User manual

User Manual
man_905K_1.10.doc Page 19
Probability of successful transmission
0%
10 %
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
1000
2000
3000
Messages Per Hour
1
2
3
4
5
Transmissions
per message
This assumes that the radio path is reliable and that there is no other radio users on this radio
channel. If intermediate repeaters are used, then each repeated message should be counted as
another message.
We suggest that you use two transmissions per message - with a higher number for a small
number of high priority inputs.
In addition to the above comments, you need to consider the affect of re-transmissions on other
messages being transmitted from the same 905K module. Once a 905K starts transmitting a
message, all transmissions for this message must be complete before another transmission can
start. The time between retransmissions of the same message is a random time between 0.5 and 2
seconds. For example, if a module is configured to transmit each message 5 times, then each
message will take approx 10 seconds. Another message cannot be transmitted from the same
module until the previous message has finished.
2.5.2 How far will the radio transmit?
The distance that can be reliably achieved will vary with each application and is dependent on
the following factors:
• Type and location of antennas (the higher an antenna is, the further it will transmit)
• Amount of radio interference from other transmitters or radio “noise”
• Obstructions such as buildings, hills or trees in the radio path.
The maximum reliable distance is 20+ miles in USA/Canada (4W RF power permitted) and
20+km in Australia/NZ (1W RF power permitted). To achieve these distance, at least one site
needs to be elevated on a hill or transmission tower - refer section 3.2 for more information).
2.6 Calculating Power Consumption
The following information may be used for calculating power consumption.