General FAQ's


Please review our general and product specific FAQ’s before contacting us. This will ensure you obtain the quickest solution to your support inquiry. If you don’t find an answer then please contact us directly at [email protected] providing as much detail as possible, or complete the form at the bottom of this page.

  • How do I Choose the Right Antenna for an AIS Device?

    One of the most essential parts of an effective AIS system is a well-suited, well installed and fully functional VHF antenna, so it’s no surprise that we’re often asked for advice about how to ensure that this part of the system is setup properly. To try and simplify things, we’d advise that when selecting an appropriate antenna or considering using an existing antenna, you consider the following points:

    1. If an antenna works well with a VHF/DSC voice radio, this is no guarantee that it will also work well with an AIS transceiver. This is because Class B AIS only operates at 2W output, whereas a VHF DSC voice radio operates at 25W output and so will still radiate a signal of some type. AIS Class B devices like the B100 do not have the power to “push through” and may not work on such an antenna (even if a VHF Voice radio can use the same antenna).
    2. Use of narrow band AIS ‘tuned’ antennas are not recommended as they are optimised at the standard AIS1 and AIS2 frequencies and may not give optimum performance when regional channel settings are used.
    3. AIS optimised ‘broadband’ antennas are suitable for use; these antennas typically have a wider bandwidth to give improved performance at the top end of the VHF band where AIS usually operates.
    4. Siting of an antenna is crucial as even a well suited antenna may not radiate a good signal if installed in a poor location. Put simply, keep the antenna upright, clear of anything that could touch it (rigging/other antennas etc), keep a reasonable distance from any other devices/antenna arrays like Radar/HF/VHF radio that may be operating at high power and also keep clear of any other metallic obstructions.

    If you’re still unsure of which antenna is right for you, please refer to the list below for some advice:

    Typical VHF antenna specification:

    • Band: Marine VHF band (nominally 156MHz to 162MHz)
    • Impedance: 50 Ohms
    • Gain: 3dBi
    • VSWR: <1.5:1 at resonant frequency
    • Max power: Typically >25W
    • Polarisation: Vertical
    • Bandwidth: Typically 6MHz
    • Cable: RG58 or better. Note the IMO recommend RG214 or better for SOLAS installations
    • Connector: PL-259 (sometimes called ‘UHF’)
  • What are AIS Tracking Websites and how do They Work?

    If you are travelling and want the folks back home to see where you are, or even if you just want to get an idea of what vessel traffic is like , prior to leaving home; AIS Tracking Websites have become a very popular and useful hobbyists tool.

    Sites such as and offer a free service where web users can search for vessels that are represented on maps or even old satellite images.

    On occasions, we are asked to explain why a customer’s vessel might not be appearing on these sites as there may be some concern that the unit is not operating correctly.

    If you are concerned that this may be the case with your AIS transceiver then please consider the following:

    • Coverage: Not all AIS websites offer complete coverage, so there is a chance that you may be out of range of a receiving station for that site.
    • Antenna setup: If you are being seen by other vessels around you, but not by the AIS website, then the issue could be associated with your choice/installation of VHF antenna. If in doubt, refer to the user manual for advice or contact us for help.
    • Unit configuration: Make sure that your AIS transceiver is correctly setup with its complete vessel details and that it is connected to a GPS antenna (as per the user instructions).
  • What is a Transceiver?

    A transceiver is a device that transmits and receives information. Class A and Class B devices are popular examples of AIS transceivers.

  • What is AIS?

    AIS is a relatively simple concept as it uses VHF and GPS to transmit data to other ships significantly increasing the safety of you, your crew or your family.

    AIS, or Automatic Identification System, is an ideal way to see and be seen in busy ports, waterways and out at sea. It is a simple concept, fusing dynamic and static data together to build up a live image of the surrounding marine environment which is then displayed on a chart plotter or on board display.

    AIS works via a combination of GPS, VHF radio, and an AIS transponder. The transponder broadcasts a ship’s information, such as speed and heading (information gathered by GPS), the ship’s name, port of origin, size and draft, and more, over VHF frequencies 161.975 megahertz and 162.025 MHz. This information is updated constantly and can be viewed by any other ship or boat equipped with an AIS unit, as well as on any chart plotter, MFD, computer or smartphone linked to the internet.

    AIS provides many benefits to mariners greatly improving situational awareness and decision making.  With AIS onboard your boat will be a safer boat.

    If you are unable to find the answer to your question please complete the form at the bottom of our contact page and one of our customer representatives will contact you within one (1) working day.

  • What is an MMSI Number?

    An MMSI (Maritime Mobile Service Identifier) is a nine digit number used to identify vessels and coast radio stations. The MMSI is similar to the phone number for the ships radio and can be used to place a radio call to a particular vessel. AIS systems also use MMSI numbers to identify vessels. With the exception of an AIS SART the same MMSI is used for all radio equipment on a vessel, so the AIS should be programmed with the same MMSI as the VHF radio.

  • What is Static and Dynamic Vessel Data?

    Information transmitted by an AIS transceiver is in two categories: static and dynamic data.

    The vessel’s dynamic data which includes location, speed over ground (SOG) and course over ground (COG) is calculated automatically using the internal GNSS receiver.

    Static data is information about the vessel which must be programmed into the AIS transceiver. This includes:

    • Maritime Mobile Service Identity (MMSI)
    • Vessel name
    • Vessel call sign (if available)
    • Vessel type
    • Vessel dimensions
  • What Kinds of AIS Devices are There in Use?

    Class A transceivers: These are designed to be fitted to commercial vessels such as cargo ships and large passenger vessels. Class A transceivers transmit at a higher VHF signal power than class B transceivers and therefore can be received by more distant vessels, and also transmit more frequently. Class A transceivers are mandatory on all vessels over 300 gross tonnes on international voyages and certain types of passenger vessels under the SOLAS mandate.

    Inland AIS stations: Similar to class A transceivers with additional features for use on Inland waterways.

    Class B transceivers: Similar to Class A transceivers in many ways, but are normally lower cost due to the less stringent performance requirements. Class B transceivers transmit at a lower power and at a lower reporting rate than Class A transceivers.

    AIS base stations: AIS base stations are used by Vessel Traffic Systems to monitor and control the transmissions of AIS transceivers.

    Aids to Navigation (AtoN) transceivers: AtoNs are transceivers mounted on buoys or other hazards to shipping which transmit details of their location to the surrounding vessels.

    AIS receivers: AIS receivers receive transmissions from Class A transceivers, Class B transceivers, AtoNs and AIS base stations but do not transmit any information about the vessel on which they are installed.

  • Where do I go to find Configuration Software?

    Simply click on the image of the product you are installing below.   This will take you into the support page for that product where you find FAQ’s, Manuals & Downloads and also Configuration Software for download.  If you need any assistance please contact us at [email protected]

Please select your specific product for detailed support, trouble shooting and technical information.

Core technology


Core technology continuously developed and proven over many years guarantees you the very best AIS receive and transmit and GPS performance, coupled with the lowest power consumption of any comparable AIS transceiver.



Quality engineered and manufactured with the best components to provide years of continuous, maintenance free operation in even the most extreme environments – impervious and protected against the long-term effects of water, damp, shock, vibration and extreme cold and heat.



Guaranteed connectivity to any chart-plotter and PC/Phone/Tablet/Watch and navigation app. This ensures you are not limited to any display device or navigation application now or in the future and can maximise AIS related functionality such as weather, MOB, anti-collision, anchor safety, vessel tracking and more.  



With features such as FLEXI-FIT bracket, integrated GPS antenna, VHF antenna splitter and unlimited connectivity options such as NMEA2000 & 0183, Bluetooth & Wifi. em-trak AIS transceivers are easy to configure and install on any boat.  



em-trak transceivers are rigorously tested and certified for global regulatory compliance. This includes FCC, USCG, Canada and EU test and certification.


Warranty & support

em-trak transceivers are designed and engineered for a life time of reliable operation in even the most extreme environments. This is supported by our best in class global warranty program with 24/7 customer support