Everything You Need to Know About the Latest Version of this Important EMC Standard
MIL-STD-461H was released on April 17, 2026, and became effective on programs initiated after that date.1
As background, MIL-STD-461 is officially prepared by the U.S. Air Force, but it is the product of a Tri-Service Working Group (TSWG) made up (not surprisingly!) of representatives from the Army and Navy as well. In addition to service members, there are industry representatives (of which the author of this article is one).
Since 1993, MIL-STD-461 has been on a five-year review cycle to ensure that it remains current and useful. This does not mean a new revision has to be released every five years, but just that a review must be performed on that cycle. It would be entirely acceptable to simply reaffirm the old version with no changes, or to entirely sunset the standard. To date, neither of these alternatives has been selected.
MIL-STD-461H has no new requirements, nor does it require any new test equipment. It includes the fewest number of substantive changes in the revision cycle history. This is not to say the change is pointless – far from it – but that the changes are focused in a different direction from requirements, procedures, and test equipment. The majority of the changes are for the purpose of ensuring that the requirements and test procedures are properly understood and implemented, and, all else failing, written clearly enough to give the Procuring Activity the “horsepower” to force a recalcitrant vendor or test house to do things properly, as opposed to legal wrangling over the meaning of a requirement.
In other words, MIL-STD-461H is yet another attempt to shut down the legal machinations of the EMC lawyers who ignore the plain meaning of the standard and twist things to suit their own needs. There is also a perception that the sophistication of the MIL-STD-461 user base is decreasing over time.
In turn, this necessitates added explanation and background for which there was previously less need. Finally, there is a history of only MIL-STD-461 being levied down to the level where testing is being performed, as opposed to levying both the standard and the applicable data item descriptors (DIDs). Because of this, requirements from the DIDs may be found sprinkled throughout the H revision of the standard. Again, there are no new requirements, but people can no longer claim that they left pertinent information out because they didn’t have the DIDs levied in their contract.
Key Issues Addressed in This Revision
An example of a response to the practice of “EMC law” is our first change: elimination of the last column of Table II, bandwidth and measurement time. That column dates back to 1993 (MIL-STD-462D) and is for analog-tuned measurement receivers. There is nothing wrong with this column for such receivers. However, although analog-tuned receivers are largely obsolete and not being used, some people use that column when they should be using the column for step-tuned receivers. Eliminating the last column eliminates this problem of different test facilities using different sweep times. Facilities still using true analog-tuned receivers will need to reference the older versions of the standard for sweep times.
On a related note, paragraph 4.3.10.3.3 now requires a step‑tuned receiver to step in quarter‑bandwidth step sizes or smaller, rather than the previous half-bandwidth steps. Half‑bandwidth steps work fine for 3 dB bandwidths, but with 6 dB beamwidths, a signal halfway between two adjacent stepped frequencies will be desensitized by 1.5 dB, whereas with quarter‑bandwidth steps, a signal in the middle will only measure 0.4 dB down. Most canned software already steps in quarter‑bandwidth step sizes, so this should not have an impact on most testing.
An example of the drop in user community sophistication is that the applicability paragraphs of requirements CS114, CS115, CS116, and CS117 are each augmented to state that the requirements are applicable to electrical cables. As opposed to non-electrical cables. (Really!)
A process begun with MIL-STD-461F (2007) is continued in MIL-STD-461H. This is the continued attempt to define what primary power is, how to arrange these cables, and what requirements apply (new definitions 3.1.8, input primary power leads, and 3.1.12, Primary power in support of paragraph 4.3.8.6.1). The fact that this is still ongoing is evidence that the obfuscation of this simple concept is still a fruitful field of endeavor for EMC lawyers, and also the decreased sophistication of the user base.
An example of how this section is willfully/ignorantly misinterpreted is an unmanned low-earth orbit (LEO) satellite program. Like similar systems and devices, the source of electrical power for this platform was solar arrays. The solar arrays, together with associated electronics, generated 28 Vdc – 32 Vdc primary power for the satellite.
An equipment subset on the platform generated 12 Vdc for its own use and distribution internal to the subset. The platform integrators insisted that the 12 Vdc distribution be treated as primary power, imposing CE101 and CE102 on the 12-volt loads, and also CS101. And because Curve 2 of Figure CS101-1 is for 28 Vdc and below, they imposed that curve on the 12 Vdc loads, meaning that at the low end of the CS101 spectrum, the 12 Vdc loads had to withstand a peak ripple of 2.8 volts riding on top of the nominal 12 Vdc load inputs. So the 12-volt input ran excursions from 14.8 down to 9.2 volts.
There was nothing that could be done to make these people see the light, and it is this kind of thing that keeps section 4.3.8.6.1 in a constant state of flux, even though there is no change whatsoever in the intent of the paragraph going back to 1993. Applicability paragraphs for requirements CE101, CE102, and CS101 all have this added statement: “This requirement is not applicable to power leads that do not directly interface with the platform power bus.”
A change that is found in the Data presentation section at the end of each requirement is added wording to “Provide photographs showing actual equipment test setup, including equipment grounding and the associated dimensions.” There may be additional requirement-specific wording as well. Once again, this change is not a real change, but an attempt to get the necessary information in the EMI test report. A complete set of such requirements may be found in the Data Item Descriptor (DID) DI-EMCS-80200C, but it is often the case that only MIL-STD-461 is flowed down to the vendor, and, absent requiring such data within the standard itself, relying on the DID does not produce the desired results.
A Detailed Rundown of the Changes
And now follows the laundry list of changes in MIL‑STD-461H:
Paragraph 4.3., Verification requirements, has two added statements. The first is to the effect that formal qualification testing may not commence without (government) customer approval. This gives the DoD the contractual power to ensure things are done properly. It used to be that such purely contractual issues were addressed elsewhere, but it was felt that too many things were being swept under the rug.
And at the end of the paragraph: “Measurement tolerances and associated uncertainties specified in section 4.3.1. shall not be used when assessing compliance/non-compliance with the limits in this standard.” This added statement changes nothing as to the original intent; it reflects that people incorrectly want to adjust limits for the measurement tolerances described in paragraph 4.3.1. An excellent discussion/expansion on this topic is added at the end of the corresponding appendix section.
The existing paragraph 4.3 “G” requirement for Procuring Activity approval of an EMI test procedure prior to the start of testing is strengthened in “H” with the addition of a “shall” statement. The intent is not changed, but the addition of the “shall” gives the Procuring Activity the authority it needs to approve or disapprove of the start of formal testing.
In “G,” paragraph 4.3.4, Ambient electromagnetic level did not require an acceptable ambient level to be recorded. In “H,” the ambient level must be recorded.
Paragraph 4.3.7.3, Overload precautions, is strengthened from advisory instruction to requirements that each measurement be demonstrated free of overload. Overload is more likely with newer time domain type EMI receivers with very wide-open front ends, as compared to traditional tunable preselectors or fixed bandpass filters.
Section 4.3.8.6, Construction and arrangement of EUT cables, has been rewritten with three sub-paragraphs. The rewrite is only for clarity; nothing has changed about how cables are built and placed.
4.3.10.4.3, Instructions for determining the worst-case frequency of a susceptibility non-compliance, is now relegated to failures occurring above 1 GHz.
Figures 2, 4, and 5 are redrawn for clarity. No substantive changes.
Table V, Requirement Matrix, has a few changes for surface ships and submarines: CS104, CS116 (subs).
The 5.4 CE101 requirement for Navy platforms is extended to 20 kHz, to support MIL-STD-1399, section 300. Figures CE101-1, -2, and -3 are redrawn with the limits extended to 20 kHz. The CE101 requirement for non-Navy aircraft is still limited to 10 kHz.
Although in some cases the requirement for AC‑powered loads applies only at the second harmonic and above, 5.4.3.5.e requires the measurement and presentation of the fundamental as part of the emission plot. This is so that limits which are proportional to fundamental current can be properly evaluated.
5.5 CE102 applicability (paragraph 5.5.1) is reworded to clearly indicate it applies to platform primary power inputs.
Section 5.5.3.4.2 adds an alternative method for verifying proper LISN impedance.
5.6 CE106: MIL-STD-461H CE106 applicability adds the following applicability caveat: “This test method is not applicable to EUTs with antennas containing active electronics, phased array antennas, or phasing antennas.”
5.6.3.4.1.c.7, the H revision adds a caveat regarding measurement bandwidth for Navy shipboard applications.
5.7 CS101 applicability (5.7.1) adds a requirement that if the test sample power input is two-phase delta, then both phases must undergo CS101 injection.
5.7.3.2.f., Test equipment, adds a line item mentioning the kinds of probes required. These are a pair of probes, a differential probe (either option for oscilloscope use), or a power-line ripple detection transducer (for use with a spectrum analyzer or EMI receiver). Previous versions didn’t mention the transducer, which led to some dangerous setups with line voltage on the oscilloscope chassis. Figures CS101-3 through CS101-6 are updated accordingly. The transducer that allows use of a frequency domain measurement was first introduced in MIL-STD-461G, is expanded upon in “H,” and for those unfamiliar with it, a full description may be found in an archival issue of this magazine.2
5.12 CS114, The exclusion of coaxial cables from the CS114 requirement is moved from the limit paragraph of “G” to the applicability paragraph of the H revision, where it really belongs.
The 77 dBuA common mode limit that was previously for Navy ships now also applies to Army ships. Figure CS114-1 reflects this change.
One of the chronic abuses of CS114 is test facilities placing the injection clamp and monitoring probe around several separate bundles simultaneously, to save time. CS114 paragraph 5.12.3.3.c.1 addresses this and is another sad example of having to add wording to the standard not to change the intent, but merely to enforce the original intent.
Section 5.12.3.3.c.1 in the H revision says, “Place the injection and monitor probes around a single cable bundle interfacing with EUT connector.” In the G revision, the statement was identical except that the word “single” was missing. The intent of the change in the H revision is to enforce that only one cable at a time is to be tested. Again, this was always the intent, but the added word “single” allows for better enforcement against those willfully
and/or ignorantly flouting the clear intent of the standard.
Figure CS114-2 (Figure 2) corrects an error in previous versions of the standard where the maximum insertion loss was extended down to 4 kHz. That curve is now loglinear from 100 kHz down to 4 kHz, whereas previously it took a jog at 10 kHz with a lower slope down to 4 kHz. The purpose of the extension below 10 kHz is to ensure that the 77 dBuA limit can be achieved by applying no more than 100 W to the BCI clamp. The H revision relaxed limit suffices; the previous limit was overkill for this purpose. The calculation is as follows:
Limit (dBuA) + 50 Ω fixture resistance – conversion dBuV to dBm + insertion loss (dB) = 50 dBm (100 W)
77 dBuA + 34 dBΩ – 107 + IL = 50 dBm
IL = 46 dB
The upshot is that any BCI clamp meeting the insertion loss limit above 10 kHz will also meet the insertion loss limit below 10 kHz, whereas previously a clamp that just met the insertion loss limit at 10 kHz might not meet the insertion loss limit at 4 kHz in the F and G revisions of the standard. There is appendix wording saying that this correction means a probe that meets the H revision insertion loss plot is suitable for testing to MIL-STD‑461F/G.
5.15 CS117, Paragraph 5.15.3.4.b, Calibration, has been modified to ensure the intent of the standard is followed. Figure CS117-3 is now labeled voltage and current waveform 3.
5.17 RE101, 5.17.3.4.c, procedures revised to ensure no signals are missed.
5.18 RE102, Section 5.18.3.3.c., 2.c., 2 & 3, include extra instructions to ensure the horn antenna elevation angle is parallel to the floor and not tilted looking up or down.
Figure RE102-2 has been redrawn and has lost some resolution. At 10 kHz, the “Internal to Pressure Hull” limit is 88 dBuV/m. This was clearly shown in MIL-STD-461G but is less obvious in the H revision.
There was a great deal of interest in modifying the use of the microwave double ridge guide horn to allow alternatives with wider beamwidth at Ku band. The ETS/Lindgren Model 3117 is cited as a popular alternative, but going back to MIL-STD-461G, we were not able to come up with a generic description of that antenna via its physical dimension parameters. Another suggestion was the use of a standard gain horn with an appropriate beamwidth for Ku band (12.4 – 18 GHz). In the end, no changes were made.
5.19 RE103, Minor changes in the 5.19.1 applicability paragraph address the relative strengths and weaknesses of CE106 and RE103.
Section 5.19.2, RE103, Navy shipboard limits, have changed.
5.19.3.4.c is new and requires a determination that the ambient requirements are met.
5.19.3.4.d.4 adds extra frequencies to the measurement system integrity check.
5.19.3.4.e.9 adds a receive antenna correction factor to the list of data reduction items when determining ERP at each measurement frequency. This is not a real change, just making sure the instructions are correct.
5.22 RS105, 5.22.1, Applicability, is constrained to equipments which have an EMP requirement.
Conclusion
Late-breaking news. Since the release of the standard, several parties have seized on an RS103 test equipment appendix statement to the effect that:
“…E-field generators with a transformer feed are not propagating an electromagnetic field. These should not be used for formal qualification testing.”
Inclusion of this statement in the appendix makes it, by definition, non-contractual, as is the intentional use of the word “should,” as opposed to “shall.” The word “shall” cannot be placed in the non-contractual appendix. In the case of small equipment, such as a typical avionics enclosure, a parallel plate transmission line is an excellent and efficient source of a traveling electromagnetic wave with which to illuminate the test sample and attached cables. But if the test sample is a floor-standing equipment rack, there are few practical alternatives to the electric field generator, and this is certainly the case below 30 MHz.
In conclusion, MIL-STD-461H provides a respite from the need to re-engineer or upgrade test facilities – unless the facility has been shirking its duties, in which case MIL-STD-461H is a new tool to make sure things get done right.
Or at least, better.
Endnotes
- MIL-STD-461H, dated 17 April 2026: Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment
- Javor, Ken. “Fifty-Year Old EMI Testing Problem Solved,” In Compliance Magazine, June 2012.
