Hi there, I would like to know which polarization (Vertical or Horizontal) is best and why when using the XTend modules with high gain antennas (15.1 dBi Yagis) at 900 MHz (naturally).
We are currently doing several layer performance tests with this equipment.
Cheers
Interferences, obstructions, etc. can all affect the communication and radiation pattern of an antenna. Typically, the antenna’s radiation pattern will be different in the veritical or horizontal planes. Which is better may not necessarily be the same for every installation, but typically high gain yagi antennas are polarized in the vertical plane. Namely, the ceter boom pointed at the receiver, the perpendicular elements are oriented vertically.
What is typically most important in whichever plane you choose to orient, it that the transmitting and receiving antennas are oriented in the same plane.
Thanks for the response 
I already did the first set of tests with Vertical polarization. I managed to create a PPP session with two computers over 1.8 Kilometers (1.11 miles).
I’ll be testing a 20 Km link in two days lets see if it works