A coax drawing can be electrically ambiguous even when it looks complete. "100 mm coax with SMA" does not tell production whether the path is 50 ohm or 75 ohm, what length tolerance controls phase, how the braid is terminated, or whether a high-impedance defect is caught before shipment. The result is not a bad-looking cable. It is a cable that passes continuity and still fails the product.
For Cable Assembly (hub) work that carries antenna, camera, sensor, GNSS, RF, or video signals, the cable type is only the first line of the specification. The drawing also has to define impedance, connector interface, finished length, bend envelope, strip geometry, and the electrical test that maps to the actual failure mode.
Start with impedance and signal path
Coaxial cable selection starts with impedance, not connector shape. Most antenna, cellular, GNSS, Wi-Fi, instrument, and industrial RF paths use 50 ohm coax. Broadcast video, SDI, CCTV, and broadband distribution commonly use 75 ohm coax. The mistake is treating those as procurement alternates because the jacket diameter looks close or because a BNC shell can exist in both impedance families.
When we quote Coaxial Cable Assemblies, the first engineering pass checks four lines: nominal impedance, operating frequency, maximum allowed insertion loss or VSWR, and the mating interface on the product. If any of those are missing, a supplier can build something physically mateable and electrically wrong. A 50 ohm RG-316 SMA jumper and a 75 ohm RG-6 BNC lead are both coax assemblies; they should never be treated as the same sourcing category.
Frequency also changes the acceptable production window. A 300 mm service lead below 500 MHz can tolerate more geometry variation than a 100 mm micro-coax jumper carrying a multi-gigabit camera link. That does not mean every drawing needs a full RF test plan. It means the drawing has to say what matters: continuity only, impedance-controlled build, insertion-loss limit at a stated frequency, or a customer-defined VSWR gate.
Common coax types and where they fit
The familiar cable names are useful only when they are tied to the rest of the build. RG-58 is a common 50 ohm choice for general RF service leads where the enclosure can accept a larger bend envelope than micro-coax. RG-174 is also 50 ohm, but smaller and more flexible, which makes it attractive inside compact instruments and antenna pigtails. RG-316 is 50 ohm and commonly specified where PTFE insulation and temperature stability matter more than lowest material cost. RG-6 is a 75 ohm family used for video and broadband-style paths.
Micro-coax changes the handling model. 1.13 mm and 1.37 mm coax can fit camera modules, thermal imagers, small antennas, and board-to-board RF jumpers, but the strip length and connector latch are less forgiving than on RG-58. Pulling on the cable to unmate a U.FL or MHF-style connector can damage the cable exit even when the electrical path still passes a quick continuity check.
For RF Cable Assemblies, we prefer to quote a matched set instead of a cable family alone: RG-316 with SMA, RG-174 with MMCX, 1.13 mm micro-coax with U.FL or I-PEX MHF, or FAKRA keyed coax for vehicle modules. The connector, cable diameter, dielectric, braid termination, and boot or strain relief have to be compatible. If the drawing calls out only "coax cable, 200 mm," the purchasing team has not given production enough information to control RF performance.
The drawing fields that prevent rework
A production-ready coax drawing should include the fields that are easy to miss during schematic-level design. First is cable family and impedance: for example, RG-316, 50 ohm, PTFE dielectric, or 1.13 mm micro-coax, 50 ohm. Second is finished length and tolerance. A 500 mm RG-316 jumper with +/-5 mm tolerance is a different build from a 100 mm micro-coax jumper with +/-2 mm tolerance, especially when cable routing or phase matching matters.
Third is connector detail. Write SMA, RP-SMA, BNC, TNC, MMCX, U.FL, MHF, or FAKRA with gender, polarity, key code, orientation, and mating connector if available. FAKRA Automotive Coaxial builds need the housing code because keying and color can prevent assembly mistakes at the vehicle module, but the inner coax termination still has to match the connector OEM strip table.
Fourth is termination process. The drawing should define whether the center conductor is crimped, soldered, or compression-terminated, and whether the braid is folded back under a ferrule, soldered to a shell, or captured by a clamp. For workmanship language, IPC/WHMA-A-620 gives the harness acceptance framework, while RF-specific dimensions still come from the connector and cable OEM datasheets. If the cable itself must meet a military coax family, cite MIL-DTL-17. If the assembly belongs in an appliance or industrial equipment file, UL 758 wire and cable recognition may also matter.
Shielding, jacket, and environment are not cosmetic
Shield choice is a performance and manufacturability decision. A single braid may be acceptable for a short internal RF jumper. A foil-plus-braid construction can improve shielding but changes strip preparation and bend behavior. A double-braid low-loss cable can reduce leakage and improve durability, but it also increases diameter, bend radius, and connector mass. Those tradeoffs belong on the drawing before the first pilot lot, not in a corrective-action report.
Jacket material matters the same way. PVC is common for general indoor leads. FEP or PTFE jackets are used when the assembly sees heat, chemical exposure, or tighter dielectric stability requirements. Outdoor and mobile equipment may need UV resistance, sealing, or a booted exit so vibration does not concentrate stress at the ferrule. The cable can meet the nominal 50 ohm requirement and still fail early if the jacket cracks, the bend radius is violated, or the shield termination becomes the flex point.
Packaging is part of the spec for small coax. Micro-coax assemblies should ship with connector protection and bend control because a 1.13 mm cable can be damaged by the same handling that would not affect RG-58. For pilot lots, we often define tray orientation or bag quantity so operators and incoming inspectors do not turn the cable exit into the highest-risk feature before installation.
How VeinWire handles this in production
We treat coax as a controlled signal assembly, not as continuity-only wire work. The first gate is DFM: impedance, cable family, connector family, length tolerance, bend radius, jacket material, shielding, and packaging are checked before quote release. If the RFQ omits impedance or test frequency, engineering stops the quote and asks for the missing line because a price based on assumptions is not a production plan.
On the floor, operators build from a strip chart tied to the connector OEM datasheet. Center conductor exposure, dielectric face, braid foldback, ferrule position, and jacket support are inspected before crimp release. For continuity and shorts, we use Cirris 1000H fixtures where the geometry supports fixturing. For RF-sensitive builds, the customer drawing defines the insertion-loss or VSWR threshold and test frequency; a 500 MHz antenna lead and a 6 GHz sensor jumper should not share the same acceptance limit by habit.
Lot control follows the risk profile. A prototype lot may receive 100% visual inspection and 100% continuity testing. A mature build can move cosmetic inspection to AQL 1.0 after first-article approval, while critical dimensions and electrical checks stay at the level required by the drawing. That is the same discipline behind our Testing & Inspection process: the test has to match the failure mode, not just produce a pass label.
Case in production: A Brazil Industrial Automation program (2022-Q4 → 2023-Q1) — A Brazilian industrial automation distributor required custom cable assemblies for their top-tier clients' motion control systems.
Challenge: The customer needed rapid technical validation and alternative component sourcing for initial small-to-medium batch orders (100-120 units) without prior manufacturing history with the vendor.
What we did: The engineering team reviewed the customer's specifications, proposed equivalent connectors and terminals with detailed datasheets, and offered sample testing before mass production, committing to a 2-3 week lead time after payment confirmation.
Result: Successfully secured the first multi-PO program and established a foundation for repeat business, transitioning the customer from inquiry to mass production within 3 weeks.
Concrete numbers: 100-120 unit batches, 2-3 weeks lead time after payment, 5 connector/housing variants per assembly
When to contact us
Bring VeinWire in before connector freeze if the assembly mixes 50 ohm and 75 ohm paths, uses 1.13 mm or AWG#40 micro-coax, needs FAKRA keying, or has a customer-defined RF acceptance limit. We are also a fit when a 5-50 unit pilot must scale into 500-5000 assemblies without changing the cable family after qualification.
Have a drawing or BOM? Submit it at /contact — engineering walks every drawing within 4 business hours.
