ground conductivity

Image:United_States_Effective_Ground_Conductivity_Map.png

Ground conductivity refers to the electrical conductivity 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 (ground wave) radio transmissions. Low frequency (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.{{cite web

|url=https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.368-7-199203-S!!MSW-E.doc

|type=DOC |year=1992 |publisher = International Telecommunication Union (ITU)

|title=Recommendation ITU-R P.368-7 Ground-wave propagation curves for frequencies between 10 kHz and 30 MHz

|accessdate=2015-10-28

}} It also affects the real world radiation pattern of 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.{{cite journal |journal=QST |title=Ground influence on antenna patterns |date=April 2016 |pages=41–42 |publisher = American Radio Relay League |author=Kazimierz Siwiak KE4PT}} For this reason ITU publishes an extensive world atlas of ground conductivities.{{cite web

|url=https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.832-2-199907-S!!PDF-E.pdf

|type=PDF |year=1999 |publisher = International Telecommunication Union (ITU)

|title=Recommendation ITU-R P.832-2, World Atlas of Ground Conductivities

|accessdate=2015-10-28

}}

Other uses

Ground conductivity is sometimes used in determining the efficiency of a septic tank, using electromagnetic induction, so that contaminants do not reach the surface or nearby water supplies.{{cite web

| last = Taylor

| first = Rick

| author2 = Lee, Doolittle

| title = Ground conductivity survey of a septic system during and after failure

| date = June 2003

| url = http://link.aip.org/link/?LEEDFF/22/555/1

| accessdate = 2008-02-10

}}{{Dead link|date=January 2020 |bot=InternetArchiveBot |fix-attempted=yes }}

References

External links

[http://www.fcc.gov/encyclopedia/m3-map-effective-ground-conductivity-united-states-wall-sized-map-am-broadcast-stations Ground conductivity maps in the United States] (provided by the Federal Communications Commission and includes large scale map)
[https://www.dl1glh.de/groundconductivity.html 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)

Category:Broadcast engineering