Other than cost, no. As long as the path length beteeen the MIMO client and access point antennas are different (between each antenna), you're fine for MIMO. The cables don't even have to be the same exact length. However, if you're running 802.11g speeds, the system switches to a diversity receive configuration, which will have problems dealing with some antenna configuration. See article on diversity at:
If you double the cable length, using the same type of cable, you double the loss. That doesn't tell me much as it would be helpful to know the cable types involved. My GUESS is that it's RG-316/u which
1.65dB/meter. To put that in perspective, 6dB loss cuts the range in half. 3dB to about 0.7. 12dB loss give about 1/4th the range. Add about 0.5dB for the connector assembly.
Ok, that's easy. That's about 1 meter long and is good for 1.65dB. If you add another meter of coax, that will 1.65 + 0.5dB = 2.2dB loss which is about a 20% loss of range. Not too horrible and worth doing if you can use the antenna at a better location.
I'd be interested in knowing what you're trying to accomplish with this exercise. It might be better dumping MIMO and going to ordinary
Currently it is connecting in G mode to a 80211g router. The computer, being a larger tower model is on the floor, under the desk. The meter or so of antenna cable limits how I can clear the three ends for line of sight to the router.
Down the road, likely early next year at the earliest (economically and 'its working don't fix it influenced) an N mode router is on the horizon.
(I understand this nic is only able to do b or g modes to the b/g router currently in use right now.)
The way things are right now there is a large mass of metal with an electrical field (the A/V equipment) right where the end of the cable can get out to 'fresh air' so to speak, out from under the desk and out from behind things.
Another few feet or three would get it up above the limited mounting location I'm stuck with right now.
(I'm just at the point of benchmarking the throughput and loss/resend type specs in my real life situation.)