50 ohm Micro-Coaxial Cables - Micro Coaxial Cable factory-(FRS)

Micro coaxial cables, essential for transmitting high-frequency signals in tightly packed modern electronics, often rely on color coding for quick identification of connector shells (often ground) and center conductors during installation and repair. Unlike larger coaxial standards (like RG-6 for cable TV), micro coaxial color coding isn’t universally mandated by a single global body. However, distinct conventions and de facto standards have emerged, making understanding them crucial for engineers, technicians, and procurement specialists.

Common Standardized Color Schemes

1. ​50 Ohm Characteristic Impedance (Common Electronics & RF):
   • ​RG174 / M17/74-RG174 / UG-936: This extremely common micro coax frequently uses ​white for the outer jacket. The inner insulator surrounding the center conductor is often ​clear or translucent, and the center conductor itself is typically ​silver-plated copper (visible through the insulation). The connector shells are almost universally ​gold (or nickel) plated brass. Specific pin colors within the connector often follow signal assignment, not strictly coax identification.
   • ​RG178 / M17/78-RG178: This thinner alternative often features a ​silver-coated copper braid visible under a ​clear or blue outer jacket. The center conductor is commonly ​silver-plated copper clad steel (SPCCS) with a clear inner insulator. Connector shells remain gold/nickel plated.
   • ​RG316 / M17/116-RG316: This slightly thicker option may use ​white, blue, or black for the outer jacket. The center conductor is usually ​silver-plated copper, and the inner insulator is commonly ​semi-rigid PTFE (Teflon), often white. Connector shells are gold/nickel plated.
   ​Key Takeaway: For these standard military-spec (MIL) derived types (RG174/178/316), the outer jacket color (white being predominant for RG174, blue common for RG178/316) and the clear inner insulation revealing the center conductor are the most consistent visual identifiers. Connector shells are distinct but not color-coded per coax type.
2. ​75 Ohm Characteristic Impedance (Video Applications – e.g., Miniature Camera Links):
   • ​RG179: Used where impedance matching is critical for video signals, RG179 often employs a ​black outer jacket. The center conductor is frequently ​copper, and the inner insulator may be ​foamed or solid polyethylene, potentially ​colored white or black. Connector shells remain gold/nickel plated.
   • ​Non-Standard Color Use: Some manufacturers may produce RG174 in black specifically for 75-ohm video applications, distinguishing it from their standard 50-ohm white version. Always check specifications! Some vendors offer ​RG179 with a distinct blue jacket as well.
   ​Key Takeaway: Black jackets are very common for 75-ohm micro coax like RG179 used in video. However, overlap exists (e.g., RG174 can be 50Ω or 75Ω; RG316 often blue for 50Ω), making jacket color ​a guide, not a guarantee. Measurement or specification checking is vital.

The Prevalence of Non-Standard & Manufacturer-Specific Color Codes

Due to the lack of an overriding standard for micro coax colors themselves (beyond common MIL types) and the custom needs of complex assemblies, non-standard or bespoke color schemes are widespread:

1. ​Internal Wiring Harnesses: Manufacturers designing multi-cable harnesses (e.g., for laptops, medical sensors, drone cameras) often assign arbitrary but consistent colors to individual micro coax assemblies purely for internal traceability. A blue micro coax might carry one specific signal, yellow another, regardless of the underlying coax type (which might all be RG174). Documenting this within the harness drawing is paramount.
2. ​Connector Pin Insulation: The color of the plastic insulator around the crimp pin inside the connector (e.g., MMCX, MCX, SMPM) is almost always chosen to signify ​signal function or polarity within the specific device (e.g., red for +V, black for GND, green for data), rather than identifying the coax cable type itself. The coaxial cable attaches to this pin.
3. ​Manufacturer Branding/Identification: Some cable manufacturers use unique outer jacket colors (e.g., specific shades of blue, purple, red) as a brand identifier or to denote a proprietary cable construction, even if the electrical specs match a standard like RG316.
4. ​Strain Relief Boots: Colored flexible plastic strain relief boots covering the back of the connector are extremely common and useful for strain relief and identification. These are ​NOT a standard for the coax cable itself but are assigned by the harness designer or manufacturer. A red boot doesn’t mean “RG179”, it likely means “Signal Path A” or “Antenna 1” in that specific application.

Practical Implications and How to Handle Ambiguity

1. ​Never Assume by Color Alone: As shown, jacket color (e.g., white, black, blue) can be used across different cable types (50Ω vs 75Ω) and different manufacturers. Center conductor insulation colors vary significantly.
2. ​Prioritize Specifications and Markings:
   • ​Cable Markings: Look for text printed directly on the outer jacket (e.g., “RG174/U”, “RG316”, “50 OHM”, “75 OHM”, “M17/78-RG178”).
   • ​Manufacturer Datasheets: Always refer to the datasheet provided with the cable assembly or the raw cable for definitive identification, including impedance, attenuation, conductor material, and exact dimensions.
   • ​Harness Documentation: If part of a larger assembly, the wiring diagram or harness assembly drawing is the ​only definitive source for what each colored cable or colored strain relief boot signifies in that specific product.
   • ​Physical Measurement: If documentation is missing, carefully measuring the outer diameter (OD) can help distinguish (e.g., RG178 ~1.8mm vs RG174 ~2.6mm vs RG316 ~2.7mm), though color will not.
   • ​Electrical Testing: Using a Time-Domain Reflectometer (TDR) or network analyzer is the most accurate way to measure characteristic impedance if unknown.
3. ​Function Over Color: Focus on identifying the cable’s ​function within its application (e.g., “this is the main antenna feedline”, “this is the high-speed camera data link”). Its electrical specs (impedance, attenuation) are far more critical than its color.

Conclusion: Color is a Tool, Not a Rule

While recognizable patterns exist (e.g., common white RG174), color coding in micro coaxial cables serves primarily as an assembly aid and visual differentiation tool within harnesses or specific manufacturer lines, not as a universally reliable, stand-alone identifier of the cable’s intrinsic electrical specifications (like impedance). The jacket color and center conductor visibility (clear insulation) provide clues, especially for common MIL-derived 50Ω cables. However, ambiguity is high, especially distinguishing 50Ω vs 75Ω or identifying custom variants. Success hinges on combining visual observation with rigorous reference to cable markings, manufacturer specifications, assembly documentation, and appropriate testing. When in doubt, always ​consult the documentation or perform electrical measurements.

Choosing the right cables for your robotics project might seem minor, but it’s critical for performance, reliability, and avoiding frustrating glitches. Micro coaxial cables – those tiny, shielded wires often used for video, data, and high-frequency signals – require careful selection. Here’s a practical guide focusing on the key factors:

1. Signal Requirements: Know Your Data

• ​Frequency & Bandwidth: What signals are you carrying? (e.g., high-resolution camera feeds from FPV drones, encoder signals in robot arms, USB 3.0 data in mobile manipulators). Higher frequencies demand cables with better shielding and lower signal loss (attenuation). Match the cable’s rated bandwidth to your signal’s needs with headroom.
• ​Impedance: Critical! Most digital video (like MIPI CSI-2 common in robotics cameras) and high-speed data require ​50-ohm or 75-ohm cables. Mismatched impedance causes signal reflections, data errors, and distorted images. Check your sensor/controller specs and match the cable precisely.
• ​Signal Integrity Needs: For very sensitive analog signals or extremely high-speed digital signals requiring low ​jitter (timing variations), look for cables with lower attenuation specifications and high-quality dielectric insulation.

2. The Rigors of Robotics: Mechanical Demands

• ​Flexibility & Bend Radius: Robots move. Arms articulate, joints rotate, mechanisms traverse. Choose cables specifically rated for ​high-flex or ​continuous flex applications. Look for ​low minimum bend radius specs – a cable that bends too sharply will fail quickly. Avoid stiff cables designed only for static installations.
• ​Cyclic Flex Life: This is how many bend cycles the cable can endure before failure. Robotics involves constant movement. Select cables with a ​high cyclic life rating (e.g., 5 million+ cycles). Ask manufacturers for robotics-specific ratings.
• ​Torsion (Twisting): Many robot joints involve twisting motions. Ensure cables are rated for ​torsional flexibility if this applies (e.g., robot wrists, rotary joints).
• ​Strength & Durability: Can it handle routing friction, minor snags, or occasional tension? Consider ​cable jacketing material (Abrasion-resistant like PUR vs. more flexible PVC). Look for ​tinned copper braid shielding for better durability than aluminum foil-only shields during flexing. ​Strain relief on connectors is also essential.

3. Space & Weight: Every Millimeter Counts

• ​Size (OD – Outer Diameter): Micro coax comes in various tiny sizes (0.81mm, 1.13mm, 1.32mm, 1.37mm are common). Measure your routing paths precisely. Smaller diameters are lighter and fit tighter spaces within robot limbs or small drones, but balance this against the required durability and signal performance. Weight reduction is crucial in flying or agile robots.
• ​Jacket Material: Thinner jackets save size/weight but may offer less protection. Material choice impacts flexibility too (PTFE/Teflon jackets are excellent performers but costlier).

4. Electrical Noise: Shielding is Paramount

• ​Electromagnetic Interference (EMI): Robots pack motors (brushed DC are noisy!), drives, processors, and wireless comms – all generating electrical noise. Poor shielding leads to signal corruption (snow on video, data drops).
• ​Shielding Effectiveness: Opt for cables with ​high-coverage braided shielding (95%+) or ​braid + foil combinations. This ensures good EMI protection in noisy robot environments. Aluminum foil shields alone are fragile during flexing.

5. Connectors: The Critical Link

• ​Micro-Coax Connectors: Tiny coaxial signals require tiny connectors (e.g., Hirose U.FL / I-PEX MHF, JAE MX39/49, Molex SlimStack). Ensure the cable you select is compatible and readily terminates to the connector type your sensors/boards use.
• ​Reliability: These micro-connectors are delicate. Specify robust connectors designed for vibration and mating cycles. Proper strain relief at the termination point is non-negotiable.

6. Environmental Factors

• ​Temperature Range: Will your robot operate in a hot factory, cold warehouse, or outdoors? Ensure the cable’s temperature rating covers your extremes.
• ​Chemicals/Oils: Industrial robots might encounter lubricants or cleaning agents. Choose jackets resistant to these (PUR/Polyurethane is often a good choice for robustness).
• ​Membrane Keyboard Applications: For cables routing under flexible PCB membranes, ensure the jacket is specifically designed for this to avoid cracking.

Key Selection Checklist for Robotics Micro Coax:

1. ​Impedance Match: 50Ω or 75Ω? (Check your device spec sheets!)
2. ​Bandwidth/Attenuation: Sufficient for your signal frequency? (Look for low dB/m loss)
3. ​Flex Rating: High-flex? Continuous flex? What’s the cyclic flex life (e.g., 10M cycles)?
4. ​Min. Bend Radius: How tightly can it bend safely? Smaller is better for tight joints.
5. ​Torsion Rating: Needed? (Specify if twisting motions are significant)
6. ​Shielding: High-coverage braid (95%+) or braid+foil? (Essential for EMI)
7. ​Conductor/Shield Material: Tinned copper braid? (More durable than plain copper or foil alone)
8. ​Jacket Material: Flexible? Abrasion-resistant? Chemically resistant? Temp rated?
9. ​Outer Diameter (OD): Small enough for the routing path? Meets weight goals?
10. ​Connector Compatibility: Does it terminate well to your specific micro-connectors (U.FL, etc.) with available tooling?
11. ​Strain Relief: How is it managed at the connector?

Where to Find Them:

Look for cable manufacturers known for interconnect in demanding, miniaturized applications. Reputable brands include:

• ​Hirose Electric (U.FL cables/connectors)
• ​I-PEX (DDK)
• ​Molex (SlimStack, Micro-Coax lines)
• ​TE Connectivity
• ​Hitachi Cable
• ​Axon’ Cable (Robotics specialist)
• ​LEONI

Pro Tip: Don’t just buy generic “micro coax.” ​Ask suppliers specifically for cables designed for “high-flex robotics,” “continuous flex,” or “medical/robotics interconnects.” Reputable suppliers can provide detailed flex life and torsion specs vital for robotic success. Be precise about your requirements – the right cable prevents signal headaches and costly robot downtime.