Published on 10/13/2026
A U.FL connector, an MHF I interface often sold as "IPEX1," and MHF4 are not three universal names for the same miniature RF connection. MHF4 is a smaller low-profile interface and should not be forced onto a U.FL or MHF I receptacle. Identify the exact module receptacle and approved mating plug before ordering a cable.
The connector on a wireless module is tiny enough that a catalog photo can look convincing and still be wrong. A misaligned plug can damage the shell or PCB pad, while the wrong cable route can turn a successful first connection into a field failure.
This guide uses the familiar search terms IPEX1, IPEX4 and ufl antenna cable while keeping exact interfaces and product variants separate. Published dimensions and ratings below are reference-family data, not universal assembly guarantees. SigmaRF can match an agreed module interface and external connector in a controlled pigtail drawing.
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"IPEX" is frequently used in reseller descriptions as shorthand, but a shorthand label is not a mating drawing. IPEX1 commonly points to an MHF I-style miniature interface; IPEX4 or MHF4 points to a different lower-profile interface. Use the module BOM or mechanical drawing, not numbering inferred from appearance.
| Search/catalog term | What to verify | Safe procurement rule |
|---|---|---|
| U.FL / UFL | Exact U.FL series plug/receptacle and variant | Use the approved mating part numbers |
| IPEX1 | Whether the intended part is MHF I and which variant | Treat shorthand as a lead, not proof |
| IPEX4 / MHF4 | Exact MHF4 plug/receptacle and cable diameter | Do not substitute U.FL/MHF I |
| MHF4L | Approved intermateability and exact drawing | Not every similarly named miniature interface is interchangeable |
Some suppliers describe U.FL and MHF I as compatible, but a new procurement drawing should not rely on a blanket cross-brand claim. Obtain confirmation for the exact mating pair, tolerances and qualification required. MHF4's published compatibility with MHF4L is specific, not permission to mate every small snap connector.
Key idea: The module receptacle part number is the starting point. The cable supplier should confirm the exact plug, cable and mated envelope against it.
| Reference interface | Published mated-height information | Cable / band notes |
|---|---|---|
| U.FL family | Nominal 1.9 to 2.4 mm depending on plug; maxima vary | Published variants reach different bands, including newer 18 GHz harness variants |
| MHF I reference | 2.5 or 3.0 mm maximum depending on plug | Cable O.D. choices include 0.81 to 2.0 mm; current family page states up to 9 GHz |
| MHF4 reference | 1.2 mm maximum | Standard plug example: 0.81 mm cable; current page states up to 9 GHz |
A 1.2 mm mated height is not enough to design the route. Include the cable exit, bend clearance, enclosure lid and any retention or service access. Smaller cable can increase loss and reduce mechanical margin; verify its exact construction and length rather than selecting only the lowest connector height.
Do not repeat an old generic "U.FL is 6 GHz" statement as a current universal limit. The family catalog includes different plugs and harnesses with different frequency performance, including newer 18 GHz variants. Likewise, a current MHF4 family page listing 9 GHz does not guarantee every purchased pigtail at that band.
⚠️ Family-level frequency headlines do not replace the actual harness specification. State the operating band, cable part and assembly VSWR/insertion-loss limits.
Align the intended mating pair and use the manufacturer's recommended insertion/extraction method and tooling. Do not press a mismatched plug into place, pry against the PCB or pull on the coax to detach a plug. The connector and cable exit need a protected route.
These interfaces are not ordinary bench connectors for repeated casual reconnection. Family pages can mix cable plugs, test adapters and high-cycle accessories in broad filters. Select the exact part's mating-cycle and handling instructions instead of copying the highest cycle count shown anywhere on the page.
Installation checks
Choose the miniature interface required by the module, then design the opposite connector and cable route around it. You usually cannot choose MHF4 purely to save height when the PCB already has a different receptacle.
Wi-Fi modulesCellular modulesGNSS receiversCompact antenna pigtails
Correct fixed module interface
Build the pigtail to the module's approved receptacle and use a suitable external connector and strain-relieved route.
Wrong shortcut
Select by photo, call all interfaces U.FL, or force an IPEX4/MHF4 plug onto a larger miniature receptacle.
At the external end, standard SMA and RP-SMA are also different mating arrangements. Specify polarity and contact details explicitly, plus bulkhead hardware and clocking when applicable. SigmaRF's Wi-Fi module connection guide and RP-SMA to MHF4 pigtail article cover those application-specific choices.
Specify the complete RF assembly
Send the frequency band, connector interfaces, finished length and routing drawing. SigmaRF can match the cable and terminations to your application.
Step 01
Recover the module evidence
Provide module make/part, receptacle part number, board drawing or approved BOM. A clear photograph can help locate the interface, but should not replace the final mating-part confirmation.
Step 02
Specify the cable and opposite end
Define the miniature plug variant, approved cable diameter and construction, opposite connector, polarity and mounting style. Give finished length in mm, tolerance, datums and any angle/clocking.
Step 03
Define the RF and handling limits
State band, VSWR and insertion loss, environment, routing and retention. Agree fixtures and reference planes, and distinguish production RF test from any mechanical-cycle qualification.
SigmaRF VNA-sweeps every assembly for VSWR and insertion loss before shipment. Its overall RF assembly capability spans 100 MHz to 40 GHz across suitable cable and connector systems, not every product discussed here. Volume work is supported in Vadodara, India, with precision work in the Cleveland area, USA. Lead times can be as short as 2 days for suitable builds, subject to parts, quantity and the agreed specification.
SigmaRF's company-wide 40 GHz capability does not make a U.FL or MHF4 pigtail a 40 GHz product. Use the exact harness rating. The RF assembly design and VNA measurement guides explain the broader mechanical and measurement decisions.
Assume a 150 mm module pigtail at its operating frequency. For this example only, assume cable attenuation of 2.0 dB/m and a combined connector allowance of 0.15 dB. Neither value is a U.FL/MHF4 family rating or a SigmaRF measurement.
Cable contribution = 2.0 x 0.150 = 0.300 dB
Estimated matched-path loss = 0.300 + 0.150 = 0.450 dB
Matched power ratio = 10^(-0.450/10) = 0.902, about 90.2%
If cable length becomes 0.300 m: estimated loss = 0.600 + 0.150 = 0.750 dB
A longer service loop has an RF cost even if it makes installation easier. Obtain the actual cable attenuation and assembled test limits, then verify the routed prototype. The hypothetical calculation shows the decision method, not promised performance.
Avoid these interface errors
Is U.FL the same as MHF4?
No. MHF4 is a different lower-profile interface. Identify the module receptacle and approved mating plug; do not force a MHF4 plug onto a U.FL or MHF I receptacle.
What does IPEX1 mean?
It is commonly used in reseller shorthand for an MHF I-style interface. Treat it as a search lead and confirm the exact plug and receptacle drawing before procurement.
What is the MHF4 mated height?
The current reference family page lists 1.2 mm maximum. Check the exact harness drawing, cable exit, lid clearance and any approved related variants.
Is U.FL limited to 6 GHz?
Not as a universal family statement. Current catalogs include multiple variants and newer harness types with higher bands. Use the selected harness specification and assembly acceptance band.
Can I use RG178 with every U.FL or MHF4 plug?
No. Each plug has approved cable dimensions and construction. A connector family name does not permit arbitrary cable substitution.
Can SigmaRF make a custom UFL antenna cable?
Provide the exact module receptacle, approved plug, cable, opposite connector and polarity, finished length, band and routing requirements. SigmaRF can confirm the build and test specification.
Tiny RF interfaces demand exact identification. U.FL, IPEX1 and IPEX4/MHF4 labels are useful search terms, but a correct mating drawing is what protects the module and the user's time.
Confirm the approved pair, protect the route and test the completed harness. That makes a miniature antenna connection repeatable instead of a photo-based guess.
Build an RF assembly around the real requirements
Send the frequency band, connector interfaces, finished length and routing drawing. SigmaRF can match the cable and terminations to your application.