Advice requested: Antenna selection for dual-band BaseBox

Hi all

I want to create a wireless solution for a small 4 floor building (±100 users max) in the city (a.k.a 2.4ghz band is congested).
I am required to make a dual band solution, using the BaseBox 2 and an R11e-5HnD (or R11e-5HacD).
The antenna’s I want to use are normal Omnidirectional antenna’s directly connected to the BaseBox.

However, I’ve got 2 problem now:

  • I’ve read that antenna spacing is important, but since I want to connect them directly to the Basebox it might ba a problem (2 antenna’s for 2.4Ghz and 2 for 5Ghz)
  • I don’t know what antenna’s to buy, there are cheap one’s and very expensive one’s and I have no idea about the quality differences or gain I should take.

Can anyone give me some advice about the most cost effective solution?

I guess you want to mount one RB on each floor. Otherwise I do not see how you could have good coverage with omni antennas in 4 floors.
In this case no matter what distance are antennas to one another.