0.031" Low Loss Semi-Rigid Coaxial Cable 50 Ohms SR-031-LL for Microwave Systems

Engineers working on microwave subsystems through 40 GHz often face a trade-off between cable diameter and insertion loss. The SR-031-LL resolves this compromise by offering a 0.031 inch (0.79mm) diameter that fits standard 0.030" connector tooling while delivering approximately 25% lower loss than 0.024" designs at Ka-band frequencies. This semi rigid coaxial cable features a seamless copper tube outer conductor and precision PTFE dielectric that maintain 50 Ohm impedance with 70% velocity of propagation. Microwave module designers select this diameter when they need to route signals between amplifier stages or from connectors to internal circuitry, where the slightly larger conductor provides measurable loss improvement without requiring oversized connector interfaces. The silver-plated copper-clad steel center conductor accepts soldering for permanent PCB attachments and maintains mechanical integrity during forming operations. Available in custom cut lengths with SMA, 2.92mm, or other connector interfaces, supported by a 10 meter minimum order quantity suitable for both development and production.

• Optimized 0.031 inch diameter – balances compact form factor with lower loss than smaller semi rigid cables, fitting standard 0.030" connector tooling without modification
• Low loss through 40 GHz – engineered for microwave applications where every 0.5 dB matters, with attenuation of 10.15 dB/m at 40 GHz
• Seamless copper tube outer conductor – provides 100% RF shielding with zero signal leakage and phase stability under mechanical stress
• Precision PTFE dielectric – maintains consistent 50 Ohm impedance with 70% velocity of propagation across temperature
• Silver-plated copper-clad steel center conductor – 0.20mm diameter with optimized plating for low skin effect losses at microwave frequencies
• 0.06 inch minimum bend radius – formable for custom routing in test fixtures and module assemblies
• PCB solder compatible – rigid construction holds shape after soldering for permanent board-level installations
• Weldable outer conductor option – copper tube accepts welding for hermetic feedthrough applications
• Custom lengths – cut to exact specifications for prototype through production quantities
• Connector options – bare ends, SMA, 2.92mm, or N-Type pigtails and fully terminated assemblies
• 10 meter minimum order – low barrier for engineering teams and small production runs

• Microwave module integration – When a defense contractor needed to interconnect multiple amplifier stages inside a compact housing for an electronic warfare system, they chose SR-031-LL because it provided 0.8 dB lower loss than 0.024" semi-rigid cable while still fitting through the available 1mm routing channels. The 0.031" diameter allowed them to maintain system gain specifications without increasing module size.
• Test fixture development – A semiconductor characterization lab building test fixtures for 40GHz power amplifiers found that standard 0.047" cables were too large for the probe pitch, while 0.024" semi-rigid coaxial cables introduced excessive loss that masked device performance. SR-031-LL provided the right balance, fitting between closely spaced launch points while keeping fixture loss under 1.5 dB.
• Satellite receiver front-ends – Engineers designing Ku-band LNBs for commercial satellites selected this cable for internal connections between the feed and first stage LNA. The copper tube construction ensures phase stability during launch vibration, and the 0.031" diameter allows multiple cables to route through tight waveguide transitions.
• Radar receiver modules – A manufacturer of phased array radar systems uses pre-formed SR-031-LL assemblies to connect T/R modules to beamforming networks. The ability to order cables bent to exact mechanical drawings reduced assembly time by 40% while ensuring consistent phase matching across hundreds of channels.
• Medical imaging arrays – Developers of next generation MRI systems with integrated RF receive coils needed non-magnetic interconnects that could route through tight spaces inside the patient bore. SR-031-LL with non-magnetic materials variant provided the solution, maintaining signal integrity while eliminating gradient field interactions.
• Automotive radar test – Engineers validating 77GHz radar sensors use 0.031'' semi-rigid cable in their test harnesses because the 0.031" diameter fits the compact connector spacing on evaluation boards, and the low loss preserves signal levels through multiple meters of cable between the radar head and test equipment.
• Quantum computing infrastructure – Researchers building dilution refrigerator setups for superconducting qubits select SR-031-LL for control lines where thermal conductivity must be minimized. The stainless steel center conductor option reduces heat leak while maintaining RF performance through 40GHz.
• 5G basestation development – When testing massive MIMO arrays with 64 channels, a basestation manufacturer needed consistent loss across all cables to maintain calibration. SR-031-LL's predictable phase and loss characteristics allowed them to build matched sets with ±0.2dB variation at 28GHz.

A: The 0.031" diameter occupies a sweet spot for many microwave applications. Compared to 0.024" cables, SR-031-LL offers approximately 25% lower loss at 40GHz (10.15 dB/m vs 16.10 dB/m) while still fitting standard 0.030" connector tooling. Compared to 0.047" cables, it requires less space and can route through tighter bends, making it ideal for densely packed modules where every millimeter matters.

A: The cable is specified through 40GHz with usable performance extending beyond. The cutoff frequency for higher order modes is 180GHz, ensuring clean propagation throughout the specified range. At 40GHz, insertion loss is 10.15 dB per meter, which works well for short internal connections under 150mm.

A: Yes. The silver-plated copper-clad steel center conductor accepts soldering using standard techniques. Recommended soldering temperature is 260-280°C with dwell time under 3 seconds to protect the PTFE dielectric. The rigid copper tube maintains position after soldering, eliminating need for additional strain relief. For hermetic applications, the copper tube can be welded to feedthrough pins.

A: For full 40GHz performance, we recommend 2.92mm connectors. SMA connectors provide excellent performance through 26GHz and are suitable for applications below that frequency. All connectors are installed using precision tooling and 100% tested for VSWR and insertion loss.

A: SR-031-LL occupies a unique position between these common diameters. It offers lower loss than UT-034 (0.034") while maintaining a smaller footprint than UT-047 (0.047"). The 0.031" diameter is increasingly popular among designers who have migrated to 0.030" connector interfaces but need improved loss performance for 40GHz applications.

A: Minimum static bend radius is 0.063 inches (1.6 mm). For consistent results, use radiused forming tools matched to the desired bend radius. Avoid repeated bending at the same point as this work-hardens the copper tube and may cause cracking. For complex shapes, we recommend ordering pre-formed cables to your mechanical drawing.

A: Yes. For applications requiring matched electrical length across multiple channels, we offer phase-matched sets with ±1° at 40GHz or ±0.5° at lower frequencies. Specify your frequency and phase tolerance requirements when ordering.

A: Yes. The construction meets outgassing requirements per ASTM E595 and has been used in multiple satellite programs. Phase stability under thermal cycling is typically better than 5° at 40GHz over -55°C to +85°C. Full test data available upon request.

A: 10 meters minimum order. This low MOQ supports prototyping and R&D where full spools aren't practical. Production quantities receive volume pricing.