What’s that you say? What does OMB Circular A-11 have to do with anything EMC related? That’s a pretty good question, and one that I would have asked myself. Until I read (because it was pointed out to me) section 31-12 of the latest edition of the Circular. It starts off:“The value of radio spectrum required for telecommunications, radars, and related systems should be … [Read more...]

Read other posts in the "Elephant in the Test Room" series here.Recap on this threadThe room: - MIL-STD RF immunity testing – 1-18GHz 200v/mThe elephant: - everyone in the room is aware that a significant fraction of the ‘calibrated’ 200v/m test field is actually created at the wrong test frequency.The culprit: - Notoriously high ‘start of band’ harmonics produced by all octave … [Read more...]

I seem to hear a never ending litany of complaints about how the US military acquisition community has to use more and more commercial equipment (COTS or CI) and that said equipment tends to be highly problematic from an EMC perspective. I tend to dwell on this subject in this blog space, hopefully from different angles, but at the end of the day, I don’t see much being done … [Read more...]

In the last couple of posts I’ve been discussing ground loops and bonding and I made a comment that at the higher frequencies, i.e. VHF/UHF and higher multiple point grounding is used. It occurs at these higher frequencies because of capacitive coupling whether we planned it that way or not. The so-called ground loop exists whenever there are multiple ground connections … [Read more...]

Military use of commercial equipment has grown exponentially over the last decade; and not just in the area of whole equipment, which is easy to see. The use of commercial components and subassemblies within systems has grown as well, so that parts of what look like a full military development effort are actually commercial items. What’s an DoD EMC engineer to do? I wish … [Read more...]

Electromagnetic compatibility (EMC) is often described in terms of RF coupling phenomena. Usually the big four: Radiated and Conducted Emission and Radiated and Conducted Susceptibility/Immunity. These four elements cover all of the EMC issues in a very broad sense. Occasionally lightning and ESD will be divorced from susceptibility and described as if these two items were … [Read more...]