Resolving RF Noise Interference in Mission-Critical Communication Systems

INDUSTRY:
Defense

TYPE OF WORK:
Electronics

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About the Client

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Whether at sea, on land or in air, tactical communications are critical to mission success and crew survival. Onboard communication systems, including intercom and radio systems (VHF, VLF, and wideband) must be free of all interference or at least maintain significant noise attenuation. The client operates mobile assets equipped with advanced electronics, including navigation, communication, and intercom systems.

Understanding the Problem

The Challenge

After upgrading the intercom system, asset operators reported persistent static interference and voice degradation when powered by the asset’s main supply. These issues were particularly noticeable during operations, making communication unreliable.

The interference severely degraded asset to asset and asset-to-base communications, undermining operational effectiveness and introducing safety risks for crew members during training and high-stakes tactical missions.

Solving the Challenge

The Solution

Enginuity Electronics team was tasked to diagnose and mitigate the issue due to prior successful collaborations and technical expertise in electromagnetic compatibility (EMC) aboard mobile systems.

Diagnostic Strategy:

Conducted system-wide component isolation.
Utilized advanced diagnostic tools including:

Spectrum analyzers
Current clamps

Focused on identifying conducted common-mode noise traveling through the mobile asset’s DC power system.

Field testing was conducted using two mobile assets using call signs A1 and A2. Testing revealed that vessel A1 exhibited greater radio noise, so troubleshooting focused on that platform. The radios included two bands: wideband digital L-band and VHF radios, both historically prone to audio noise.

During testing, the interference was characterised by multiple components, including “whirling” and “clicking” sounds, which occurred only when the vessels were operating on water. This insight narrowed the problem to environmental or power-related factors affecting the intercom and radio systems.

The Intercom system was highly susceptible to DC voltage variations and power line noise, resulting in audible noise during operation.
The radio battery charger, even with its factory-installed ferrite choke, was a major source of common-mode noise when connected to the same power bus as the intercom.
Transient currents (notably ~19A during VHF transmission at 12VDC) also contributed to voltage instability and EMI.

The team implemented filters and chokes to attenuate the noise, successfully restoring communications to a high quality (rated by crews as 8-9/10). Due to time constraints and the need for rapid deployment, they created a specification for permanent filter components for future vessel installations.

Summarizing the Outcome

The Conclusion

To address the EMI-related disruptions, interim actions included installing DC filters and ferrite chokes at critical points and reconfiguring power inputs for the intercom and VHF amplifier using DC-DC converters. These measures stabilized voltage, filtered power lines, and significantly improved audio quality.

For long-term reliability, recommendations include adding a dedicated DC EMI filter near the intercom’s power input. Additionally, optimizing wiring layouts will help minimize EMI in future installations.

As a result, communication systems operated reliably under normal loads with reduced noise and no further disruptions. This success was driven by collaborative troubleshooting, the use of proper EMC tools, and validation of manufacturer recommendations.