Category Archives: Nomad Portable AIS Transponder

Nomad Portable AIS Transponder

In the Spring of 2019, I had the most fortuitous experience of being gifted a portable AIS transponder.  The unit is a Nomad,™ manufactured by Digital Yachts, Ltd.® in the UK.  This small, portable unit is a Class “B” transponder.  The manufacturer states the target market for the Nomad is “charter and delivery captains, pilots, tenders and back up for main systems.”

The Nomad comes with a short, non-removable power cord terminated in a USB connector, and a removable rubber-ducky VHF antenna on a 20′ length of coax terminated with a BNC connector.  The unit has a wi-fi interface, and a removable wi-fi antenna is included in the box.  The unit is designed to be portable, hence power is provided via a USB A/B-style connector.  Necessary product support software is downloadable from the Digital Yacht website.  Users will need this software to get the most from the unit.

The Nomad has an internal wi-fi access point supporting connection of up to 7 wi-fi client devices.  The wi-fi Access Point gateway IP address is not configurable, and the device cannot, itself, be used as a client on a local LAN.  The wi-fi interface supports access to two different types of data: internal performance data and AIS target data.  The AIS target data consists of NMEA0183 AIS sentences (!Axxx) destined to running on smart devices.  Any app on any operating system platform that can interpret NMEA0183 sentences can display the data (Aqua Maps®, Navionics®, SEAiq®, Coastal Explorer®, OpenCPN®, MacENC®, etc).

An application software package called “ProAIS2“ is available for Windows and Mac operating environments.  Via ProAIS2, the user performs initial configuration of the vessel name and MMSI number associated with the vessel, and re-programs the vessel identity information when the unit is relocated to a different boat.  Not counting download and installation time, initial programming of the Nomad is very straight-forward and takes less than 10 minutes.

An Android-only utility app called “AISConfig,” downloadable from the Google Play Store, allows the user to connect an Android® device to the Nomad via the wi-fi Access Point.  This utility displays key internal operating parameters. including internal operating voltage, VHF antenna Standing Wave Ratio (SWR), transmit and receive message counts, and status of the internal GPS receiver.  The app is useful in optimizing the location of the rubber-ducky VHF antenna on the host boat.

For convenience, click here for the Digital Yacht America download site.

(Note: in preparing this review, I found “AISConfig” in the Google Play Store with an update date of October, 2019.  The description suggests the app may now include the capabilities of ProAIS2, but that was not my experience in May, 2019.)

During the 2019 cruising season, Sanctuary and crew cruised round-trip from Charlotte Harbor, SW Florida, to Fairport, NY, on the Western Erie Canal.  That round trip gave me 3500 statute miles of experience observing Nomad performance on the Okeechobee Waterway, the A-ICW through the Port of Charleston, the Elizabeth River and the Port of Norfolk, the Chesapeake and Delaware Bays, the Port of New York, the Hudson River and the Erie Canal.  Northbound, we were accompanied by my brother, who has an Android tablet on which we installed the DY “AISConfig” utility app.  Southbound, I did not have an Android device, so monitoring the internal operation of the transponder was not possible.   South-bound, we cruised with a companion boat from Baltimore, MD, through Myrtle Beach, SC.  Our companion’s boat was fit with a permanently-mounted competitor’s AIS transponder.   On this 3500 StM cruise, I feel we utilized our Nomad in much the way a charter or delivery captain might use it.

In my use, the Nomad portable AIS transponder performed quite well.  Although I did encounter certain limitations, the Nomad was completely adequate for providing Sanctuary’s visibility and separation safety in busy commercial marine traffic areas.  Southbound, I followed both Sanctuary and our companion’s boat on the iOS version of the MarineTraffic® app.  The Nomad VHF radio performed almost as well as the permanently-mounted unit on our companion’s boat.  The slight performance differences seem to be due to antenna gain and placement associated with our companion’s permanently-mounted AIS installation vs. the VHF rubber-ducky antenna we were using.

Figure 1, above, is a screenshot of the MarineTraffic app as Sanctuary transited Northbound from Isle of Hope, SC, in the lower left, across the Savannah River, through Calibogue Sound past Hilton Head Island, across Port Royal Sound and into Beaufort, SC, at the upper right.  I had limited previous experience with the MarineTraffic app.  From an understanding of the technology and modest prior experience, I knew the app isn’t reliable on “rural” waterways like the St. Lawrence River, the Great Lakes and portions of U. S. Inland Rivers.  I was quite surprised at the number of coverage voids along the A-ICW.

Looking at the MarineTraffic screenshot, there are many obvious voids in our track.  Large bulk cargo ships and CNG tankers regularly use the Savannah River.  I expected better coverage from AIS land stations around this area, and in the vicinity of Parris Island, SC.

Figure 2, following, is a MarineTraffic screenshot as Sanctuary transited into and through the C&D Canal and down Delaware Bay.  In this screenshot, land station coverage in the region seems significantly better than in Figure 1, although there are still some void coverage areas.  Note that this screenshot shows the detail of our overnight stop in Delaware City.

Figure 3, following, shows two side-by-side screenshots in the area of the Neuse River and Adams Creek on the A-ICW in North Carolina.  The left hand view shows Sanctuary’s track as reported by our Nomad.  The right hand view shows the track reported via the permanently-mounted unit on our companion’s boat.  The permanently-mounted VHF antenna did somewhat better hitting land stations than we did with our rubber-ducky.  That said, it’s clear that the Nomad with the rubber-ducky antenna is perfectly adequate for purposes of safe on-water vessel separation.

Figure 4, following, shows two side-by-side screenshots of tracks transiting the A-ICW Southbound from Morehead City, NC, through Bogue Sound and Camp Lejeune, to an area south of New River Inlet.  The left hand view show’s Sanctuary’s track as reported by our Nomad.  The right hand view shows the track reported by the permanently-mounted AIS on our companion’s boat.  Our two AIS tracks appear on MarineTraffic as nearly identical.

Years before we installed our Nomad, Sanctuary had been fit with an Icom® MXA-5000™ AIS receiver.  The receiver is integrated into an NMEA0183 network aboard the boat.  Aboard Sanctuary, I have a multiplexer installed that allows my iGadget apps to see all NMEA0183 and N2K data aboard.  This includes AIS data from in-range AIS targets, HDG, COG, SOG, BTW, DTW, XTE, DPT, DBT and much more.  Since I had this solution installed and working long prior to installing the Nomad, I did not use the Nomad’s limited built-in wi-fi data feed to display AIS targets on my iPad™.  Instead, my Nomad appears to apps on our iPad to be just another nearby AIS target.

This arrangement actually worked for me as an alternative to having the AISConfig utility to monitor our Nomad.  We have been using our iPad as our primary navigation tool for several years.  First with SEAiq, and in the recent two years using Aqua Maps® U.S. & Canada™ with the Aqua Map “Master” extensions.  When my Nomad transmits a location datapoint, Aqua Maps running on my iPad shows me as a target 7 feet away.  As I continue to move, prior to the next position transmission, I see separation distance increase.  At the next Nomad position transmission, the target distance closes again.  More importantly, I know when Sanctuary’s name disappears from the display that the Nomad had stopped transmitting.  At that point, I can verify the LEDs, confirm an issue, and take corrective action.

The Nomad is a functional, cost-effective and easily transported tool appropriate to any charter or delivery captain’s portable toolkit, and certainly is an alternative for permanent installations.  However, all Class “B” AIS units share significant AIS Data Architecture protocol limitations, so If purchasing a new transponder for permanent installation aboard a pleasure craft, I recommend either a Class “A” or a Class “B+” transponder, depending on the buyer’s cost tolerance.  Class “A” is best, and Class “B+” is significantly better than Class “B.”

The Nomad product and the Nomad unit both had some usability limitations.  These were manageable inconveniences.

  1. A GPS receiver is built-into the Nomad.  The GPS antenna is located inside the unit, and the manufacturer’s instructions are to have that end facing the sky.  On large sounds and bays and other open waters – areas with a clear view of the sky – the unit functioned well when located tucked away inside our flybridge’s fiberglass console cabinet.  However on narrow waterways like the Hobucken Cut in NC (A-ICW MM155-MM158), the Rock Pile in SC (A-ICW MM353 – MM356), the Waccamaw River (A-ICW MM 367–385) and along much of the Erie Canal, the crown of the adjacent forest could and did block the weak GPS satellite radio signals.  This resulted in GPS dropout even when the Nomad was located out in the open atop our flybridge instrument console.  When GPS dropout does occur, there are no position transmissions.
  2. From the perspective of this iPad owner, a monitoring utility for the Nomad that runs on an Apple® iOS platform is missed.  I had start-up problems with my unit which required that we work with Digital Yacht Tech Support.  The problems I encountered were intermittent, and took several hours of runtime to expose themselves.  I do not have the space on my flybridge to mount and use a PC in a manner that provides physical security for my PC.  My Tech Support experience was excellent and responsive.  However without the coincidental availability of my brother’s Android tablet and the DY AISConfig app, it would have been more difficult to obtain the necessary diagnostic data.  The ProAIS2 configuration utility can collect the data, but in my use case, was not a practical alternative.  I am certainly not the only cruising boater who has only Apple® products, so I see this as a support gap which I hope Digital Yacht will address.
  3. The electronics of the Nomad’s internal VHF radio monitors the SWR of the VHF rubber-ducky.  When the SWR gets “too high,” the VHF radio quits transmitting.  Performance here was unpredictable and erratic.  Northbound, I could monitor SWR status via the Android AISConfig utility on my brother’s Android tablet.  Sanctuary’s flybridge is fit with a full enclosure supported by a Stainless Steel frame.  That frame seems to interact with the Nomad VHF antenna.  At times, a given antenna location on the flybridge showed a 1.2 SWR, which is quite good.  Other times, the same location showed a 2.0 SWR, which is quite bad.  Sometimes the unit would work fine with an SWR of 1.8, and sometimes it would not transmit with an SWR of 1.4.  By changing the location of the antenna, I could “get it to work,” but it took more attention to the device than I thought was appropriate, particularly on narrower sections of waterway.
  4. There are four colored LEDs on the Nomad related to AIS operation, and two LEDs related to wi-fi network operation.  The four AIS status LEDs are on one end of the unit and the two wi-fi network activity LEDs are on the other end.  Three of the operational status LEDs indicate fault conditions, and one – “Power” – indicates the unit is happy (and presumably transponding.)  The LEDs are in a place that can be hard to see.
  5. The internal power supply in the Nomad contains a buck-boost regulator that converts the 5v USB input voltage to >19v inside the Nomad, so that it has enough power to make its transmissions.   Some PC computer USB ports can provide sufficient power (Amps) to the Nomad, but some cannot.  The manufacturer recommends using a USB3 source rated at 2.4A.  Using my Macbook Pro with current-generation USB-C connectors to power the Nomad was not an option for us.  I tried multiple options to power my Nomad, including a 12v cigarette lighter adapter, with varying degrees of “success.”  The one that worked best for me was a 120V-to-USB “power brick” that comes with the newest version of the Apple iPad Pro (18 Watt).  That brick was able to provide sufficient power (Amps) at 5V for the Nomad unit to operate reliably.  I also verified that an Anker® 20100mAhr external LiON battery could reliably power the Nomad, but battery life limitations made that unsatisfactory as an all-day solution.  I found that if input power was marginal or inadequate, the unit experienced random GPS position errors and/or failed to transmit.  Charter and delivery captains need to plan carefully to provide an adequate 5V power source.

Finally, there are some legal considerations for Nomad users in the United States.  FCC regulation in the U.S. prohibits end users from editing the vessel identity information in DSC radios and AIS transponders.  U.S. Federal Agency (FCC) regulations have the force of law, so it’s “illegal” for U.S. users to program the vessel identity data in an AIS transponder.  Most of us never have a need to do that, but obviously charter and delivery captains were not taken into consideration when the regulations were developed.  Note: If the Nomad is not programmed with vessel identity information, it operates as an AIS receiver-only, not a transponder.

There is a disclaimer in the Digital Yacht ProAIS2 transponder configuration software reminding U.S. users of the FCC prohibition.  Users must “accept” the disclaimer to proceed.  A charter or delivery captain with a need to periodically re-program the unit will also need a “special code” from Digital Yacht to reset the unit once it is initially programmed.  The good news is, Digital Yacht does make the reset code available upon request.  The user accepts responsibility for their use in accordance with the laws of their nation.  My personal attitude is, as long as vessel identity data that legally corresponds with the host vessel is programmed into the unit, users are “in compliance” with the spirit and intent of the regulatory requirements.  That doesn’t make it “legal” to program the unit, but for some captains in some cases, it may make it risk-worthy for the potential safety advantage that AIS provides.

Figure 5, right, is a screenshot of the ProAIS2 utility running on Windows 10.  It shows the operational status of our Nomad  after being correctly configured with Vessel Name and MMSI Number.  The three red Xs indicate problems with the GPS receiver, the AIS transponder and the VHF antenna.  Note, this screenshot also shows the internal chipset voltage is low, at only 14.8v.  After correcting the low voltage, the red Xs were cleared.


Figure 6, left, shows a screenshot of the “AISConfig,” Android-only, utility app showing realtime Nomad internal performance and status data on an Android Tablet.  There is no way to obtain this data on an Apple iOS platform at this time.  The data can be extracted using the ProAIS2 utility on a Mac OSX or MS-Windows operating system platform.

The four status indicators shown on the app correspond to the physical operational LEDs on the Nomad device.  As above, when the unit is transponding normally, the “Power” LED is the only LED illuminated.  Observe also in this screenshot, the SWR being reported by the AISConfig utility is quite high at 2.0:1, yet the device appeared to be working normally at that time.  I cannot explain how this is engineered to work, but as reported above, the realtime behavior I experienced over 3500 StM was erratic in regard to SWR.


A personal disclaimer: I am generally not a fan of AIS transponder use on pleasure boats.  A great many pleasure boat “captains” do not understand the tool or the limitations of the underlying technology.  Many abuse the tool by leaving it “on” all the time.  I believe the tool creates a false sense of safety and security in/for many users.  That is especially true for Class “B” AIS transponders.  It remains my opinion that there are only 5 situations where AIS Transponders are appropriate for continuous use on pleasure boats (at least in the U.S., where AIS carriage on recreational vessels is NOT mandatory):

  1. any operations on the great inland rivers of the U.S.
  2. operations in conditions of reduced visibility (<1 NM in fog, t’storms, snow)
  3. offshore passage operations
  4. night operations
  5. vessel-not-under-command situations

Aboard a slow-moving trawler/cruiser/sailboat on the open sounds and bays of the US East Coast, other than the above five cruising situations, there is just no compelling safety need for an AIS transponder.  As required by USCG Navigation Rules, pilots at the helm of recreational craft should just keep a proper helm watch by looking out the windows.  In most of the U.S. Southeast, and in many densely populated pleasure boating areas everywhere, AIS “clutter” caused by owners leaving their units “on” and transmitting while the boat itself is safely secured at the dock completely obscures the chart plotter screens of those boats that are in transit in the area.  I recently heard it described as “looking like an active beehive.”  This makes it impossible to rely on a distance proximity alarm, and creates a huge distraction for a pilot at the helm of a transiting boat.  It’s often impossible to differentiate moving vessels from stationary vessels that should have AIS “off” anyway.

For those who choose to have AIS on their boats, I implore:  please, do not abuse AIS; turn it “off” when operating in clear conditions of visibility.  Turn it off when secured in a slip or on a mooring.

For navigation safety, keep a constant and competent visual watch.  In combination with the fact that the vast majority of recreational boats do not carry AIS at all, especially in congested areas, do not let the “glass helm” distract from what’s happening on the water around you.

Additional information on the technology of AIS can be found in an article on this website.