Choose RF connector types by matching the system impedance, operating frequency, RF power and mechanical interface, then verify the complete connector, cable and PCB transition.
This guide compares the main coaxial connector families and explains the electrical, environmental and purchasing checks that design and component engineers should complete before selecting a part.
Key Takeaways
An RF connector is part of the transmission line, not simply a mechanical attachment. These principles provide a starting point for selection.
- Keep connectors, cables, terminations and measurement ports consistent with the required 50 Ω or 75 Ω system impedance.
- A connector-family name does not guarantee a frequency rating. Check the selected part, cable termination and PCB launch over the complete operating band.
- Conventional MCX and MMCX connectors serve compact multi-GHz interconnects; SMP addresses higher-frequency and blind-mate microwave assemblies. These families are not interchangeable.
- RF power capability depends on frequency, temperature, cable construction and operating conditions. A dielectric withstand test voltage is not a continuous operating rating.
- Confirm contact configuration, mating durability, installation torque and sealing conditions. SMA and RP-SMA must not be treated as the same interface.
- Validate the assembled signal path using appropriate RF measurements; for multi-carrier infrastructure, include passive intermodulation requirements as well as return loss.
Key Parameters When Selecting RF Connectors
RF connectors carry high-frequency signals between cables, boards and modules while maintaining a controlled electromagnetic geometry. Their selection influences insertion loss, voltage standing wave ratio (VSWR), usable bandwidth, power capability and long-term reliability. Manufacturer family specifications provide an initial screen, but the selected configuration determines the usable performance [1, 2].
Characteristic impedance
Most general RF and microwave systems use 50 Ω interfaces, while broadcast, video and cable television commonly use 75 Ω interfaces. Match the connector impedance to the cable, source and load. Mixing impedances introduces a discontinuity that can produce reflections, standing waves and measurement error [3].
Mechanical resemblance does not establish electrical or dimensional compatibility. Where a family includes both impedances, check the interface drawings and the manufacturer’s mating instructions rather than assuming that all versions can be connected safely.
Frequency range and signal integrity
Connector geometry, dielectric materials and manufacturing tolerances determine the frequency range over which the interface meets its specified performance. The cable attachment and PCB launch can impose a lower limit than the connector interface itself. Compare insertion loss and return loss or VSWR across the required band, not only the catalogue maximum frequency [1, 2].
Conventional MCX and MMCX families are commonly specified to 6 GHz, whereas SMP products can support operation to 40 GHz. Standard SMA products commonly cover DC to 18 GHz, with specifically designed extended-frequency versions operating higher. Do not transfer an extended-frequency rating to an ordinary part from the same family [1, 2, 4].
Power handling and voltage limits
Larger interfaces such as Type N and 7/16 DIN are candidates for higher-power RF paths, but physical size alone does not establish an allowable power. Check the rated RF power at the actual frequency and temperature, together with the cable and termination limits. For example, Amphenol RF publishes 3000 W at 1 GHz and 25 °C for its 7/16 family; that is a conditioned manufacturer rating, not a universal capability at every frequency [5].
For continuous-wave and pulsed transmitters, assess average heating and peak electrical stress separately. Use the supplier’s applicable derating information, including any restrictions associated with mismatch and installation conditions. Continuous operating voltage and dielectric withstand voltage serve different purposes and must not be substituted for one another [2, 4, 5].
Coupling mechanism and mating durability
Bayonet, threaded and push-on interfaces balance access, mating speed, retention and repeatability. BNC is convenient for frequent patching, threaded SMA and TNC provide secure coupling, and SMP supports compact plug-in and blind-mate arrangements. Check the selected part’s mating-cycle rating and permitted engagement and disengagement forces [1, 2, 4].
Small size does not automatically mean short mating life. Amphenol RF lists a minimum of 500 mating cycles for its MMCX family, subject to the configuration-specific limitations stated by the manufacturer. The complete application must also protect the PCB attachment and cable termination against handling loads [4].
Physical size, environment and installation
Compact connectors reduce board area and enclosure height, while larger interfaces provide more space for robust cable attachment and mechanical support. For outdoor equipment, verify interface sealing, panel sealing, cable entry, corrosion resistance and the required mated or unmated condition. A threaded coupling is not, by itself, a waterproof qualification [1, 5].
Common RF Connector Types and Families
Table 1 compares the original connector families using conservative selection guidance. The frequency entries describe representative family capabilities, not guaranteed ratings for every part, cable or impedance version. All selections require confirmation against the individual product documentation [1–5].
| Connector | Impedance | Frequency guidance | Coupling | Typical applications |
|---|---|---|---|---|
| SMA | 50 Ω | Commonly DC to 18 GHz; selected extended versions to 26.5 GHz or higher | Threaded | RF and microwave circuits, antennas, filters, attenuators and laboratory interconnects |
| SMB | 50 Ω or 75 Ω; select the correct version | Conventional family guidance: DC to 4 GHz | Snap-on | Compact RF modules and instruments requiring quick connection |
| MCX | 50 Ω or 75 Ω; part-dependent | Conventional family guidance: DC to 6 GHz | Snap-on | Compact wireless equipment, GPS and portable devices |
| MMCX | Commonly 50 Ω; verify any other variant | Conventional family guidance: DC to 6 GHz | Microminiature snap-on | Embedded radios, compact antenna connections and dense RF assemblies |
| SMP | 50 Ω | Products available to 40 GHz | Push-on; blind-mate configurations | Microwave modules and high-density board-to-board interconnects |
| BNC | 50 Ω or 75 Ω | Conventional products to 4 GHz; verify the selected impedance version and application | Bayonet | Laboratory instrumentation, general RF and video |
| TNC | Commonly 50 Ω; 75 Ω versions also exist | Conventional 50 Ω family guidance: DC to 11 GHz; do not apply this automatically to 75 Ω parts | Threaded | RF communications and vibration-prone installations |
| Type N | 50 Ω or 75 Ω | Selected 50 Ω products to 18 GHz; 75 Ω products require separate verification | Threaded | Antenna feeders, microwave equipment, radar and RF test |
| UHF, PL-259/SO-239 | Not a defined constant-impedance interface | HF/VHF applications; the cited manufacturer overview specifies use to 200 MHz | Threaded | Amateur radio and legacy equipment |
| 7/16 DIN | 50 Ω | Family products to 7.5 GHz | Large threaded coupling | High-power feeders and low-PIM infrastructure |
Miniature and Microminiature Families: MMCX, MCX and SMP
MCX, MMCX and SMP address size-constrained RF connections, but their frequency ranges and mechanical arrangements differ. Select them by bandwidth, retention, accessibility and assembly tolerances rather than treating them as one interchangeable miniature category [1, 4].
MCX and MMCX for compact cable connections
MCX and MMCX use snap-on coupling and small footprints. They suit compact wireless equipment, GPS receivers, embedded radios and short internal antenna connections. Conventional products cover multi-GHz applications, with the cited MCX and MMCX families specified to 6 GHz [1, 4].
Compare connector height, cable bend requirements, mating access and retention forces alongside electrical performance. Check the durability rating of the exact part and provide strain relief so that cable handling does not load the solder joints. For repeated servicing, evaluate the complete assembly rather than rejecting or accepting a connector solely because it is miniature.
SMP for microwave and blind-mate assemblies
SMP supports microwave interconnects to 40 GHz in the cited family. Its plug-in format is useful for modular assemblies and board-to-board connections where a threaded connector would be difficult to access. Select the mating arrangement, retention and permitted mechanical movement as a coordinated interconnect system [1].
Do not assume that MCX or MMCX provides the same blind-mate capability or millimetre-wave performance as SMP. Equally, a high frequency rating does not establish suitability for a high-power feeder: power and thermal limits require a separate check.
SMA and SMB: Workhorses for RF and Laboratory Use
SMA provides a secure threaded interface for general RF and microwave work, while SMB offers convenient snap-on connection in compact equipment. Their coupling and bandwidth characteristics suit different service and measurement requirements [1, 2].
SMA applications and frequency limits
SMA is a 50 Ω interface commonly specified to 18 GHz. HUBER+SUHNER lists extended versions to 26.5 GHz, while Amphenol RF lists selected extended-range designs to 34 GHz. These are manufacturer-specific capabilities and do not increase the rating of an ordinary SMA connector or cable assembly [1, 2].
- RF front ends, phase-locked loop and voltage-controlled oscillator outputs, filters and attenuators.
- Antenna connections in wireless and microwave equipment, with the correct standard or reverse-polarity interface.
- Laboratory cable connections to signal sources, spectrum analysers and network analysers where the instrument port and connector rating are suitable.
SMA, RP-SMA and precision instrument interfaces
RP-SMA reverses the centre-contact configuration while retaining the threaded interface arrangement. Check both the coupling geometry and the centre pin or socket: identifying a connector from its thread alone can lead to the wrong mating part [2].
SMA, precision 3.5 mm and 2.92 mm interfaces must not be treated as identical measurement connectors. Although compatible mating arrangements exist, connector condition and dimensional compliance matter. Keysight warns that a poor-quality or damaged SMA connector can damage a precision 3.5 mm interface. Inspect connectors and use the instrument manufacturer’s approved mating practice [6].
SMB for quick connection
SMB uses snap-on coupling and is useful where compact packaging and quick connection are priorities. Conventional family guidance is DC to 4 GHz. Select the correct 50 Ω or 75 Ω version, and verify retention and environmental requirements rather than assuming that its electrical performance or mechanical security is equivalent to SMA [1, 3].
BNC and TNC: User-Friendly Test and Field Connectors
BNC and TNC serve general RF, instrumentation and communication applications. BNC emphasises convenient bayonet coupling; TNC uses a threaded interface that better controls the mated geometry under mechanical loading [1].
BNC for bench, rack and video connections
BNC, or Bayonet Neill-Concelman, is available in 50 Ω and 75 Ω versions. Its quarter-turn bayonet coupling is convenient for patching instruments and racks. Conventional products are available to a few GHz, but the rating must be checked for the selected impedance version, cable and application [1, 3].
Use 50 Ω products for a 50 Ω RF or measurement path and suitable 75 Ω products for a 75 Ω video or broadcast path. Do not infer broadband video suitability from the connector’s appearance or from a generic BNC frequency figure.
TNC for secure threaded coupling
TNC, or Threaded Neill-Concelman, uses threaded coupling in place of the BNC bayonet. The cited conventional family supports operation to 11 GHz, with improved control of interface dimensions and suitability for higher vibration loads. Select a qualified sealed configuration where outdoor exposure is required [1].
Some TNC products use 75 Ω impedance. Their frequency and interface specifications must be checked separately; the common 50 Ω microwave rating must not be applied automatically [3].
Type N, 7/16 DIN and UHF: High-Power and Infrastructure Connections
Type N and 7/16 DIN are established choices for mechanically robust RF connections and antenna feeders. UHF connectors remain relevant to legacy HF/VHF equipment, but they are not equivalent to a controlled-impedance microwave interface [1, 3, 5].
Type N
Type N uses threaded coupling and is available in 50 Ω and 75 Ω versions. Selected 50 Ω products operate to 18 GHz, depending on the connector and cable. This capability must not be generalised to 75 Ω versions, which have separate specifications and interface requirements [1, 3].
Applications include RF test equipment, radar, microwave links and antenna feeders. For outdoor use, confirm the actual sealing arrangement and installation instructions, including the panel and cable entry. For transmitter service, compare the complete connector and cable assembly’s RF power rating at the operating conditions.
7/16 DIN
7/16 DIN is a rugged 50 Ω threaded interface used for medium- and high-power RF and low-PIM infrastructure. The cited families operate to 7.5 GHz. Its mechanical size and contact design make it a candidate for demanding feeder connections, but installation torque, cable preparation and environmental sealing remain essential [1, 5].
Do not interpret a low-frequency kilowatt rating as an allowable power across the complete frequency band. Compare the supplier’s operating conditions with the intended continuous-wave or pulsed service, and apply the limits of the cable, connector pair and termination together.
UHF: PL-259 and SO-239
UHF connectors have undefined rather than controlled constant impedance. They remain useful for mechanically robust connections in amateur radio and legacy HF/VHF equipment. HUBER+SUHNER specifies its UHF family for applications to 200 MHz; the historical name does not imply suitability throughout the modern UHF frequency band [1].
For a new broadband or microwave design, select a defined-impedance family with verified return loss over the required band. Retain UHF where compatibility with an existing installation is the governing requirement and the resulting electrical performance is acceptable.
Low-PIM alternatives: 4.3-10 and NEX10
Infrastructure selection should also consider 4.3-10 and NEX10 where size, installation access and passive intermodulation are important. These interfaces separate electrical contact functions from mechanical coupling functions and provide alternatives to larger feeder connectors. They are different interfaces, not interchangeable substitutes for Type N or 7/16 DIN [1].
Passive intermodulation, or PIM, is unwanted signal generation caused by nonlinear behaviour in passive transmission elements. In multi-carrier systems, compare the specified PIM test conditions and the assembled connection’s performance, not only insertion loss and VSWR. Include the mating connector, adapters and cable termination in the assessment [1, 3, 5].
50 Ω vs 75 Ω: Matching Impedance to the Application
The correct impedance is primarily a system requirement, not a connector preference. Use the impedance expected by the source, load and transmission line, and maintain it through connectors, adapters and measurement equipment [3].
- 50 Ω is widely used in RF transmitters, microwave circuits and general RF test equipment. Typical connector choices include SMA, SMP and suitable 50 Ω versions of BNC, TNC and Type N.
- 75 Ω is widely used in broadcast, video and cable television. Select the appropriate 75 Ω connector version and verify its bandwidth for the actual signal format.
A 50 Ω component inserted into a 75 Ω path, or the reverse, creates a local impedance discontinuity. Its effect depends on frequency, electrical length and the surrounding network. A short mismatch may be tolerable in a particular low-frequency application, but it should not be accepted without checking the system’s return-loss, amplitude and timing requirements.
Do not confuse characteristic impedance with DC contact resistance. A continuity test can identify an open circuit or short circuit, but it cannot demonstrate broadband impedance matching [3].
Practical Selection Guidelines for Designers
Treat the connector, PCB launch, cable and mating interface as one interconnect. Start with the electrical requirements, then qualify the mechanical arrangement, assembly process and sourcing route.
Define impedance and system topology
Decide whether the signal path is 50 Ω or 75 Ω and identify every interface between the source and load. Record connector family, contact configuration, adapters and terminations. Check instrument-port impedance before planning measurements.
Set frequency and power targets
Use the complete operating band and RF power conditions to narrow candidates. SMA may suit a compact microwave signal path, while Type N or 7/16 DIN may be more appropriate for a higher-power feeder. Neither selection is complete until the exact part and cable assembly meet the requirements [1, 2, 5].
Consider environment, servicing and mating cycles
Compare access, required tools, cable support, vibration, temperature and exposure to moisture or contaminants. For repeated patching, check both durability and serviceability. For blind mating, use a system designed for the permitted alignment tolerances rather than expecting an ordinary snap-on cable connector to compensate for board misalignment [1, 4].
Integrate the PCB and mechanical design
Match the selected connector to the board stack-up and mounting arrangement. Review the signal pad, ground return, ground-via placement, board edge, solder volume and panel support. A poorly implemented transition can negate the benefit of a high-performance connector.
Use the manufacturer’s recommended layout as the starting point, then validate the actual board and assembly. The connector’s interface rating is not a guarantee that an arbitrary PCB footprint will achieve the same bandwidth.
Inspect and mate correctly
Inspect contact surfaces, threads and centre contacts before mating, especially when connecting to precision instruments. Reject damaged or contaminated connectors. Follow the applicable cleaning, gauging and torque instructions, and avoid transferring twisting or bending loads into the connector body or PCB [6].
Do not use one universal SMA torque value. The required torque can depend on connector material and the mating arrangement. Follow the selected connector and instrument documentation, using suitable tooling where specified [2, 6].
Design and purchasing checklist
The following checklist translates the selection into verifiable specifications for engineering approval and purchasing.
- Interface: family, impedance, plug or jack configuration, centre pin or socket, standard or reverse polarity, and mating drawing.
- RF performance: operating band, maximum insertion loss, minimum return loss or maximum VSWR, shielding requirements and availability of suitable measurement data.
- Power: average and peak operating conditions, RF power versus frequency and temperature, continuous voltage, and the separate dielectric withstand requirement.
- Mechanical fit: board thickness, mounting style, panel cut-out, cable compatibility, bend clearance, strain relief, retention and mating cycles.
- Environment: temperature range, vibration and shock requirements, corrosion exposure, and sealing of the interface, panel and cable entry in the required condition.
- Qualification and safety: required application approvals, documented test methods, material declarations and installation precautions. Do not treat an RF connector’s dielectric withstand figure as approval for a hazardous-voltage application.
- Catalogue versus custom: prefer a documented catalogue part where it meets the requirements. For a custom launch, cable assembly or mechanical variant, agree the drawing, performance limits, qualification evidence, inspection method and change-control requirements before release.
- Supply chain: verify the manufacturer’s part number, approved mating part, tooling, traceability and replacement availability. A visually similar substitute requires engineering review.
Validate with measurement
Characterise critical interfaces over the required band using a vector network analyser and an appropriate calibration and fixture strategy. Examine input and output match and forward transmission for the assembled path. Define whether the result includes the cable and PCB launch or whether those contributions have been removed from the measurement.
Use consistent connector condition and mating practice so that repeated measurements are meaningful. For low-PIM infrastructure, verify the specified intermodulation requirement as a separate acceptance criterion; a satisfactory small-signal transmission measurement alone does not establish low-PIM performance [3, 5, 6].
Conclusion
Select RF connectors as part of a complete controlled-impedance path. MCX and MMCX suit compact multi-GHz connections; SMP addresses dense microwave and blind-mate systems; SMA and SMB cover different threaded and quick-connect needs; BNC and TNC offer practical test and communication interfaces; and Type N, 7/16 DIN and compact low-PIM alternatives serve demanding feeder applications.
The family narrows the options, but the approved part number, mating interface, cable termination, PCB launch and operating conditions determine whether the design is suitable. Complete the selection with assembly-level electrical and environmental validation.
FAQ
These answers address common compatibility, bandwidth and qualification questions when selecting RF interconnects.
Start with system impedance, operating frequency and RF power, then check size, cable compatibility, mounting and environment. Select the exact part rather than relying on a family name. Confirm the mating interface and installation requirements, and validate the complete connector, cable and PCB transition over the required operating band.
Use the impedance required by the system throughout the signal path. Mixing 50 Ω and 75 Ω components creates a discontinuity that can cause reflections and measurement error. Mechanical compatibility also needs verification. A tolerable mismatch in one low-frequency installation does not establish suitability for a broadband RF or video application.
RP-SMA reverses the centre-contact configuration while retaining the threaded interface arrangement. Check the centre pin or socket as well as the external coupling geometry when identifying a mating part. Do not order from the thread appearance alone. Both the connector drawing and the equipment documentation should identify the required interface.
Do not assume millimetre-wave capability from their miniature size. The conventional MCX and MMCX families discussed here are specified to 6 GHz. SMP products support higher microwave frequencies, including operation to 40 GHz in the cited family. Always verify the exact connector, cable termination and board transition for the intended frequency band.
Type N and 7/16 DIN are candidates, while compact low-PIM interfaces may suit infrastructure with tighter space constraints. Confirm RF power at the actual frequency and temperature, then check cable limits, sealing and installation instructions. A large body or threaded coupling alone does not establish power capability, waterproofing or application qualification.
How to Select and Validate an RF Connector
Use this procedure to move from system requirements to an approved interconnect specification.
Select an RF connector by qualifying the complete electrical and mechanical interconnect.
- Define the electrical requirements
Record system impedance, operating band, average and peak RF power, and acceptable insertion loss and return loss. Identify the source, load, cable and measurement interfaces.
- Select the exact interface and part
Choose a connector family and documented part number. Confirm impedance, contact configuration, cable compatibility and mating dimensions. Check whether the equipment requires standard or reverse-polarity contacts.
- Check mechanical and environmental suitability
Verify mounting, board stack-up, cable routing, strain relief, mating access and durability. Confirm temperature, vibration, corrosion and sealing requirements for the complete installed assembly.
- Build and inspect the interconnect
Implement the recommended cable termination and PCB launch. Inspect contacts and mating surfaces, reject damaged parts, and follow the applicable assembly, cleaning and torque instructions.
- Measure and release the approved configuration
Measure the assembled path over the required band using an appropriate calibration and fixture strategy. Check power and environmental evidence, and PIM where required. Release the approved part numbers, drawings and acceptance criteria.
Further Reading
These related articles provide background on connector construction, PCB transitions, cable behaviour and RF measurement data.
- What is RF Connector — an introduction to coaxial connector construction and the functions of the centre conductor, dielectric and shield.
- Coaxial Connectors and How to Connect with PCB — a more detailed discussion of connector launches, grounding and PCB transition design.
- Samtec Explains Low-Loss Coaxial Cable Construction — an example of how cable construction affects flexibility, loss and phase stability.
- What Filter S-Parameters Are Good For — an explanation of reflection and transmission data used to assess RF signal paths.
References
The following manufacturer resources support the family characteristics and installation guidance cited in this article. Individual product drawings and datasheets take precedence over general family summaries.
- HUBER+SUHNER, Coaxial Connectors Overview, HUBER+SUHNER, undated online resource, accessed 2026.
- Amphenol RF, SMA RF Coaxial Connectors, Amphenol RF, undated online resource, accessed 2026.
- Amphenol RF, Glossary of Terms, Amphenol RF, undated online resource, accessed 2026.
- Amphenol RF, MMCX Connectors, Amphenol RF, undated online resource, accessed 2026.
- Amphenol RF, 7-16 Connectors, Amphenol RF, undated online resource, accessed 2026.
- Keysight Technologies, 3.5 mm Precision Connectors, FlexDCA User Guide, Keysight Technologies, undated online resource, accessed 2026.
Latest technical review and revision: 3 November 2026. Connector-family guidance, compatibility precautions, selection checks and references reviewed.
