Article by: RobRed

Applicable Models: Any Vehicle

Last Updated: Monday, February 13, 2017

If you didn’t buy an APRS equipped radio this is for you.
If you did buy an APRS equipped radio this is still for you.

I’ve had a variety of ham radios over the years, mostly hand held units until about 2011. When I started my Land Cruiser 100 series build back then I decided it was time to step up my game in the communications department. I wanted the extra power and range a mobile radio would add with the convenience that a fix mounted controller could provide. I opted to go big and purchase a Yaesu FTM-350. A rather top-of-the-line unit with an oversize LCD display in the remote control head, Dual VFO and all the bells and whistles.

Two of the fascinating features of the FTM-350 is its optional GPS capability and its built-in APRS functionality. Wait What? I know what GPS is of course but A P R what? I scoured the user guide and found out just how cool my new radio was.

FTM-350 Receiving an APRS Beacon

I was immediately fascinated with this APRS functionality and wanted to implement it. I went back to Ham Radio Outlet and purchased the optional GPS module for the FTM-350 and began experimenting. In addition to the location reporting functions APRS can provide altitude, course, speed and maybe best of all text messaging. How cool would it be to send text to other stations or see their location relative to yourself? How about sending a text or email to a non Ham’s phone or computer? The lightbulb for me is I realized APRS would be fantastic for tactical positioning when large groups would hit the trail in our off road adventures.

Since 2011 only a few of my friends have adopted a radio with APRS capability. It’s been a slow uptake. I wondered why this was and started asking why more people are not taking advantage of this cool functionality. I quickly found out two compelling reasons, budget and useability. But even friends with APRS found it to be a novelty at best and not something that was user friendly on a trail in Death Valley. I realized I agree with my friends. I love the APRS idea but my radio tells me lat/lon of the other stations in text. When I message, I have to use the rotary dial on the FTM-350 to select letters to compose a text message. Though the FTM-350 allows for pre-populated messages this was woefully short on usefulness. I want a true terminal for my APRS activity. I want to see a moving map with other stations and I want a QWERTY keyboard to type messages.

I went to work on the Internet to find a solution for my APRS desires. I came across AVMAP. A GPS navigation solution that could interface with ham radio to receive and display GPS data output from a radios data port. Awesome. Well except that this little gem was $500 plus and only compatible with Kenwood radios. Boo.

AVMAP Receiving APRS Data

I continued my search for a solution for months. I came across a few interesting things over that time but surprisingly, very little useful information. How could folks not want these capabilities? Was it a secret and I didn’t know the special handshake?

During my search for a solution I came across a free website, APRS.FI. This website provided a service to track APRS beacons and plot them on Google maps. You see APRS data is repeated locally by area relay stations (digipeaters) for widespread local consumption. In Addition to the RF relay, data is typically ingested into the APRS Internet System (APRS-IS) via an Internet-connected receivers (IGate) and is distributed globally for ubiquitous and immediate access. APRS.FI uses this and the web app displays station data.

Perhaps APRS.FI could solve some my problem of tracking and messaging? Oops, not so fast. APRS.FI is a great service but requires an internet connection. Great when you’re in the city but in Death Valley not so much. You should tell your non-Ham friends they can use APRS.FI to track you. Especially useful for significant others. APRS can be turned off so let’s not freak out.

APRS.FI Tracking on a Recent Mojave Road Trip (Click to Enlarge)

After searching for a couple of months I changed my search parameters in Google to include “TNC”. TNC, which stands for Terminal Node Controller. It’s the term and the function that makes APRS work in your radio. A TNC is composed of a modem and software and is already built into my FTM-350. So why did I add this term to my searches? During my time looking for this solution I kept seeing posts about how limited the FTM-350 TNC was and I agree it is limiting. So maybe I wasn’t looking for maps and messaging but a whole new TNC solution. BINGO.

I discovered the MobilinkD. The MobilinkD, used in conjunction with an Android phone and software can provide exactly the functionality I wanted – moving maps and easy messaging. Yahtzee!

So what is this magical device?

The MobilinkD is a Bluetooth TNC that steps in where the FTM-350 builtin TNC was or provides the hardware for your non-APRS radio. Here’s how it works: Using a compatible interface cable connect the MobilinkD to the data port (mobile) or speaker mic port (handheld) of your ham radio. This is an audio and signaling connection. Pair your Android phone to the MobilinkD via Bluetooth. Download and run APRSDroid software on your phone. Tune your radio for 144.390. You can now take over the world. You’re welcome.

MobilinkD 2.0

APRS packets are transmitted via RF audio (that screechy modem sound). The MobilinkD listens to and transmits the audio received on your designated frequency (144.390Mhz). When a packet is received the MobilinkD hears and decodes this packet and sends it to your designated Bluetooth device (Android phone) for the APRSDroid App to decode and display. Conversely when you are ready to beacon your position to the world APRSDroid sends the packet back to the MobilinkD TNC via Bluetooth. The MobilinkD thens transcodes the digital packet from APRSDroid to audio, keys up your radio to transmit and blasts the audio out via RF for other APRS stations to hear.

What do you need?

My Land Cruiser install I’m using the following:

  • Android device. In my case an old 7” Galaxy tablet I have laying around
  • MobilinkD 2.1 Bluetooth TNC
  • Radio interface cable made by Ham Made Parts
  • APRSDroid software.
  • Dedicated 12v to USB hardwire power port so I don’t have to charge the MobilinkD battery.

If you don’t have an Android phone or tablet because you’re an Apple fan you’re out of luck as Apple doesn’t allow access to Bluetooth Serial Port Protocol (SPP) in iOS, which is needed. You can interface with a variety of software running on Linux or Windows computers as well. No one has ever heard of a Windows phone.

APRSDroid Map Display


What about the APRS function in my Yaesu?

This solution has now provided me the exact, easy to use functionality I always thought APRS could. I can see my position and other stations overlaid on a map. Reading and sending text messaging to other stations is super easy.

In my case I’m no longer using the built-in TNC in my FTM-350. The MobilinkD takes over. If you didn’t have APRS in your radio before – you have it now. Since the MobilinkD runs on its own internal rechargeable battery or USB power it will easily work with handheld and mobile radios alike.

Whats The Cost?

To implement this solution is about $100 plus an Android device. Many of us have old phones or tablets laying around and of course you can use your currently operational Android device as well.






MobilinkD TNC

Ham Made Parts Interface Cable


Android Phone or Tablet with Bluetooth

Discussion of sending text or email from APRS

Land Cruiser Command – iPad Mini, FTM-350, ID5100, Android Tablet (Click to Enlarge)