User manual

905U-D Radio Modem User Manual
Man_905D_1.10.doc Page 14
horizontal and must be pointed exactly in the direction of transmission to benefit from the gain
of the 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 stations transmitting to a common station, then the Yagi antennas
should have vertical polarisation, and the common (or “central” station should have a collinear
(non-directional) antenna.
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.
905U
Antenna installed
with drain holes
down
Coax feed looped
at connection
90
o