In our This vs. That series, we're comparing (and contrasting) two seemingly similar products. A lot of products seem the same at first glance but can greatly affect the outcome of your next application. Today, we're comparing the RG178 and RG316 coaxial cables.
RG178 and RG316 are both high-temperature, high-performance coaxial cables. These cables are manufactured in accordance with the MIL-DTL-17 specs and are designed for use in high-temperature applications.
The RG178 coax cable and RG316 coax cable can be used in radio frequency communications, data transmission, wireless communication, and direct burial. More specific applications include GPS systems, PDAs, security equipment, mobile phones, broadcast equipment, remote controls, and more. These cables are very similar, but what sets them apart? Let’s find out.
Construction Differences
Although both RG178 and RG316 feature stranded, silver-coated copper-clad steel conductors, silver-plated copper braid shields, PTFE dielectric materials, and an FEP jacket, there are also stark differences between the two. One of the main differences in the construction of these cables is in the center of each, starting with the diameter of the conductors. RG316 is almost double the size of RG178 because the dielectric diameter causes the overall diameter to be larger and contributes to a difference in weight.
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| Conductor Type | Stranded (7/.004) | Stranded (7/.0067) |
| Conductor Diameter | 0.012” | 0.020” |
| Conductor Material | Silver-coated Copper Clad Steel | Silver-coated Copper Clad Steel |
| Dielectric Diameter | 0.033” | 0.060” |
| Dielectric Material | PTFE | PTFE |
| Shield/Outer Conductor | Silver Plated Copper Braid | Silver Plated Copper Braid |
| Jacket | FEP | FEP |
| Overall Diameter | 0.071” | 0.098” |
| Weight (lbs/MFT) | 6.3 | 9.89 |
Electrical Similarities
In terms of electrical specifications, RG178 and RG316 are fairly similar. They share the same minimum and maximum temperature ranges and have similar impedance, but vary slightly in voltage rating and capacitance.
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| Min. Temperature Rating | -55°C | -55°C |
| Max. Temperature Rating | 200°C | 200°C |
| Max. Voltage | 1000 | 900 |
| Impedance (ohms) | 50 +/-2 | 50 |
| Capacitance (pF/ft) | 29.4 | 32 |
The difference in attenuation between RG178 and RG316 cannot be caused by the conductor material since they are both composed of a silver-coated, copper-clad steel conductor. Although these cables are similar, the RG178 has almost twice as much attenuation as RG316. This is because the sizes of the RG178 conductor are smaller than the RG316 conductor, so it experiences more loss because of its size. In most cases, the larger a conductor is, the less loss a cable will experience.
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If you are unsure about what coaxial cable you need in order to meet the needs of your application, consult with a qualified engineer or with one of Allied’s knowledgeable sales reps. To learn more about RG178 and RG316 visit the coaxial cable main product page.