Petrel-X User Manual 1.1
9
AIS Transmit Mode
In AIS Transmit Mode, the Petrel-X will maintain its GPS lock and activate its AIS functionality to
transmit and receive AIS messages. While in this mode, the unit’s Bluetooth functionality is
inactive.
The Petrel-X will continuously receive AIS messages and interpret them in order to build an
internal AIS slot map. This slot map is used to avoid slot collisions with other AIS devices when
the Petrel-X chooses to transmit.
The Petrel-X will wait at least 1 minute before transmitting to ensure it has fully mapped which
AIS slots are in use. Once this process is complete, it will use its slot map and slot selection
algorithm to find two consecutive free slots. Two slots are required because the Petrel-X
transmits AIS message type 21, which fills two AIS slots.
A Petrel-
X’s AIS transmissions contain an
MMSI
and an
AIS name
.
●
The AIS name is made of up to 20 characters, which can be a combination of uppercase
letters (A-Z), numbers (0-9). Some special characters are also supported, such as dashes
and commas. The AIS name can be set by the user.
●
The MMSI is set during the assembly phase and cannot be changed by the user.
A Petrel-
X’s first transmission after entering AIS Transmit Mode will always be on AIS channel B.
It will then proceed to alternate between channels A and B for successive transmissions.
If the Petrel-X loses its GPS lock while in AIS Transmit Mode, it will return to GPS Search Mode
and attempt to regain the GPS lock. Repeatedly losing and regaining GPS lock may cause the
unit’s transmission period to deviate from the usual 3 minutes, and
cause it to perform
consecutive channel B transmissions.