On an empty channel, an analog TV receiver shows a "snowy" noise pattern.
Noise in analog video and television is perceived as a random dot pattern that is superimposed on the picture as a result of electronic noise and radiated electromagnetic noise picked up by the receiver's antenna – it is the "snow" that is seen with poor analog television reception or on VHS tapes. When there is no transmission, the "snow" is mostly due to thermal noise from the device itself, stray electromagnetic fields from other electric devices, and cosmic background radiation that are being interpreted as a luminance signal. In Sweden the phenomenon is often called Myrornas Krig, "Battle of the Ants".
