Below are the questions asked during the live event, along with their respective answers.
Q: What is a good way to reduce the noise floor before RE02 measurement? We have low notches.
A: Use a high gain, low noise preamplifier. Tuned receivers generally have a lower noise floor than Spectrum analyzers. Make sure the analyzer attenuations are set to 0. If allowed by the standard, reduce the resolution bandwidth. If not allowed, you could do this just to see better what is going on; however, final data would require the proper bandwidth.
Please explain “notches” as MIL-STD limits do not have notches. Sounds like you may have a high level signal combined with what you are measuring and you are trying to remove it from over driving your analyzer. We would need more specifics, please feel free to contact us directly at D.L.S. Electronic Systems, Inc. 847-537-6400.
Q: What is the best way to perform gap testing when a buying COTS that are tested to do-160 but needs to be qualified to 461 levels?
A: There’s not “gap testing” as much as there’s a completely different testing philosophy between MIL and RTCA. A complete retest may be in order to fully satisfy the procurement agency. Most tests have different levels and methodology of execution; therefore, a full retest would be required. If the final customer agrees to take some of the data (for ex: emissions of radiated susceptibility), but requires tests that are not cross referenced such as CS115, CS116 then a comparison along with the required testing can be performed. List all required tests, and performed testing. You can select tests that are close to the requirement and try to get a buy off of no retest from the government body before developing a test plan.
Some examples are, MIL requires a 2m vs. a 1m power cord and MIL requires 10m of I/O cable to be in the setup vs. 3.3 in RTCA. MIL also requires 50µH LISNs vs 5µH LISNs with a 10µF capacitor.
Q: Are there any prerequisites for attending your March class? That is, advance knowledge, training, etc?
A: No, an electrical engineering background is a plus. I would add that basic understanding of RF theory would help, but is not necessarily required. We begin at a very basic level and expand as the class goes on until we are making calculations (using simple math) to estimate emissions for a system.
Note, Be sure to schedule a product review when you sign up for the class. As one class member said during his product review, “I would not have even known what you were talking about had I not just taken the class”.
To find out more about the class, click here.
Join us for the March seminar where guest speaker Michel Mardiguian, primary author of Controlling Radiated Emissions by Design, (the book we use during the class) will be conducting several live demonstrations.
Q: Is there a guideline in analysing COTS wavier comparing with Mil-Sd 461g?
A: No, but if you can you give us more information, we may be able to give you some suggestions. Did the waiver make reference to some testing that was done and accepted? Was it accepted for 461E/F and needs to be compared to 461G?
Q: I understand ESD is required to be applied to internal pins on connectors – true?
A: No, CS118 is applicable to an operating unit in normal use. Discharge points are applicable to areas accessible to final user during normal operations, such as: keyboards, knobs/buttons, displays, unit accessible areas, seams etc.
Q: Could Don briefly discuss the purpose of CS103?
A: CS103 is Conducted RF Susceptibility on antenna ports for receivers and amplifiers where signals can interfere and create intermodulation.
CS103 is meant to test the ability of the unit to withstand the intermodulation products of two strong out-of-band signals. Due to the nature of a receiver and its connected equipment (filters, antennas), the out of band signals are easily “ignored.” The small intermodulation product (fo = 2f1-f2 or fo = 2f1+f2) can be enough to overwhelm a sensitive receiver, even if f1 and f2 are ignored. As radios and radio systems are highly specialized, the details of the test are usually figured out before hand and laid out in a test procedure.