Gain is most of what decides how much separation you need. 3-element Yagi is taken here at 7.50 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 | 1.57 ft | 0.50 ft | 82.4 ft |
| 80 meters | 3.10 ft | 0.98 ft | 41.7 ft |
| 60 meters | 4.43 ft | 1.40 ft | 29.3 ft |
| 40 meters | 5.92 ft | 1.87 ft | 21.9 ft |
| 30 meters | 8.38 ft | 2.65 ft | 15.5 ft |
| 20 meters | 11.7 ft | 3.71 ft | 11.0 ft |
| 17 meters | 15.0 ft | 4.74 ft | 8.64 ft |
| 15 meters | 17.6 ft | 5.56 ft | 7.38 ft |
| 12 meters | 20.6 ft | 6.53 ft | 6.28 ft |
| 10 meters | 23.9 ft | 7.55 ft | 5.43 ft |
| 6 meters | 24.8 ft | 7.85 ft | 3.10 ft |
| 2 meters | 24.8 ft | 7.85 ft | 1.07 ft |
| 1.25 meters | 24.8 ft | 7.85 ft | 0.70 ft |
| 70 centimeters | 20.5 ft | 6.48 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.