We have Line 6 Mic recievers that you can rack together and loop the antennas from one to the next (see page 26 of the manual).
You can buy the cable from Line 6 here, but you can get BNC-BNC cables here for a fraction of the price.
Line 6 doesn't give any technical spec for their cables, but the other cables are listed as HD-SDI video cables. In my mind, a BNC connector is a BNC connector, and a copper is copper. Is there any reason why we couldn't, or shouldn't use an HD-SDI cable to loop our antennas?