Safety distance, estimate
The quick estimate for one antenna. For the whole station with several transmitters, the combined assessment and the route to the notification there's the BEMFV assistant (German EMF verification ordinance).
Safety distance, estimate
Far-field estimate against the limits of the 26. BImSchV (German EMF exposure ordinance) for the general public. It doesn't replace a BEMFV notification, for that there's the BEMFV assistant.
How the page calculates
- mean EIRP = P ยท duty cycle ยท 10^(gain in dBi / 10)
- r = โ(30 ยท EIRP) / E limit
- Power flux density S = Eยฒ / 377
- Limit E: 0.15 to 1 MHz 87 V/m, 1 to 10 MHz 87 / โf, 10 to 400 MHz 28 V/m, 400 to 2000 MHz 1.375 ยท โf, above that 61 V/m
Average power is what counts: SSB voice averages about 40 % of peak power, CW about half, FM, RTTY and FT8 transmit continuously. From that and the antenna gain comes the average EIRP, and from that the distance beyond which the field strength limit is met.
The far field starts roughly at a distance of ฮป/(2ฯ) to ฮป. If the calculated distance is below that, the number doesn't mean much; then the BEMFV assistant helps.
Related terms
- BEMFV
- German ordinance on the verification procedure for protection against electromagnetic fields
- 26. BImSchV
- German ordinance that sets the limits for electromagnetic fields
- Notification
- if you transmit more than 10 W EIRP, you must notify the Bundesnetzagentur (BNetzA, German regulator) of your station