Westermo RM-505U-2-E - Manual (Page 15)

User Manual
MAN_505_1.7.DOC Page 15
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 505U module. Once a 505U 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 4
seconds. For example, if a module is configured to transmit each message 5 times, then each
message will take up to 16 seconds. Another message cannot be transmitted until the previous
message has finished. In the above example, the maximum number of messages which can be
transmitted reliably is approx 4 per minute. If more messages are required, then a lower number of
re-transmissions should be selected.
2.4.2 How far will the radio transmit?
The 505U will operate reliably over large distances. The distance that may 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
•
Maximum radio transmitter power allowed in the country
The transmitter power level of each 505U is set in the factory to the maximum power allowed in the
country of sale. The maximum output power of the 505U is 500mW, however only 250mW can be
achieved using internal batteries. If internal battery supply is used, then the 250mW power can be
increased to 500mW by using a 3dB gain antenna such as a 3 element Yagi or a 3dB collinear
antenna - refer to the section 3.2 Antenna Installation.
The following distances are expected "line-of-sight" distances which can be expected to be achieved
with reliable operation. This range can be increased by higher gain antennas, or higher antennas, and
is decreased by radio interference and obstructions.
Power Level mW Distance km
500 10
250 7
100 5
10 2