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AM Groundwave Field Strength Graphs ( 540 to 1700 kHz )
per 47 CFR Sections 73.183 and 73.184
Sections 73.183 and 73.184 refer to AM groundwave field strength Graphs 1 through 20.
However, these graphs are not available in the FCC's rules. Therefore,
we have provided three versions of these graphs, using
PDF, scanned JPEG images, and PostScript files.
Best quality and smallest file sizes will be obtained from the PDF versions
of these curves (added June 2004). The PDF graph files can be printed on
larger paper (e.g., 11" x 17") with excellent quality. Most users will
find this option to be the best choice.
For the scanned JPEG versions, three sizes are provided here. The "small" size
at 700 pixels wide will fit on a standard 8½ inch sheet of paper.
The "medium" size at 1000 pixels wide will fit on two standard sheets of
paper (print in landscape mode). The third is an
unreduced size. Any of the scanned graphs may be viewed as JPEG images on most
Internet browsers.
For each graph number (1 through 20), there are two graphs provided. The
first graph contains two sets of curves. The bottom set of curves covers
distances between 10 to 5000 km from the transmitter site, while the top set
of curves covers distances between 0.1 and 50 km on an expanded scale.
Electric field strengths in millivolts per meter are listed on the left
margin. The numbers on the individual curves represent ground conductivities, with the
best conductivity (5000) corresponding to seawater (salt water) and the
lowest conductivity (0.1) corresponding to poorly conducting soil.
Ground conductivities in the United States typically fall between 0.1 and 30
milliSiemens per meter (mS/m, formerly millimhos per meter, where 1 mho = 1 / ohm) (see the map). The "A" series of graphs (Graph Number dash A) contain an
expansion of the top set of curves, covering distances between 0.1 and
50 km from the transmitter site.
Groundwave Curves in PDF format
All 20 groundwave curves, plus the expanded upper curves and blank
log-log graphs, are contained in this zip file. Download it and unzip
it to your preferred file location.
OR
Groundwave Graphs for PostScript Printers. 883 KB. Zipped file
contains all the groundwave graphs listed on the left in Postscript
format. The PostScript graphs provide better printing
quality than the scanned graphs, but they are available in
only one size (8½ by 11 inches).
