MIMO antennas questions

Hi, does anyone know whether it is required that all antennas used for a single MIMO card are the same (i.e. the same dBi, or even the same shape/length). I’m asking because I now have the 4x4 MIMO Wifi6 card with 2 standard short pole antennas and two of the pigtail-and-ducttape antennas from Mox Wifi6 upgrade kit. Of course I could buy two new pole antennas, but I’d like to keep the number of antennas protruding the chassis at the minimum. I’m not really interested in gaining super performance, I’m mostly interested in not hindering the performance of the two pole antennas.

Another related question - would it be possible to turn off two of the four MIMO channels? I really don’t need the 4x4 MIMO, but I don’t dare running the two antenna connectors without anything connected. That’s why I connected the MOX pigtails. If some MIMO channels can be turned off, how do I tell which physical connectors correspond to the turned off channels? I haven’t found this assignment in the datahseet of the Wifi card.

I have found some documentation on OpenWRT wiki, but it only seems to allow setting a single TX and a single RX antenna. I’d like to use both poles for both TX and RX. It is also not clear to me whether it is still needed to set diversity 0 to get this config respected. I could also try with iw phy phy0 set antenna <tx bitmap> <rx bitmap> but I’ve never played with this… I also don’t know where would be the best place to set these values on router startup.

In my specific use-case, the card should only be used as Wifi STA (client), so it actually should never need MU-MIMO, just single-user (so I guess I’ll just need to limit the number of spatial streams used between my card and an AP). Just if this would change anything…

Thanks for ideas.