The SXT unit comes with a powershot lead which makes the suggestion to use shielded cat5e cable for earthing the unit a rather difficult one if the powershot lead is preventing the shielded cable to pass the earth.
The manual than also talks about some place on the motherboard where an earth can be connected but to be honest, it leaves me clueless.
So, how to earth an SXT? (or Groove)
I haven't looked into the groove's info yet but I wouldn't see how to earth these units? For the Ethernet cable the same counts as for the SXT where the groove has no access to any direct motherboard or radio grounding.