Noise in Radio Reception

Noise in radio systems is divided into two general classifications. The first is atmospheric noise defined⁴⁴ as "noise caused by natural electrical discharges in the atmosphere." This is commonly called atmospherics abroad, and static in the United States. The second type is electrical noise, defined⁴⁵ as "unwanted electrical energy other than crosstalk present in a transmission system." These last two words are here construed to cover the entire system for transmitting a message or program.

A third source of radio noise is known by several names, interstellar interference being applied by one writer,⁴⁶ and cosmic static by another.⁴⁷ This interference is of interest but apparently is of little practical importance. Methods of measurement, results, and a list of articles on the subject are given in reference 47.

It is emphasized that the sources of noise now being considered do not include background noise, defined⁴⁵ as "noise due to audible disturbances of periodic and/or random occurrence."