At a job site we typically have 10 vehicles connected to a single vehicle (star layout) by a 100m 5 conductor cable carrying power(unused), ground, shield, CANH, and CANL. The shield is grounded on both ends, but the ground is effectively the battery ground, which as far as I know isn't tied to any other external reference.
What (if anything) keeps the shield from acting as giant antenna? My understanding is the shield is meant to block EMI from entering the can bus, and may also be to limit external emissions from the bus, but I thought that to prevent radiation both ends needed to be well grounded; I'm not sure how (or if) a floating battery based ground effects it.
Disclosure: Not a EE/CE major.