I have 4G RBI through Ultimate Broadband. I'm about 20km from Kaitaia 4G tower and decided to add another external antenna as performance has been kinda sketchy and would occasionally drop back to 3G or 4G with Rsrp around -105dBm.
Speedtest with 1 antenna. PING 62ms, DOWNLOAD 41.23Mbps, UPLOAD 8.06Mbps.
Speedtest with 2 antennas. PING 59ms, DOWNLOAD 94.47Mbps, UPLOAD 24.78Mbps.
Tests taken a few minutes apart.
Check this old post out for the details of why using 2 antennas is best for 4G. https://www.geekzone.co.nz/forums.asp?forumid=40&topicid=191699
Now if only I could do something about these accursed data caps!