Tag Archives: class B

Class B Splitter

Estamos muy contentos de anunciar que lo tenemos :)

Nos referimos al splitter de VHF para el clase B. Un equipo que permite utilizar la misma antena de VHF de la emisora con el transpondedor AIS CTRX de clase B. El primero con certificado CE!!

  • Reduce notablemente el tiempo de instalación, así como el coste de la misma.
  • Mejora notablemente la cobertura, al llevar una misma antena para AIS y la emisora en la parte más alta de la embarcación
  • Permite funcionar en modo a prueba de fallos, dando prioridad a la voz VHF, incluso en caso de fallo de la corriente.

We got it!! We mean the VHF class B Splitter!! It lets you use the same VHF antenna with your radio transmitter and your AIS transponder. The first one with a CE certificate!!

  • Reduces notably the time and cost of installation
  • Improves coverage, since you use the same antenna for AIS and the radio in the top part of your boat
  • Has a failsafe operation mode, giving priority to VHF voice operation, even in case of failure of the splitter power supply


AIS class B in USA

Could it be this time?

Panbo, after his talks with representatives of the FCC, seems to be sure that class B will finally be approved in the US in a matter of weeks.

The fight for competences for the control of the spectrum between FCC and other american governmental bodies seems to be the reason why class B is taking so long to be approved. After all, it is expected that hundreds of thousands of boats will be transmitting AIS data in the US. It’s good that we are a little bit ahead in Europe :)


Doubts about AIS class B

Boaters keep on wondering what kind of data class A receivers are able to see.

Right now, most class A are only able to see mmsi and location of class B. IMO is likely to take a decision on how to solve this problem soon. They are most likely to decide that large boats should upgrade their class A equipment to make it compatible with class B in our opinion, during the next few years. It just doesn’t make sense having such a powerful navigation system, in which the two most important standards are just not compatible.

Some boaters wonder if large boats can decide whether to see class B or not. In some cases it may be possible via software to filter class B data, but why should someone decide to do so? Too much information? May be in extremely crowded waters?

We must take into consideration that there is no navigation system able to substitute the good criteria of the captain/skipper.


Nevertheless, in the future, it will be possible with the new standard for base stations to disconnect the transmission of class B when overinformation could affect navigation of large boats, or when overcapacity could affect the system. But this will only be possible in VHF coverage from the coast, never far away from it.

Capacity problems are practically impossible in class A, due to the SOTDMA (self-organizing time division multiple access) protocol that they use to organize transmissions. This protocol guarantees practically unlimited capacity to the system. Transponders communicate with each other to “decide” when to transmitt or not.

Class B uses CSTDMA (carrier sense time division multiple access) to organize them. Class B transponders “listen” during the first part of the slot, to know if somebody else is transmitting, and in negative case, transmit themselves during a therefore shorter slot (and thus smaller amount of data).

In order to have class B capacity problems, a large amount of boats should be transmitting frequently in the same area. If they are moored, transmission will be only once every 10 minutes, and thus overcapacity problems are very unlikely.

We believe that an actual problem in AIS in the future will be though, the asignation of mmsi numbers.

AIS class B reach

We’d like to keep some track of the ranges at which our customer send and receive AIS data with their class B ais transponder.

For now, some customers have been able to receive data from ships as far as 110NM; not bad, is it?

Another one has been seen from a large boat at a distance of 16NM. It could be better, but few people don’t carry an AIS transponder on board, so we are sure this data will get better eventually.

BWR puts a bet on AIS class B

The organization of the Barcelona World Race encourages participants to carry AIS Class B Transponders on board.

Since the beginning, Class A was mandatory for participants, but the organization, aware of the better fit of the new class B transponders for smaller vessels, has now amended the former rules.


Quoting the amendment:

• Each boat shall fit a Class A or Class B AIS transceiver, The device
must be properly configured with all Boat Data. This transceiver
must be in use in the following locations, or as specified in the Sailing
- between the start line and the Straights of Gibraltar
- within 50 nm of each race gate 2,3,4,5,7
- within 100nm of Race Gate 6 (south of Cape Horn)
- between the Straights of Gibraltar and the finish line.
Its use is also recommended at other times where shipping may be

Reason for amendment

Class B AIS units are now available, and the hardware is designed to be
suited to smaller boats – physically smaller, and significantly lower in power.