RF Connector Frequency Limits: SMA, N, 2.92 mm
Connector choice is usually settled by two things: the highest frequency the assembly must carry, and the interfaces already present on the equipment. A connector rated below the operating frequency will still mate mechanically while quietly degrading the measurement or link, which is why the number matters more than the thread type.
Numbers below are typical limits cited by manufacturer datasheets and the common engineering references (Keysight, Rohde & Schwarz). Precision, standard and extended grades of the same family have very different limits — for example, precision N reaches up to 18 GHz while standard commercial N is typically rated 11 – 12 GHz. Treat these as engineering reference, not as the specification of any supplied component.
Two mating groups must be distinguished: SMA / 3.5 mm / 2.92 mm, and 2.4 mm / 1.85 mm. The two groups do not mate with each other. Inspect pin depth, condition and the manufacturer's instructions even within a compatible group; mechanical compatibility does not guarantee frequency performance.
Apply this reference
For an assembly inquiry covering cable loss, phase stability, power and installation conditions, continue with RF Cable & Connector Notes: Loss & Power.
At a glance
- ▹BNC ≈ 4 GHz, TNC ≈ 12 GHz: laboratory and lower-frequency RF.
- ▹SMA and N both reach ≈ 18 GHz in their precision grades; standard grades are lower.
- ▹3.5 mm reaches ≈ 26.5 GHz and mates with SMA with better tolerance; 2.92 mm (K) reaches ≈ 40 GHz and mates with 3.5 mm and SMA.
- ▹2.4 mm (typically 50 GHz) and 1.85 mm (typically 67 GHz, with selected designs at 70 GHz) are intermateable. Neither mates with 2.92 mm, 3.5 mm or SMA. The lower-rated component limits the assembly.
- ▹Connector limit is set by onset of higher-order modes and mechanical tolerances; precision series specify tighter tolerances and quote limits as typical, not absolute.
Reference table
| Connector | Typical upper limit | Mating / type notes |
|---|---|---|
| BNC | ≈ 4 GHz | Bayonet coupling. Common on laboratory instruments and lower-frequency RF. |
| TNC | ≈ 12 GHz | Threaded BNC variant, better vibration resistance. |
| SMA | ≈ 18 GHz (precision grade) | Screw coupling. Standard SMA parts are typically rated 18 GHz; precision/military grades support higher. Common on general-purpose RF and test equipment. |
| N type | ≈ 18 GHz (precision grade) | Precision N reaches up to 18 GHz. Standard commercial N is typically rated to 11 GHz or 12 GHz. Rugged screw coupling for field and higher-power use. |
| 3.5 mm | ≈ 26.5 GHz | Precision air-interface connector; mates with SMA mechanically but with better tolerances. |
| 2.92 mm (K) | ≈ 40 GHz | Designed to mate with 3.5 mm and SMA. Inspect cleanliness, pin depth and condition first: a damaged or out-of-tolerance SMA pin can harm a precision interface. |
| 2.4 mm | ≈ 50 GHz | Designed to mate with 1.85 mm. NOT mate-compatible with 2.92 mm / 3.5 mm / SMA; forcing incompatible interfaces can damage both parts. |
| 1.85 mm | ≈ 67 GHz; selected designs specify 70 GHz | Designed to mate with 2.4 mm, NOT with 2.92 mm / 3.5 mm / SMA. The connector, cable and instrument datasheets set the assembly rating; a 2.4 mm connection does not inherit a 1.85 mm rating. |
| 1.0 mm | ≈ 110 GHz | High-frequency measurement and link hardware. Used at the upper end of typical laboratory bands. |
Typical upper frequency limits for common RF connector types. Values are typical engineering reference points.
Frequently asked
Can I mate 2.92 mm with SMA?
These interfaces are designed to mate, but inspect pin depth, cleanliness and condition first. An out-of-tolerance SMA pin can damage a precision connector. A mechanically compatible SMA connection is not automatically rated for 40 GHz. The separate 2.4 mm / 1.85 mm group does not mate with SMA / 3.5 mm / 2.92 mm.
Can I mate 1.85 mm with 2.4 mm?
Yes, these precision interfaces are designed to be intermateable. Check the manufacturer's mating instructions and condition before connection. A 2.4 mm component commonly rated to 50 GHz still limits an assembly containing a higher-rated 1.85 mm connector.
Which connector should I use at 40 GHz?
2.92 mm (K) is the usual choice at 40 GHz, since it is rated to that frequency and mates with the SMA interfaces common on test equipment. Check the cable and instrument interfaces as well, because the weakest rated part in the chain sets the limit.
What actually limits a connector's upper frequency?
The onset of higher-order modes, together with the mechanical tolerances of the interface. As frequency rises, small dimensional errors and air gaps become electrically significant, which is why precision connector series specify tighter tolerances and quote limits as typical rather than absolute.
Related reference
Reference sources
Sources support the cited engineering concepts, not product availability or supplied-component ratings. Confirm the selected model's datasheet.
First published 2026-09-26; last updated 2026-10-19. Editorial update, not an engineering sign-off. Reference content only — no models or pricing, and not a statement of supplied-component specifications.