Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3 kHz to 30 kHz and wavelengths from 10 to 100 kilometres. Due to its limited bandwidth, audio (voice) transmission is highly impractical, and therefore, only low data rate coded signals are used. The VLF band is used for a few radio navigation services, government time radio stations (broadcasting time signals to set radio clocks) and for secure military communication. Since VLF waves penetrate about 40 meters into saltwater, they are used for military communication with submarines. The band is also known as the myriametre band or myriametre wave as the wavelengths range from one to ten myriametres (an obsolete metric unit equal to 10 kilometres).
Because of their large wavelengths, VLF radio waves can diffract around large obstacles and so are not blocked by mountain ranges, and can propagate as ground waves following the curvature of the Earth. The main mode of long distance propagation is an Earth-ionosphere waveguide mechanism. The Earth is surrounded by a conductive layer of electrons and ions in the upper atmosphere, the ionosphere D layer at 60 km altitude, which reflects VLF radio waves. The ionosphere and the conductive Earth, form a horizontal "duct" a few VLF wavelengths high, which acts as a waveguide confining the waves so they don't escape into space. The waves travel in a zigzag path around the Earth, reflected alternately by the Earth and the ionosphere, in TM (transverse magnetic) mode.
Is it wise to come to me
To guide you spiritually
Dead eyes stare back from the void
Reflecting what I see
I am the key that locks the door
The link between the worlds
Take my hand
Dare to walk with fire
Let the dead rest in peace
Step aside leave them be
Let the dead rest in peace
Sacrilege, final sleep
I am here to satisfy
Your curiosity
If you think it's worth the risk
To be stuck with me
There are things you cannot see
That's why you come to me
Take my hand
Dare to walk with fire
Let the dead rest in peace
Step aside leave them be
Let the dead rest in peace
Sacrilege, final sleep
Was it wise to come to me
To guide you spiritually
Your dead eyes stare back from the void
Now you're stuck with me
Let the dead rest in peace
Step aside leave them be
Let the dead rest in peace
Sacrilege, final sleep
Let the dead rest in peace
Step aside leave them be
Let the dead rest in peace