dual-polarization, recommendation

RouterOS Wireless Networking
1

Hi,
Just i need some recommendation about this:

“When used dual-polarization antennas,
isolation of the antenna recommendation to
be at least 25db”

How it goes,how can i calculate, would you like to give an example.

Thanks

2

If you refer to isolation between polarizations, you can not calculate it, measure it.
The minimum acceptable is -20dB.
If you refer to isolation between two antennas, there is no standard, the higher, the better.