Seriously, How Hard Can Choosing an Ethernet Cable Be? (Spoiler: It's Complicated)

With Contributions by Adam Roycroft

I wanted to write today about a topic that is under the radar for most. I mean ~seriously~ can choosing an ethernet cable really be that difficult? Up until a few months ago, I was baffled that we had users buying Unshielded Ethernet Cables when it feels impossible to escape EMI/ Noise in most industrial settings. This should be easy... Use a standard SHIELDED ethernet cable and be done with it!

That said, a growing number of users are opting for Unshielded Ethernet cables in low- or no-noise environments, reporting no performance issues. Their preference is largely driven by cost efficiency, as unshielded options can offer savings of 50% or more compared to shielded alternatives.

To them I say, "You know what... I get it!"

I have been on the other side of the table and in the world of hyper-competitive bidding on industrial machine builds and slim margins- every dollar counts. If it works, then great!

But let's talk about the subset of users who have had issues with Unshielded Ethernet Cables. It isn't always as easy as saying, "Just use a Shielded Ethernet Cable and move on!" when issues arise.

As much as I truly want to say that… it isn't always black & white.

Let's rewind for a second… Inside each Ethernet Cable there are multiple conductors that are Twisted together into what we call TWISTED PAIRS. This is one of the ways that the cable protects itself against noise & interference. There are 2 main types of Unshielded Ethernet Cables: Non-bonded Twisted Pairs and Bonded Twisted Pairs.

Non-Bonded Twisted Pairs are what you would find in typical Unshielded Ethernet Cables. Bonded Twisted Pairs are physically mated together. The claim is that this is a superior performing cable to Non-Bonded Twisted Pairs when used in "low-to-no noise" applications because there are no air gaps between the 2 conductors. An air gap between twisted pair conductors disrupts their noise-canceling geometry, leading to increased susceptibility to electromagnetic interference (EMI) and common-mode noise.

This concept was very interesting to hear about, so of course we wanted to do some research and testing to verify these claims. Ultimately, we want to be able to steer users in the right direction based on their application. Without getting overly technical and into the weeds. So, I put together a Quick Selection Guide:

Unshielded NON-BONDED Twisted Pair Ethernet Cables

This is your standard, most flexible, and most economical cable.

 PROS

• Lowest Upfront Cost: The most economical choice if a low purchase price is the primary goal.

• Simple & Flexible: Ideal for general applications where standard performance and noise immunity are acceptable.

• Suitable for Flexing: The un-bonded conductors allow some movement, making it the top choice for continuous, unsupported flex applications (like robotic arms) where cable life is critical. Always review specific datasheets for further details.

CONS

• Standard Noise Immunity: Offers only standard protection against electrical interference.

• Vulnerable to Gaps: Handling, installation, and reuse may cause the conductors to shift or "gap." This could negatively impacts noise-canceling geometry and reduces noise immunity.

Unshielded BONDED Twisted Pair Ethernet Cables

With this design, the two conductors in each pair are permanently adhered (bonded or glued) together. This maintains the pair's geometry, regardless of rough handling.

PROS

• Resilient to Stress: The bond prevents the conductors from shifting during installation and reuse, maintaining consistent electrical performance.

• Improved Long-Length Performance: Offers better noise immunity than Non-Bonded for longer cable runs (10m+)

CONS

• Rigidity in Continuous Flex: The bond's rigidity can concentrate stress when the cable is continuously bent (like in a cable track), potentially leading to early mechanical failure.

  Example: One test showed a high-flex, non-bonded cable achieving 10 million cycles versus a bonded pair failing prior to 600,000 cycles in the same rolling bend test.
  Source: When bonds are too rigid - the case against bonded pairs | Quabbin Wire & Cable

Shielded Ethernet Cables

Shielded cable is the ultimate option when it comes to cable-based noise immunity. It adds a metal foil or braid layer beneath the outer jacket, acting as a direct electrical barrier against interference.

PROS

• Ultimate Noise Immunity: Offers robust noise immunity performance at any cable length. The top choice for high-noise sources like drives, inverters, or welding equipment.

• High Resiliency: Ideal when you need to design machines with the highest fault tolerance and resiliency or are experiencing costly downtime.

CONS

• Highest Cost: You’ll pay more for this level of performance.

• Installation Difficulty: Some variations can be thicker and less flexible, making it more challenging to install and route. Look for "High Flex" ratings when applications call for it.

• Requires Proper Grounding: The shield only works if it is properly grounded. Incorrect termination can actually introduce ground loops into the system by turning the shield into an antenna.

As you probably have gathered, choosing the right Ethernet cable for an industrial setting is a tricky balance. Should you save money now or invest in long-term reliability? It all comes down to cable construction and how well it can fight off electrical noise. Every application is unique. Placing a single cable too close to a noisy power line may cause interference in one machine, even if an identical machine nearby remains unaffected.

Here are my final thoughts:

• Want to save the most money in applications with low to moderate noise interference and cable flexibility needed?
  Go with Unshielded Non-Bonded Cables. There is no noticeable benefit in noise protection when using Unshielded Bonded Cables in applications where the cable runs are under 10 meters. If the application requires in bending/flexing of the cable you risk cable breakage/short lifecycles when using the Bonded variation. With the Non-Bonded variation, you risk air gaps allowing noise interference in when bending/flexing, but that is only in noisy applications. At that point, it may be time to evaluate the jump to Shielded Ethernet Cable.

• Want better noise protection in cable runs over 10 meters?
  There could be some benefits to using Unshielded Bonded cables here. Again, the concern is bending/flexing that can shorten the lifecycle of the cable. In static, long length applications this would be a good fit, although at a higher price than the Non-Bonded variation.

• Need Reliable Uptime and Maximum Noise Protection?
  Shielded Cable is the only way to go. Luckily, the gap in pricing between Shielded & Unshielded has improved, making Shielded both an economical and high-performance option in almost all applications.