Practical test: 4 satellite messengers that send signs of life

Satellite transmitters are useful when travelling at sea or in remote areas where mobile phone coverage is unreliable. They are an inexpensive way to communicate with your loved ones and keep them up to date with the progress of your trip.

While an Iridium satellite phone suitable for outdoor use costs around 1,500 euros, an Iridium satellite transmitter is available for as little as 250 euros. And unlike long-range radio systems, it does not require any complex installations or a radio licence to operate. In addition, monthly tariffs are manageable, starting at 18 to 20 euros.

Iridium as the gold standard

There is now a wide range of such messengers for various outdoor activities. We have focussed on devices that use the Iridium satellite communication system. With its polar orbiting satellites in a low orbit of around 780 kilometres, it is virtually predestined for such services.

Firstly, unlike geostationary communication satellites, which are located at an altitude of around 36,000 kilometres above the equator, there is no need to align the antenna precisely with the satellite. Experience has shown that this is difficult with a handheld device on a swaying boat. Products such as the Motorola Devy Satellite Link we have therefore left out.

Secondly, the Iridium network seamlessly covers the entire globe, including the polar regions, which also sets it apart from other systems with low satellite orbits such as Globalstar. After all, the attraction of a satellite messenger is that it no longer has to take network coverage into account, which is why we have also excluded devices for the patchy Globalstar network.

The remaining test candidates were:

• Bivy Stick from ACR >> available here
• InReach devices Mini 2 >> available here
• Satellite Messenger Plus from Garmin >> available here
• Zoleo Messenger >> available here

The test candidates

Not for restricted vision

Satellite communication generally requires a clear view of the sky. In a narrow canyon, you can only reach satellites that are at the zenith above you. Here you may have to wait until one arrives. Even on the high seas, contact can be lost temporarily in the trough of a wave. This leads to delays in the exchange of messages.

Shielding also occurs in urban canyons and enclosed spaces. There is a reason why all satellite transmitters have an eyelet so that they can be attached to the outside of a rucksack or clothing when hiking - also with a view to unclouded positioning via the built-in satellite navigation system (GNSS). At sea, operation on deck is therefore recommended.

The prerequisite for this is a waterproof design, which all tested devices have. For the InReach Mini 2 There is even a cockpit mount with a 12-volt power supply (marine bundle). Various mounts are also available for the Bivy Stick, although there is no explicit solution for on-board use. A car mount with suction cup is available for the Zoleo Messenger.

More about communication on board:

• Starlink Mini now also available in Germany - and what it costs
• Walkie-talkie: The whole crew on the same wavelength - four devices put to the test
• New "Crew" headset from Sena for more straightforward arrangements

Nuances in the connection quality

In outdoor use, sending messages via satellite did not cause any significant problems with any of the devices tested. All test candidates also worked well in the car under the windscreen. Differences only became apparent in difficult reception situations with a restricted view of the sky.

The Zoleo messenger sometimes had to give up, while the Bivy Stick at least occasionally sent messages. The Garmin devices were not so easily defeated either. However, these nuances could also be due to the respective test situations.

A nice feature of the Garmin devices is the option of sending a test message after switching on, to which you receive a confirmation if the transmission is successful. This allows you to check at any time whether the satellite communication is working locally.

Smartphone as a user interface

To keep the size and cost of the devices within limits, they use the smartphone as an interface for writing and reading messages and for device configuration. To do this, the corresponding Android or iOS app must first be installed on the smartphone, to which the satellite messenger is paired via Bluetooth.

There are three ways to communicate: Messages can be sent to a mobile phone number (SMS) or to an email address. There are also direct messages to other users of the respective app (app-to-app messages). If you allow the app to access the contacts stored on your phone, they can be selected directly.

You cannot make phone calls with a satellite messenger. It is also not possible to send pictures, voice messages or even file attachments. The devices only support pure text messages with a limited number of characters (see table). One exception is the InReach Messenger Plus, but more on this later.

Show where you are with the satellite messenger

Another function is sharing the current location. When the location is embedded in a message, a link is sent that opens a map view in the browser. Automated location updates are also possible. However, additional costs may be incurred for tracking (see rate table). The tracking interval can be set (see product table).

A location message can also be sent in the form of a check-in message. This also contains a short status message, for example "I'm OK" (Zoleo). An unlimited number of check-in messages can be sent in all tariffs. However, they only reach so-called check-in contacts, which must be defined in advance.

With ACR and Zoleo, the number of check-in contacts is limited to five. Zoleo only allows configuration via the online user account, which requires a mobile internet connection. With ACR and Garmin, this can be done directly in the app. Furthermore, the text of the status message is predefined with Zoleo. With ACR it can be customised, with Garmin you can choose between several texts.

Other text messages and messages to other recipients can be sent with or without a location. They are again charged to the budget.

Always the most favourable way

However, this only applies to transmission via satellite. Within the mobile network, the messenger apps use the smartphone's hardware. There, sending text messages and location messages worked with all apps even without a connection to the messenger.

However, the recipient cannot see which network was used to send a message. The phone number or email address of the messenger always appears as the sender ID. This ensures that any replies are also received outside the mobile network via Messenger.

The device-specific phone number and e-mail address help to limit the circle of people who can send you messages via Messenger. Finally, messages received in the satellite tariff are counted in the same way as those sent.

Special features of message reception

Outside the mobile network, message reception is only ever checked at certain intervals. With the InReach messengers, you can choose between a performance mode and a power-saving mode, and with the Zoleo device between intervals of 12, 24 and 60 minutes as well as "always on".

Only the Bivy app requires the messenger to be connected to the mobile phone network in order to retrieve messages. This is a little annoying, as it does not automatically pair with the smartphone when the app is opened like the other test candidates.

For emails from an InReach messenger, a Noreply address appears as the sender if the recipient uses a standard email client such as Outlook. To reply, click on the link sent with the email, which opens the sender's Garmin Explore page in the browser. There you will find an input window for a text reply.

This may seem cumbersome, but it forces the recipient to observe the restrictions of satellite communication, such as the number of characters, when replying.

Wide range in battery life

How long the messenger's battery lasts depends, among other things, on the message retrieval and tracking interval. Added to this is the accuracy of the position determination, which can also be adjusted on the ACR and Garmin devices.

In the test, the Bivy Stick with its very simple battery indicator was the first to give up. With a 10-minute tracking interval and moderate positioning accuracy, it lasted an average of just 40 hours, which corresponds to a capacity reduction of 2.5 % per hour.

The messenger from Zoleo performed better, with an average capacity decrease of only 1.5% per hour in test operation with comparable settings (message retrieval: every 12 minutes). This results in a battery life of a good two and a half days.

The two Garmin devices performed best. With the InReach Messenger Plus, we were still able to send a status message after a full four days despite multi-GNSS and performance-optimised message retrieval (tracking interval: 10 minutes). The InReach Mini 2 was even more frugal.

Lightshows, buttons and displays

In practice, however, the mobile phone battery is more likely to become the bottleneck, with the Messenger app and the Bluetooth connection constantly sucking away in the background. One alternative is to use the messenger independently. After all, at least check-in messages can be sent directly on the device for all candidates. However, without a smartphone app, everything has to be transmitted via satellite.

The Bivy Stick and the Zoleo Messenger use multi-coloured LEDs to indicate the device status and successful transmission. With the Zoleo, however, the hectic, successively flashing lights put on a show that quickly gets on your nerves - you don't want something like that in the cockpit at night.

The two Garmin devices rely instead on a display whose backlight only switches on at the touch of a button. These are monochrome, transflective MIP displays that utilise ambient light for illumination during the day and only ever control the pixels that change.

Both displays are very easy to read. Incoming text messages are displayed directly. However, entering text using the few operating buttons can be tedious. However, other standard functions such as retrieving messages, sending status messages and making settings are quick and easy.

Supplementary emergency call function and weather forecast

All tested devices also have an "SOS" button for emergencies. With ACR and Zoleo, messenger emergency calls are handled by Global Rescue, a US company founded in 2004. Emergency calls from InReach messengers are forwarded to the International Emergency Response Coordination Centre. The IERCC was acquired by Garmin in 2020. The manufacturer even offers SAR insurance through Garmin Insurance Services LLC.

However, pressing the "SOS button" on the messenger does not replace a maritime radio distress call, especially as only this can reach ships in the vicinity. Nor can a satellite messenger replace an EPIRB (ship-related registered satellite distress transmitter of the COSPAS/SARSAT system), which in turn is integrated into the global maritime distress and safety radio system GMDSS. The Messenger emergency call is also sent to private emergency contacts.

The messengers also offer the option of calling up a location-based weather forecast - with ACR only for the current location, with Garmin and Zoleo alternatively also for a different location. However, this is not a marine weather report. Only with Garmin can the weather call-up be switched to "Marine", which also includes sea state and current information.

Conclusion on the satellite messenger practical test

The main benefit of satellite messengers at sea is the exchange of short messages and location data independent of mobile phone networks. In this respect, all candidates proved to be a functional solution in the test.

Zoleo attracts customers with a favourable price structure, while the products from maritime experts ACR and Garmin appear to be more optimised for use on board. However, the InReach devices clearly stand out with their own display and extended features.

This means that compatible plotters and smartwatches from the manufacturer can also be used as a user interface for the Garmin messengers. They also support autonomous waypoint and track-back navigation, for which an electronic compass has been integrated. Land-based routes can be created using the Garmin Explore app. With the Garmin GPSMAP 86i, there is also a handheld chartplotter with a built-in InReach messenger.

The InReach Messenger Plus even allows you to send photos and voice messages via satellite. However, this is only possible to mobile phone numbers, and the recipient also needs to install the Garmin Messenger app to view and listen. At the same time, the Plus version costs twice as much as the regular InReach Messenger - you should think twice about it.