The Mobilinkd TNC has produced a major change in how amateurs use APRS. Prior to its existence, operators were limited to two choices: larger, wired TNCs and expensive radios with APRS built-in (native APRS). The first choice wasn't suitable for portable or mobile use, and configuration tended to be tricky. The second choice was good for portable and mobile use, but was even harder to set up and use. You were also limited to the relatively tiny display on the radio.
The Mobilinkd solution solved these issues neatly. Since most of us have a smart-phone with us, it could be used as the display, the user interface, and the "brains" of the station. And you could use the mobile rig you already had (or an HT). Bluetooth, rather than a cable, connected the TNC to your phone.
It was a big change. Other solutions came, and some went.
Mobilinkd just released the TNC4, and I got one. So, I had to configure it. That's where I ran into "issues".
Need to configure?
The only time you really need to configure a Mobilinkd TNC is when you first get it, or if you change the radio you are using with it. Even then, the default settings it comes with out of the box will work in most cases (while not being optimum).
For a new radio, adjusting the audio levels is a very good idea -- both for receive and transmit.
For mobile use, you would want to configure the power options so that it turns off when you park, and turns on when you start your vehicle. This assumes you are powering it with USB from your vehicle's electrical system.
How do I configure it?
The instructions are found on Mobilinkd's downloads page. They include screenshots and helpful tips for specific applications.
Configuration is done with an app. There are apps for Windows, Linux, Android, and iOS -- though the iOS app is not included on the downloads page, and must be obtained from the Apple Store.
Because the Mobilinkd TNC is actually a modem (not a "real" TNC), configuration doesn't include adding your callsign, setting an N-path, or any comment text. All of that is done on your APRS client (APRSDRoid, YAAC, UI-View, APRSIS32, etc.).
Instead, configuration involves Bluetooth pairing, setting RX/TX audio levels, DCD (Digital Carrier Detect), and power options.
Problems
I ran into problems right away when I tried to configure my new TNC4. First, I discovered that you can't use the Windows config app on the TNC4. Instead, you need to use the Android app.
Fortunately, I have a few Android devices: a tablet, an old smart-phone, and my current smart-phone. So, I pulled out my Android tablet (an old Nexus 7 that I still use with APRSDroid), and started the config process.
Unfortunately, it wouldn't really pair with my new TNC4. The tablet said it was paired, but the configuration app wouldn't connect to the device. And I got message saying "Bluetooth Permission Denied". Pairing wasn't something I expected to have issues with. The TNC4 has fancy new BLE Bluetooth to allow you to pair it with iOS devices, and pairing my other Mobilinkd TNCs with any other device has always been pure simplicity.
Since I don't have any Linux or Apple devices to use as a potential work-around, I was pretty much dead in the water. As it turns out, the Linux configuration app also no longer works with the TNC4. I tried my old smart-phone, and got the same result. Last, I tried my Pixel 3a (my current smart-phone)... and it paired.
This left me with a configured TNC and a fair amount of bewilderment. So, I dug into the Mobilinkd support forum.
The answer
Recently, Mobilinkd had issued an "upgrade" to its Android configuration app. This "upgrade" broke the Bluetooth permissions for older versions of Android. This is why my Pixel 3a running Android 12 worked with the app, but my other devices (like my old Samsung Galaxy running Android 5.1) didn't work.
Someone else on the support forum had a similar problem. The solution is to go to (on your Android device)
https://play.google.com/apps/testing/com.mobilinkd.tncconfig
This allowed me access to another "upgrade" (v1.4.3), which actually works with older versions of Android. After about an hour, the upgrade appeared as available on Google Play. I installed it, and I was able to use my older devices with the config app.
It may very well be that this app is now official, and you don't need to use the "testing" page. I don't know, because that's not how I got the new config app version.
The developer, WX9O (Rob), fixed this very quickly. And, to be clear, my new TNC4 paired perfectly fine with my older Android devices when using APRSDroid. It was only the Android configuration app that wouldn't work. I can only assume that an otherwise-configured TNC4 would continue to work with Linux APRS clients, too.
Implications
I can understand the abandonment of the Windows configuration software. It's a lot of work to keep updating it with all of the changes in that operating system. And Mobilinkd is selling a hardware device, not software.
Still, potential buyers of the Mobilinkd TNC should be aware that they won't be able to configure it using Windows or Linux. I was unaware of that, for example. It is mentioned on the product description page that configuration is done with a smartphone app. I just assumed that the Windows app I had used for years would also work.
Most amateurs that use the Mobilinkd TNC for APRS operation are, in fact, using smart-phones with the device. It shouldn't be too hard for most amateurs to find someone with an Android or iOS phone to help them configure their Mobilinkd TNC, if all else fails. And the TNC4 will still work with Linux or Windows APRS clients once it's configured. It will also work with old versions of Android once it's configured.
In the Big Picture, this shouldn't deter anyone from the benefits the Mobilinkd TNC4 offers.
My take
One of the cool things about apps like APRSDroid is that you can run an APRS station with an old Android phone/tablet. You don't need to tie up your shiny new phone 24/7 to run a station on RF or the -IS (Internet Service). And you don't need a cell plan on that old phone/tablet, either, if you have wi-fi for the -IS end of things. Rather than throw an old phone or tablet away, it can be re-used for amateur radio.
For portable and field operation, you also don't need to risk your expensive new phone, be it iOS or Android, to run an APRS station. You can often get someone's old phone for nothing when they upgrade. And that old phone or tablet will work with a Mobilinkd TNC for RF operation, once it's configured.
Likewise, you can take an old Chromebook that would otherwise end up in a landfill, install Linux on it, and use that as an APRS station using YAAC as the client software. And, the Mobilinkd TNC4 will work with that old Chromebook once it's configured on another device. Now you have a home station, or something you can set up as a demo at Field Day or a club presentation. If it gets rained on, or someone spills their drink on it, or if it gets knocked off the table, no tears will be shed.
This backwards compatibility, combined with marginal system/hardware requirements for APRS client software, has made getting into APRS very cheap and easy. Even as the Mobilinkd TNC moves into cutting-edge territory, such as its support for the M17 digital mode or its 2.5ppm TCXO, it continues to work with my old Android 5.1 phone. I can still use it for RF messaging, monitoring local RF-based APRS activity, or RF beaconing.
And now, thanks to the upgrade of the configuration app, I can continue to use that old phone to adjust the audio levels if I want to use a different radio with my TNC4 in the future.
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