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Extending that graph to show the range to the 70 µV/m field for the elevated systems would have a lot of error, because those curves do not account for groundwave propagation across the lossy earth. The longer the path, the greater the error.

Here are some numbers that **do** account for those propagation losses, using NEC4.2 …

System Description:

- Frequency = 1670 kHz
- Earth Conductivity = 5 mS/m, d.c. 13 (average earth)
- RF Ground Configuration: 12 x 3-m Radial Wires, buried 0.1-m
- Tx Power Output at Loading Coil Input = 85 mW, unmodulated
- Loading Coil Resistance at 1670 kHz = 18.5 ohms
- 3-m Vertical Whip Attached to the Transmitter
- Vertical Conducting Path Connecting the Transmitter Chassis to RF Ground
- Loading Coil Adjusted for Best System Performance

This system with its transmitter located 0.2 meters above the earth produced a groundwave field of 57 µV/m at a horizontal distance of 1 km.*

If the transmitter is elevated 5 meters then the distance to the 57 µV/m field is 2.9 km.

For an elevation of 10 meters the distance to the 57 µV/m field is 4.2 km.

IMPORTANT The increased range is *not* due to the height of the transmitter+whip, but to the greater radiating length of the antenna system conductor leading from the transmitter chassis to r-f ground, when the transmitter+whip are elevated (see illustration below).

* Note that this field at 1 km is almost 4X that permitted by FCC §15.209 at a distance of only 30 meters.