Ground conductivity refers to the
electrical conductivity
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allow ...
of the subsurface of the
earth. In the International System of Units (SI) it is measured in millisiemens per meter (mS/m).
Radio propagation
Ground conductivity is an extremely important factor in determining the field strength and propagation of
surface wave
In physics, a surface wave is a mechanical wave that propagates along the Interface (chemistry), interface between differing media. A common example is gravity waves along the surface of liquids, such as ocean waves. Gravity waves can also occu ...
(ground wave) radio transmissions.
Low frequency
Low frequency (LF) is the ITU designation for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km, respectively, it is also known as the kilometre band or kilometre wave.
LF radio waves exh ...
(30–300 kHz) and
medium frequency (300–3000 kHz) radio transmissions are particularly reliant on good ground conductivity as their primary propagation is by surface wave. It also affects the real world radiation pattern of
high frequency
High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten ...
(3-30 MHz) antennas, as the so called "takeoff angle" is not an inherent property of the antenna but a result of a
ground reflection
Ground may refer to:
Geology
* Land, the surface of the Earth not covered by water
* Soil, a mixture of clay, sand and organic matter present on the surface of the Earth
Electricity
* Ground (electricity), the reference point in an electrical c ...
. For this reason ITU publishes an extensive world atlas of ground conductivities.
Other uses
Ground conductivity is sometimes used in determining the efficiency of a
septic tank, using
electromagnetic induction
Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field.
Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk ...
, so that contaminants do not reach the surface or nearby water supplies.
References
External links
Ground conductivity maps in the United States(provided by the
Federal Communications Commission and includes large scale map)
Measurement of the ground conductivity and relative permittivity with high frequency using an open wire line (OWL)(Practical example with network analyzer and mathematics for the conversion)
Broadcast engineering
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