The world of radio communication covers an extremely wide frequency spectrum, but most everyday applications focus on the VHF, UHF, and SHF bands. In contrast, there are extremely low frequency ranges such as VLF (Very Low Frequency: 3–30 kHz) and ELF (Extremely Low Frequency: 3–300 Hz), which, due to their unique physical properties, offer special communication capabilities. These bands are primarily used for underwater, military, and strategic communications.
In this article, we take a detailed look at how these bands work, the technological challenges involved, their applications, and recent developments.
What is VLF and ELF?
VLF and ELF are characterized by extremely long wavelengths:
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VLF (Very Low Frequency): 3–30 kHz frequency range, wavelengths of 10–100 km
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ELF (Extremely Low Frequency): 3–300 Hz frequency range, wavelengths of 1,000–100,000 km
Because of their low frequencies, these waves can propagate over very long distances, penetrate the Earth’s surface, ground, and even seawater.
Why is the propagation of these frequencies special?
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Earth-ionosphere waveguide: VLF waves travel between the Earth’s surface and the ionosphere with minimal attenuation.
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Underwater penetration: Higher frequencies are absorbed after a few meters in water, but VLF waves can reach hundreds of meters in depth.
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High stability: They are not affected by tropospheric or ionospheric disturbances.
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In the case of ELF: Signals can reach submarines thousands of kilometers away underwater.
These properties make these bands ideal for submarines, strategic missile systems, and global military communication.
Application areas
Underwater communication
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Main communication systems for submarines: since seawater blocks most radio waves, VLF and ELF remain the only viable solutions for deep-sea vessels.
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One-way communication: due to limited antenna sizes on submarines, communication is typically receive-only.
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Transmission of critical commands: used for strategic commands (e.g., launch authorizations) with extremely high security.
Military strategic communication
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Nuclear deterrent systems: maintain constant connection with strategic weapon systems.
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Jamming resistance: extremely difficult to jam or intercept with conventional equipment.
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Global coverage: capable of reaching any location on Earth.
Geological and geophysical research
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VLF geological sounding: analyzing underground layers through electromagnetic responses.
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ELF earthquake prediction: sensitive to certain geodynamic changes.
Civilian and scientific applications
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Space research: studying the magnetosphere and lightning discharges.
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Animal research: some species, such as whales, may perceive ELF signals.
Technological challenges
While the physical advantages are significant, implementing these systems is highly complex:
Antenna size
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For VLF: antennas several kilometers long are required.
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For ELF: antenna systems may need to extend tens of kilometers.
High power demands
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Generating such long waves requires extremely powerful transmitters.
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For example, the famous Wisconsin ELF transmitter operated with several megawatts.
Cost and infrastructure
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Antenna systems occupy several square kilometers.
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Construction, maintenance, and operation are extremely expensive.
Data transmission rate
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Extremely low: only a few bits per second.
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Suitable primarily for emergency messages, commands, and brief communications.
Notable VLF and ELF stations
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USA: Wisconsin ELF transmitter (decommissioned), Cutler VLF (Maine)
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Russia: Zevs ELF (Kola Peninsula)
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China: Project “J” ELF system, Ningxia VLF station
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India: INS Kattabomman VLF station
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France: Sainte-Assise VLF transmitter
Many of these stations are classified due to their close connection with military defense systems.
Modern development directions
AI-based signal processing
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Noise reduction, weak signal detection, and decoding through machine learning.
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Potential for significant efficiency gains in existing systems.
Mobile VLF transmitters
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Development of airborne or naval VLF transmission platforms.
Micro-antenna research
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Development of smaller antennas for long waves using new materials (e.g., metamaterials).
New civilian applications
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Minimal communication systems for disaster situations.
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Global emergency warning system development.
Advantages and disadvantages summary
| Advantage | Disadvantage |
|---|---|
| Long-distance underwater communication | Very large antenna size |
| High jamming resistance | Low data transmission rate |
| Difficult to intercept signals | High power consumption |
| Global coverage | Extremely high construction costs |
Frequently asked questions
Why isn’t this technology used for civilian communications?
Due to low data rates, enormous antenna sizes, and high costs, it’s impractical for everyday use.
Can submarines really receive these signals?
Yes, properly equipped VLF/ELF systems can reach submarines hundreds of meters below the surface.
Can ELF/VLF communication be jammed?
Technically yes, but it’s extremely difficult as the signals propagate deeply.
Does this technology use artificial intelligence?
New developments are already integrating AI-based noise filtering and signal decoding.
Is exposure to such low-frequency radiation dangerous?
According to current studies, ELF/VLF radiation poses no direct health risk to the general population.
VLF and ELF frequency bands continue to play a crucial role in some of the world’s most critical military and strategic communications. With further advances in technology, particularly in AI and signal processing, these systems may become even more efficient and find new applications. While widespread civilian use remains unlikely, their importance in specialized fields will remain significant for years to come.
