RG174 and RG316 are both compact 50 ohm coaxial cable options for SMA-SMA cable assemblies, but they suit different operating conditions. RG174 is commonly considered for short internal jumpers where moderate temperature resistance, easy routing, and cost control matter. RG316 is more suitable when the assembly requires a PTFE dielectric, an FEP jacket, silver-plated construction, or a wider operating temperature range. RG316 can have moderately lower attenuation in a matched product comparison, but long or high-frequency cable paths may still require a larger low loss coaxial cable.
RG174 vs RG316 at a Glance
RG174 is usually the lower-cost, easy-routing option for short internal RF connections. RG316 is selected more often when PTFE and FEP materials, silver-plated construction, or a wider cable temperature range are required. In a short SMA-SMA assembly, the attenuation difference may be smaller than the material and environmental difference.
| Selection condition | RG174 | RG316 |
|---|---|---|
| Short internal SMA jumper | Suitable starting option | Also possible, but the material advantage may not be required |
| Wider temperature range | Limited by the selected PE and PVC construction | Better starting option with PTFE and FEP construction |
| Lowest cable cost | Usually more suitable | Usually higher cost |
| Moderate attenuation improvement | Higher attenuation in the matched comparison | Moderately lower attenuation |
| Long RF cable path | Usually not preferred | May still be too lossy |
| Operation above the approved frequency range | Use a specifically rated cable | Use a specifically rated cable |
| Repeated movement | Flex life must be verified | Flex life must be verified |
| Outdoor installation | Complete assembly sealing must be reviewed | Complete assembly sealing must be reviewed |
RG174 and RG316 Construction Differences
RG174 Basic Structure
A common RG174 construction uses a stranded copper or copper-covered steel center conductor, a PE dielectric, one braided shield, and a PVC jacket. In one matched datasheet example, the cable has a nominal outside diameter of 2.79 mm, a 90% tinned-copper braid, and a minimum installation bend radius of 28 mm.
RG174 is often used for short connections between wireless modules, antennas, RF boards, and panel interfaces. Its small diameter allows routing through compact enclosures, although the approved temperature range, attenuation, conductor material, and shield coverage still need to be confirmed from the exact cable specification.
RG316 Basic Structure
A common RG316/U construction uses a stranded silver-plated copper-covered steel center conductor, a PTFE dielectric, one silver-plated copper braid, and an FEP jacket. In the matched example used in this article, the nominal outside diameter is 2.50 mm, the braid coverage is 95%, and the minimum installation bend radius is 25 mm.
Standard RG316/U normally has one braided shield. It is not the same as RG316D or another double-shielded variant. When higher shielding effectiveness is required, the cable specification needs to identify the additional shield layer clearly.
Summary of Key Structural Differences
The figures below use a matched pair of product datasheets, keeping the comparison frequency, units, and specification format consistent. RG174 and RG316 products from another source may use different conductors, braid coverage, jackets, or temperature limits.
| Parameter | RG174 example | RG316 example |
|---|---|---|
| Characteristic impedance | 50 ohm | 50 ohm |
| Center conductor | Stranded bare copper-covered steel | Stranded silver-plated copper-covered steel |
| Dielectric | PE | PTFE |
| Shield | One tinned-copper braid, 90% coverage | One silver-plated copper braid, 95% coverage |
| Jacket | PVC | FEP |
| Nominal outside diameter | 2.79 mm | 2.50 mm |
| Example operating temperature | −30°C to +75°C | −70°C to +200°C |
| Minimum installation bend radius | 28 mm | 25 mm |
| Nominal attenuation at 1 GHz | Approximately 1.115 dB/m | Approximately 0.951 dB/m |
Electrical Performance Comparison
How Does RG316 Attenuation Compare with RG174
RG316 has moderately lower nominal attenuation than RG174 in the matched comparison, but the difference changes with frequency. The two figures are almost the same at 100 MHz. The difference becomes more visible near 1 GHz.
| Frequency | RG174 | RG316 | Difference |
|---|---|---|---|
| 100 MHz | 0.276 dB/m | 0.272 dB/m | 0.004 dB/m |
| 400 MHz | 0.623 dB/m | 0.574 dB/m | 0.049 dB/m |
| 1 GHz | 1.115 dB/m | 0.951 dB/m | 0.164 dB/m |
Shielding and Finished Assembly Performance
Both cables are designed around a 50 ohm characteristic impedance. The RG designation alone does not confirm shielding effectiveness because braid material, coverage, shield count, and termination structure can vary between cable products.
Standard RG316/U commonly uses one silver-plated copper braid. A foil-and-braid or braid-and-braid construction needs to be identified as a separate double-shielded cable version. If the assembly is installed near motors, power converters, digital switching circuits, or other noise sources, review the shielding data for the selected cable instead of assuming that every RG316 has two shield layers.
Power Handling and Cable Length
RG316 uses materials that can tolerate a wider temperature range, but this does not create a universal power rating for every SMA-SMA assembly. The usable power level also depends on frequency, cable attenuation, ambient temperature, connector design, contact termination, cable bundling, and system VSWR.
The approximate loss of a cable path can be estimated as follows: Total cable path loss = cable attenuation in dB/m × cable length in metres + connector and adapter losses
When both RG174 and RG316 exceed the permitted loss, compare low loss coax and standard coax by frequency, cable length, routing space, and connector size.
Application Examples
RG174 is a practical starting point for a short internal SMA jumper between an RF board and a panel port when the selected cable meets the required attenuation and temperature limits. RG316 is more suitable near higher-temperature areas or when the assembly requires PTFE dielectric, FEP jacket, or silver-plated construction.
For long antenna feeders, 5.8 GHz links, strict insertion-loss budgets, or repeated-motion test leads, compare a specifically rated cable and finished assembly instead of selecting RG174 or RG316 by cable name alone.
Mechanical and Environmental Differences
RG174
The PE dielectric and PVC jacket used in many RG174 cables provide a compact cable construction for controlled indoor routing. In the matched example, the operating temperature range is −30°C to +75°C.
RG174 is often described as a flexible cable, but the exact handling feel depends on conductor stranding, braid density, jacket compound, and cable source. A minimum bend radius describes the permitted routing radius. It does not state how many repeated bending cycles the cable can withstand.
RG316
The PTFE dielectric and FEP jacket used in common RG316/U cables provide a much wider temperature range. In the matched example, the specified operating range is −70°C to +200°C.
This wider cable temperature range does not automatically apply to the complete SMA-SMA assembly. The SMA connector, solder, crimp contact, heat shrink, boot, label, and strain relief may have lower temperature limits.
RG316 should not be selected for repeated bending based on its PTFE construction alone. Test leads, moving fixtures, robotic routing, and frequently repositioned cables need documented flex-cycle or phase-stability performance from the selected cable assembly.
Wiring and Installation
Keep the cable above its minimum bend radius and avoid forcing a sharp bend at the rear of the SMA connector. A tight bend near the termination can pull the braid away from the ferrule, stress the solder joint, change the cable geometry, or create intermittent return-loss changes during movement.
An FEP jacket does not make an SMA-SMA cable assembly waterproof. Outdoor installation also requires suitable connector sealing, panel sealing, heat shrink, boots, cable entry protection, UV resistance, and water-ingress control.
FAQ
Conclusion
RG174 is a practical cable option for short SMA-SMA jumpers when a PE dielectric, PVC jacket, moderate temperature range, and controlled cable loss meet the application requirements. RG316 is more suitable when the assembly needs a PTFE dielectric, FEP jacket, silver-plated construction, or a wider temperature range. Its attenuation advantage is moderate and does not make it a replacement for every low loss cable. Before confirming an assembly, review the operating frequency, cable length, temperature, routing radius, SMA termination drawing, insertion loss, and return loss together. For a custom length, right-angle connector, mixed RF interface, or defined test requirement, you can share the cable and connector details with the Bafitop team for review.