0.390" Non-Magnetic Semi‑Rigid Coaxial Cable 50 Ohm High Power RF Transmission Lines

The SR-390C is a 50Ω semi-rigid coaxial cable and direct drop-in replacement for the UT-390C. At 0.390 inches (9.91 mm) outer diameter, this RF transmission line is designed for high-power, high-voltage RF applications up to 12 GHz. Construction features a silver-plated copper center conductor, solid PTFE dielectric, and a precision-drawn solid copper outer conductor. The solid outer conductor forms permanently when bent — holding routing geometry without spring-back — and provides near-complete EMI shielding, ideal for radar & defense, high power test & measurement and industrial microwave systems. SR-390C matches all UT-390C dimensions exactly. Existing connectors, tooling, and assembly fixtures are fully compatible. RoHS compliant. Custom lengths and terminated assemblies available on request.

• High Power Handling Up to 3,425W CW at 500 MHz. Built for radar, broadcast, and industrial systems where smaller cables fall short.
• Low Attenuation 3 dB/100ft at 500 MHz, 4.6 dB/100ft at 1 GHz. Efficient energy delivery over longer runs.
• Permanent Form Retention Solid copper outer conductor bends once and stays. No spring-back. Reliable geometry in vibration-prone installations.
• Superior EMI Shielding Solid outer conductor eliminates signal leakage and noise ingress — far beyond what braided coax achieves.
• High Voltage Rated 26,700 VRMS withstanding voltage supports plasma, accelerator, and high-power test applications.
• UT-390C Drop-In Compatible Identical OD, dielectric diameter, and center conductor. No redesign, no new tooling.

• Radar & Defense - High-power transmitter feeds, TR module interconnects, and EW system cabling requiring kilowatt-level power and complete shielding.
• Broadcast Transmitters - FM, TV, and digital broadcast RF feeds operating at VHF and lower microwave bands with continuous high-power output.
• Industrial Microwave Systems - 915 MHz and 2.45 GHz heating, plasma generation, and microwave processing equipment with sustained power delivery demands.
• Scientific & Research RF - Particle accelerators, cyclotrons, and RF cavity systems combining high CW power and high voltage in a single cable path.
• High-Power Test & Measurement - Power amplifier characterization, load-pull test setups, and high-power VNA signal chains needing stable high-power interconnects.
• Telecom Infrastructure - High-power base station cabinet cabling and antenna feed lines where low loss and mechanical stability are priorities.

Q: Is SR-390C semi-rigid coaxial cable dimensionally identical to UT-390C?

A: Yes. OD (0.390"), dielectric diameter (0.332"), and center conductor (0.102") all match UT-390C exactly. All UT-390C connectors and tooling are directly compatible.

Q: What limits the maximum frequency to 12 GHz?

A: At 12 GHz, the TE11 higher-order mode begins to propagate in the coaxial line, degrading VSWR and signal integrity. For applications above 12 GHz, specify a smaller-diameter cable such as SR-141 or SR-086.

Q: What happens if I bend tighter than 0.750"?

A: The outer copper wall deforms, locally shifting impedance. In high-power applications this creates a reflection point that can arc under voltage stress. Always use a tube-bending tool.

Q: Can I solder connectors directly to the outer conductor?

A: Yes. SR-390C semi-rigid coaxial cable features solid copper tube outer conductor, it accepts both tin-lead and silver-bearing solders. Pre-tin the outer surface before connector attachment for reliable mechanical and electrical bonds.

Q: What is the difference between the 90°C operating temp and 175°C integrity temp?

A: 90°C is the maximum for reliable long-term system operation. 175°C is where the copper tube itself begins to soften structurally. If your cable surface reaches 90°C, you are at the thermal limit of the power budget and should derate.

Q: What is the minimum order quantity?

A: Bulk cable is available in 5-foot straight lengths with a 100-foot minimum order. Custom assemblies have variable MOQ — contact us with your requirements.

Q: What is the lead time?

A: Bulk cable: 5–10 business days. Custom terminated assemblies: 2–4 weeks. Expedited production available on request.

Q: What quality certifications apply?

A: SR-390C semi-rigid coaxial cable conforms to MIL-DTL-17 dimensional and electrical standards. RoHS compliant. Certificates of conformance and full material traceability available for OEM and regulated industry customers.

Q: What connectors are available for terminated assemblies?

A: N-type, 7/16 DIN, TNC, and custom RF connectors suitable for 0.390" OD cable. Specify length, connector gender, and interface type when requesting a quote.