Westermo RM-505U-2-E - Manual (Page 23)

User Manual
MAN_505_1.7.DOC Page 23
Three element YAGI antenna.
YAGI antennas are directional. That is, they have positive gain to the front of the antenna, but
negative gain in other directions. Hence YAGI antennas should be installed with the central beam
horizontal and must be pointed in the direction of transmission to benefit from the gain of the
antenna. The high gain spread of a 3 element Yagi is approx 30º, so great accuracy is not required.
Also note that YAGI antennas normally have a drain hole on the folded element - the drain hole
should be located on the bottom of the installed antenna.
The YAGI antennas may be installed with the elements in a vertical plane (vertically polarised) or in
a horizontal plane (horizontally polarised). For a two station installation, with both modules using
YAGI antennas, horizontal polarisation is recommended. If there are more than two 505U modules
transmitting to a common 105U module, then the YAGI antennas should have vertical polarisation,
and the 105U module should have a dipole or collinear (non-directional) antenna.