I am not able to get any kind of usable signal on my 4G hub.
This is a brand new hybrid setup, but I had the old router with 4G USB dongle before, same issue.
So when my DSL does down, it rarely switches over to 4G and if it does, it's useless.
My phone on the other hand has a strong 3 bars and gets 80Mbps with speedtest, when sitting in the same room with the router. So there obviously is sufficient 4G signal.
So I am doubting that getting some antennas is going to help.
I did try using the antennas off an old router, to see if that would help, it didn't. But not sure if they are the right type of antenna though.