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WHITE PAPER Development Tactics and Techniques for Small Form Factor RF Signal Recorders mrcy.com 5 5 MIL-STD-461 is another popular military specification requirement for RF signal recorders. MIL-STD-461 provides the requirements for the control of electromagnetic interference (EMI) emissions and susceptibility characteristics of electronic, electrical, and electromechanical equipment and subsystems designed or procured for use by activities and agencies of the Department of Defense (DoD). (NTS, 2018) RF test laboratories use anechoic chambers to run a series of MIL-STD-461 tests that include radiated emissions, radiated susceptibility, conducted emissions and conducted susceptibility for a range of frequencies. It is typical to cover a radiated range up to 18 GHz and a conducted range up to 10 MHz on power leads. It is important to take the appropriate design steps to meet MIL-STD-461 compliance since iterative independent laboratory testing becomes very expensive. Design techniques used to control EMI include the use of RF emission filters and RF gaskets to prevent radiated electromagnetic emission and susceptibility. Additionally, an in-line EMI power filter designed for the internal power supply can be used to protect against conducted emission and susceptibility. Figure 5: A Talon RTX Extreme 1/2 ATR Recorder signal recorder being tested to MIL-STD-461. One of the advantages of sealing all system electronics from the outside environment is that the electronics can self heat more easily than if they were directly exposed to the cold environment. This self heating process is compromised if a fan in the plenum tube is blowing cold air across heat sinks, so it is very important to provide control over this fan. Integrated fan controllers should be provided to monitor the environment and switch fans off to allow for self-heating and then re-engage when components become hot. This balance between hot and cold is easily calibrated, ultimately providing a recording system that can operate at both temperature extremes. It is significant to note that while the measures described for thermal management will help to provide an ideal environment for the recorder 's electronics, it is important to use industrial grade components whenever possible. DESIGNING FOR MILITARY SPECIFICATIONS AND COMPLIANCE MIL-STD-810, Environmental Engineering Considerations and Laboratory Tests, is a United States military standard that emphasizes tailoring equipment 's environmental design and test limits for the conditions that it will experience throughout its service life. The standard also establishes test chamber methods that replicate the effects of environments on the equipment rather than imitating the environments themselves. MIL-STD-810 addresses a broad range of environmental conditions that include: low pressure for altitude testing; exposure to high and low temperatures plus temperature shock (both operating and in storage); rain (including windblown and freezing rain); humidity, fungus, salt fog for rust testing; sand and dust exposure; explosive atmosphere; leakage; acceleration; shock and transport shock; gunfire vibration; and random vibration. The standard describes environmental management and engineering processes that can be of enormous value to generate confidence in the environmental worthiness and overall durability of a system design. (Wikipedia, 2018) While operating environments vary greatly, meeting as many criteria in the MIL-STD-810 specification is imperative to providing a reliable and robust product. Anodized metal with form-in-place gaskets allow for sealed protection against rain, humidity, fungus, salt fog and sand and dust exposure. CAD software provides simulation analysis tools to assist with thermal design and structural integrity. Well executed design techniques help assure a smooth laboratory testing process. WHY THE OBSESSION WITH SWaP? The term SWaP has become a commonly used buzzword to describe the requirement for electronic systems that are small in size, weight and power consumption. Why the obsession with SWaP? A lot of it has to do with sophisticated electronics small enough for unmanned vehicles. Another is placing computer power, displays, communications, and sensors on an already overburdened infantryman. Overall, today 's focus on small, lightweight electronic systems that don't use much power has to do with bringing as much capability to the forward edge of battle as possible. (Keller, 2013)

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