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Powerpoint presentation on basic concepts about VLF.
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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