AIS transmission levels in port

As members will be aware the matter of VHF transmission levels (Wattage) is dealt with in ISGOTT, but so far AIS (Automatic Identification Systems) transmission levels have not been mentioned.


We are reliably informed that ISGOTT is under review at the moment. At present, the recommendation in the newly-drafted ISGOTT is to switch AIS off unless there is an overriding requirement not to do so.
This is because if the AIS is polled while the ship is in port, the system will exceed the current maximum allowed output of 1 watt – in fact it will poll at up to 20 watts.

We understand that the revised ISGOTT will also cover the use of a dummy load aerial so that you do not lose all your dynamic information when the AIS system is turned off whilst at the same time ensuring the system cannot be polled.

In essence, the recommendation from ISGOTT is (will be, in due course when this is published) to switch the system off when in port and carrying out cargo operations.

If members decide to switch the system off when the terminal/port recommends otherwise (for security reasons for example) we recommend that members cite safety reasons for doing so.

Contact: Howard Snaith