Topband: details about the WFAN skywave plot

[Richard Fry]

>... So I would expect the skywave plot to be elongated to the east through 
>south at the 0.25 mV/m contour line. It appears that the data was generated 
>using a signal strength prediction program as "50% of the time" was used in 
>the qualifying remarks (50% implies a median value - which likely comes 
>from our monthly median model of the ionosphere).  But the prediction 
>program didn't look at ground around the antenna.

The link below leads to the FCC methodology and formulae used to determine 
the skywave signals of AM broadcast stations.

http://www.gpo.gov/fdsys/pkg/CFR-2012-title47-vol4/pdf/CFR-2012-title47-vol4-sec73-189.pdf