What is MIL-DTL-85?

MIL-DTL-85 is a U.S. military specification that specifies the performance requirements for rigid waveguides with a rectangular configuration. Waveguides are transmission lines (typically in hollow metallic tubes) used to guide high-frequency electromagnetic waves in applications like microwave communications, radar, and broadcasting. 

The MIL-DTL-85 specification outlines general requirements for waveguides to meet the performance requirements for Military Applications. Waveguides supplied for use in U.S. military applications must meet all the requirements of this specification. 

Key requirements outlined in MIL-DTL-85 for waveguides include:  

• Requirements for material used in waveguide fabrication (recycled, recovered, and environmentally friendly materials should be used)
• Design, construction, and physical dimensions requirements
• Finishing requirements (i.e., waveguide must be smooth, bright, dry, and free of scales or oxide)
• Length and marking requirements
• Voltage standing wave ratio (VSWR) shall not exceed 1.02:1
• Requirements for Perpendicularity, bow, and twist
• Workmanship requirements (i.e., waveguide shall be free from defects, uniform in composition and wall thickness, straight, free from internal and external mechanical imperfection, etc.) requirements
• Other requirements (e.g., pressurization, squareness of cut, etc.)

Manufacturers (contractors) supplying waveguides to the U.S. military must meet all the requirements specified in the MIL-DIL-85 to ensure that their products perform reliably and can withstand the harsh environmental conditions found in military operations. The contractor must submit waveguide samples (as specified in the MIL-DTL-85 document) for inspection and verification. This document also outlines details regarding materials inspection and conformance inspection to verify whether the submitted waveguide samples fully meet all requirements specified in this standard. If the submitted samples meet the all requirements of the MIL-DTL-85 specification, the contractor can supply waveguides covered by this specification to U.S. military applications. 

Waveguides covered under this specification are military-unique and function as transmission lines in military electronic equipment and radio systems. They must function in and withstand military unique environments worldwide for prolonged periods. 

The MIL-DTL-85 military specification is used by all Departments and Agencies of the Department of Defense. It is revised periodically, and MIL-DTL-85 Revision K Notice 2 - Validation: 2021 is the active, most current revision (As of October 2024).

The table provides other key information about MIL-DTL-85: