Bandwidth (RF Bandwidth)
Bandwidth is the frequency range a signal occupies in the spectrum and it sets the width of the filter window the receiver opens. As the window narrows, less noise gets in and sensitivity improves; in return the data rate that can be carried falls. In remote controls the preference is usually not for speed but for narrow band and range.
The receiver's noise floor rises in direct proportion to the filter width: quadrupling the bandwidth also raises noise power roughly fourfold, that is by 6 dB. Those 6 dB mean, by the 6 dB rule, that theoretical range is halved.
- Narrow band: typically works in channels of a few tens of kHz, sensitivity is good, but the frequency stability of the transmitter and receiver crystals becomes critical.
- Wide band: provides high data rate and frequency tolerance, at the expense of sensitivity.
The information a remote control carries is a few bytes; a few kilobits per second is more than enough. So in RF design, leaving the bandwidth wider than necessary means spending range for nothing in return. In the field the counterpart of this is: raising the data rate to solve a range problem does not work, it works against you.
Context in which this term is used: 433 MHz or 2.4 GHz?