User Manual v1.9
Manual
WI-I/O 9-K
v1.9
Page 19
number of update transmissions per hour.
The probability of success for an individual message depends on the transmission density and the
number of re-transmissions for each message. This is shown in the following graph:
Probability of successful transm ission
0%
10 %
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
1000
2000
3000
M essages 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 WI-I/O K module. Once a WI-I/O K 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
