Radio noise

In radio reception, radio noise (commonly referred to as radio static) is unwanted random radio frequency electrical signals, fluctuating voltages, always present in a radio receiver in addition to the desired radio signal.

Atmospheric noise and human-caused noise as a function of frequency in the LF, MF, and HF radio spectrum according to CCIR 322.[1] The vertical axis is in decibels above the thermal noise floor. The graph shows that as frequency drops atmospheric noise dominates other sources, and that as frequency rises, although all noise quiets, human-caused noise exceeds atmospheric noise.

Radio noise is a combination of natural electromagnetic atmospheric noise ("spherics", static) created by electrical processes in the atmosphere like lightning; human-made radio frequency interference (RFI) from other electrical devices picked up by the receiver's antenna; and thermal noise present in the receiver input circuits, mostly caused by the random thermal motion of molecules inside resistors.

  1. ^ Cite error: The named reference CCIR-322 was invoked but never defined (see the help page).