What is APRS?

 APRS On Dash

Automatic Packet Reporting System is about adding situational and spatial awareness to your radio work. With a quick glance at a screen, you should see all the operators in your area and, ideally, what frequency they are currently monitoring. Despite popular opinion, APRS isn’t LoJack for ham radio and it’s not Automatic Position Reporting System. If you’re only beaconing your position, you’re not tapping into the full potential of APRS. The core of APRS is knowing who is out there and how to reach them.

Have you ever passed a car with amateur radio plates and wondered how to contact them? With APRS, you’d click on their icon and it would display the frequency that they’re currently monitoring. Ever driven into a town and wondered what their repeater frequencies were? With APRS, their tower can beacon out frequencies, tones, and net times. Have you ever been involved in a public service event where the net control station struggled to keep up with the amount of traffic being passed? With APRS, routine updates and position data is displayed automatically in the operations center without tying up the voice frequency. This reduces transcription errors and frees the primary voice frequency for more urgent reports. Plus, the served agency can see your assets overlaid on a Google Map or an open source map like Offline Street Maps.

They say a picture is worth a thousand words. That’s the idea behind APRS. In this screen capture from APRS.fi, you see all the stations whose reports were picked up by internet gateways around Williamson county over a 24 hour period as well as the last three hours of trails.

 24 Hr APRS Snapshot

In addition to the uses mentioned above, there are a few other features worth noting. One, your family can see where you’re at while you’re on the road even if they don’t have their amateur ticket. Two, you can send and receive text messages over the air, even if cell phone networks are overloaded in an emergency. Three, you can send short emails even if you’re in an area that doesn’t have cell coverage. Four, search and rescue. Imagine seeing on a map breadcrumb trails of where all of your search teams have been and where they are now. Better yet, where haven’t they been? Five, mark critical alerts and locations on the map for all to see. Flooding, wild fires, shelter locations, and vehicle accidents are just a few examples.

The vision of WCARES

1. Build out coverage in the Williamson county area to increase our ability to serve the Williamson County EMA and other sponsored agencies. We’re seeing this fulfilled with our support of the Harpeth River Ride where race organizers will be able to see the position of all the assistance vehicles, know which ones are currently in service, and which ones are available for tasking.

2. Provide travelers passing through the area’s three interstates with local information like voice repeater information and weather warning data. Additionally, support them with coverage to aid in their own communications. To this end, WCARES is increasing the number of Digipeaters and IGates in the county. WCARES’ five voice repeaters are currently on APRS with frequencies, tones, and net times displayed for travelers and new hams. WCARES events are being marked on the map to aid people in finding them. The National Weather Service is publishing weather warning overlays to APRS.

3. Use APRS to teach radio propagation and encourage a community of makers and innovators within our community. Looking to get into APRS inexpensively? This page is a good starting point.

Exploring APRS

Here is information to help you get started and to help us meet our goals.

APRS – What are my Options? This is a list of current equipment that is out there to get you on the APRS network. Prices, capabilities, and links are included.

The Hardwired Cell. Build an APRS setup with the HT and Android smartphone that you may already own and roughly $20 worth of software and cabling. In my case, this setup revolves around a decommissioned HTC Evo smartphone that Sprint had offered to buy back from me two years ago for $25 after I upgraded phones as well as APRSDroid and a Wouxun KG-UV6D handheld transceiver. While it’s true you can use APRSDroid through the internet connection on your phone, I was looking for a radio solution. I found it in their AFSK mode (Audio Frequency Shift Keying). I also later used the same homebrew cable with a Samsung Note 10.1 tablet and a Samsung Galaxy S3 smartphone. For reasons that I haven’t totally discovered, yet, my basic cable setup doesn’t work on 100% of the Android devices that I’ve tried. Using a phone or tablet has a lot of promise. Touchscreen, GPS, processor, and battery in a very compact form factor. This project was my first foray into APRS.

The Bluetooth Adapter Rig. Help your phone, tablet, or computer talk to your radio using a low cost Bluetooth TNC. This is pretty much the same setup as was mentioned above, however, the audio Frankencable gets replaced with a Mobilinkd Bluetooth adapter. This is the setup I currently use in my car and I dig it. This is one of the cheapest assembled TNCs that I’ve found that facilitates two way communications on the APRS network. A picture of this setup can be seen at the top of this page.

Raspberry Pi Virtual TNC. Build a mobile or base station APRS rig using the inexpensive Raspberry Pi computer ($25-35), a virtual TNC called Dire Wolf (free), and the Linux based APRS program Xastir (free). With the low cost and small form factor, this setup can be perfect for the car or for a go kit. Plus, Dire Wolf supports Digipeating and IGating.

Build an IGate with APRSISCE/32. This article was written to help amateurs get an IGate running quickly and easily using an old Windows computer and Mobilinkd. However, it can also be used to help someone setup a plain APRS base station, IGate or not.

Getting Started in APRS. In April of 2014, WCARES put on an event called WCARES University. These were the slides from that event.

Dallas Clements, K7DCC

Note: APRS is a registered trademark of Bob Bruninga, WB4APR

This article was originally published February 24, 2014 and last updated June 5, 2014. If you have any questions or comments, contact me at my call at arrl.org.