> As for cross-talk between antennas, I'm not sure this setup removes it
> completely; there's probably leakage around connectors, and possibly in
> the cables attaching the outwards-facing SMA connectors on each machine
> to whatever the tiny connectors on the cards are called. Don't have the
> equipment to measure any of that, though, so for now it remains a hunch...
>

Yeah, that's going to depend on the noise-floor of the receivers.  I've
found that -105dBm receive radios (other technologies) needed physical
separation and cables rated at 60dB of shielding in order to keep
cross-talk down.

The cables from the SMA connectors to the boards are likely pretty leaky
(the board connectors are probably u.fl connectors)