APRS

Tracking our movements from Telluride CO to San Luis Obispo CA

Amateur radio also known as ham radio can be used for all sorts of things other than just two way communication. Having an amateur radio license opens the door to many modes of radio frequency that can be used in a variety of creative ways. One of those ways is APRS or Automatic Packet Reporting System.

Automatic Packet Reporting System

APRS is a radio based system of digital communication for real time information. These digital communications can be anything from GPS locations, text messages, email, weather station information, announcements and all sorts of other telemetry. The most popular way to use this APRS network is to track your location in real time and see the path you've taken. This information can be viewed online by non licensed operators using websites like APRSdirect.com or APRS.fi. It can be very useful for loved ones or friends and family to track your progress across the globe.

View of the Los Angeles area via APRSDirect.com

The APRS network is completely voluntary and is created and maintained by individuals who want to partake in the expansion of the network. In the most basic form the way the network works is you have a global system of repeaters usually placed on mountain tops listening for a transmission from you. This transmission you're sending out has your real time GPS coordinates (and more if you'd like) which gets picked up by a repeater called a digipeater. This digipeater repeats the signal until it finds a way to an internet gateway called IGates. IGates are placed near an internet connection and listen for digipeaters or stations nearby to take those transmissions and send them out to the internet to be viewed all in one place. In the photo above you can see mostly vehicles moving about that are utilizing the APRS network and being shown on aprsdirect.com.

Basic view of APRS network

The first step to connecting to the APRS network is to assemble some radio equipment. There are so many different ways to build a capable APRS setup I'll just concentrate on the basics here in relation to using it in a vehicle. The main three components are an antenna, radio and TNC. The antenna is used to transmit and receive the APRS radio communications. The radio is used as the power behind the antenna to modulate the radio signal coming from the TNC. The TNC (terminal node controller) is the brains of the operation that has the necessary software/programming to send out and receive the APRS radio packets. You can either pieced together a system using different components or purchase an all-in-one set up that is mostly plug and play.

Mobile and monitoring on the Dempster Hwy highlighting the APRS antenna

My Hardware

In my truck I have pieced together a system using some existing parts I had laying around. The antenna I use in the truck is a Comet SBB-5NMO. While this antenna is a little overkill as it's dual band (you only need the one 2m band) it has great propagation and is able to fold backwards when I'm going though trees or low hanging obstacles. It can also be used as a back up dual band antenna for my main ham radio.

I'm using a Yaesu FT-2900R for the radio. This radio is quite powerful as it can transmit at a full 75 watts. While you can get away with as low as 5 watts having more power will ensure your APRS packets get out in more challenging terrain. I have once transmitted from my truck to a digipeater over 300 miles away.

For the TNC I'm using a Argent Data Systems Tracker4. I purchased this TNC due to it having WiFi connectivity and browser-based configuration along with a few other special features. It connects to the radio using a cable purchased through Argent Data. This TNC has some neat features however it seems the company released it before being fully tested and working correctly. Have had a few issues with the WiFi and setting parameters into the TNC. Because of this and a few other issues I would not recommend using this as a TNC unfortunately. I'm currently looking for a different TNC I can replace it with. Look below for some other options especially from Byonics.

All of this equipment is mounted under the drivers seat. It's out of the way yet easy to access if need be. You can also take a quick glance at the equipment to make sure it's working correctly. I have also locked the radio buttons from being accidentally changed. Additionally I have wired the equipment to my sPod Bantam switch panel so I can turn off the tracker with a quick button press if I want go into stealth mode or conserve battery.

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Tucking everything under the seat

Getting Started

For someone who might have just gotten their license, wants an easier or smaller setup there are some really great products out there. The next APRS system I install will definitely be one of these for their simplicity but also the freedom to customize :

Byonics MicroTrak RTG

All-in-One TNCs

Byonics MicroTrak RTG

This fully plug and play setup comes with everything you would need to install APRS in your vehicle. Antenna, radio and TNC. What makes the Byonics products stand out is they have the radio and TNC built into a very small package. The unit even comes pre-program for you with whatever specifications you want. Comes in 10W or 50W.

Byoncis MicroTrak MTT4BT

Another similar offering by Byonics this particluar setup includes Bluetooth so you can use a device like a cell phone to connect to the TNC. Useful for using programs like APRSDroid.

PicoAPRS Transceiver

They claim this is the smallest APRS transceiver in the world. Tiny enough to fit in your pocket while hiking and has a battery lasting 10hrs making it portable.

Mobile/Handheld Radios

There are also standard hand held and mobile ham radios that include APRS as well that can be an all -in-one solution to be able to communicate with other people while transmitting APRS automatically in the background. Some popular radios:

Yaesu FTM-400DR

AnyTone AT-D878UV

Kenwood TM-D710G

Antenna Upgrade

While having a fancy radio or one with tons of power is nice, it's all pretty useless if your antenna isn't going to preform well. If you upgrade one thing to your APRS setup I'd recommend the antenna.

Tram 1189 Glass Mount Antenna
A great antenna that only requires a window to mount. No holes to drill or mounts to fuss with. I recently installed one on a friends RV and it works great.

Tram 1154

One of the easiest mounting method is to mount using a magnet. This particular antenna is a 5/8ths wave so your transmit and receive will be better than most.

VHF Trunk Antenna with Mount

Great for a car trunk. Easy to mount and comes a standard NMO style mount to be able to upgrade later on.

APRSDroid

Tracking your vehicle and seeing it on the internet map is neat and can be handy for others to track your location easily but what if you don't have the internet? After all the APRS network works in many places that do not have reliable cell phone service. Well you can use APRSDroid on an Android cell phone or tablet and receive or transmit APRS information locally to your location where ever you might be.

For example you might be traveling in a remote area camping or off roading without cell phone service. While exploring the area you see an icon appear on your APRSDroid showing a small truck driving nearby. It will show their call sign and usually what frequencies they are monitoring. This allows you to make a contact over simplex or even a local repeater to start a conversation you might have never had without the help of APRS. It's actually happened to me on several occasions and have meet some really interesting folks.

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Once you download the app and connect your Android device to your TNC (either though USB, Bluetooth or WiFi) you can load the app and APRSDroid takes over and acts as it's own TNC. This allows you to view other APRS stations nearby on a map without an internet connection. You can message those stations as well. Or you can even send text messages or emails to other people using the app without any internet needed.

By default the APRSDroid app does not come with offline maps but I recently decided to give it a try. It will require downloading the app as an .apk file (android app filetype) rather than downloading it from the Play Store. Depending on your phone you might have to change a setting to allow .apk files on your device.  You can download the APRSDroid apk file here or use this direct link.

Once you have the app installed the final step is to download offline maps for your device. The APRSdroid Offline Maps page has details on how to create your own map but I found it to be a little confusing. Thankfully a fellow ham (KS9N) has created a full map of the United States ready to be transferred to your phone. I've created a torrent you can download here as the file is a little of 2gb. Just drop this file into the top directory of the device and APRSDroid will use it as it's map source. Torrent link. Direct download link.

Of course android isn't the only platform you can use APRS data on. Aprs.fi is building an iOS app that should hopefully be ready for release soon more about that here. There are also a few other APRS clients listed here for all types of platforms.

Future Projects

Look out for a blog post in the near future when I upgrade the TNC in the truck. I'm also planning on installing a APRS iGate or Digipeater after I get all the hardware configured. So keep checking back for more APRS related projects.

Future iGate or Digipeater

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