[BC] WLW Superpower Coverage

[Richard Fry]

Paul Christensen:
>Running those conductivity numbers, can you solve in the other direction
>and compute the required power to throw a 0.1 mV/m contour 1000 miles
>southwest using a 195-degree tower at 700 kHz?

I'm using a Fortran program I helped develop long ago where the FCC AM 
curves were digitized.  I haven't looked at the code lately, but pushing 
the tx power up to 500 megawatts into a 195 degree omni radiator on 700 kHz 
reported that the 0.1 mV/m groundwave contour for a 10 mS/m path falls at 
661.5 miles.  At that point, I (and the program) gave up.

Robert Meuser:
>... the FCC charts will not take you out that far for the ground 
>conductiviy
>given. The chart bottoms at about 800 KM for that ground conductivity.
>The power required for that distance is 50 megawatts more or less.

See my response above.  The current FCC charts for 700 kHz* are shown for 1 
kW of radiated power, and bottom out at around 850 km (528 miles) for 10 
mS/m paths.  That is within the range of my earlier post, and
needing only to be adjusted for the power difference.

  * http://www.fcc.gov/fcc-bin/73184?type=1&no=6

RF