The Linksys WRT3200ACM advertises a "Tri-band" feature which I've figured is just two 5ghz antennas. I'm a little bit confused on the benefit of this is and how to properly set it up in OpenWRT. So far, I have a 5.180 Ghz network set up on one of the interfaces, but the second one capable of 5 Ghz is inactive.
What's the proper way of using two 5 Ghz antennas? I assume I set them to the same BSSID, but do I have to configure them on separate channels?
This has been discussed many times in this forum already, please check the search history.
But in short: the third radio (SDIO/ mwifiex) based is not meant to be used, it was originally intended to passively monitor the 5 GHz spectrum for DFS interference and is very low-speed, with only a single and tiny internal antenna. Range and performance of this third radio are very low.
You have two full featured (but buggy, thanks to the abandoned driver/ firmware) radios on your device, one for the 2.4 GHz band, the other for the (entirety of-) the 5 GHz band (but not very good at dealing with DFS events, so better avoid those channels).
Forum search for "third radio" (there might be other useful search keywords, try yourself)