MIL-STD-1605A(SH)
(2) Classify unintentional RF equipment/system. Table II lists the classifying categories of potential degradation measured by the test equipment. All unintentional emissions shall be located, documented and evaluated during testing to determine their impact on the equipment's operational performance. All test equipment
displays and readings shall be saved in a format which is compatible with common government word processing and spreadsheet software to enhance analysis and distribution of information. Analyzer trace data shall be saved in a format which will allow import into spreadsheets and contain both analyzer configuration and trace data. The test
data sheets shall include clear and concise description of equipment under test, the jack or circuit where test
equipment was connected, sketches of test equipment configurations and file names of the data collected during the testing of individual systems.
TABLE II. Unintentional emissions classification.
Detected Noise Level (Unintentional Emissions) |
Classification |
Category |
<10 dB |
Mild 1/ |
III |
10-20 dB |
Medium 2/ |
II |
> 20 dB |
Severe |
I |
NOTES: 1/ Unintentional emissions must not impact more than 10% of channels or frequency range of selected equipment. If it does, it is considered Medium. 2/ Unintentional emissions must not impact more than 50% of channels or frequency range of selected equipment. If it does, it is considered Severe. |
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e. Continuation of tests. Repeat steps 5.1.3.1.b through 5.1.3.1.d for each RF sensor equipment/system installed in the frequency range as in accordance with 5.1. Once completed, documented, and classified, source location shall be carried out for any Category I or II unintentional emissions detected.
f. Source location. Isolate the offending equipment(s)/system(s) in the frequency range which contained medium to severe RF noise using one or more of the following methods.
(1) Monitor the affected RF sensor with test equipment and sequentially switch suspected equipment/systems on/off, observing the unintentional emissions measurements. If unintentional emissions drops significantly when an equipment/system is shut down, the equipment/system should be noted in the test report for further analysis/action.
(2) Place a receiver antenna in suspected spaces in order to localize the offending spectrum resulting in unintentional emissions observed as medium to severe. In each of the select spaces, the nomenclature/model of the antenna and receiver utilized to measure the spectrum shall be noted, whether or not unintentional emissions was detected.
(3) For locating equipment/systems/cables in spaces where similar unintentional emissions, as detected in
5.1.3.1.c, is found, a near field probe can be used to scan equipments/cables in select spaces. The near field probe should have adequate sensitivity to find the source of highest emissions that resembles the characteristics of the medium to severe unintentional emissions. The nomenclature/make and model of the receiver, near field probe and offending emissions shall be recorded.
(4) If other techniques of source location are used, provide sufficient documentation and reporting to permit others to duplicate the test.
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