905U-L Wireless I/O Installation Manual
905U-L Wireless I/O
Page 17 of 40
Version 1.9
Dipole and collinear antennas
This section contains important information for using dipole and collinear antennas. For
more information, see the next sections.
Dipole antennas
Unity gain dipole antennas are commonly used on unlicensed channels. The dipole
antenna does not provide any gain, so the power transmitted from the antenna is the
same as the power out of the module.
A dipole antenna that comes supplied with integral 15 ft cable does not require additional
coaxial cable.
You should mount dipole antennas vertically, preferably no less than 1 metre away from a
wall or mast for maximum performance.
Collinear antennas
Collinear antennas transmit the same amount of radio power in all directions horizontally,
and are easy to install and use. They provide gain by compressing the radiated signal to a
flattened disc shape, and reducing the amount of signal radiated above and below the
horizontal plane.
Collinear antennas are generally used at a central site with more than one remote site, or
at a repeater site.
Collinear antennas are similar in appearance to dipole antennas; however the antenna is
longer.
Collinear antennas are supplied without cable, and require additional coaxial cable.
You can use collinear antennas to:
Transmitter
– to compensate for the losses in long lengths of coaxial cable.
Receiver
– to increase receive sensitivity.