RF Testing  ·  SCIF / TEMPEST
Medical Imaging  ·  Audiophile

Preventing EMI
Since 1978.

DJM Electronics designs and manufactures precision EMI filters for digital signal lines: Ethernet, USB, HDMI and others. Our filters are utilized in RF test laboratories, classified government facilities, medical imaging suites, and high-end audio installations around the globe. Founded in 1978, DJM Electronics is based in San Diego, California. All of our products are 100% Made in the USA.

DJM Electronics ACTIV 10G, Pasif 1G, and ACTIV POE Ethernet EMI filters in front of an open anechoic chamber, with Rohde & Schwarz spectrum analyzers and EMC test equipment in the lab
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About DJM Electronics

Forty-Eight Years in the EMI and RF Shielding Industry.

Founded in Los Angeles in 1978, DJM Electronics spent decades building deep expertise in electromagnetic compatibility and RF shielding. In 2004, DJM developed the world's first active Ethernet EMI filter, solving a problem that passive components could not: How do you pass high-speed digital signals through a shielded enclosure without compromising electromagnetic isolation or the digital signal? That original innovation led to three US patents and a product line that now covers Ethernet at speeds from 10Mbps to 10Gbps, USB 2.0 and 3.1, HDMI and other digital signals.


Our filters are designed and built to provide maximum performance while still being easy to install — no special knowledge, no special skills and no special hardware. We make it easy. Every product ships tested and ready from our facility in San Diego, California.

DJM Electronics original logo, established 1978
Trusted by leading organizations across defense, government, medical, and industry
ETS-Lindgren· Boeing· National Security Agency· Lockheed Martin· GE Healthcare· Central Intelligence Agency· Northrop Grumman· BAE Systems· Siemens Healthineers· Palmer's Contracting Group· General Dynamics· L3Harris· Naval Research Lab· NASA· Raytheon· NAVAIR· US Air Force· US Army· Leidos· SAIC· General Atomics· Philips Healthcare· SpaceX· Qualcomm· Honeywell· CACI· Los Alamos National Lab· Sandia National Lab· Intel· Texas Instruments· NIST· NOAA· Parker Hannifin· Viasat· Sierra Nevada Corp· Thales· Nokia· Trimble· Collins Aerospace· Verizon· United Launch Alliance· FEMA· NAVWAR· LG Electronics· Motorola· Braden Shielding· Frankonia EMV· Ramsey Electronics· Shielding Resources Group· TDK RF Solutions· Universal Shielding· Shieldex· The Ohio State University· Princeton University· MIT· NRC Canada· Royal Canadian Mounted Police· NetGear· Roku· Sonos· Google· Apple· AudioQuest· MSB Technology· TotalDAC· ETS-Lindgren· Boeing· National Security Agency· Lockheed Martin· GE Healthcare· Central Intelligence Agency· Northrop Grumman· BAE Systems· Siemens Healthineers· Palmer's Contracting Group· General Dynamics· L3Harris· Naval Research Lab· NASA· Raytheon· NAVAIR· US Air Force· US Army· Leidos· SAIC· General Atomics· Philips Healthcare· SpaceX· Qualcomm· Honeywell· CACI· Los Alamos National Lab· Sandia National Lab· Intel· Texas Instruments· NIST· NOAA· Parker Hannifin· Viasat· Sierra Nevada Corp· Thales· Nokia· Trimble· Collins Aerospace· Verizon· United Launch Alliance· FEMA· NAVWAR· LG Electronics· Motorola· Braden Shielding· Frankonia EMV· Ramsey Electronics· Shielding Resources Group· TDK RF Solutions· Universal Shielding· Shieldex· The Ohio State University· Princeton University· MIT· NRC Canada· Royal Canadian Mounted Police· NetGear· Roku· Sonos· Google· Apple· AudioQuest· MSB Technology· TotalDAC·
Digital Signal EMI Filters

Ethernet, USB, and HDMI
Active and Passive.

Engineered for the full spectrum of high-speed data environments. Every product is tested to specification before it leaves our facility.

ACTIV Series
DJM-A10G
10G
Active Ethernet EMI filter utilizes DSP to achieve 100dB. Supports 10Mbps to 10Gbps on any standard CAT cable. Installs in a single circular hole on any shielded enclosure.
Active Ethernet
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DJM-APOE
POE
Active Ethernet EMI filter with simultaneous Power over Ethernet. 802.3bt Type 3, 60W maximum. One penetration for both data and power.
Active Ethernet PoE 60W
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DJM-AUSB3
USB 3.1
Active EMI filter for USB 3.1 Gen 2 SuperSpeed+ connections. Full DSP signal reconstruction combined with USB power delivery profiles up to 60W.
Active USB 3.1 USB-C 60W
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PASIF Series
DJM-P01G
1G
Passive Gigabit Ethernet filter. No power required. Compact form factor for smaller enclosures and installations where 100dB performance is not required. Passes PoE transparently when connected to a PoE switch.
Passive Ethernet 8-Line
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DJM-PUSB2
USB 2.0
Passive USB 2.0 EMI filter. No power required. Compact form factor for small enclosures and SCIF installations.
Passive USB 2.0 4-Line
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Custom
DJM-CUST
Custom EMI Filters
Custom EMI filter solutions for unique interfaces, signals, form factors, and military specifications. Contact our engineering team to discuss your application.
By Specification
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Applications

Four Demanding Environments. One Proven Solution.

DJM filters operate in classified facilities, hospital imaging suites, federal infrastructure, and audiophile reference systems worldwide.

RF Testing / EMC
Radiated and conducted interference coming from data lines corrupts measurements and compromises CISPR compliance. DJM filters eliminate noise at the source without affecting measurements.
MIL-STD-461CISPRFCC Part 15IEEE 299
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ACTIV POE EMI filter in RF and EMC test laboratory
SCIF / TEMPEST / Government
Existing CAT cables to a DJM filter replaces two fiber media converters, fiber jumper cables, a waveguide, and power on both sides of the wall. Simpler, quieter, and fully compliant with ICD-705 and TEMPEST requirements.
ICD-705EMSECIEEE 299
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ACTIV 10G EMI filter in military SCIF secure facility
Medical Imaging / MRI
MRI scanners are so sensitive that standard Ethernet connections through the shield wall destroy image quality. Media converters are equally unsuitable since they generate their own RF emissions inside the suite. A DJM filter is the only practical solution.
MRI CompatibleIEEE 299
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ACTIV POE EMI filter in MRI medical imaging suite
Audiophile / Hi-Fi
EMI and network noise distort the sound fidelity of analog signals at the digital to analog interface. DJM filters remove the interference before it gets there. No latency, no signal degradation.
Streaming AudioReference Grade
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ACTIV AUDIO EMI filter in professional recording studio
Technical Resources

Engineering Articles, Explanations and Documentation.

White papers, application notes, and technical briefs from the DJM engineering team.

Resource Index

Technical Resources

White papers, application notes, tech briefs, and engineering articles from the DJM team. Reference material for EMI filter selection, installation, and compliance.

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Support Index

Product Support

Installation instructions, wiring diagrams, and troubleshooting procedures for all DJM products. Start here if you need help with your installation.

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Installation Guide

ACTIV 10G Installation Guide

Step-by-step mounting and wiring instructions for the ACTIV 10G Ethernet EMI Filter. Covers panel cutout, connector orientation, and cable preparation.

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Troubleshooting Guide

ACTIV 10G Troubleshooting

Systematic diagnostic procedures for the ACTIV 10G. Covers link failure, speed negotiation issues, PoE faults, and shielding integrity verification.

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