SMA vs SuperSMA vs 2.92 mm: Are They Mechanically Compatible?

SMA, SuperSMA, and 2.92 mm connectors look very similar, but they are designed for different frequency ranges and performance levels.

The key question for engineers is:

Can they physically mate with each other, and is it safe to do so?

Quick Answer

• SuperSMA and SMA: mechanically compatible when built to the same MIL-STD-348 SMA interface.

• 2.92 mm and SMA: mechanically compatible.

• 2.92 mm and SuperSMA: generally mechanically compatible through the SMA-style interface, but electrical performance depends on the lower-performance connector.

Southwest Microwave specifies its SuperSMA interface to MIL-STD-348 SMA Figures 310-1 and 310-2, while Keysight confirms that 2.92 mm connectors mechanically mate with SMA and 3.5 mm connectors.

SMA vs SuperSMA vs 2.92 mm

Southwest Microwave rates SuperSMA as mode-free through 27 GHz, while its 2.92 mm connector family is rated to 40 GHz.

Is SuperSMA Compatible With Standard SMA?

Yes, mechanically.

Southwest Microwave's SuperSMA uses what it describes as the basic PTFE dielectric SMA interface and conforms to MIL-STD-348 SMA interface dimensions.

The main difference is performance.

SuperSMA is designed with:

• Thicker outer conductor walls

• Improved mechanical durability

• Low VSWR

• Better repeatability

• Mode-free performance through 27 GHz

For example, Southwest Microwave specifies maximum VSWR of:

• 1.10:1 from DC to 18 GHz

• 1.15:1 from 18 to 27 GHz

for its SuperSMA series.

So a SuperSMA connector can often be used where a standard SMA interface is required, while providing better high-frequency performance.

Can a 2.92 mm Connector Mate With SMA?

Yes.

A 2.92 mm, also known as K connector, is mechanically compatible with SMA and 3.5 mm interfaces. Keysight specifically states that 2.92 mm connectors mate with both SMA and 3.5 mm connectors.

However, mechanical compatibility does not mean the connection will perform to 40 GHz.

If a 40 GHz 2.92 mm connector is mated with an 18 GHz SMA connector, the overall connection should be treated according to the lower-performance SMA interface.

Can SMA Damage a 2.92 mm Connector?

It can, especially if the SMA connector is low quality, worn, or dimensionally incorrect.

Keysight warns that excessive mating of low-quality SMA components to a 2.92 mm female connector may degrade the 2.92 mm receptacle.

Before mating SMA to precision 2.92 mm equipment, check:

• Center pin condition

• Pin depth

• Threads

• Connector cleanliness

• Mechanical damage

• Correct torque

For expensive test equipment, a connector saver or precision adapter is often a safer option.

Can SuperSMA Be Used Instead of 2.92 mm?

It depends on frequency.

If the system operates below approximately 27 GHz, SuperSMA may provide sufficient performance.

If the application requires operation around 30–40 GHz, 2.92 mm is normally the better choice.

Does Mechanical Compatibility Guarantee RF Performance?

No.

Even if two connectors physically mate, RF performance can still be limited by:

• VSWR

• Insertion loss

• Connector geometry

• Dielectric design

• Manufacturing tolerance

• PCB launch design

A 2.92 mm connector connected to a standard SMA interface will not automatically provide 40 GHz system performance.

The complete signal path must support the required frequency.

Which Connector Should You Choose?

Choose SMA for general RF and microwave systems where operation is mainly below 18 GHz.

Choose SuperSMA when you need:

• SMA mechanical compatibility

• Better durability

• Lower VSWR

• Reliable operation up to 27 GHz

Choose 2.92 mm when you need:

• Operation up to 40 GHz

• Test and measurement applications

• Millimeter-wave PCB launches

• Better high-frequency repeatability

Summary

SMA, SuperSMA and 2.92 mm connectors are closely related mechanically, but they are not electrically identical.

The simplest rule is:

• SMA: general-purpose microwave interface

• SuperSMA: higher-performance SMA interface up to 27 GHz

• 2.92 mm: precision interface up to 40 GHz

They may physically mate, but always design the system according to the lowest-frequency connector in the signal path.

Related Products

• Southwest Microwave SuperSMA Connectors

• Southwest Microwave 2.92 mm Connectors

• Southwest 212-511SF

• Southwest Microwave End-Launch Connectors