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Radiometrix Ltd
TR2M Data Sheet
page 5
Received Signal Strength
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
2.1
2.3
2.5
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
RF Level (dBm)
Figure 5: RSSI voltage variation with respect to RF level at TR2M
If the microcontroller has a built-in Analogue to Digital Converter (ADC), the Received Signal Strength
Indicator (RSSI) output voltage level can be read by the microcontroller to estimate its distance from
transmitting TR2M unit or identify areas of weak signal reception.
RSSI can also be used to make a decision to switch to the second antenna in fixed installations within
building where the probability of null-spots are higher.
Regulatory Restrictions
There is a generic 10% duty cycle restriction on the 433MHz ISM band through out European countries
with few exceptions. Annex 1 Band E, Band E2 of European Radio Communications Committee (ERC)
Recommendation 70-03 dated February 2004 specifies the following:
433.050MHz (Ch0)
434.050MHz (Ch40)
433.775MHz (Ch69)
10mW ERP, 10% duty cycle
for Channelised Narrow Band and Wide Band usage
10mW ERP, 100% duty cycle
for <25kHz Channelised Narrow Band usage
433.05MHz
434.040MHz
434.79MHz
433.050-434.790 MHz, Non Specific Short Range Device, band is primarily intended for Telemetry,
Telecommand, Alarms, Data in general and other similar applications. Audio and Voice signals should
be avoided in the band.
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