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WatchMate's Alarm Capabilities #1
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Compact, low-power Transponder, VHF Radio and AIS Display
We've put the Comar CSB 200 together with the Standard Horizon MATRIX GX2000, to give you a great low-power AIS solution for those long crossings! Click here for the wiring diagram or visit our Support pages for more AIS solutions.
Comar AIS-MULTI and AMEC CYPHO-101 win Practical Boat Owner "Best Buy" award!
PBO has long been our favorite British sailing magazine. Now we have even more reason to like it as the January issue's "Gear Test" recognizes our two favorite AIS receivers!
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If placed by noon PST, Monday through Friday, most orders ship same-day. (Excluding Class B AIS which must be programmed before shipping)
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Home > Support > Class B AIS FAQs
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Q: What information do I need to provide with my Class B AIS transponder order?
A: FCC regulations require Class B AIS units to be programmed with vessel information before shipping to US addresses.Milltech Marine provides this service free of charge.
- To make it more convenient for you to provide vessel information, we have prepared this quick and easy online form. Please complete and submit at time of order.
- We are required to have proof of valid MMSI, so please also send a copy of the issuing document.
- If you do not have a copy of your MMSI issuing document, contact the issuing authority or organization. To search the FCC licensing database, click here. For BoatUS information, click here.
If you prefer to not use the online form, you can download the Vessel Static Information form and fax (425-484-6218) or email.
Q: What is "MMSI"?
A: MMSI is an acronym for "Marine Mobile Service Identity." From the USCG: "MMSIs are nine digit numbers used by maritime digital selective calling (DSC), automatic identification systems (AIS) and certain other equipment to uniquely identify a ship or a coast radio station. MMSIs are regulated and managed internationally by the International Telecommunications Union in Geneva, Switzerland, just as radio call signs are regulated. The MMSI format and use is documented in Article 19 of the ITU Radio Regulations and ITU-R Recommendation M.585-4, available from the ITU."
Q: Will Class B AIS work with my Chartplotter?
A: All of the Class B AIS Transponders offered by Milltech Marine will work with any AIS-enabled chartplotter with NMEA 0183 RS422 input (nearly all current-model plotters). To be sure, check with the chartplotter manufacturer or refer to the manual (in the product specifications, look for NMEA 0183 RS422 output and AIS capability.)
Q: Can I use my existing GPS for my new Class B AIS transponder?
A: Class B AIS units will not accept any GPS NMEA data input from an external receiver. The specifications for Class B AIS requires a discrete and dedicated GPS system because the unit is transmitting the vessel position and must synchronize with the AIS network.
The CSB 200 must use its own internal GPS receiver and a compatible external powered LNA (Low Noise Amplifier) GPS antenna (such as the AMEC AGGRESSOR-111-C ).
Through its NMEA and serial connections, the Comar CSB 200 outputs both AIS and GPS data. It may be possible to use the GPS data for one of your other systems (e.g. DSC VHF radio), eliminating the need for other GPS systems. Through software settings, GPS can be filtered from the outgoing data, if needed.
Q: Should I use a dedicated antenna for Class B AIS or a Class B AIS/VHF radio antenna splitter?
A: Antenna splitters simplify installation and reduce cable runs. Signal loss is minimal (<3dB) and is far outweighed by the advantages of an antenna optimally located at the highest point available (sailboat masthead, power yacht cabin top or arch). Be sure to use a splitter specifically designed for Class B AIS. Splitters designed for use with AIS Receivers are not compatible with AIS Transponders.
Q: When using a Class B AIS transponder, can I turn transmission of my vessel information on and off?
A: Yes, both the Comar CSB 200 and the ACR Nauticast-B allow the installation of a manual switch for turning transmission on and off.
Q: How do I know if my Class B AIS is transmitting?
A: Both the Comar CSB 200 and the ACR  Nauticast-B have very effective self-diagnostics. For example, the Comar CSB 200 is equipped with Built In Integrity Testing. The tests run continuously or at appropriate intervals simultaneously with the standard functions of the equipment. The tests detects any failure or malfunction that will significantly reduce integrity or stop operation of the CSB200 unit.
The tests include:
- AIS TX malfunction (synthesizer not locked and TX time-out not
- exceeded)
- Antenna VSWR exceeds limit
- CSB200 Class B AIS
- R2.0 32Rx channel 1 malfunction (synthesiser not locked)
- Rx channel 2 malfunction (synthesiser not locked)
- Internal GNSS not in use
- No valid SOG information
- No valid COG information
- Background noise > -77dBm
- GPS failure
- VSWR exceeding the maximum allowed level
- The input voltage is out of the specified range
If the unit's LEDs show power On and do not show an Error or Timeout, then it is almost certainly transmitting your data. See the product documentation for complete information on product diagnostic options.
Q: Is my Comar CSB 200 operating normally if the Timeout LED occasionally comes on?
A: Yes. This happens when the unit is unable to transmit at its specified time. This will happen if the GPS momentarily lost signal, or the time slot that the unit was going to transmit in was already occupied by a Class A transmitter that has priority. No operator intervention is needed and the unit will return to normal in a short time
Q: Even though my Class B AIS is transmitting, why do some vessels with AIS take a long time to see my vessel name or not see it at all?
A: AIS information is sent in different message types. The MMSI, position, course and speed are sent frequently so this information shows first and will show on all AIS receivers, Class B and Class A. The Class B Static Data Report, or "Type 24" message, such as name of the vessel, type of vessel, destination,etc., is sent less frequently. This information takes longer to show on AIS displays and will not show on older Class A devices.
If a Class A AIS-equipped vessel does not see your vessel's name after a reasonable period of time, is typically due to AIS hardware or software on the receiving vessel that is not current. Many SOLAS vessels were outfitted with Class A AIS before the Class B Static Data Report format was defined. This means that they may not see your name, but they will see your vessel as a target with MMSI number, position, course and speed.
Q: Can large vessels with Class A AIS filter out Class B AIS?
A: No. At minimum, your class B transmissions will always show up on the Class A display as a target. Some Class A vessels will "filter" the display so that only the Class B target symbol shows and must be cursored over to display alphanumeric information (MMSI, speed, heading, etc.). They do this to differentiate between SOLAS Class A vessels (very large commercial vessels with slow rate of turn) and smaller Class B vessels.
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