I've been testing all antenna, bare in mind, it work for me, but might not work for you.
All the indoor antenna/wifi amplified are no good. Unless it's for your own indoor coverage e.g better wifi strength. No improvement for source DL/UL.

Outdoor antenna Log type, I tested probably work best performance wise best DL/UL out of any other outdoor antenna.
Second would be the polarization Parabolic Grid Gain Outdoor Antenna that everyone was talking about I got mine from taobao and it perfect for rural place.

If you are looking for outdoor antenna. B618 isn't good because the internal antenna is wasted. Get a compatible for 4G+ and support a lot of bands frequency router gateway. That is what I found work your RM as the performance probably top of the roof for what a user can improve on hope this help someone else.