# Ground conductivity

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**Ground conductivity** refers to the [electrical conductivity](/source/Electrical_conductivity) of the subsurface of the [earth](/source/Earth). In the International System of Units (SI) it is measured in millisiemens per meter (mS/m).

## Radio propagation

Main article: [Radio propagation](/source/Radio_propagation)

Ground conductivity is an extremely important factor in determining the field strength and propagation of [surface wave](/source/Ground_wave) (ground wave) radio transmissions. [Low frequency](/source/Low_frequency) (30–300 kHz) and [medium frequency](/source/Medium_frequency) (300–3000 kHz) radio transmissions are particularly reliant on good ground conductivity as their primary propagation is by surface wave.[1] It also affects the real world radiation pattern of [high frequency](/source/High_frequency) (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](/source/Ground_reflection).[2] For this reason ITU publishes an extensive world atlas of ground conductivities.[3]

## Other uses

Ground conductivity is sometimes used in determining the efficiency of a [septic tank](/source/Septic_tank), using [electromagnetic induction](/source/Electromagnetic_induction), so that contaminants do not reach the surface or nearby water supplies.[4]

## References

1. ["Recommendation ITU-R P.368-7 Ground-wave propagation curves for frequencies between 10 kHz and 30 MHz"](https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.368-7-199203-S!!MSW-E.doc) (DOC). [International Telecommunication Union](/source/International_Telecommunication_Union) (ITU). 1992. Retrieved 2015-10-28.

1. Kazimierz Siwiak KE4PT (April 2016). "Ground influence on antenna patterns". *[QST](/source/QST)*. [American Radio Relay League](/source/American_Radio_Relay_League)

1. ["Recommendation ITU-R P.832-2, World Atlas of Ground Conductivities"](https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.832-2-199907-S!!PDF-E.pdf) (PDF). [International Telecommunication Union](/source/International_Telecommunication_Union) (ITU). 1999. Retrieved 2015-10-28.

1. Taylor, Rick & Lee, Doolittle (June 2003). ["Ground conductivity survey of a septic system during and after failure"](http://link.aip.org/link/?LEEDFF/22/555/1). Retrieved 2008-02-10.[dead link]

## External links

- [Ground conductivity maps in the United States](http://www.fcc.gov/encyclopedia/m3-map-effective-ground-conductivity-united-states-wall-sized-map-am-broadcast-stations) (provided by the [Federal Communications Commission](/source/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)](https://www.dl1glh.de/groundconductivity.html) (Practical example with network analyzer and mathematics for the conversion)

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Adapted from the Wikipedia article [Ground conductivity](https://en.wikipedia.org/wiki/Ground_conductivity) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ground_conductivity?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.