Cutting the Noise

Electromagnetic interference can appear as a sudden
jamming of communications or it can manifest itself slowly,
unnoticed, over a long period of time.

By Anne M. G. Bilgihan

    The most devastating enemy of the INSCOM mission cannot be seen or heard without special instrumentation, but it can severely reduce the effectiveness of our systems. It can appear as a sudden jamming of communications or it can manifest itself slowly, unnoticed, over a long period of time to cover low level signals. This enemy can be part of our local environment or can be "friendly fire," generated by our systems. This enemy is electromagnetic interference, or EMI. Our defense against this antagonist is the INSCOM electromagnetic compatibility program.

    The INSCOM Mission Support Activity, a field operating activity of the G4, is the center for the INSCOM electromagnetic compatibility program. The program is a global network which providing INSCOM units the assistance, training and equipment needed to identify and eliminate electromagnetic interference.

    The INSCOM program is a part of the DoD Interservice electromagnetic compatibility committee. The committee’s program received renewed emphasis in the 1980s as a result of increasing degradation of the electromagnetic environment by the proliferation of new equipment and communications systems both in the DoD and in the private sector.

    The committee is concerned with the compatibility, or non-interference, among equipment and antennas within a site and to minimize interference from the rapidly developing local areas. Each service cryptologic element appoints a committee representative who works with service counterparts to develop solutions and directions and provide technical assistance to the cryptologic sites. Each INSCOM site appoints a local electromagnetic compatibility coordinator to direct local efforts to solve interference problems.

    INSCOM provides technical assistance to INSCOM sites and to other activities upon request. The engineering support, training and equipment assistance enables site personnel to find and fix sources of interference. These sources can be from "noisy" equipment within the site or from nearby transmitters, power lines and industrial sources. Mission Support Activity personnel provide each site with an initial "baseline" survey which provides a "snap shot" of the electromagnetic environment of that location. The electromagnetic compatibility team, led by experts from the Mission Support Activity, includes Trouble Shooter V contract engineers, experts from other services and participants from the involved site. Professors and Army students from the Naval Postgraduate School have participated in previous surveys.

    The Mission Support Activity precedes its baseline electromagnetic compatibility survey with a thorough check of the antenna and radio frequency distribution systems by the antenna certification, evaluation and repair team. The team corrects any problems which may interfere with reception. Once on site, the electromagnetic compatibility team uses spectrum analysis equipment to identify electromagnetic interference effecting the site. They monitor the electromagnetic environment using the site antennas to identify the total spectrum. They use current probes to document interference current on the cables and support structures. A special three axis display, which shows the spectrum change over time, creates a time picture which helps identify the type of interference (i.e., power line noise, factory processes, transmitters).

    After identifying the types of interference, the team works outside with a portable receiver tuned to the frequencies of interest and a portable wide band antenna to locate the source of the external interference. The most difficult source of interference to control is power line noise, due to the necessity of coordination with the local civilian power company. Surveys locate power line noise sources not only to the particular power pole, but also to the actual hardware.

    Following the survey, a mitigation plan is developed; responsibility to correct electromagnetic interference problems rests both with the site and the Mission Support Activity. Corrections may include replacing malfunctioning equipment which may be causing the interference or improving installation techniques to guard against transmission of noise current. External interference may be eliminated by coordinating with the local community to repair power line and other sources from the neighboring areas.

    Cleaning the electromagnetic environment of a site is an involved process which often requires coordination and cooperation among the site, Mission Support Activity, other DoD organizations and the local community. Mission Support Activity technical personnel provide engineering support from in-house resources, other government agencies and through the current Trouble Shooter V engineering services contract. Mission Support Activity personnel also establish proper engineering and installation practices for inclusion in DoD and INSCOM regulations.

    Training is provided during surveys or through interservice programs to increase awareness of the continual possibility of mission degradation due to electromagnetic interference.

    To obtain help, contact one of the representatives listed in the box below.

Anne M. G. Bilgihan is the INSCOM electromagnetic compatibility coordinator, electronics project officer and engineer with the Mission Support Activity, INSCOM.

INSCOM Electromagnetic
Compatibility Representatives

Within the United States: INSCOM Electromagnetic compatibility coordinator: Anne M. G. Bilgihan IALO-MSA-SE, DSN 235-2094, commercial (703) 706-2094

Contractor POC: William C. Adams (Chris) MFEC TS 5, principal engineer, commercial (703) 913-1958

66th MI Group: Eric B. Griffin, IAPG-CE, commercial 011-49-821-498-2737/2885; DSN 434-5787/5885.

Contractor POC: Mark Beighey, MFEC TS 5, principal engineer, commercial 011-49-821-498-2803; DSN 434-5803.

751st MI Bn, 501st MI Bde: Sgt. 1st Class Guy Manor, Acting EMB Chief, IABDK-FS-LM, DSN 753-3325/3328, commercial 83-333-690-3325/3328.

Contractor POC: George Foster, MFEC TS 5, senior engineer, IABDK-FS-LM, DSN 753-3140, commercial 82-333-690-3140

702d MI Group: Sgt. 1st Class Michael D. Carter, NCOIC Configuration Management Office, DSN 791-0471, commercial (706) 791-0471

Alternate: Randy Williams, MFEC TS5 equipment installer, DSN 780-0478, commercial (706) 791-0478

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   Last Updated: April 30, 1997