Is there a way to lock primary and secondary to a band I choose? Or is this something out of my control?
I found n41 + n25 to be best but it won’t stay. Just rolls back to n41 + n41
Either that or it just stays connected to primary and secondary drops off. Should secondary stay connected?
X62 / B One 5G
The only way I know of to do that is to select which bands may be used by the modem, as in the example which follows. I suppose you could deselect all but B25 and 41 but I don’t think I would do that.
It is the carrier that selects which bands are in use, subject to the availability of those bands in the given modem. It’s also the carrier that decides the extent to which LTEA will be employed at a given time. We’ve seen some carriers (particularly AT&T) vary hugely in the way secondary bands are used over time – even when the modem has not changed location.
After reading your reply about carriers limiting secondary+ (if they wanted to) I did a little more research on it. What a bummer. I guess if they left it open for all it would get pretty congested fast though. I was really excited about the SD X75. Potential vs reality again 
n41 + n25 does run the best it seems for me… when it finds it. sometimes it will jump around to n41 + n41 or n25 + n25 though and ping suffers as does upload.
I’ll play with antenna placement and might just select the best single band or play with auto. Thank you for your reply!
Your comment about antenna placement is good. Sometimes just rotating the device makes a great difference.
In the example I showed you the two bands deselected were found to be “slow.” When they were no longer available speeds increased. What I would probably not do is select just a single band or two.
