Data Hacking

154 Part II — Software Hacks
FIGURE 7-8: USB Bluetooth dongle for PCs
The range over which Bluetooth devices can work varies dramatically. The maximum range for
most Bluetooth devices is 100 meters, but some have only the power to operate over distances
as short as 10 meters. These are the maximum distances under ideal conditions, but several factors
can dramatically reduce the range:
Partitions: Walls and car and boat skins can all have an adverse effect on the range. The
denser and thicker the partition, the worse the effect.
Trees/vegetation: Both of these can have an adverse effect on the communication range.
Tree trunks are particularly bad for the signal because they are filled with moisture,
which absorbs the signal.
Electronic interference: Interference from other electronic devices, and even wiring, can
have an unfavorable effect on distances over which devices communicate.
Power consumption: If your devices have a low-power mode, this can dramatically cut
the distance over which your devices can exchange data. For the best performance, make
sure low-power mode is disabled.
Bluetooth devices are in fact divided into three classes:
Class 1 has a maximum power output of +20 dBm and a range of up to 100 meters.
Class 2 has a maximum power output of +4 dBm and a range of up to 20 meters.
Class 3 has a maximum power output of +0 dBm and a range of up to 10 meters.