Evolution of Regulatory Standards of Interference

This paper traces the development of interference regulations from the original requirement that waves be pure and sharp to the present complex formula for attenuation of spurious emissions. It also shows how different philosophies of regulation developed. In broadcasting, the regulations grew up around the concept of a "protected service area." In the communication service, on the other hand, regulations developed in the direction of limiting the bandwidth and confining emissions within the authorized band. The paper also traces the history of ISM regulation with its philosophy of assigned frequencies on which unlimited radiation is permitted with an associated requirement for severe limitation of radiation on other frequencies. It also discusses the "low-power rules" which establish the conditions under which low-power equipment may be operated without becoming a source of interference. The paper describes briefly the voluntary work in this area by industry, and touches on local regulations concerning interference.