the BNC: a bayonet that has been mated a few hundred times loses contact pressure, and a loose BNC shows up as intermittent signal long before anyone suspects the cable.

Where the loss shows up

Coaxial attenuation climbs with frequency, roughly with the square root of frequency, so doubling the run length does not double the loss in a way you can ignore — it compounds with frequency. That is why the two questions we ask first are the highest frequency you care about and the length you need. Give us both and we will quote the cable and the termination that holds the margin, with the measured figures stated per order rather than a generic datasheet claim.

Typical applications for this sma to bnc coax cable

RF test benches — signal generator or analyzer to a device under test
Antenna and radio front-end bring-out leads
Telemetry and instrumentation links inside a rack
Replacing stacks of adapters on a crowded bench
Prototype and pre-compliance setups where the connection changes daily

How to specify your build

Impedance — 50 ohm is the default for SMA; confirm the BNC side matches.
Connector gender and angle on each end: SMA male straight or right angle, BNC male.
Cable — RG-58 as standard; alternatives on request.
Length and the highest frequency of interest.
Termination method — crimp or solder.
Marking — heat-shrink labels with your part number.

Workmanship and testing

Assembly and inspection follow IPC/WHMA-A-620 Class 3 workmanship criteria under our ISO 9001 quality management system, and every unit is 100% continuity and pinout tested before it is packed. Conductor range is 32 to 12 AWG. Strip dimensions and crimp heights are set from the connector maker’s geometry and checked on the first article. Where a standard sets a limit for the category, the connector interface or the jacket, that is the industry-general definition of the rating. The values your assembly is built and verified to are the ones stated on your drawing, per order.

Custom builds and ordering

Send the mating part numbers and we will confirm the interface before we cut cable. Prototype builds start from 5 pcs and ship in 3 working days; production orders start at MOQ 500 pcs and ship 14 working days after approval. New tooling adds about 10 working days, and we hold 100 sets of mold tooling in house. OEM and ODM builds ship under your part number and labeling, with material certificates and first-article reports on request. Factory audits and video line tours of our Longgang, Shenzhen plant can be arranged through Alan Kang.

Related RF and coax assemblies

Full range: signal and data cable range.

Frequently Asked Questions

Can I use a 50 ohm BNC where a 75 ohm BNC is fitted?

They will often mate, and that is the problem — the mismatch reflects signal. Check the marking on the jack; 75 ohm BNCs usually have a thinner dielectric and are marked.

SMA or RP-SMA?

They are different. RP-SMA reverses the pin and socket, and using the wrong one means no contact at all. Send a photo if you are not sure.

How long can I go?

It depends on the frequency and the loss budget, not on a number we can quote generically. Give us the top frequency and we will build to the reach you state.