Gain is most of what decides how much separation you need. Rubber duck 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 | 0.59 ft | 0.19 ft | 82.4 ft |
| 80 meters | 1.17 ft | 0.37 ft | 41.7 ft |
| 60 meters | 1.66 ft | 0.53 ft | 29.3 ft |
| 40 meters | 2.22 ft | 0.70 ft | 21.9 ft |
| 30 meters | 3.15 ft | 1.00 ft | 15.5 ft |
| 20 meters | 4.41 ft | 1.39 ft | 11.0 ft |
| 17 meters | 5.64 ft | 1.78 ft | 8.64 ft |
| 15 meters | 6.60 ft | 2.09 ft | 7.38 ft |
| 12 meters | 7.76 ft | 2.45 ft | 6.28 ft |
| 10 meters | 8.97 ft | 2.84 ft | 5.43 ft |
| 6 meters | 9.33 ft | 2.95 ft | 3.10 ft |
| 2 meters | 9.33 ft | 2.95 ft | 1.07 ft |
| 1.25 meters | 9.33 ft | 2.95 ft | 0.70 ft |
| 70 centimeters | 7.71 ft | 2.44 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.