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Email, weather and gribs at sea using a Satellite Phone

by Art on

This is the third article of a series discussing how to connect to the internet at sea using a variety of hardware and software. I recommend reading the articles in order of their publication to learn the most about this complex subject. The articles in this series are: Email, weather and gribs at sea using WiFi, Email, weather and gribs at sea using 3G/4G, Email, weather and gribs at sea using a Satellite Phone (this article), Email, weather, gribs at sea using Satellite Terminals and Email, weather and Gribs at sea using Software.

Update: I just published a new article about using the iSatPhonePro 2 which is much better than the Iridium Extreme (perhaps next year Iridium will leap-frog Inmarsat again... Anyway, go read iSatPhone2 versus Iridium Extreme to catch up on the latest satphones.

In the two previous articles I covered a bit about setting up an internet connection using a WiFi booster as well as using a 3G/4G modem. Both of these are effective ways to connect however they’re restricted by the need to be relatively close to shore. In the case of WiFi, usually within a mile or two at best (depends on line-of-sight). Using a 3G/4G signal (like you use from the smartphone) you can extend the range to perhaps 10 nm offshore but only if your are cruising along a populated area that has good mobile phone service.

So what do you do when you are further offshore? Depending on your sailing program you may never sail far enough away from land that you’ll need other choices but, for those of you who regularly sail long passages it may be worth it to work out a system that allows you to have reliable internet. In my opinion, you shouldn't venture offshore without a dependable way to receive weather updates. Email from family and friends is always nice but having solid weather information is much more important.

There are basically two technologies to accomplish this. The first I will cover in this article, internet connections using a satellite phone. In a future article I'll go over using a satellite broadband connection using hardware like the Inmarsat Fleet Broadband system and the mini-vSat system from KVH.

Satellite Phones

There's a number of products out there in the satellite phone market but, for mariners, there's really only two that are viable as they cover most of the world. The other products are mostly regional (GlobalStar and Thuraya). If you only sail in the areas they cover, perhaps a satellite phone from these companies would work for you. . The Iridium satellite phones and the IsatPhone Pro from Inmarsat are the most popular. There's a number of other websites out there with pcomparisons of these models.

IsatPhone Pro and Iridium Extreme I bought my IsatPhone Pro in early 2011 at the Dusseldorf Boat Show as Inmarsat was selling the phone for about €400 and a package of 1'000 minutes of usage for €850. I used it only for phone calls while at sea and had mixed results from it. At times the phone alone was OK , but the calls dropped off a lot. I never used it for retrieving weather as the data connection capability wasn't needed as I had a Fleet Broadband 250 onboard and used that. The technology behind the IsatPhone and Iridium networks is vastly different and these factors weigh heavily with regard to reliability of connection and speed. I found the IsatPhone Pro's connection reliability to be highly directional while the Iridium is not. Let's look at a couple of graphics to help understand why.

IsatPhone Pro

IsatPhone Pro coverage map The IsatPhone Pro relies on the Inmarsat satellite network which consist of three equally-spaced satellites placed around the Earth at a geostationary point perpendicular to the equator. This, of course, means they stay in one spot and for best results you have to 'aim' the satphone at the location of a particular satellite as you sail along. At times, this can be hard to do as buildings, other boats or even your mast can obstruct the direct view of the nearest satellite. Using the unit handheld to make a call (on a rolling deck) is hard to do and calls drop all the time. Maintaining a data connection without the use of a dedicated external antenna can be infuriatingly difficult. Another common complaint is the need for the IsatPhone Pro to lock on to a GPS connection before it can connect to the Inmarsat satellites. This takes a couple of minutes and is a bit of a pain. A plus is the purchase price as it is about 1/2 the price of the Iridium phone. As you will see later on, that is not the only measure of cost. There are the airtime costs which we’ll go over later in this article.


Iridium coverage map The Iridium depends on a constellation of 66 satellites arranged in a similar fashion to the satellites used to provide GPS positioning. This means one is always in view and the Iridium phone connection will be handed off to the passing satellite that is in the best position relative to your location., The reports I read claim the connections for voice and data are much better than the IsatPhone Pro. As such, I have ordered one, along with an external antenna for my boat so I will be reporting my own results. There are two models available, the 9555 and the 9755 Extreme. The differences are that the 9755 has GPS built-in (albeit to compete with the ISatPhone Pro although it doesn't require a connection before making a call) as well as a dedicated SOS button to post an alert to someone (or a rescue agency). It is also more rugged and water resistant. It should be noted, this SOS feature is not a substitute for an EPIRB or PLB just another tool to use when you need it.


Two more areas for comparison are data transfer speed and cost for airtime minutes. In addition to being able to place a normal phone call you can also hook up a USB cable to either of these phones and make a data connection.. This is the method used to hook up to the internet and upload or download email, weather, or grib files.

History Lesson

Analogue modem from 'yesteryear' I've been working with computers since the 1970's so I remember how we hooked up to the internet using a device called an 'analogue modem'. Back then the speeds were incredibly slow, in the range of 300 bits per second. You'd place a call to the data center with your phone and put the handset in a receptacle of the modem where it would 'warble' sounds back and forth with the data center. On the computer you could watch the characters flow by at speeds like someone was typing it. Amazing stuff at the time but too painfully slow to think about these days. Over the years the speed picked up to 2'400 baud (2'400 bits per second), 9'600 baud, etc. The last modem I had was from a company called Hayes Microcomputer Products and ran at 56'000 baud. They introduced a command language for modems called the 'AT command set'. Now, all this history may be boring to you but there's a point.

The satellite phones of today act like a modem of yesteryear and actually use the same "AT command set". They also operate at the old speeds of 9'600 baud. Now you see where I'm going with this… they are really slow! This means whatever you want to send or receive over them needs to be as small as possible. Because Inmarsat and Iridium charge you per minute (or increment thereof) you can see the correlation between the size of what you need to send or receive and its directly relationship to cost.


As it turns out the Iridium phone has a slightly faster throughput than the IsatPhone Pro. Coupled with the ability to get online quicker (in 20 seconds rather than several minutes), the Iridium has an edge here in terms of speed. In addition, Iridium charges you in 20 second increments while, on the IsatPhone Pro, your calls get rounded up to a the next full minute. This is offset a bit because the rate-per-minute for the IsatPhone Pro is a little less than the rate-per-minute for Iridium.

So, the overall speed and cost difference between both phones is not that much however I think the additional reliability of connections found with the Iridium network are important if you are going to depend on this for connections well offshore. If you are a coastal sailor then perhaps the IsatPhone Pro would be sufficient.

Wrapping up, I wanted to point out that through the use of some clever software, you can compress the data and vastly reduce your costs. As this topic will apply to not only satellite phones but for every device used to connect to the internet I'll cover this in a separate article at the end of this series. Stay tuned!

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