

Underwater Coaxial Cable – 50/75 Ohm PUR Options
Underwater coaxial cable with 50 ohm and 75 ohm transmission options for compact subsea connector, RF, video and telemetry circuits. Select coax-only or coax-plus-six-conductor constructions, with standard PUR or water-blocked variants.
- Impedance options: 50 Ω and 75 Ω
- Circuit options: one coaxial element, or one coax plus 6 x 0.50 mm² (20 AWG) conductors
- Coax references: RG-58 and RG-400 constructions are included in selected 50 Ω options
- Outside diameter: approximately 5.59 to 9.80 mm, depending on configuration
- Outer jacket: polyurethane; black or ultramarine blue by configuration
- Documented duty: selected water-blocked options carry configuration-specific voltage, temperature and 7000 m depth data
- Selection boundary: the cable is not specified as an armoured or load-bearing tow line
For an RFQ, send the impedance, frequency, allowable attenuation, length, connector, depth, temperature and auxiliary-circuit load.
Underwater Coaxial Cable for Compact Subsea Connections
This underwater coaxial cable family gives equipment designers one selection page for 50 Ω RF and telemetry circuits, 75 Ω video or data circuits, and versions that add six 0.50 mm² auxiliary conductors for power, control or sensor functions. Eight reference constructions cover compact RG-58 and RG-400 routes, higher-temperature FEP-insulated coax, and water-blocked PUR-jacketed options.
Choose by the complete signal and installation duty, not by impedance alone. Connector impedance, operating frequency, cable length and attenuation must be reviewed together. A PUR jacket does not by itself establish pressure or depth capability: the 7000 m value applies only to the three configurations that state it, and the cable, moulding and connector must be confirmed as one assembly.
- Use this family for: compact underwater connector tails, camera, telemetry, instrument and equipment wiring.
- Confirm before ordering: 50 Ω or 75 Ω interface, frequency, run length, voltage, bend geometry, depth and termination.
- Choose another route when: the cable must carry towing, suspension or winch load.
Browse the marine and offshore cable range or use the subsea cable selection guide to compare load-bearing and hybrid alternatives.
Underwater Coaxial Cable Construction
The eight options use a controlled-impedance coaxial element inside a polyurethane outer jacket. Conductor plating, dielectric, braid, waterblocking, inner jacket and auxiliary circuits vary by row; do not combine ratings from different configurations.| Configuration | Coaxial element | Dielectric / insulation | Screen | Auxiliary conductors | Water block | Inner jacket | Outer jacket |
|---|---|---|---|---|---|---|---|
| 50 Ohm High-Temperature Coax | RG-400 construction; 20 AWG 19 x 32 silver-plated copper centre conductor | FEP, nominal 0.966 mm | 38 AWG double braid, silver-plated copper | None | Not stated | Natural E-CTFE, nominal 0.38 mm | Black polyurethane, nominal 1.27 mm |
| 75 Ohm High-Temperature Coax | 22 AWG 19 x 34 stranded tinned-copper centre conductor | FEP, nominal 1.78 mm | Tinned-copper braid | None | Not stated | Grey FEP, nominal 0.25 mm | Black polyurethane, nominal 1.27 mm |
| 50 Ohm Coax + 6 x 20 AWG | RG-400 coaxial element, 4.95 mm diameter | FEP on six auxiliary conductors | Coaxial-element screen | 6 x 0.50 mm² (20 AWG) stranded silver-plated copper | Not stated | Not separately stated | Black polyurethane; source wall-thickness unit requires confirmation |
| 75 Ohm Coax + 6 x 20 AWG | 75 Ω coaxial element | E-CTFE on six auxiliary conductors | Coaxial-element screen | 6 x 0.50 mm² (20 AWG), 19-strand silver-plated copper | Not stated | Not separately stated | Black polyurethane; source wall-thickness unit requires confirmation |
| Water-Blocked 50 Ohm Compact Coax | RG-58 construction; 0.33 mm² (22 AWG), 7-strand bare-copper centre conductor | Polyolefin dielectric, 2.30 mm nominal OD | 95% tinned-copper braid with elastomeric water-block compound and aluminium-foil contact layer | None | Flooded screen construction | Thermoplastic elastomer, nominal 0.53 mm | Ultramarine-blue polyurethane, 85A, nominal 0.81 mm |
| Water-Blocked 50 Ohm Coax + 6 x 20 AWG | 0.36 mm² (22 AWG), 7-strand tinned-copper centre conductor | Polyolefin coax dielectric; polypropylene on auxiliary conductors | 95% tinned-copper braid with elastomeric water-block compound and aluminium-foil contact layer | 6 x 0.50 mm² (20 AWG) stranded tinned copper | Flooded screen plus elastomeric compound in the interstices | Thermoplastic elastomer, nominal 0.50 mm | Ultramarine-blue polyurethane, nominal 1.30 mm |
| Water-Blocked 75 Ohm Compact Coax | 0.14 mm² (26 AWG) stranded bare-copper centre conductor | Polyolefin dielectric, 2.70 mm nominal OD | 95% tinned-copper braid with elastomeric water-block compound and aluminium-foil contact layer | None | Flooded screen construction | Thermoplastic elastomer, nominal 0.40 mm | Ultramarine-blue polyurethane, 85A, nominal 0.80 mm |
| Water-Blocked 75 Ohm Coax + 6 x 20 AWG | 0.14 mm² (26 AWG), 7-strand bare-copper centre conductor | Polyolefin coax dielectric; polypropylene on auxiliary conductors | 95% tinned-copper braid with elastomeric water-block compound and aluminium-foil contact layer | 6 x 0.50 mm² (20 AWG) stranded tinned copper | Flooded screen plus elastomeric compound in the interstices | Thermoplastic elastomer, nominal 0.40 mm | Ultramarine-blue polyurethane, 85A, nominal 1.20 mm |
What the construction changes in service
- The 50 Ω route is intended for equipment built around a 50 Ω RF interface; the 75 Ω route is intended for a matching 75 Ω video or data interface.
- The flooded braid and interstitial compound reduce longitudinal water migration only on the configurations where those layers are stated.
- The six auxiliary conductors can consolidate electrical functions, but their voltage drop and heating must be calculated for the actual current and length.
- No supplied option includes armour or a declared tensile member. Towing, suspension, free-swimming tether and repeated-reeling duty require another construction or separate mechanical evidence.
Applications for 50 and 75 Ohm Underwater Coaxial Cable
Use these compact PUR-jacketed cables where an underwater connector or equipment interface needs one controlled-impedance transmission path. The coax-plus-six-conductor versions can combine that path with low-voltage power, control or sensor circuits after the complete electrical and thermal schedule is checked.- 50 Ω options: RF, telemetry, test or communication circuits built around a verified 50 Ω source, connector and load.
- 75 Ω options: underwater camera, video and data circuits built around a verified 75 Ω interface.
- Six-conductor options: combined signal plus auxiliary power, lighting, control or instrumentation where one cable and connector envelope is preferred.
- Water-blocked options: assemblies that require the documented flooded-screen or interstitial water-block construction.
Selection checks that prevent the wrong order
State the operating frequency, allowable end-to-end loss and cable length; attenuation rises with frequency and cannot be judged from impedance alone. Match the cable and connector impedance. Check OD and bend radius against the mould, gland, backshell and available routing space. For submerged service, define fresh or sea water, depth, pressure, duration, temperature and whether the cable is static, handled or repeatedly deployed.Use a related construction when mechanical duty changes
- Choose a hybrid coaxial power and signal tow cable when mixed circuits must also carry deployment load.
- Choose a 50 ohm coaxial armoured tow cable for a load-bearing 50 Ω route.
- Choose a screened underwater PUR cable when the project needs multiple copper circuits but no coaxial element.
Underwater Coaxial Cable Specifications
All values are configuration-specific reference data for quotation.| Configuration | Impedance | Outside diameter | Operating voltage | Temperature | Bend radius | Maximum depth |
|---|---|---|---|---|---|---|
| 50 Ohm High-Temperature Coax | 50 Ω | 7.38 mm nominal | 300 V | -40°C to +150°C | 10 x cable OD | Not stated |
| 75 Ohm High-Temperature Coax | 75 Ω | 7.75 mm nominal | 300 V | -80°C to +200°C | 10 x cable OD | Not stated |
| 50 Ohm Coax + 6 x 20 AWG | 50 Ω | 9.80 mm nominal | Not stated | Not stated | Not stated | Not stated |
| 75 Ohm Coax + 6 x 20 AWG | 75 Ω | 9.80 mm nominal | Not stated | Not stated | Not stated | Not stated |
| Water-Blocked 50 Ohm Compact Coax | Approximately 50 Ω | 5.59 ± 0.30 mm | ≤1000 VDC | -20°C to +70°C | 64 mm | Not stated |
| Water-Blocked 50 Ohm Coax + 6 x 20 AWG | 50 Ω | 9.70 ± 0.40 mm | ≤600 VDC | -20°C to +70°C | 100 mm minimum | 7000 m maximum |
| Water-Blocked 75 Ohm Compact Coax | 75 Ω | 5.60 ± 0.30 mm | ≤600 VDC | -20°C to +80°C | 64 mm minimum | 7000 m maximum |
| Water-Blocked 75 Ohm Coax + 6 x 20 AWG | 75 Ω | 9.80 ± 0.40 mm | ≤600 VDC | -20°C to +80°C | 102 mm minimum | 7000 m maximum |
Electrical and physical reference data
| Configuration | Capacitance | Attenuation | DC resistance | Weight |
|---|---|---|---|---|
| 50 Ohm High-Temperature Coax | 29.4 pF/ft nominal | Not stated | Not stated | Not stated |
| 75 Ohm High-Temperature Coax | 20.1 pF/ft nominal | Not stated | Not stated | Not stated |
| 50 Ohm Coax + 6 x 20 AWG | 32.0 pF/ft | 4.50 dB @ 100 MHz; 10.5 dB @ 400 MHz; 17.0 dB @ 1000 MHz; test length not stated | Not stated | Not stated |
| 75 Ohm Coax + 6 x 20 AWG | Not stated | Not stated | Not stated | Not stated |
| Water-Blocked 50 Ohm Compact Coax | 30 ± 3 pF/ft | 0.5 dB/100 ft @ 1 MHz; 2 dB/100 ft @ 10 MHz; 5 dB/100 ft @ 50 MHz; 7 dB/100 ft @ 100 MHz; 30 dB/100 ft @ 1 GHz | Centre conductor ≤54.5 Ω/km; screen ≤21 Ω/km at 20°C | 39 kg/km in air; 13 kg/km in seawater |
| Water-Blocked 50 Ohm Coax + 6 x 20 AWG | 30 ± 10 pF/m, conductor to screen | 6.50 dB/100 m @ 10 MHz; 23 dB/100 m @ 100 MHz; 98.4 dB/100 m @ 1 GHz | Coax centre conductor ≤54.5 Ω/km; screen ≤21 Ω/km at 20°C | 119 kg/km in air; 45 kg/km in seawater |
| Water-Blocked 75 Ohm Compact Coax | 65 ± 10 pF/m, conductor to screen | 5.25 dB/100 m @ 10 MHz; 16.7 dB/100 m @ 100 MHz; 45.9 dB/100 m @ 750 MHz; 65.6 dB/100 m @ 1.5 GHz | Centre conductor ≤128 Ω/km; screen ≤18 Ω/km at 20°C | 37 kg/km in air; 12 kg/km in seawater |
| Water-Blocked 75 Ohm Coax + 6 x 20 AWG | 65 ± 10 pF/m, conductor to screen | 5.25 dB/100 m @ 10 MHz; 16.7 dB/100 m @ 100 MHz; 45.9 dB/100 m @ 750 MHz; 1.5 GHz source line requires confirmation | Coax centre conductor ≤128 Ω/km; screen ≤18 Ω/km; auxiliary conductor ≤33 Ω/km at 20°C | 122 kg/km in air; 45 kg/km in seawater |
Specification boundaries
- The 7000 m value belongs only to the two 75 Ω water-blocked options and the 50 Ω water-blocked six-conductor option.
- No depth rating is stated for the compact water-blocked 50 Ω option or the four black-jacketed options.
- The attenuation test length is not stated for the 50 Ω high-temperature six-conductor option; confirm it before using those values in a link budget.
- Two legacy construction sheets record the PUR wall-thickness unit incorrectly. Final wall thickness requires an approved drawing.
Standards and Project Test References
| General coaxial reference | IEC 61196-1 provides general definitions, requirements and design/test-method framework for coaxial communication cables. Use only when it is named in the agreed project specification. |
|---|---|
| Electrical verification | Agree impedance, capacitance, conductor and screen resistance, voltage test, attenuation frequencies, sample length and connectorised assembly acceptance. |
| Submerged-system verification | Where applicable, define depth, hydrostatic pressure, immersion duration, water migration, temperature, bend geometry and the moulded connector or penetrator interface. |
| Supply documentation | Confirm the approved drawing, marking, inspection plan, test report format, packaging and any project-specific certificate requirements before production. |
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View productRequest a cable recommendation and quotation
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