Foreword?This document provides a standard set of methods and procedures for determining the shielding effectiveness of shielding enclosures. The enclosures of concern include those used for testing groups of equipment@ vehicles@ computing systems@ and smaller units whose electromagnetic emission and susceptibility require determination without disturbance from other sources. MIL-STD 285 was the common reference for many years@ but the applicability of that document lessened with the advent of technological changes. Further@ restructuring within U.S. Government policies and procedures has resulted in an emphasis on the use of commercial standards and the discontinuance of documents such as MIL-STD 285. The basic premise of MIL-STD 285 is still in position??the shield effect is to provide an insertion loss to outside influence. This standard offers testing based upon the performance specifications of the shield@ rather than a fixed set of parameters that may not be applicable to the shield in question. Specific test procedures and frequency ranges are then selected as needed.ScopeThis standard provides uniform measurement procedures for determining the effectiveness of electromagnetic (EM) shielding enclosures at frequencies from 9 kHz to 18 GHz (extendable down to 50 Hz and up to 100 GHz).The owner of the shielding enclosure shall provide the frequencies at which the shield will be tested@ and the shielding effectiveness limits for pass/fail. This standard suggests a range of test frequencies that would provide very high confidence in the effectiveness of the shield.