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6193-3201
In countries which allow the full 902-928MHz band (such as USA and Canada), there
are eight hopping sequences, or “hop-sets” (numbered 0 to 7, user-configurable). Each
sequence uses only half of the frequencies available in the band. Sequences 0-3 use the
same frequencies, but in a different sequence. Sequences 4-7 use the other frequencies.
For example, consider two systems close together. If the systems have hopping sequences
in the same group (0-3 or 4-7), then there is some degree of isolation because of the
different hopping sequence, however they will occasionally hop onto the same frequency
and cause momentary interference. However if one system uses a sequence in the first
group (0-3) and the second system uses the second group(4-7), each system is isolated
from each other. Note that this is only true if the antennas are at least 30 metres (100
feet) apart to prevent “blocking” – that is, saturation of the other receiver when one unit
transmits.
The hop-set is automatically determined from the System Generator String. If you wish
to change the hop-set to move to a different group, the best way is to change the System
Generator String and check what the new hop-set is.
In countries which only allow a sub-set of the 902-928 MHz band, there is only one
group of frequencies and it is not possible to separate systems in this way because the
band is smaller and all hopping sequences use all frequencies available.
3.9 Radio Configuration Menu
The RM-90 can be configured to different radio transmission rates. A reduction in rate
increases the reliable range (transmission distance). An “automatic rate” function is pro-
vided which automatically selects the highest data rate for reliable operation. This feature
starts at the highest rate and reduces rate if the received radio signal strength is below a
user-configurable limit.
The factory-default settings for the radio port will be correct for the majority of applica-
tions. Only make changes if you experience operating problems.
Select the “Radio” Menu to change the following configuration parameters. If a change is
made, you need to select “Apply Changes and Save” to retain the changes.
Power Level
The transmitter power level desired in mW.
By default this is set to maximum power of 1
Watt (1000mW). The lowest setting is 100mW.
Data Rate
The radio baud rate in bits per second (bps).
Available rates are 19200, 38400, 100000,
200000bps and Auto.
The default value is Auto. In Auto mode, the RM-
90 will automatically adjust the data rate to the
fastest rate for reliable operation in each radio
path.
