Hector Martin

For the record I still think those little posts while perhaps standard, are likely trouble. Sure lets put little antennas on the fanciest signal processing chip in the architecture. Oh and with a convenient signal collector shield they are in the center of.

1000BASE-T runs at 125Mbaud (with 4 pairs and 2 bit per symbol encoding = 1Gbps). That's a peak frequency of 62MHz. Guess how much of that signal will be radiated by your 3.87mm antenna, which is a quarter-wave monopole at 19 *G*Hz? And then of course there's a *shield* around it

Am I right in thinking that the Ethernet pairs are differential, and that's likely to reduce radiation due to destructive interference as well?

Yup. I was going to mention that but I ran out of characters :-)