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A Comparison of CAT6A UTP vs. F/UTP: What’s Similar? What’s Different?

Published by Cablesys on Aug 15th 2018

Image of bulk cable

CAT6A is the top pick for supporting 10 Gigabit Ethernet (10 GbE) networks right now.

Unshielded Twisted Pair (UTP) and Foiled/Unshielded Twisted Pair (F/UTP) cables are the two versions of CAT6A cables. F/UTP means Foiled/Unshielded Twisted Pair, which contains 4 unshielded twisted pairs wrapped in an overall foil shield. This is different than S/FTP, or Screened/Foiled Twisted Pair cable, which has 4 shielded pairs that are individually wrapped in a braided shield.


CAT6A is made in a particular manner that aids in the removal of crosstalk and Alien NEXT. (Alien NEXT is the measurement of the signal coupling between wire pairs in different and adjacent cables.) This also encompasses conductors bigger in size (23 AWG minimum), tighter twists, an additional internal airspace, an internal separator in between pairs, and thicker outer jacket. These features also make the outer diameter bigger, up to 0.35 inches, which is significant in comparison to CAT6 at 0.25 inches. The diameter increase allows for more distance in between adjacent links, which minimizes between-channel signal coupling. Nevertheless, Alien NEXT still affects CAT6A UTP performance and applications.

Based on the standards, Alien NEXT can be enhanced through placing CAT6A UTP cable freely in pathways and raceways with space between the cables. This differs from the tightly bundled runs of CAT6/5e cable we usually use. The tight bundles show a worst-case scenario of six cables wrapped around one, negatively affecting the center cable by Alien NEXT. Testing for Alien NEXT is an involved and tedious process where all potential wire-pair combinations are checked. It can take nearly 50 minutes to test one link in a bundle of 24 CAT6A UTP cables.


Although we can’t eliminate Alien NEXT and the time it takes to test for it, it can be greatly minimized by using CAT6A F/UTP. The foil shield acts as a wall that hinders external Electromagnetic Interference (EMI) and Radio-frequency Interference (RFI) from coupling onto the twisted pairs. It also hinders data signals from escaping from the cable, making the cable harder to tap and more beneficial for safer installations. Studies also have shown that CAT6A F/UTP cable provides significantly more headroom (as much as 20 dB) compared to CAT6A UTP in 10-GbE over copper systems.

Smaller Diameter, More Fill Capacity

CAT6A UTP cable has a general allotted diameter of 0.354 inches. CAT6A F/UTP cable has a common outside diameter of 0.265-0.30 inches. That’s smaller than the smallest CAT6A UTP cable. The outside diameter (O.D.) increased 0.1 inches, from 0.25 inches to 0.35 inches. This defined a rise of 21% in fill volume. Overall, CAT6A F/UTP cable gives at least 35% more fill capacity in comparison to CAT6A UTP cable.

In addition, due to the large diameter, CAT6A UTP demands a bigger bend radius, more pathways, less heavy patch panel connections, and comprehensive Alien NEXT testing.

Although shielded cable is known to be bigger, bulkier, and harder to manage and integrate than unshielded cable, this is not true of CAT6A F/UTP cable. CAT6A F/UTP cable is actually less difficult to handle because it needs less bend radius and utilizes smaller pathways. In addition, modernizations in connector technology have made terminating CAT6A F/UTP cable easier. Regarding grounding, the stipulations for UTP and F/UTP cable occur under TIA/EIA J-STD-607-A Commercial Building Grounding (Earthing) and Bonding Requirements for Telecommunications.

The Benefits of CAT6A F/UTP vs. UTP

In conclusion, there are various advantages of using CAT6A F/UTP over CAT 6A UTP in 10-GbE networks.

  1. Shielding removes Alien NEXT and EMI/RFI problems and testing.
  2. Shielding increases data line security.
  3. Narrow, less dense cable provides higher port density.
  4. Smaller outside diameter cable is easier to manage and lowers installation costs.
  5. Shielded cable occupies limited space in conduits.

For more information, reference the article What’s Really Different About CAT6 and CAT6A?