BarnacleBill
New member
The conductivity and mineralization levels of the earth hold a great interest not only to metal detector hobbyists but also those in the field of radio. Within the radio area, radio engineers that design AM radio stations, & shortwave radio stations, are very interested in the "ground", as are amateur radio operators that use radios at around the same frequencies.
The best place to locate an AM radio station antenna is in a salt marsh near the ocean, because the conductivity of the saltwater helps the signal travel greater distances. The next best place is in brackish freshwater marshes, which is why you will notice many antenna fields in marshes or swampy areas. They're not located there because the land is cheap.
Therefore the FCC produces conductivity maps that help engineers design the RF screen(radio ground) systems. The poorer the conductivity of the soil, the bigger & more expensive the RF screen system has to be. Remember these maps DO NOT concern iron mineralization, only how much like saltwater the ground is. I live in an area where inland the ground is a very poor conductor listed on the map as a 1 to 2. Notice down in Texas the numbers can be 18 to 30, making it a great place for antenna systems.
The link to the full maps is here, where you can download the zipped files: http://www.fcc.gov/mb/audio/m3/
Here is the overall map at very poor resolution and a few sample locations I have extracted and re-sized to a lower resolution.
Overall Map:
[attachment 27522 fccmap.jpg]
New England Area(me):
[attachment 27524 fccne.jpg]
Michigan:
[attachment 27523 fccmich.jpg]
Wash-Ore:
[attachment 27526 fccwash.jpg]
Texas:
[attachment 27525 fcctex.jpg]
The purpose of the this post is simply to provide more information about the "ground". Remember that iron content has to be considered also.
HH
BarnacleBill
The best place to locate an AM radio station antenna is in a salt marsh near the ocean, because the conductivity of the saltwater helps the signal travel greater distances. The next best place is in brackish freshwater marshes, which is why you will notice many antenna fields in marshes or swampy areas. They're not located there because the land is cheap.
Therefore the FCC produces conductivity maps that help engineers design the RF screen(radio ground) systems. The poorer the conductivity of the soil, the bigger & more expensive the RF screen system has to be. Remember these maps DO NOT concern iron mineralization, only how much like saltwater the ground is. I live in an area where inland the ground is a very poor conductor listed on the map as a 1 to 2. Notice down in Texas the numbers can be 18 to 30, making it a great place for antenna systems.
The link to the full maps is here, where you can download the zipped files: http://www.fcc.gov/mb/audio/m3/
Here is the overall map at very poor resolution and a few sample locations I have extracted and re-sized to a lower resolution.
Overall Map:
[attachment 27522 fccmap.jpg]
New England Area(me):
[attachment 27524 fccne.jpg]
Michigan:
[attachment 27523 fccmich.jpg]
Wash-Ore:
[attachment 27526 fccwash.jpg]
Texas:
[attachment 27525 fcctex.jpg]
The purpose of the this post is simply to provide more information about the "ground". Remember that iron content has to be considered also.
HH
BarnacleBill