RF connector choice sets a system’s usable frequency. SMA works to about 18 GHz, 3.5mm and 2.92mm to 26.5 and 40 GHz, 2.4mm to 50 GHz and 1.85mm to 67 GHz. SMA, 3.5mm and 2.92mm intimate, while 2.4mm and 1.85mm intimate, and choice also depends on power, repeatability and phase stability.
Pick the wrong connector and it quietly caps your system’s usable frequency, or worse, a careless mate cracks an expensive precision interface. Connectors look interchangeable at a glance, yet at millimetre-wave the small differences decide everything. Knowing the common RF connector types, what each one reaches and which ones mate safely is one of the cheapest ways to protect a high-frequency design.
A coaxial connector behaves cleanly only up to the frequency where unwanted modes start to appear, and that limit is tied to the interface diameter. Shrink the gap between inner and outer conductor and the mode-free band moves higher. That single idea explains the whole family tree: the tiny 1.85mm reaches 67 GHz precisely because it is small, while the roomy, rugged SMA tops out far lower. Choose a connector below your top frequency and the system will never perform to spec, whatever else you do.
For lower-frequency work, Type N, BNC and TNC still have their place on power, ruggedness and cost.
This is where hardware dies. SMA, 3.5mm and 2.92mm share a mating geometry, so they intimate safely with care. Separately, 2.4mm and 1.85mm intimate with each other. Force a 2.4mm onto a 2.92mm because the threads almost catch and you can permanently damage both. When in doubt, use a proper precision adapter rather than trusting the thread. These same interfaces run through the RF microwave passive components in a typical chain, so the rule follows you everywhere.
Beyond frequency, a few factors decide the part:
A connector is only as good as the assembly behind it. Termination quality, cable choice and torque all shape the result, and a grit-contaminated interface degrades fast. Phase-stable Teledyne Storm Microwave cable assemblies pair the right connector with the right cable so the whole path holds performance. Treat torque wrenches, gauges and clean caps as part of the design, not accessories.
At these frequencies, part quality and traceability are not optional. Authorised parts come with the tolerances and paperwork your qualification needs, and a custom assembly built to your band, length and phase target saves a lot of debugging later. As an AS9120B-certified distributor, we match connectors and assemblies to the job rather than the nearest catalogue number.
Building a high-frequency or millimetre-wave system? Talk to the Emerges team about RF connectors and phase-stable cable assemblies matched to your band, power and package.
Are SMA and 3.5mm connectors compatible?
Yes. SMA, 3.5mm and 2.92mm share a mating interface and intimate with care, though you only get performance up to the lowest-rated part in the pair.
What is the difference between 2.92mm and 2.4mm connectors?
2.92mm reaches 40 GHz and mates with SMA and 3.5mm. 2.4mm reaches 50 GHz and mates only with 1.85mm. The two must not be cross-mated.
Which connector is best for test and measurement?
A precision air interface such as 3.5mm, 2.92mm or 2.4mm, chosen for repeatability and the frequency range of your instrument.
What is a phase-stable RF cable assembly?
A cable and connector set built to hold electrical phase as the cable flexes or moves, which keeps measurements and array feeds accurate.