g/networking • Posted by u/cat6_carlos • 1 days ago

Fluke DSX-8000 failing Cat6A on NEXT — cable looks fine, terminations look fine

Hospital build, Belden 10GXW Cat6A in 3/4" EMT. Testing with a DSX-8000. About 8% of channels failing NEXT, only 2-3dB over the limit. All in the same wing.

These channels pass insertion loss, return loss, length, and propagation delay. NEXT only.

Pulled patch panel connections, re-terminated with fresh cable ends. No change. Fill ratio in the EMT is under 40%.

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u/cat6_carlos OP • 1 days ago

Update: it was the surgical lighting. Three Stryker LED surgical lights in that wing, generating RF noise in the 200-400MHz range that's coupling into the Cat6A. Moving the cable routing away from the lights and adding additional grounding on the EMT eliminated the NEXT failures.

120

u/rack_and_stack_rob • 1 days ago

Verify your DSX-8000 reference is set correctly for TIA Cat6A, not Cat6. The NEXT limits are different and forgetting to switch the standard is the most embarrassing failure mode. I've done it. Don't tell anyone.

u/wireless_wendy • 1 days ago

Also check if the EMT has any metal-to-metal contact issues — if the conduit isn't properly bonded and is acting as an antenna for environmental RF, that can couple into the cables. Check your grounding and bonding of the conduit system in that wing.

u/fiber_splicer_faye • 1 days ago

Selective NEXT failures in a specific area almost always have an EMI root cause in hospitals. Check proximity to: imaging equipment (MRI, CT — though MRI rooms should be shielded), surgical lighting systems, large UPS, or high-amperage power runs. Cat6A unshielded is susceptible to external noise if the source is close enough.