868 MHz Band (SRD860)
The 863–870 MHz range is a sub-GHz band allocated to short-range devices in Europe and is itself divided into sub-bands with different conditions of use. The permitted power, duty cycle and channel access rule of each sub-band are defined separately; which sub-band may be used under which condition is subject to national regulation.
868 MHz offers a balance between 433 MHz and 2.4 GHz. Since the wavelength is about 35 cm, behaviour around obstacles is still good; as the quarter-wave antenna is about 8 cm, it is easy to fit into the device. Free-space loss at the same distance is about 6 dB higher than at 433 MHz; at 100 m about 71 dB is calculated.
- Sub-band structure: the range is not a single whole. Some sub-bands allow higher power but impose a stricter duty cycle condition; others do the opposite.
- Channel access: instead of a duty cycle limit, methods that listen to the channel and transmit if it is free may be used.
- Occupancy: the band is heavily used by meter reading and sensor networks.
For this reason, which sub-band a product works in and under what conditions should be read not from memory but from the declaration of conformity and the product label. For AXI's ST and SF series sets, the dump data contains no frequency information.
Context in which this term is used: 433 MHz or 2.4 GHz?