scope:

This Recommended Practice provides information and guidance for characterizing radiated levels of electromagnetic (EM) noise or interference that may be present in various environments between 10 kHz and 40 GHz. It provides methods that may be used to plan for and execute the electromagnetic environment characterization of a particular environment or location. The EM Site Survey is intended to be a systematic, documented investigation of the measurable characteristics of the electromagnetic fields at one or more frequencies and locations as necessary during a designated time period, which yields results that are interpretable and communicable among subsequent investigators.

This recommended practice describes the basic methods as well as reasons why noise levels may vary with location, time, and frequency and how those considerations should be incorporated into the site survey test plan. Guidance is provided on test methods that can be used to determine noise levels under various circumstances and in various environments. Example test equipment used for a site survey is provided. This equipment includes antennas and measurement instrumentation as well as recommended equipment settings. The Recommended Practice also discusses the various detector types that may be used during a site survey. Guidance for the documentation of the test plan and the site survey results in a test report are included in this recommended practice.

Purpose

The purpose of this Recommended Practice is to provide the necessary background, guidance, and methodology needed to plan an electromagnetic site survey, perform the survey, document the results, and analyze its outcome.

Ambient EM signals form the EM environment (EME) and can affect the operation of electronic equipment and impact the reception of intentional wireless signals. As interference to wireless signals, the ambient EME degrades the performance of systems such as critical radio systems used in communications, radio location, navigation, and guidance. Here, the EME dictates receiving and transmitting equipment designs. Even the usage intervals of some radio systems are controlled by the EME; e.g., the EME determines night time AM broadcast restrictions on radiated power and antenna patterns. There are also numerous examples of the EME impact on non-wireless devices such as instrumentation and control systems, human machine interface devices, and other electronic equipment.

Surveys may therefore be initiated for a number of purposes: 1) to characterize the performance of existing radio systems, 2) to estimate the possible effect of electromagnetic fields upon biological processes in human and animals, or 3) to estimate the possible effect upon the operation of electrical and electronic apparatus or 4) to characterize radiated or conducted emissions on the site. (It should be noted that the effects and safe levels of electromagnetic fields upon humans and animals as well as equipment and environments are not covered in this recommended practice.)

The recommendations in this Recommended Practice are intended to supplement the published data on the EM environment. An EM site survey should be a systematic, documented investigation of the measurable characteristics of the electromagnetic fields at one or more frequencies and locations as necessary during a designated time period. Because of the diversity of applications, there are currently significant differences in measurement instrumentation, methods of test execution, data reduction techniques, data analyses, and data reporting. Such disparities have limited the reliability of these data, caused much work to be repeated, and frequently led to erroneous interpretations. Therefore, electromagnetic site surveys should be carried out in a systematic manner with appropriate instrumentation that yields results which are interpretable and communicable among subsequent investigators.