Gain is most of what decides how much separation you need. Ground plane is taken here at 1.00 dBi, which is typical. The table gives the distance the general public needs to be, band by band, at 100 watts.
| Band | Steady carrier | SSB voice | Near field starts |
|---|---|---|---|
| 160 meters | 0.74 ft | 0.24 ft | 82.4 ft |
| 80 meters | 1.47 ft | 0.46 ft | 41.7 ft |
| 60 meters | 2.10 ft | 0.66 ft | 29.3 ft |
| 40 meters | 2.80 ft | 0.89 ft | 21.9 ft |
| 30 meters | 3.96 ft | 1.25 ft | 15.5 ft |
| 20 meters | 5.55 ft | 1.76 ft | 11.0 ft |
| 17 meters | 7.10 ft | 2.24 ft | 8.64 ft |
| 15 meters | 8.31 ft | 2.63 ft | 7.38 ft |
| 12 meters | 9.77 ft | 3.09 ft | 6.28 ft |
| 10 meters | 11.3 ft | 3.57 ft | 5.43 ft |
| 6 meters | 11.7 ft | 3.72 ft | 3.10 ft |
| 2 meters | 11.7 ft | 3.72 ft | 1.07 ft |
| 1.25 meters | 11.7 ft | 3.72 ft | 0.70 ft |
| 70 centimeters | 9.70 ft | 3.07 ft | 0.36 ft |
All figures at 100 watts to the general public limit, ground reflection included. Where the required distance is smaller than the near-field figure in the last column, the estimate has stopped being meaningful — in plain terms, there is nothing to worry about beyond not standing at the antenna.
Work out your own station in Exposure Forge — six questions, and it prints a dated record you can keep.