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hop within the required regulations. In particular, under FHSS rules (less than 663kbps)
the radio must have enough frequency bandwidth as required under FCC rules. Under
DTS rules (greater than or equal to 663kbps) there is no limit on the minimum
bandwidth for the radio (it may operate on one frequency).
As an example, the lower and upper edge of the band may be reduced if the full 902 to
928MHz ISM range is not needed. Additionally, if an internal band is to be excluded
from the transmission it may be added in the “Exclude” range. Thus, if the frequency
range to be transmitted is 905-910 and 915-920, then the “Band Start” will be set to
Upper” set to 915.
The MAS input requires a “Xmit Freq” and a “Recv Freq” which will correspond to the
frequencies that have been approved by the licensing authority.
In both ISM and MAS, the transmit power must be set in units of milli-Watts. The ISM
rules require that the power not exceed 1000mW with additional restrictions based
upon the antenna while the MAS rules are specified in the license granted and typically
run no higher than 5000mW.
For FHSS rules (less than 633kbps), the “Hop Pattern” should be set to 1 whereas for
DTS the Hop Pattern may be set from 0 to 9. The setting of 1 creates a pseudo random
sequence of frequencies; a setting of 2-9 is a uniform step through the allowed
frequencies. For FHSS (data rates < 663kbps) the Hop pattern must be set to 1. For
DTS modes, any Hop pattern may be set. Additionally, if a hop pattern of “0” is used for
DTS, the constant frequency is set as “ISM Freq”; however, note that this should only be
set if using a DTS mode.
Radio Receive Modes (Remote Transmit Modes)
The ISM Slave Transmit Rates (Master Receieve Modes) may be set with multiple
selections. The radio will start operation at the lowest speed and, if successful, will
increase to the next selected speed. Thus the radio dynamically changes the data rate
based upon signal quality measures. It is suggested that no more than three different
receive modes (rates) are selected for any radio. The available modulations range from
the FHSS modes of 57kbps – 305kbps to the DTS modes of 663kbps – 3535kbps. The
primary difference between the modes is the bandwidth of the signal and the required
strength of signal received at the radio. Since modulation and packet size are related to
the required sensitivity, there is more detail on choosing the optimal receive mode
elsewhere in the manual.
As a general rule, as the data rate increases, the required signal strength at the receiving
radio also increases. Thus, for long distance low signal installations, a lower data rate
will be more successful than a high data rate. If the signal is strong with little
interference, then any rate may be chosen, however there are still interactions based on
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