Distance claims in the extender market are written by the marketing department and tested by nobody. So we bought five of the most popular “8K 40m” extenders, put them on a single 40.2-meter certified CAT6 run, and fed them a worst-case FRL stress pattern for 72 hours straight.

The gauntlet

  • 8K@60 4:4:4 10-bit stress pattern (full 48Gbps FRL)
  • 72-hour continuous soak with 200 hot-plug cycles
  • Dolby Vision + eARC + CEC simultaneity check

Two units held the full signal for the entire soak with zero retrain failures. Two more managed 8K@30 but dropped to 4K120 under sustained load. The fifth never managed 8K beyond 12 meters.

What separated the survivors

Both surviving units share a retimer-based FRL architecture and ship with certified-copper requirements printed on the box, not buried in a PDF. The three failures all used redriver designs that marginally pass at 25°C and fall apart at 45°C — exactly the temperature inside a closed rack.