Watch AIS information evening presentation

The CYCA Cruising Committee hosted Members and guests for an information evening on AIS and Satellite Safety Systems.

Ian Veitch, of All Sat Communications, discussed the importance of GPS beacons, the various satellite constellations and provided some tips for using AIS correctly.

BLA’s Mike Mee also showcased Vesper’s Cortex, which has been labelled the world’s most advanced VHF radio.

You can watch the full video below and visit the Australian Maritime Safety Authority website for more information on beacons.

AIS – Frequently asked questions

Q. On receipt of an AIS Man OverBoard (MOB) message, does the receiver device re-transmit the message so as to cover a larger area of recipients?

No, it’s limited to the receiver area only.

Q. How does the quality of cabling and connections in the cabling affect performance?

It’s vital to have a good cable, antenna and connections. It’s also important for an AIS antenna to have a high quality coax cable and connectors. This can be measured with the VSWR.

Q. If there are separate VHF and AIS aerials, what is the recommended minimum distance between the aerials?

The recommendation is either 2m horizontal or 1m vertical, as per Digital Yacht. You can also use your existing VHF antenna by using a ZeroLoss VHF splitter (SPL1500 or SPL2000).

Q. For Class B/CSTDMA, the alert message “too much traffic to transmit” can be displayed on the transmitting vessel. Does this happen with Class B/SOTDMA?

A Class B+ SOTDMA works as a Class A, meaning that the Class B+ SOTDMA will always transmit no matter how much traffic there is.

Q. Is the MMSI on an AIS MOB registerable with AMSA? If not, why not?

No. AMSA register your VHF Radio MMSI, but the MOBs are not registered. Every AIS MOB comes with their own pre-registered MMSI number.

Q. Can the MMSI for the MOB’s vessel be programmed into the AIS MOB beacon for use with a DSC message from the AIS MOB?

Yes, as long as the MOB model is dual AIS and DSC.

Q. Do port authorities turn off Class B transmissions, thereby rendering them useless in congested ports?

No, port authorities can’t turn them off. It is from the vessel that it is being controlled. A port authority in their software to display AIS can choose to see only Class A, but they cannot turn off the Class B transmissions.

With any AIS MOB signal, it takes precedence over Class A and Class B transmission. It is called impolite AIS and when other AIS transponders receive an MOB, alert they pause their transmissions automatically.

Q. Does the Class B/SOTDMA offer better satellite reception for use by ground stations, either fixed or mobile?

The satellite reception of the vessel’s location is via the same GPS as everyone is using. The transmission power is what will extend range. Class B SOTDA transmits at 5 watts vs Class B at 2 watts.

All the Class B+ and Class A AIS transponders can be received by AIS satellites. As the Class B+ SOTDMA are 5W instead of 2W for a normal Class B, they are more likely to get picked up by AIS satellites. However, it is very expensive and not common. It’s around $160 per month with Marine Traffic to be tracked via satellite.

Special offer

You can SAVE 15% off web prices on Digital Yacht products.

Simply use the promo code CYCA15 at the checkout on the Digital Yacht or All Sat websites.

You can also check out the 2021 Vesper Marine Catalogue and brochure.

In addition to the marine safety products available through All Sat and Vesper, here are some other recommendations:

Personal Locator Beacons

AIS MOB Beacons

AIS Class B/SOTDMA Transceivers (with integrated VHF antenna splitter)

AIS Class B/SOTDMA Transceivers

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