On 80 meters, how far someone needs to be from your antenna depends on three things: how much power you run, how much gain the antenna has, and how much of the time you are actually transmitting. The tables below work all of that out for the usual combinations.
You may not need to evaluate at all
Before working out distances, check whether the exemption covers you. On 80 meters, with the nearest person 30 feet away, the threshold works out to about 20,513 watts ERP. Come in under that and no further evaluation is required. The threshold scales with the square of the distance, so doubling the separation quadruples the power you are allowed. More on the exemption test.
Distances with a dipole on 80 meters
| Power | Steady carrier — public | Steady carrier — household | SSB voice — public | SSB voice — household |
|---|---|---|---|---|
| 5 W | 0.37 ft † | 0.17 ft † | 0.12 ft † | 0.05 ft † |
| 25 W | 0.84 ft † | 0.37 ft † | 0.27 ft † | 0.12 ft † |
| 50 W | 1.19 ft † | 0.53 ft † | 0.37 ft † | 0.17 ft † |
| 100 W | 1.68 ft † | 0.75 ft † | 0.53 ft † | 0.24 ft † |
| 400 W | 3.35 ft † | 1.50 ft † | 1.06 ft † | 0.47 ft † |
| 600 W | 4.11 ft † | 1.84 ft † | 1.30 ft † | 0.58 ft † |
| 1500 W | 6.49 ft † | 2.90 ft † | 2.05 ft † | 0.92 ft † |
Distances are from the antenna to the nearest point a person can occupy, measured in a straight line — so antenna height counts. Figures assume a dipole at 2.15 dBi and include ground reflection, which is the conservative case. “Steady carrier” is FM, FT8 or RTTY at full output. “SSB voice” is unprocessed single sideband while transmitting about half of a 30-minute window. † This figure falls inside the near field, which on this band starts at about 41.7 ft. The estimate stops being meaningful there, so read it as “no separation to worry about beyond not standing at the antenna” rather than as a measurement.
What a beam changes
Gain concentrates the signal, so the same power needs more separation. With a 3-element Yagi on 80 meters, 100 watts of steady carrier needs 3.10 ft from the general public, against 1.68 ft for a dipole at the same power.
| Power | Steady carrier — public | Steady carrier — household | SSB voice — public | SSB voice — household |
|---|---|---|---|---|
| 5 W | 0.69 ft † | 0.31 ft † | 0.22 ft † | 0.10 ft † |
| 25 W | 1.55 ft † | 0.69 ft † | 0.49 ft † | 0.22 ft † |
| 50 W | 2.19 ft † | 0.98 ft † | 0.69 ft † | 0.31 ft † |
| 100 W | 3.10 ft † | 1.39 ft † | 0.98 ft † | 0.44 ft † |
| 400 W | 6.21 ft † | 2.78 ft † | 1.96 ft † | 0.88 ft † |
| 600 W | 7.60 ft † | 3.40 ft † | 2.40 ft † | 1.08 ft † |
| 1500 W | 12.0 ft † | 5.38 ft † | 3.80 ft † | 1.70 ft † |
Distances are from the antenna to the nearest point a person can occupy, measured in a straight line — so antenna height counts. Figures assume a 3-element Yagi at 7.5 dBi and include ground reflection, which is the conservative case. “Steady carrier” is FM, FT8 or RTTY at full output. “SSB voice” is unprocessed single sideband while transmitting about half of a 30-minute window. † This figure falls inside the near field, which on this band starts at about 41.7 ft. The estimate stops being meaningful there, so read it as “no separation to worry about beyond not standing at the antenna” rather than as a measurement.
Where the numbers stop meaning anything
Closer than about 41.7 ft from an antenna on 80 meters you are in the near field, and power density is not a meaningful thing to calculate there. Any calculator that hands you a number inside that radius is guessing. The honest answer is that nobody should be that close while you are transmitting.
Household and public are not the same limit
People who know the station is there and have been told about it fall under the higher controlled limit, averaged over 6 minutes. Everyone else — neighbors, visitors, anyone on the sidewalk — gets the stricter uncontrolled limit, averaged over 30 minutes. On 80 meters those limits are 64.000 and 12.800 mW/cm².
Work out your own station in Exposure Forge — six questions, and it prints a dated record you can keep.