"Wimpie" wrote
A broadcast transmitter (100 MHz) with ERP = 10kW produces
about 30mV/m at 3 miles and h=5 ft.
____________

Although you didn't define the height of the transmit antenna, just picking
a height of 984 feet to be on the high side, and referring to the FCC's
F(50,50) propagation curves shows that for 10 kW ERP a field of about 42
mV/m will be generated at a radius of 3 miles and an elevation of 9 meters
(29.5 feet) above the earth, assuming flat terrain.

Field strength at lower elevations for these conditions varies about in an
inverse relationship with height, so at 5 feet it would be 5/29.5, or 17% of
42 mV/m, which is about 7 mV/m.

This is quite a bit different than your number, so I was curious as to your
method.

RF