"Frank" wrote
At 1000 m, between a height of zero meters, and 1000 m
the field strength is in the range of 5 mV/m peak. (i.e. including
ground wave). Not sure why the calculation does not agree
with Richard Fry's analysis, but may be due to the fact that
NEC computes ground losses for the surface wave.
_____________

Below is a development of my earlier analysis, now based on the worst-case
ground conductivivity for a site in Tennessee, per the FCC's "M3" map of
same for the contintental US.

The field strength values below are referenced to the MW propagation charts
of the FCC for the power, radiator efficiency and presumed groundwave path
conductivity in this situation. These values are traceable to measured
data.

This approach shows an inverse distance field strength at 1 mile to be 11.2
mV/m. At 1 km the inverse distance field would be about 1.61 X that much,
or about 18 mV/m (which agrees with the analysis I posted earlier in this
thread).

Groundwave path loss at 1 km for 529 kHz is very small regardless of earth
conductivity, so the measured field at that distance should be almost the
same as the calculated inverse distance field (18.5 mV/m).

Using "real" earth conductivity shows (below) less field at about 15 miles
than in my first analysis. But there I just picked an arbitrary value of 6
dB for ground loss at that distance.

As a side note, the FCC permits shunt-fed monopoles for use by some
non-directional AM broadcast stations, and they must (and do) produce the
same minimum allowable field strength for 1 kW at 1 km as if they were
series-fed.

+ + + +

FCC Approach

Frequency = 529 kHz
Power = 0.05 kW
Inverse Distance Field at 1 mile = 11.2 mV/m
Groundwave Path Conductivity = 2.0 mS/m

Radius to a Given Field Strength:

Field Strength Radius
0.500 mV/m 10.3 miles
0.250 mV/m 15.5 miles

RF