I have no experience of 802.11N, so I need some advice regarding antennas for a 500 meters wireless link. Do I need dual-polarization antennas, or just two directonal antennas?
What are you trying to push speed wise? 100meg easy with a RB-SXT
Yes, around 100 Mbit/s or more. I was thinking about the SXT unit, but this time I just need antennas for two another RB units.
If you want full duplex 100m then you will need dual polarity. Otherwise you will be Max half duplex.
Thank you, exactly what I needed to know. I have been rethinking, so I will buy a couple of SXT 5HnD units and do something else with my other units.
Remember also it depends on what type of traffic you will be needing. the SXT is not a super powerful device, and the CPU’s will max out with TCP traffic.. somewhere around 30-50 Megabits.
Using MPLS with VPLS Tunneling will help cpu usage on the units, but you wont reach max speed w/ tcp on a SXT.. UDP should no problem. you need something with a bit more Oomph. 411AH’s for ex. and you can use some ARC Integrator enclosures + Dual Pol flat panels, or they have grids for the same price if you’re going further.
-Brad
Is that official MT information or just a personal opinion?
My personal opinion.
However, my opinion is based on usage of the actual product. I use them in production links. Others are having similar experiences to me as well.
I believe MT staff would probably agree, but i wont speak for them, i’ll let them chime in! 
-Brad
Thanks for your input, I really appreciate it. I read somewhere that with NV2, you’ll get twice the TCP speed compared to similar CPE devices before NV2 was introduced.
My experience is not that optimistic. At least yet.