Very Low Frequency(VLF)

Michelle M. Gomez and April Rose G. Bogñalos

VLF

Bandwidth 3kHz – 30 kHzWavelengths 10km – 100 km

VLF

• can diffract around large obstacles • can propagate as a ground wave following the

curvature of the Earth• has very low path attenuation, 2-3 dB per

1000 km• atmospheric noise is high in the band• VLF waves can penetrate seawater to a depth of

roughly 10 to 40 metres (30 to 130 feet)

VLF• propagates in vertical polarization

VLF Allocation

Below 9 kHz – International Telecommunication Union

11kHz-30kHz – Navy Communication

Military communication(myriametre wave)Submarine communications

Radio navigation services

VLF Stations• worldwide radio signal propagation

VLF Stations

VLF Stations

VLF as Metal Detector

Induction balance(3kHz-30KHz)• Transmitter coil - outer coil loop of wire.• Receiver coil - inner coil loop of wire.

The polarity of the magnetic field is perpendicular to the coil of wire. Each time the current changes direction, the polarity of the magnetic

field changes.

END