Category Archives: Tech Blog

Technology is an integral part of modern Overland travel.  It helps enhance our journeys in so many ways, be it aiding in navigation such as with mapping and global positioning devices, to helping us stay entertained if the weather turns unfavorable and you end up being stuck in the tent for a day.  At Integrated Overland, we love tech, and we want to share our experiences with it.

Track Your Adventures for Free – Part IV – The Software

This article is Part IV of a series called Track Your Adventures for Free where I outline how to use Ham Radio and your Smartphone as an affordable APRS tracking system.  For reference, here are links to the first 3 parts:

In part III we modified a smartphone headset and our Baofeng UV-5R headset to create an interface between the speaker and microphone of the two devices.  As a refresher, in part I we discussed how APRS works using digital packets that are encoded in analog signals.  The ham radio will receive these analog signals, which are audible to the human ear, and we must get these analog signals to our smartphone so it can decode the digital packets of information that are encoded in the signal.  These packets will contain the APRS position and identification data from transmitting stations.  On the other side of things, our smartphone will also use its internal GPS to determine your current position, and then use this data to create an AX.25 encoded analog signal that it will send to the ham radio to broadcast your position. Great, but how do we accomplish this?

The answer, for Android based smartphones, is to use a piece of software called APRSDroid.  It is available on the Google Play store for $4.99, lifetime updates included via the play store.  However, the developer also provides the software for free on the APRSDroid Website.  You can download the APK to your Android phone and install it outside of the market at no cost to evaluate it.  Just keep in mind that because it was installed manually, updates will not come via the Google Play store like other apps.  You will have to keep track of new releases as they come out and manually install them.  I recommend purchasing the app once you have evaluated it and made sure it works out for you simply to support the developer in his great work and also to ensure you always have the latest version.

After you install the application either manually or purchasing it on the Play Store, open the application and you will be greeted with the following:

APRSdroid Start

For many of you, this will probably be the first time you hear about APRS-IS.  APRS-IS (Automatic Packet Reporting System-Internet Service) is the common name given to the Internet-based network which inter-connects various APRS radio networks throughout the world (and space). APRS-IS is maintained and operated by volunteer Amateur Radio operators to provide world-wide capabilities to the Amateur Radio APRS RF networks and to promote the Amateur Radio service as a whole.  Because you will be injecting information into the APRS-IS system, which is designed for licensed amateur radio operators (Hams), you must be properly identified to obtain the privilege.  Assuming you do not already have an APRS-IS passcode, you should click on the “Request Passcode” link to continue.

Continue reading Track Your Adventures for Free – Part IV – The Software

Track Your Adventures for Free – Part III – Making the Connection

This article is Part III of a series called Track Your Adventures for Free where I outline how to use Ham Radio and your Smartphone as an affordable APRS tracking system.  For reference, here are links to the first 2 parts:

In part II I closed on the mention of modifying the BaoFeng headset and a smartphone headset such that the speaker output of the BaoFeng radio is connected to the microphone input of the Smartphone, and also have the Smartphone speaker output connect to the BaoFeng radio’s microphone input.  This is, for the most part, simple, but at Integrated Overland we like to build things that are technically sound and designed to remain functional.  Yes, you could simply cut the wires off the ends of the cables and connect the Speaker + and – to the microphone + and -, but this will result in problems down the road that have the potential to damage either your radio or smartphone, or both.  I am going to explain the technical details behind this, but I want to start off by ensuring you that doing it right is still a simple process and only requires adding 4 resistors.  Don’t be discouraged by the tech talk, this is still very simple, and you can feel free to skip ahead if you just want to implement the solution.  You can also skip the solution altogether and just pair the wires together, at the very end of the article I will discuss how to do this in a way that will minimize the risk, but given how simple the solution is, you may want to give it a shot.

So what’s the problem? The problem is that for both the radio and Smartphone, the speaker signals are designed to drive earphone speakers and produce audible noise.  This means that the speaker outputs are higher power outputs.  However, the microphone input for both and for most devices in general is designed to operate with low power signals that are generated by the microphone.  This means that you are trying to put higher power signals from the speaker into a port that is designed for lower power signals.  The speaker output levels for typical devices can range anywhere from 2V to 20V in amplitude (partially depending on the volume level).  A microphone input level is typically on the lowest end of this spectrum at around 0.2V to up to around 2V.  On an even more technical side note, the speaker and microphone ports have different impedance levels, but this is less important as we aren’t trying to achieve maximum signal transfer in either case.

So our basic problem is simple, we have a voltage level problem, we need to reduce the voltage, which is much easier than needing to amplify the voltage.  We have to shift a 2V-20V signal into a 0.2V-2V signal.  Incidentally, this is a 10 to 1 reduction, and because we all love technical details, we’ll mention this is a 20dB reduction.

The basic solution to a basic problem then becomes a basic voltage divider circuit (and the cessation of usage of the word basic).  We need a 10:1 voltage divider, which can be achieved with 2 resistors.  The resistors have to have a 10 to 1 difference to meet the criteria, so you can use a 1kΩ resistor, and a 100Ω resistor, or different combinations of 10 to 1 ratio values.  However, I recommend that you use a 10kΩ resistor and a 1kΩ resistor.  Why? Because this would put roughly a 10kΩ impedance on the speaker side (high side), and a 1kΩ impedance on the microphone side.  This is more suitable for the application.  Now, to properly cover the basics, below are 2 images of what this voltage divider circuit looks like.

 Voltage Divider Example 1   Voltage Divider Example 2

These two circuits above are exactly the same.  I simply wanted to illustrate that the way these are shown in the schematic is not relevant to its operation in case we have readers who are unfamiliar with schematics.  What matters is the order, meaning that the input side has to enter into the higher value 10kΩ resistor, and then at the other side of the 10kΩ resistor, you tap your output, but this same point is connected to ground via the 1kΩ resistor.  How you lay it out in application does not matter as long as the connections are made at the correct point.

So we have solved the problem of reducing our signal levels, now how do we apply the solution to our particular problem? The answer is as follows:

Continue reading Track Your Adventures for Free – Part III – Making the Connection

Track Your Adventures for Free – Part II – The Hardware

In Part I of Track Your Adventures for Free, I made mention of using APRS as a tracking system at a much lower cost than APRS ready radios such as the Yaesu FTM-400DR and the popular Kenwood TM-D710A that are upwards of $500 for the radio alone.  These radios are exceptional, a beautiful rendition of hardware, but unnecessary.  What makes them uniquely suited for APRS is that they have GPS capability to determine your position, and they also have a built in TNC (Terminal Node Controller), which is essentially in charge of converting your digital data into an analog audio tone representation of that data using the AX.25 protocol.  It serves as a modem allowing you to transmit your digital position data obtained from the GPS, and also decodes the AX.25 coded tones that arrive from other users and converts them to digital data on receive.  Other functions are supported, such as messaging, but we can discuss those features as we progress.

While a TNC might seem complicated, it is a rather simple and primitive device in comparison to today’s technology.  Our smartphones are millions of times more capable, and this is what we will be taking advantage of.  With the Yaesu and Kenwood radios, you still have to connect to an external device if you want to see the position data on a map.  This is usually done by connecting it to an expensive GPS unit for mapping (only a limited set are supported), or to a smartphone/computer running mapping software.  Using a smartphone or computer to also perform the TNC function therefore seems logical.

To summarize, what you need for APRS is:

  1. A radio capable of transmitting and receiving in the 2 meter (144MHz) ham band (highly recommend one that supports VOX [voice activated transmission]).
  2. A GPS receiver.
  3. A device that can serve as a TNC to convert your GPS data into an audio signal
  4. A way to connect your TNC device to your radio
  5. Ideally, a device that can put position data on a map to help you visualize where APRS users are relative to you, and also display messages and allow you to compose messages if you choose to use that feature.

That’s it.  If you get these 5 items, you are ready for APRS.  What most people don’t realize is that a smartphone is capable of doing 2, 3, and 5.  So what’s left? A radio, and a way to connect your smartphone to your radio. So lets look at the simplest solution:

Continue reading Track Your Adventures for Free – Part II – The Hardware

Track Your Adventures for Free

Adventures are meant to be shared! But for those of us in the Overland community, our adventures often take us to places where there is no voice or data reception.  While smartphones have the ability to beacon your position to share with friends and family back home, they are only as effective as your carrier’s coverage area.  Most people make the switch to a satellite based tracking device such as the SPOT Connect or InReach to fill this void.  However, these devices require that you pay a subscription for both their emergency beaconing features, and an additional fee if you want to track your travels.  This isn’t always cost effective, and comes with several limitations.

A trend we see among the Overland community is that most are licensed ham radio operators or have plans to become licensed.  Those who are licensed can take advantage of the Automatic Packet Reporting System (APRS) that is deployed all over the world through a network of volunteer ham radio operators and organizations.  APRS is a digital communication system designed to support several tactical communication objects, one of which is Global Position System (GPS) data.  The network is formed by a collaborative deployment of digital repeaters (digipeaters) that listen for packet data on the designated local APRS frequency.  In North America, that frequency is 143.390 MHz, and if you tune your radio to that frequency you will hear the AX.25 protocol frames being transmitted much like an old modem or fax machine sound.  The digipeters listen for local signals and re-transmit them at a higher power to propagate them over long distances much like a traditional voice repeater works.  However, APRS packets can go through a specified number of hops through various digipeters, and this is selectable via the “PATH” instruction in your digital packet.  Using PATH, you decide how far your actual transmitted signal is physically repeated on the network. This gives you some control over how your position beacon packets propagate.  Most importantly, your packet will usually hit an APRS Internet Gate (known as an iGate) that will connect to the APRS Internet System (APRS-IS).  APRS-IS is the reason why you are able to share your data with others, because your position packet data is then available on the website and that information can be accessed accross the world by anyone with an internet connection and who knows your call sign.  It is important to note that APRS does not require the internet, that is just a bonus. It can work from radio-to-radio, allowing groups to track each other real-time.  This again, highlights the use of PATH because of the geographical location of your group members.  If you are all within 50 miles of each other, then a single digipeter transmission should cover your group, but if one is 100 miles away you would want to increase your PATH to ensure that your radio waves reach their particular radio.

Continue reading Track Your Adventures for Free

A Quick Smartphone GPS Backup Plan

Paper maps are a last resort for us when trying to get anywhere off pavement.  We rely on our GPS system to rapidly pinpoint our location and mark us on the map in real time.  It means the difference between having to take 5 minutes to plan out a route, versus twice as long to flip through paper maps.  But, what happens if you primary GPS system fails? Chances are that you are going to have a less than enjoyable time if you have to spend the rest of a long trip meticulously tracking yourself on a paper map.

Since most of us have a smartphone with GPS, it is a good idea to set them up as a backup system in case this happens.  We’ve tried several options for offline and off-road navigation on our Android based smartphones, but the fastest, easiest, and ultimately best solution as a backup has been Google Maps.  As of Google Maps version 5.0, you can download pretty large sections of maps for offline use.  The sections do have a size limit (though fairly large), but you can download multiple sections to cover entire states.  Most importantly, the downloads are fast and the map file sizes are the most reasonable! An entire state can download in a matter of minutes, and only take about 400MB of space.

Here is a walk-through of how easy it is to setup an offline map in Google Maps:

Continue reading A Quick Smartphone GPS Backup Plan

Hard Wiring a SPOT Device

Safety is important to us, and we chose to use a SPOT CONNECT Satellite Messenger as a fail safe device in case things go wrong in the field and we need urgent help.  The SPOT device was designed to be versatile, portable, and rugged.  A part of achieving portability is to function using batteries — very specialized Energizer Ultimate Lithium batteries that are expensive and difficult to find in more remote cities.  Our SPOT device sits inside of our vehicle 99% of the time, and yet we were still consuming a pair of these batteries every 4 days when using the active tracking features.  We were surprised and a bit disappointed that SPOT did not offer a 12V vehicle power option, since the performance of the device would be more reliable having a consistent power source.  After further researching the device, we decided to develop a solution that would retain all portability and ruggedness of the SPOT device while allowing us to plug it in to the vehicles power.

The first step in the development process involved figuring out just why SPOT insists that the device be used with the Energizer Ultimate Lithium batteries exclusively.  We wondered if it was a result of needing a specific steady voltage over the battery life cycle, or if the current demands from the SPOT device were too much for a standard lithium battery.  So we opened up the device to take a look at its insides and do some testing.  You start by taking the back cover off your SPOT device and removing the batteries.  The first thing you notice when you start the tear down is another warning on the circuit board that reads: “AA Lithium Batteries Only.”

Continue reading Hard Wiring a SPOT Device