You can run two sector antenna's of one card.
It only has to be a ´n´ (or mimo) able card with two chains.
You can connect a sector to each of the chains (=connectors) of the card. They both run in full sync and on both you get the full power of that chain.
For instance, with an R52Hn you get twice 21dBm on each chain. It works perfect. I have on AP like that with 35 customers.
The big advantage compared to using a splitter (which is the ´old fashioned way´) is that you don't have the splitter loss (half the power) plus the extra connector losses.
Compared to separate radio's for each sector you now also save on one frequency.
This system works also better if you for instance where thinking of 2 180º sectors. By splitting each 180º in two 90º sectors (side by side or opposite of each other in a 4 sector setup) you also get better gain over the same ´pie´. Because to get a similar gain on a 180º it has a smaller vertical beam as a 90º antenna so in the latter you have also better service to a broader range, depth wise spoken.
Side advantages are that instead of two cards you can now do with one. Less power consumption and less heat production.
You can now easy use a rb433 with three cards. One backhaul in 5Ghz for instance and two of these dual chain cards both with their frequency with as much as possible separation to serve in total 4 sectors!
In my setup I use two 90º RSLL (Reduce side lob) antenna's and they are only 1 meter apart from each other and covering a total of 180º!
Because both antenna's are now in full sync (they are connected to the same card and both chains of it share the same clock cycle) there is no self interference.
The only thing that might happen in theory is that at some distance and in a very small beam both radio waves that are in complete phase with each other could become in a 180º phase shift because of the different path length (half a wave difference). You would get a "zero" amplitude wave. So this could be a small ´black´ spot.
In reality the change you would have a client just in that spot would be small. Also because the area will be a bit dynamic due atmospheric circumstances that have influence on the radio waves.
It works like a charm with me and haven't come across any negative side effects yet.
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Rudy R. Puister
WISP operator based on MT routerboard & ROS.