Blue Charm Beacons broadcast a calibrated RSSI figure as part of each regular broadcast. Some scanners will use this calibrated figure in a formula to estimate distance from the beacon.
For iBeacons, by definition of the protocol, this calibrated RSSI equates to the beacon’s expected broadcast signal strength as received by the scanner when the beacon is 1 meter away from the scanner.
As the TX broadcast signal power (outgoing) of the beacon is lowered, it makes sense that the received signal strength at the scanner will be lower/weaker, even when the beacon is still one meter away from the scanner. The address this situation, the firmware of our beacons has a chart of calibrated RSSI values for each TX level.
For example, when the beacon is set to default TX level 0dBm, the expected received signal strength on the scanner when the scanner is one meter away from the beacon is -59. So the beacon broadcasts a calibrated RSSI of -59 when the TX of the beacon is set to 0. When the TX is lowered to -4, the beacon firmware automatically adjusts the calibrated RSSI to -63.
Below is a simple table showing the chart of TX choices and their associated calibrated RSSIs figures that the beacon will broadcast at each TX level:
TX
+8 (only some of our beacons can be set to this TX level)
+4
0
-4
-8
-12
-16
-20
-40
Calibrated RSSI at 1 meter
-51
-55
-59
-63
-67
-71
-75
-79
-99