905U-E Wireless Ethernet Bridge
User Manual
Man_905U-E Rev 1.0
Page
12
3.3
Radio Rates
The 905U-E is capable of using several radio transmission rates. A reduction in speed will
increase the range.
3.8
Radio Interference
The 905U-E operates on the 902-928MHz license-free radio band (restricted to 915 – 928 MHz
in Australia and 921 – 928MHz in New Zealand). Devices on this radio band must use a spread
spectrum technique to allow multiple users to share the band with minimal interference.
The 905U-E uses a frequency-hopping spread spectrum technique. The 905U-E will not interfere,
or be interfered by, radio devices on other bands, such as two way radios or wireless telephones.
There can be interference from other devices on the same band. As the “hopping sequence” used
by the 905U-E is different to other devices on this band, the probability of two devices using the
same channel is small, and if this does occur, the probability of sharing the same channel on a
re-transmission is even smaller.
In countries which allow the full 902-928MHz band (such as USA and Canada), there are eight
hopping sequences, and the first four do not use the same frequency channels as the last four -
this can give isolation between two systems. That is, a system with hopping sequence 1 will
hear messages from another system using hopping sequence 3, but will not if the other system
used hopping sequence 5. The hopping sequence may be configured under the Radio Settings
Configuration menu. In countries which only allow half the band (such as Australia and New
Zealand), it is not possible to separate systems in this way because the band is smaller and all
hopping sequences use all channels available.