Cat6A U/FTP Cable: Shielded Pairs, Open Bundle
Quick answer / TL;DR: Short answer: Cat6A U/FTP wraps each of the four pairs in its own foil with no overall shield. It meets the full Cat6A 500 MHz channel and 100 m 10GBASE-T reach, comes in a smaller diameter than F/FTP or S/FTP, and terminates with less fuss because there is no overall drain wire or braid to manage. It trades some mechanical robustness for that convenience.
The screening family tree: no shield, overall foil, braid plus pair foils.U/FTP is the least understood Cat6A construction and often the most practical. Every pair carries its own aluminium foil, and there is no overall shield around the four pairs. The cable delivers the full 500 MHz Cat6A channel and 10GBASE-T at 100 m, while staying noticeably thinner and more flexible than F/FTP or S/FTP.
The logic is that crosstalk between pairs inside one cable is the dominant problem at 500 MHz. Shielding each pair attacks that directly. Alien crosstalk between cables is handled by the pair shields as well, because each pair's foil also blocks outward leakage.
How U/FTP Differs From F/FTP and S/FTP
Three shielded Cat6A constructions dominate the market, and they differ only in where the metal sits. U/FTP puts foil on each pair. F/FTP puts foil on each pair plus one overall foil. S/FTP puts foil on each pair plus an overall braid.
All three meet the same 500 MHz electrical specification. The differences are mechanical, thermal and installation-related rather than bandwidth-related. That is the key point most buyers miss: you are not choosing performance, you are choosing handling.
| Construction | Pair shield | Overall shield | Nominal OD at 23 AWG | Relative flexibility |
|---|
| U/FTP | Foil each pair | None | about 7.0 to 7.5 mm | best of the shielded group |
| F/FTP | Foil each pair | Foil | about 7.5 to 8.0 mm | moderate |
| S/FTP | Foil each pair | Braid | about 7.5 to 8.5 mm | moderate to stiff |
| SF/FTP | Foil each pair | Braid over foil | about 8.0 to 9.0 mm | stiffest | |
The diameter difference looks small on paper and feels large in a conduit. A 25 mm conduit that takes three S/FTP cables may take four U/FTP cables of the same category, which changes the tray and conduit schedule rather than the cable order.
Why Per-Pair Shielding Is the Right Tool at 500 MHz
At 500 MHz the wavelength inside the cable is short enough that pair-to-pair coupling inside a single jacket becomes the limiting factor. Twist balance alone gets you to Cat6; it does not get you to Cat6A with margin. A foil around each pair raises the isolation between pairs by a large margin and simultaneously stops that pair from radiating outward.
Because each pair is individually enclosed, the cable does not strictly need an overall shield to control alien crosstalk. The pair foils already do it. This is why U/FTP can pass Cat6A alien crosstalk requirements without a braid, and why it is popular in European specification practice.
The Bonding Question
Each pair foil needs a drain path. In U/FTP the four drain wires are usually gathered and bonded together at the connector, then to the jack shell. Because there is no overall shield, there is no separate outer bond point, which simplifies the termination but puts more emphasis on getting the four pair bonds right.
- Bond all four pair drains at the jack, not just one
- Use jacks designed for U/FTP; a Cat6A F/FTP jack will still work but the overall contact is unused
- Verify continuity from each pair drain to the jack shell before terminating the far end
- Keep untwisted length under 13 mm at the termination point
- Test the permanent link, not just the patch cord
Real-World Applications
Retrofit into existing conduit
The most common real reason to choose U/FTP over S/FTP is a building with 20 mm conduit already in the slab. The smaller diameter of U/FTP can double the cable count that fits, and re-cutting conduit is rarely an option in an occupied building.
Data centre cabinet-to-cabinet runs
Inside a cabinet, bend radius and airflow matter more than external EMC. U/FTP bends more easily than S/FTP and blocks less of the cold aisle. Where the environment is already controlled and the runs are short, the braid adds weight without adding value.
Healthcare imaging rooms
An MRI or CT room needs cable that does not carry interference in or out. Per-pair foil gives strong isolation at high frequency. In these rooms the decisive factor is usually the overall bonding plan and the shielded enclosure, not which shielded construction was chosen.
Educational campus refurbishment
Schools retrofit into older containment with tight bends and shared trays with power. U/FTP tolerates the bends better than braided constructions, and the cost sits below F/FTP while still giving a full Cat6A channel for future 10G.
Related reading: The full shielded family compared — blogs/news/cat6a-shielded-cable
Related reading: Whether Cat6A shielding is necessary at all — blogs/news/is-cat6a-shielded
Standards and Verification
Cat6A is defined in ISO/IEC 11801-1 at 500 MHz and in ANSI/TIA-568.2-D for the North American channel. Component requirements sit in IEC 61156-5. Confirm the cable is tested to the Cat6A component standard rather than described as enhanced.
For U/FTP specifically, ask for two extra items: a statement that all four pair shields are bonded at the connector, and a shield attenuation figure per pair rather than a single overall number. A single figure for the whole cable tells you nothing about an architecture where the shields are separate.
For 10GBASE-T at 100 m, the Cat6A channel limit is 100 m by definition. Ask for the channel test report covering all four pairs at 500 MHz with NEXT, PSNEXT, ACR-F and return loss, and check that the report names the connector and cord models used in the test.
U/FTP is less common in North American distribution than F/FTP and S/FTP. If your project is in the United States, confirm stock and lead time before the specification is issued, because a construction that is standard in Europe can be a special order there.
Frequently Asked Questions
Is U/FTP as good as S/FTP?
For electrical performance at Cat6A, yes: both meet the 500 MHz channel and 100 m 10GBASE-T. S/FTP adds a braid that improves mechanical robustness and low-frequency shielding. Choose S/FTP for harsh environments and U/FTP for tight spaces and easier termination.
Does U/FTP need an overall ground connection?
It needs the pair shields bonded, which in practice means bonding the gathered drain wires to the jack shell and then to the panel. There is no separate overall shield to bond, which is exactly why termination is simpler than with F/FTP.
Why is U/FTP thinner than F/FTP?
Because it omits the overall foil and its drain wire. Removing one foil layer and one conductor saves roughly 0.5 to 1.0 mm of diameter, which is decisive when the constraint is conduit fill rather than cable performance.
Can I terminate U/FTP in a standard Cat6A jack?
A shielded Cat6A jack will accept it, but confirm the jack bonds four pair drains. Some jacks provide a single overall contact designed for F/FTP, which leaves three pair shields floating. Check the termination diagram before ordering 500 jacks.
Is Cat6A U/FTP suitable for PoE?
Yes, and the foil helps with heat spreading along the bundle. The limit is still bundle thermal derating rather than the shield. For high-power Type 4 PoE in a dense bundle, check the vendor's current-carrying and temperature-rise data.
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