#### Notes:

Rev.3 corrects the 26km free space distance calculation at the end of page 3, the effect of adding 35 dB attenuation to a Class B AIS. Free space is valid for calculating VHF propagation distances less than a kilometer only. ITU-R P.1546-6 is used for calculating propagation distances greater than a kilometer instead. Pages 4 and 5 added. The analysis is otherwise unchanged and the recommendations to IMO NCSR remain valid.

Using ITU-R P.1546-6 Figure 4:

Using ITU-R P.1546-6 Figure 4:

Normal Class B AIS detection range is = 28 km = 15.1 nm

Class B AIS detection with 35 dB attenuator is = 4.2 km = 2.3 nm