The Offshore Voyaging Reference Site

Marine Electronics Recommendations—Communications


Let’s assume you want to go voyaging and have just bought a new boat with no electronics at all. First let’s deal with communications:

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when talking about costs, your solutions isn’t so terribly expensive. Sure compared to semaphore flags and a morse-mirror, the thousands hurt. But comparing those to the cost of fully integrated and networked navigation suits, getting dedicated pieces often turns out to be the cheaper solution, even if it’s only because you pay for less features you don’t need.

Around the topic AIS and VHF, I found two more things to consider:

GPS-receiver: Although many appliances have integrated GPS, having at least one external GPS-antenna is probably a good idea. I ended up attaching a mushroom-antenna to my AIS and have the transponder then distribute the data-stream to the other appliances via NMEA-0183.

VHF-Antenna: Two antennas on the mast(s) or an antenna-splitter? The second option are another $200 or so, but there is one less cable going up a mast.

Perhaps it’s worth mentioning for those just wanting passive AIS to look at a VHF with integrated AIS-display. That saves all the hassle with the antenna. By the AFI-philosophy the Icom M506 would be the preferred good choice.


Hi John,

During the last ARC we used Iridium Go, mounted below deck with an outside antenna. Having read a lot of other users’ complaints regarding this device, I was really afraid that I would not be able to communicate with the organisers and other people and. to download forecasts (MformthismImusedmthenOcens Grib Exploer Plus for iPad). On the contrary the Itidium Go worked for me.
I send and received e-mails (text ones) and tiny compressed pictures). With the Grib Explorer plus I was able to weather route our boat. The only problems I encountered were: 1. When using for voice calls – you need always to be logged in on your smart phone in order to get rings also from it when someone calls you, otherwise when you hear only the device ring by the time you log in, an automatic answering machines switches on and you lose the opportunity to receive the call (may be it is a matter of settings of the automatic answers); 2. When you send messages, each time a message was sent, I was logged out. Fair to say that log in on my IPhone 6+ took only a few seconds. Same story with IPad. Nevertheless, I was quite satisfied with the device . It never failed. Form time to time it loses the sattelite connection and then it emits a particular sound, which stops when it finds it again. This happened often (several times per 24 hours) but I am not sure whether it is a fault of this particular device (the Iridium Go).

I believe that the Iridium Go is the future way to go and sure there is a way to improve the applications. In theory if you lose the will-fi connection or the applications get bugged, you have no connection but it never happened to us. If you lose your only phone/tablet with downloaded applications, the Iridium Go becomes useless, but on board normally there are a few smartphones/tablets.

Dick Stevenson

Hi John,
I enjoy your acronym, AFI, and fully agree its message. Icom’s service life always exceeds my wish to get some new capacity; this time leading me to exchange a fully functional 15 yo unit for one that had push button DSC alarm capacity (ICOM M604 radio) and integrated seamlessly with my ICOM MA-500TR (AIS). I have used the AIS unit now for 2-3 seasons in the crowded waters of Northern Europe and in some North Sea passages and found it to do all I wish it to do. (In addition to all AIS functions, it also allows you to turn off the transmit capacity, something I wish more recreational vessels would do when in the crowded waters like the Solent- and even more so when they return to their marina.) I notice commercial vessels making small adjustments to their courses 4-6 miles out and passing at a reasonable distance and my need to make radio contact is much reduced. I suspect they are happier as well as interpreting a swaying bouncing tricolor from a distance has to be work. Much easier to get course/speed/bearing data to work from.
I do not use DSC very often and therefore do not have its use ready at hand in my head when needed and must go to the radio’s directions. However, I have used the function you queried about first hand and it is marvelous. No memory of DSC usage is required nor is there need to access and then program their MMSI number: just highlight the vessel on the AIS (something done all the time anyway to collect info) and initiate contact. I have rarely used this as commercial vessels in this part of the world are well behaved and generally predictable, but one or two whose intentions were unclear got my DSC blast and answered forthwith. Badda bing badda boom. If technology is to make life simpler, then this combo succeeds.
My best, Dick Stevenson, s/v Alchemy

Dick Stevenson

Hi again,
Our AIS antenna is on our pushpit which gives me all the range I want. Commercial vessels (with their high antenna location) come in 12-15M out and I have never felt my AIS functionality compromised by its lower location. This location has a number of benefits: easier installation and troubleshooting, less clutter on the monitor, no need for antenna splitters, which, I believe, need to be powered by the DC grid to work, and (maybe) some redundancy for a lightening hit.
When planning the coax cable runs, I suggest having cable connections in one location. This demands extra cable length for some runs (not an issue if you buy good cable), but the benefits are worth it. You can then easily swap the VHF from the mast head antenna to the pushpit antenna if you lose the mast or take the mast down for canal transits. (For us the coax is from a below decks VHF, a cockpit VHF and an AIS. For ease of swapping an A/B or an A/B/C switch is helpful: there is no need for a splitter and its complications, but do buy a good quality switch). Finally, there is no need for extra fittings at the mast head to give the antennas adequate separation.
My best, Dick Stevenson, s/v Alchemy

Christopher Barnes


Amen to the tried and true model that is not connected to much…

+1 Icom radio, ours is great

+1 Iridium SatPhone, not hard to setup data transfer and for our style of crusing (off and on intensive use of sat phone then very little when coastal crusing). We ended up with X-gate compression service, works fine, awful email interface, but is easy to use on the mounted iPad when at sea for downloading GRIBS.

+1 for Furuno FA500 AIS displaying on a Furuno 1835 Color Radar (with ARPA option) having all the collision avoidance data on one screen is pretty great when you have a mix of targets broadcasting and not broadcasting AIS data (like two nights ago in the English Channel)

+1 to seperate antennas for VHF and AIS, we lost 70% of one in a lighting storm and we’re happy to have the other ready to switch over if/as needed. I like Dick concept of separating them (ours are both up the mast).



Hi John,
Re AIS, the SE Asian perspective is that both Singapore and Thailand (Phuket) now require an AIS transmitter to be fitted (and working) as a mandatory requirement for entry, and while not mandatory t this time, Australia’s Border Force has told us informally that they investigate all vessels coming from Asia as a matter of course if they are not transmitting an AIS signal. No doubt as the world progresses further in becoming a less safe place for all vessels we will see this being a continuing trend.

That said, and having made several transits of the Straits of Singapore and up/down the Malaca Straits in the last 18 months, AIS is a mandory safety requirement (both transmtting and receiving) in my view. It makes everyone on board a lot happier to know that vessels from tugs towing barges at 3 knots to 300 K ton LNG tankers travelling up to 22 knots can see us and we can see them in terms of heading, speed and likelihood of collission.

re. The Vesper AIS unit we run it it has given good service sans a firmware issue that the Malaysian agent helped me fix wth little drama. We do run an arial spilitter and have lost a unit due to an electrical storm which meant either no AIS or no VHF until it could be replaced – again from the Malaysian Agent with no drama. The splitter will go as soon as we can organise this as electrical storms in this region are common and we can not afford to loss our AIS.

A consideration that emerges out of this experience (and yours re Vesper) when investing in electronic equipment is the capacity to source repairs or replacements. Particulary when operating in parts of the world were remoteness and none english speaking government utilitie like Kustoms can present critical challenges.

Rusty Gesner

We bought our Iridium GO thru PredictWind (fulfilled by Atlantic Telecom) and their instructions and support made setting if up pretty easy and straightforward. The unlimited data and unlimited SMS is invaluable (however the Iridium SMS sometimes goes on a walkabout). PredictWind provides very good support by email and if needed will call you back by phone and walk your thru things. And they include the ability to ping a personalized tracking webpage hourly with our GPS position.
PredictWind by internet has been great, but downloading via the GO is quite slow. However animating the GRIB in the PredictWind Offshore app is invaluable and makes it very understandable and easy to analyze to make weather routing and departure timing decisions.
I agree with you on the OCENS weather bundle, but some of OCENS new smartphone apps for Iridium are great and pretty inexpensive. The GOs SMS is not private, but OCENS OneMessage via the GO is. OCENS OneMail lets you review headers and selectively download mail from your gmail account. OCENS SpotCast with WaveCast give quick 3-day text weather, wind and wave reports at our coordinates (or any that we specify). OCENS support has been great. I correspond directly with one of their executives, and they have fixed and updated their app in a couple of days when I reported a bug.
We got the Vespers XB-8000 blackbox AIS transponder and splitter. Installation was pretty easy, it has functioned flawlessly, and displays on a smartphone or via wifi or NMEA or a wide range of other devices.

Niels Otto Wind-Jensen

Dear All,
Interesting and inspiring article, John !
I have used the ICOM MA-500TR AIS Transponder since 2011 on a 3 year trip round Ireland and now 2015/2016 on the Norwegian West Coast, with success. The unit came with its own bulky GPS receiver, but with ICOM UK’s good help, I had it converted to accept the GPS signal from the Nexus NX2 Server via RS-232.
Using a separate VHF aerial (for redundancy) situated on top of our open doghouse gives safe coverage to follow other vessels, however, shore based stations are only picked up in closer proximity. This means that AUK cannot readily be followed by
Occasionally we get an ‘ANT MALFUNCTION’ error message, but I have been unable to trace the reason for his.
The next project is to install a dedicated 12V solid state PC permanently in the chart-table for running OpenCPN with two 15” monitors, a fully dimmable one in the doghouse and a simpler one on the chart-table. The AIS will be interfaced to this PC. The reason for opting on OpenCPN is that I like to have a choice on my electronic chart supplier.
Kind regards,
s/y AUK, OE32

Dick Stevenson

Hi Niels,
Was there a reason, other than the bulk of ICOM’s GPS antenna, that you discarded it and got GPS input elsewhere? And was it a complicated adjustment or not so hard after it was figured out? If possible, can you give an idea of what needs to be done? It is always nice to have alternatives and we already have a Furuno GPS unit bringing in GPS data.
We head for the west coast of Ireland next season.
Thanks, Dick Stevenson, s/v Alchemy

Niels Otto Wind-Jensen

Hi Dick,
I did not see a reason to mount another GPS receiver on the boat; the Nexus GPS and the standalone Koden GPS already gives me redundancy. The ICOM AIS unit was sent to ICOM UK Ltd. who did the modification. After that it was a matter of finding the correct wires to link up and that was no big deal. Good luck in Ireland and do not forget to call into Inishbofin and Clifden.

Dick Stevenson

Hi Niels,
Thanks for the info. Clearly not a swap one does in the field. thanks for the cruising suggestions.
My best, Dick


Hello John,

I’ve been having a long hard look at the Iridium Go and I like what I see, in spite of there being a lot of complaints about it not being usable for Internet. All I really care about is being able to download mail, send text messages and be able to make and receive calls.
From your warning it sounds like you need to be very tech savvy to set it up. What were your key difficulties/obstacles?

Rumen’s experience sounds positive and similar to how I would use it, so I’m optimistic again about the Go. This was not the case after emailing, because they suspended sales of the Go after receiving too many complaints. Here’s what they said: “Customers are complaining that the Internet service does not work, which it doesn’t really… and as such, we were taking the brunt of customer complaints even though we had no control over the network.”
Not a big problem for me, since that’s not why I’d be getting the unit … and hopefully it will improve when they upgrade their network next year.

Best regards,


Hello Andreas,

If by internet service, it is understood broswsing, it does not work but I think this is not a short coming of the Go only. They should not have included “Web” in their “Mail and web application’, therefore I never used the icon “web”.

Keith Jones

Hi John,

I’ve had a number of friends and customers upgrade their legacy instruments lately, some due to need and others have done so for the new features of AIS targets on chartplotter and Ipad connectivity. I’ve taken a different approach on our boat – taking the AIS and GPS output from the Vesper AIS receiver ($300 standalone unit with display) and hooking it to a RS232 to Wifi adapter. Running AIS compatible software on the computer or tablet it is an easy setup then have your device connect to the wifi. Outlay is software ($0-$400) plus adapter ($50-$100). We still have our legacy standalone systems that we’re happy with and have added AIS targets, weather and current information, etc. on the tablet and laptop. Far better than the 5 figures that is often spent.

Agree with Dick on the separate antenna. Also everyone should have on board an adapter to connect their handheld VHF to masthead antenna – 5 watts from a high gain antenna 60′ up has surprising range.



Bob Hinden


Very nice article! I agree with a lot of what you said, but not surprising not everything.

After purchasing Surprise in 2013, I updated the electronics. I replaced the original VHF with the ICOM M604. Good radio, main reason for getting it was for the keyboard for the reasons you pointed out. My only complaint was that the connectors to connect it to NMEA was really a kit and soldering wires to the tiny pins was a real pain. I would have expected better from ICOM.

Surprise came with an excellent marine SSB and separate HAM transceiver (both ICOM), backstay antenna, antenna switch, single antenna tuner, and Pactor modem. Other than having to upgrade the modem, all has been great. I like radio, have a ham license (KI6ASK), and am a long time sailmail user.

I installed a Vesper XB-8000 AIS Transponder, antenna splitter (using top of the mast VHF antenna), and separate WatchMate display. This is connected to the boat computer (USB) and to the ICOM VHF (NMEA). I like the ability to make an DSC call from the WatchMate. [I wish the NMEA sentences for this were standardized, so all chart plotter software could have this feature, seems to be an ICOM thing at the moment.] It’s been reliable system, but the NMEA wiring was a project. I have seen tracks using MarineTraffic, this was especially nice when I had the boat delivered from Santa Cruz to San Francisco. Was very nice to see where the boat was off the coast of California. I assume from this I am putting out a good signal.

On a related topic, I installed a semi-custom industrial computer from Logic Supply. It run on ship’s power, no fans, SSD disk, or any moving parts. It’s been fast and reliable, and low power. All great for a boat. Happy to provide more details. Computers on boats would make for a good article.

Currently, I am considering upgrading my original Iridium phone to the Iridium Go or the Extreme model. I would use Sailmail with either. Based on your article I am leaning to the Extreme, The issues I see with the GO are having to use WiFi to connect to the computer and I think the Go wouldn’t be a good choice in a life raft. On the other hand, the price for the SIMs for the GO are more reasonable, I really hate buying Iridium time and having it expire. Another tradeoff.

Hope this is useful.


Marc Dacey

It’s very useful to me, because it aligns closely with what we wish to do in our two-helm, pilothouse nav/comms setup. The fanless PC would suit me down to the ground. The only question in my mind is whether to double up with a simple, stand-alone plotter at the outside (“sailing”) helm or to have a waterproof “repeater” screen to see the output of the below-decks nav display. I’m glad you like the Vesper gear: I’ve found reports of it impressive.

Raymond Smith

My Vesper AIS has given me no problems and has been a real asset both crossing the Atlantic and in the Med. I understand your reluctance to recommend it since you had a hassle with the company, but fail to understand why you would recommend a unit you have never tried. Better, imho, to ask for feedback from others on both systems.

Dick Stevenson

Hi Raymond,
I suspect the answer is embedded in the AFI acronym and John does ask for feedback after acknowledging a lack of first hand knowledge. Like so many of these marine electronics products, once they are working and figured out, they often give good service. My ICOM AIS MA-500TR was good out of the box and almost plug and play in the set-up/installation. That is a good deal of what I look for in a product after determining the likelihood of good service.
Dick Stevenson, s/v Alchemy

Eric Klem

Hi John,

I am curious as to how much of your gear you have doubles of or repeaters for so that they work both on deck and down below? Since this post is about communications, do you have 1 radio, 1 radio with a RAM mic, 2 radios or something totally different? On our last boat, I mounted our radio right at the companionway so that it worked reasonably well on deck and down below. Our current boat has a single fixed radio down below and we use a handheld in the cockpit which is not ideal. I have been thinking of going to a RAM mic for the cockpit but it hasn’t yet made it up the priority list. I have used this system on a few boats and it is okay and probably a better compromise for me than 2 radios and the associated antenna issues. We do definitely use the radio both up on deck and down below and it is very dependent on where we are sailing and whether we are underway or not.


Dick Stevenson

Hi Eric,
I know you were directing the question to John, but I thought I would step in w/ Alchemy’s set-up and a comment about the set-up that many have not considered. We have 2 VHF radios, 1 in the nav station (in actuality rarely used) and 1 in the companionway just before exiting, both sharing the masthead antenna with an a/b switch (not a splitter). The companionway radio has a RAM in the cockpit near the helm. We find this important on passage, especially coastal overnighters, as we monitor ch 16 at all times and if either of the below decks radios is on, the talking is hard not to pay attention to and disturbs the off watch crew sleeping. The RAM is heard mainly in the cockpit where the on watch person is the bulk of the time and does not disturb the sleeping crew below.
My best, Dick Stevenson, s/v Alchemy

Eric Klem

Hi Dick,

Thank you for the thoughts. I agree completely about not having a radio on below decks when there are off watch crew asleep. I have occasionally forgotten and left the radio at our nav station on and then had to crawl out of my comfy bunk to turn it off. I find the radio below is really only good when we are not underway but then it is really nice.

Your solution of an a/b switch makes sense, I really don’t want to end up with a splitter. It seems to me like whether a switch is used or a single radio with a RAM mic, the key is that most of the radio work is from on deck but you do still want the ability to use it down below.


Keith Jones

Hi Eric, I’m not sure what kind of switch Dick is using. I have upgraded some of my ham and marine switches to the Alpha-Delta brand (model 2-b). They have a built in and replaceable lightning surge protector and you can ground the radios by moving the switch to the center position (unusual switch feature), also the unused radio is always grounded. I’ve had cheaper switches wear out and not have the added features so I upgraded a couple of switches last year, I got mine at DXEngineering.

Hope this helps,



The only thing I’d add is a few Uniden Atlantis 250 handheld VHF units.
For under $100 each, they have excellent range and quality for a handheld (I routinely get “5-by-5” on radio checks to a station 5+ NM away), are durable and reliable, don’t seem to have any flaky-charger issues, and can run on a pack of AA cells if you run the lithium battery flat and have no way to recharge it.

Dick Stevenson

Hi Keith,
Excellent addition to the recommendations. I am using a Ham quality a/b switch (not the a/b switches that are sold at the usual recreational marine culprits), whose name escapes me–but likely suggested by you in years past.
My best, Dick Stevenson, s/v Alchemy

Bill Koppe

Hi John,
Having an Iridium 9505 handset I found using it a real pain with lot`s of dropped connections.
I then went to a Sailor SC 4000 fixed unit and had great connections.
This unit costs US$2200 and will save that in usage fees. While data is slow we used the free grib files that come with Maxsea and that was very efficient. SMS messages are 60c
Aerials are now to be hidden in the boom gallows timber beams
Bill Koppe

Bill Koppe

Hi John,
Yes used the external antenna.
Bill Koppe


Hi John,
Thanks for the advice and the UUP Plus tip
Bill Koppe

Neil McCubbin

Many traditional SSB radio functions are partly replaced by satellite systems, but in many parts of the world SSB nets are great tools for cruisers.
In Northern Europe we did not find any active nets, but there are many good ones further south, Caribbean and Pacific
We have a low-end ICOM HAM & Marine radio and tuner and consider them worth the cost. ( both replaced troublesome equipment from competitors)

Terry Thatchet

John, my son and I are updating systems to go offshore. I figure I can use AIS, since I use radar and chart plotter now. I have to say however that I am quite concerned about my ability to get everything set up with sat phone and whatnot in order to receive weather. I am kind of a Luddite, or at least an old guy with some computer phobia. I don’t carry a computer on board but it looks as if that will be necessary for weather maps. Can I get a laptop that runs on 12 volt? How do I hook it up to a sat phone? How do I learn how to run the wire and set up an external antenna? In sum,where can I go to start getting an understanding of the basics of how to set things up. You and all the others commenting seem so knowledgeable that I feel overwhelmed.


Valuable analysis as I select an AIS Tx solution, thank you. I now think to ft the Vesper XB-8000 black box, integrated to our Zeus2 at helm.

I found this linked content of considerable interest, which highlights the common geaneology of AIS units across several brands:

Neil, S/Y L’escale.

Marc Dacey

Coming back to this: I just got off the phone with U.S. marine goods sellers, who seem a decent outfit. I’m considering buying the Vesper XB-8000 Class B AIS transceiver from them (I think Vesper have improved, John, and this model has a number of desirable features for me). On the page listing the Vesper, I noticed that they won’t sell them without inputting an MMSI number and that some sort of FCC compliant must be filled out, along with a fax of one’s MMSI number. Fair enough, and they said they could input my Canadian-issued MMSI at their end, as they are required for American reasons to do.

But, needless to say, I can see a number of ways for this to screw up.

Has anyone in Canada actually bought an AIS from Defender and had it arrive with the correctly input Canadian MMSI number? This would reassure me, as the operator on their 1-800 customer service line had not had the question posed to her before and had to “call the president” (of Defender, I assume, not Mr. Trump) to answer my question in the affirmative. So anyone out there try this yet? Thanks. I realize this is an unusual comment, but the odds are quite good in this crowd of passage-making early adopters that someone has encountered this issue.

Marc Dacey

Thanks, John. I have more spare U.S. than Canada dollars at the moment (a good problem to have, I guess) and was looking to spend them. The Vesper service check is duly noted.

andrea jasson

Hi John,
you mention using a combination of Iridium + SSB receiver. That’s a combination I like because it provides some sort of redundancy for weather info (and because I have an Iridium phone already..) I was wondering if I could ask you a couple of questions…

-Does the radio receive signal just as well as a normal SSB transceiver? And Have you tried one in more confined environments – like a Patagonian (or Norwegian maybe in your case?) fiord? Can I rely on it for weather info – considering the Iridium is there as a back up for the occasional misconnection?
-Will it require a modem pactor and sail mail to download Gribs, Synoptic charts and… emails (is this asking too much?)
-Will it require an external antenna and other hardware (demodulator) and if so could you advise a brand? (I have two spectra running backstays – no backstay to use as an antenna)
-As for the Iridium, you mention that for it to work at its most, I would need an external antenna , is there one you’d recommend?
-Does the Iridium require a modem pactor to send/receive emails and get gribs + weather maps?

As you can probably tell, I am definitely not a techie…

Many thanks!

andrea jasson

Yep, go seems nice, though the monthly cost including sailmail or UUPlus seem a bit steep.

Any chance you have a rough idea of how much downloading gribs via handheld iridium May cost (I know it would be a rough estimate!)




garry crothers

Can you recommend a particular vhf aerial suitable for aluminium hull. I know some manufacturers need a dc block fitted to isolate the screen.




I have a spare masthead METZ aerial that I can use. It does work, i’ve tested it with my existing vhf, but not with an SWR meter.
I get an earth leakage fault on my meter when I connect it to the VHF. I initially though that the cable had frayed and exposed the sheath which was touching the mast. I’ve examined the cable entry into and out of the mast and there is no visible signs of damage, Though possibly it could be frayed within the mast, but I thought that would likely show up as an intermittent problem. The Metz guide shows that there is an internal loading coil which manifests as a DC short across the coax. This is what I’m guessing is causing my problem, but I may be totally wrong, and there might be exposure of the coax sheath within the mast, hence the query.


Alwin Bucher

Regarding this business of isolating the antenna from the mast – this is another one of those topics where you will find a rabbit hole of conflicting information on the sailing forums.

There appears to be a valid reason why marine VHF antennae and their mounts are invariably set up to connect the shield to the mast by default, and this I think corresponds to most designs requiring some kind of “counterpoise” to function well.

One of the few sources of authorative information on this subject is available from Stan Honey, who specifically mentions that:

… VHF whips that are about 36 inches long and have a matching transformer in a small cylinder at the base do not require a ground/counterpoise connection to the mast.

However, for other designs I think the implication is that an inner/outer DC blocker is the way to go (he does go on to discuss these). Unfortunately these appear to be near to impossible to source, at least in Europe, and in any case will probably be more expensive than a new 36″ VHF antenna.

I entered this rabbit hole because our DC leak meter on our new-to-us aluminium boat fired so long as the VHF antenna was connected to the radio – thankfully the outcome is that I am now content to isolate the antenna mount.

Arne Mogstad

Hi. Regarding AIS, there is now a “new” one, called SOTDMA, or Class B+. It is not really new, both in the sense that its now several years since it was introduced, and that SOTDMA have been the way Class A transponders have communicated for a longtime.

For sailboats, I se only two potential benefits: wattage increased from 2 watts to 5 watts, and guaranteed transmission slot (maybe valuable in a very busy area?) The increased transmission frequency is not really applicable to most sailing boats (and frankly quite few motorboats as you need to exceed 14 knots).

Anyway, does anyone have any input on this? It feels a little like buying a dying technology when I need to replace mine now. It’s not really such a big price-bump, it is more the limited selection (Icom does not make a Class B SOTDMA transceiver). Em-Trak seems one of the few reasonable choices. Any knowledge or experience would be highly appreciated!

Kindly, Arne 🙂