It is needed to space 2 Single (SISO) Antennas For MIMO.
Regarding the vertical mast, the first antenna must be installed pointing towards the transmitter with a 45° clockwise angle, the second antenna must be installed pointing towards the transmitter with a 45° anticlockwise angle.
This will make a 90° angle between both antennas receiving both vertical and horizontal polarities.
It is also possible to mount the first vertically and the second horizontally and this gives the 90° angle on both antennas which is needed.
But it seems that the +45° and -45° is providing a better reception.
It is required to have 70 cm distance between the two antennas to have a good reception.