Radio Frequency (RF)
RF is the frequency region in which information is carried by an electromagnetic wave propagating through space rather than along a conductive wire. The bands used in wireless remote controls fall roughly between 300 MHz and 2.5 GHz. The difference from a wired signal is that the transmission path is a shared and uncontrollable medium.
In a wired remote control the signal stays inside the copper conductor and is largely isolated from the outside world. In RF, the energy is released from the antenna into free space; every device using the same band, every reflecting metal surface and every noise source becomes part of the transmission path.
- Consequence 1: range is not a fixed number. The catalogue value is for open area and line of sight; the same set gives a far shorter distance in an enclosed steel structure.
- Consequence 2: because the band is shared, regulation comes into play. Output power, band and transmission duty ratio are not left free.
- Consequence 3: because the link can drop at any moment, the loss-of-signal behaviour has to be designed on the machine side.
You see the counterpart of these three consequences in AXI's wireless sets: range values are given with an open-area note, the receiver antenna is supplied with a cable gland so that it can be taken outside the enclosure, and the outputs are taken to a safe state when the signal is cut.
Context in which this term is used: 433 MHz or 2.4 GHz?