Every microwave hop must be on either a vertical or horizontal polarity. One of the most common mistakes in antenna and/or feedhorn installation is improper polarity installation. Both antennas of a microwave hop must be on the same polarity. If they are on opposite polarities then a receive level degradation of 20-30 dB will be encountered. Also, if waveguide is involved, many non-qualified contractors will think that if the long axis of the waveguide is horizontal then the polarity is horizontal. This is exactly the opposite of what is accurate. The wave of a microwave signal travels on the short axis of the waveguide. Therefore, if the slit in the feedhorn and/or the long axis of the waveguide is horizontal then the antenna is vertically polarized.