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RESOURCES
The tables worth parking in a second tab. Cross-references, attenuation figures, handling limits and the standards that hold real sway over these parts.
01 / Cross-reference
Ultra-miniature equivalents, rated straight.
Six trademarks, one nominal 2.0 mm footprint, and a pile of hopeful marketing copy. The rating column says what happened on our bench, whatever the datasheets promise. 0 shown.
| Interface | Owner | Mates with | Mated height | Rated to | Bench rating |
|---|---|---|---|---|---|
| U.FL | Hirose | MHF I, AMC, UMCC | 2.5 mm | 6 GHz | Fully interchangeable |
| MHF I | I-PEX | U.FL, AMC, UMCC | 2.5 mm | 6 GHz | Fully interchangeable |
| AMC | Amphenol | U.FL, MHF I | 2.5 mm | 6 GHz | Fully interchangeable |
| UMCC | Molex | U.FL, MHF I, AMC | 2.5 mm | 6 GHz | Fully interchangeable |
| W.FL | Hirose | MHF II | 2.0 mm | 6 GHz | Conditional — below 6 GHz |
| MHF II | I-PEX | W.FL | 2.0 mm | 6 GHz | Conditional — check retention |
| MHF III | I-PEX | HSC, some AMC4 | 1.6 mm | 9 GHz | Conditional — verify sample |
| MHF 4 | I-PEX | MHF 4 only | 1.2 mm | 15 GHz | Do not mix |
| MHF 4L | I-PEX | MHF 4L only | 1.2 mm | 15 GHz | Do not mix |
| HSC | Hirose | MHF III (partial) | 1.6 mm | 9 GHz | Do not mix with U.FL |
Ratings from mated samples, n = 10 per pairing · “Conditional” means mechanically compatible with a measurable penalty or a retention caveat.
02 / Bench references
Two tables worth committing to memory.
Cable attenuation (dB per metre)
| Cable | 1 GHz | 2.4 GHz | 5.8 GHz | 10 GHz |
|---|---|---|---|---|
| 0.81 mm | 2.0 | 3.1 | 5.0 | 6.9 |
| 1.13 mm | 1.4 | 2.2 | 3.6 | 4.9 |
| 1.37 mm | 1.1 | 1.8 | 2.9 | 4.0 |
| RG-178 | 1.1 | 1.7 | 2.8 | 3.9 |
| RG-316 | 0.7 | 1.1 | 1.9 | 2.7 |
Published figures, vendor-side. Thin coax gives up roughly three times the loss per meter that RG-316 does, which is the whole reason ultra-miniature runs stay short.
Torque & handling limits
| Interface | Torque | Mating cycles | Disconnect method |
|---|---|---|---|
| SMA | 0.6 N·m | ~500 | 8 mm torque wrench |
| RP-SMA | 0.6 N·m | ~500 | 8 mm torque wrench |
| MMCX | Snap-on | ~500 | Straight axial pull |
| MCX | Snap-on | ~500 | Straight axial pull |
| U.FL / MHF | Press fit | ~30 | Extraction tool only |
| SMP | Push-on | 100–1000 | Axial, no tool |
Nobody reads the mating-cycle column. It explains most of the ultra-miniature failures that land in our inbox.
03 / Standards
What holds sway over these parts.
Small RF interfaces live under a patchwork of formal standards and de facto vendor drawings. Telling the two apart settles arguments before they start.
MCX dimensions
The European spec pinning down MCX interface geometry. Why MCX from two different vendors mates without drama, where ultra-miniature parts go their own way.
RF connector series
The umbrella family covering RF connector specs by series, including whichever corners of this subject got formally standardized.
Interface dimensions
The standard fixing SMA and SMB interface dimensions. Your court of last resort when two SMA parts sit there refusing each other.
Assembly acceptability
Acceptance criteria for cable and harness assemblies. Class 3 is what people invoke for anything that must not fail in service.
U.FL, MHF, AMC, UMCC
Trademarks with proprietary drawings, standards in nobody's book. Will they work together? That’s a question of observed fact, which is precisely why the cross-reference above had to be built.
Coaxial cable
The cable-side standards behind RG designations. Micro-coax under roughly 1.4 mm sits outside them and answers to vendor drawings instead.
04 / Glossary
Terms people sling around loosely.
VSWR
Voltage standing wave ratio. How much signal bounces back off a joint rather than carrying on through it. 1.0 is perfect, 1.30 is a decent small connector.
Insertion loss
What you gave up by putting a part in the path, in dB. Climbs with frequency, and climbs quicker on thin coax.
Mated height
The whole stack from board surface to the top of the plug once it is home. This number decides if your enclosure lid shuts.
Reverse polarity
Same shell, center-contact gender swapped. A regulatory dodge with nothing electrical behind it. RP-SMA will not mate with SMA.
Blind mate
A connector that finds its own alignment as boards come together, shrugging off radial and angular offset. SMP is the one you meet.
Pigtail
A short run of coax wearing a different connector at each end. An assembly by any strict reading, and everyone calls it an adapter regardless.