50-75 ohm is impedance of the cable. pretty sure you want it to be 50-ohm for sure. Past that there are different classifications of the actual cable like LMR-XXX or RG-XX, where each classification basically says 'at these frequencies, this is how much signal loss you can expect per X distance'. I suggest LMR-240 because that's the best bang for the buck you'll probably find. if you're running really short (like 6 in jumpers) it probably won't make much of a difference over the more common RG-8 cable, but with the price difference, i'd rather get the one with less signal loss. Then the connector is the last important piece (BNC i believe in this case). Do an amazon search for "LMR-240 bnc" for examples. Keep in mind if you get a jumper, you'll probably need to get a coupler/gender changer for one side. Or look at the rack mount kits that will give you a front rack panel with a couple short jumpers so you can get the antenna mounts in front of your rack space. (i.e. Shure UA440)