ETH006 – Automatic Packet Reporting System(APRS)

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Hello everybody and welcome back to Everything Ham Radio! In this episode we are talking about the  Automatic Packet Reporting System or APRS for short. Last week we talked about Packet. APRS is alike in some ways, but different in others. While you can not talk keyboard-to-keyboard on APRS, you can send short message. You can even send a short email using APRS, which we will talk about a little later.

HISTORY

Over the years since APRS came about, I have heard different stories about how it came into being. One video that I watched that someone put on at a ham radio convention somewhere, was very adamant that the P in APRS stands for and also has stood for Packet, not Position like he heard a lot of people saying. When I first learned about APRS, I was always told that the P stood for Position, and to me it made a lot of sense that that is what it stood for because the general purpose of it that I saw, or maybe the commonly used purpose of it, was for “asset tracking”. By assets I mean things like, storm spotters during a Skywarn event or Sag-wagons during a bike race.

As I was doing research for this article and podcast episode, I still found somewhat conflicting reports. In the article on Wikipedia, it said that during the early 1990’s, the P stood for Position, not Packet, but was later changed to Packet when GPS technology became more readily available.

So What Is The Truth?

As the saying goes, “If you want the truth, take it straight from the horse’s mouth.” So that is exactly what I did. I went to the official APRS website that is maintained by the creator of APRS and looked at his history page.

Bob Bruninga, WB4APR, created the first incarnation of APRS in 1984. At the time he was working with the Amateur Radio Research And Development(AMRAD) group. The first real use of it was to report the position and status of a 100 mile cross country endurance horse race. At this time, however, the system was called Connectionless Emergency Traffic System(CETS).

On his history page, he says that in 1992, he realized that he could use his callsign to change the name to reflect it and changed it to Automatic Packet Reporting System. He says that he published a paper talking about it at the ARRL 11th Computer Networking Conference that year. However, if you look at the references, in 1992, the paper that he wrote was called Automatic AX.25 Position Reporting System. So I’m still not entirely sure if he ever intended for the P to stand for Position or not.

According to Wikipedia, he did name it Automatic Position Reporting System then later changed the P to Packet once GPS technology became more readily available and more information could be put out in the packets of information that was sent out.

NETWORK

APRS World Frequency Map
APRS World Frequency Map

Earlier I said that APRS was similar to Packet. The way that APRS and packet are similar is that they both use TNC’s as digipeaters to extend the reach of the user. However, that is pretty much where it ends. APRS uses basically the same infrastructure as packet did, but on a different frequency. Also, instead of using a connection to extend the reach of the user, the signal is just transmitted, then each station that hears it will retransmit it, if there is still room left in the PATH.

What is the PATH?

The PATH is what is used to determine how many times a packet is retransmitted by digipeaters. The standard setting for the PATH is WIDE1-1,WIDE2-1 for mobile or portable stations. Each time the packet is retransmitted, the number after the hyphen(-) is subtracted by 1. So for the above settings, station A is the mobile units. It transmits a packet with the WIDE1-1, WIDE2-1 settings. The first station to receive this packet will reduce the WIDE1-1 to WIDE1-0 and retransmit it. The next station will take the WIDE1-0,WIDE2-1 and reduce it down to WIDE1-0,WIDE2-0 and retransmit it. Then finally the third station will receive it and will not retransmit it because both the WIDEn-N settings are at -0.

If you have used packet before this would be the equivalent to doing a via k5clm,kc5pwq when you are connecting to someone. The difference is that because you are connecting or sending your packet via a set station, it will only go in one direction. With APRS, the first digipeater to retransmit the signal may be four different stations in four different directions. Think of this as using a beam or directional antenna vs using an omni directional antenna.

USES

Position Reporting

APRS Traffic
APRS Traffic Snapshot on June 08

The primary, or should I say the most common, use for APRS is position reporting. Of course, you will have to normal every day position tracking. As a matter of fact, you can go to http://www.aprs.fi and look at APRS from anywhere in the world. The author of this page has written an integrate APRS with Google Maps. Seeing people moving about every day can be interesting at times, but there are other uses for it to.

If you club does communications for a Bike of Foot race, you could put a tracker in the Sag-wagons, or bike repair vehicle and always know where they are if you need them. You could have a tracker in the lead and trail vehicles in a parade, so you will always know where the parade is along it’s route. How about during storms? If all of the spotters had a tracker with them, the net control or the National Weather Service, would always know where the report is coming from. There are so many uses for this feature that it really makes me wonder why more people don’t have it. But in all honesty, I don’t use APRS either because I can’t or haven’t boughten the equipment to do it. Here is one more use that I can think of before we move on. If you APRS tracker is installed to automatically turn on when you turn on your vehicle, then if the worst happens and your car gets stolen. You can go to you local law enforcement and report it stolen but say “Hey, I have a tracker in my car and this is where it is.”

BULLETINS/EVENTS

Another thing that you can do with APRS is to set a bulletin message to display for your local area. For example, let’s say that you have a club meeting that is coming up. You can set an BEACON text to transmit the date, time and gps coordinates of your monthly meeting, weekly net, or a local hamfest.

LOCAL REPEATERS/VOICE FREQUENCIES

Along the same lines as above, local repeaters also can broadcast their information, if it is setup to do so. This way, when someone that is not from the area, can look at their radio and get local repeater information, frequency, tone, average range, etc.

One of the good things that came out of Hurricane Katrina, was the FREQUENCY field was added to APRS packets. This allowed people to set up what frequency they were on in order for people to contact them via voice. During Katrina is was recommended from the ARRL that this field be put in and for all amateurs in the area set this up in their stations so that it was known where all amateurs were during the clean up.

There are so many other uses for APRS that would take a long time to write about it. Check out the APRS official website for more information.

EQUIPMENT

There are several radios now available that have a built in TNC for APRS use. Several Kenwood Radios, both mobile and hand held, an Alinco mobile, and I believe the Icom DStar and Yaesu System Fusions radios all have built in TNC’s that can be used for APRS.

DTMF Kenwood TM-D700A Kenwood TM-D710A Alinco DR-135TPMKIII FTM-400DR Dual Band Mobile Radio Icom ID-5100A
Kenwood TH-D72A Kenwood TM-D700A Kenwood TM-D710A Alinco DR-135TPMKIII Yaesu FTM-400DR Icom ID-5100A

If you don’t want to buy a higher priced radio, or you already have an extra radio lying around that isn’t being used, you can buy just a TNC like a Kantronics KPC-3+ or Bridgecomm I believe has a TNC. You can also use the soundcard on your computer with a APRS program.

If neither of these options tickle you fancy, you can buy a TinyTracker product. I believe I have heard of another thing that is basically the same thingthat you can buy, but for the life of me I can’t think of where I heard of it atTiny Tracker APRS

LINKS


Amateur Radio Club Spotlight

Cabot Small Town Amateur Radio Service

Club call sign: W5STR

Website: http://www.w5str.org/

Facebook: https://www.facebook.com/groups/844368612323782/?hc_location=ufi

Repeaters

  • 145.410 – PL 85.4
  • 442.475 + PL 114.8
  • Echolink Node: W5STR-R Node Number 507018
  • Club Simplex: 147.570

Meetings

Meetings are held on the second Sunday of the month at 1:30pm. Members will normally meet at a local restaurant at about 11:30 on the day of the meeting to have lunch

Meetings are held at the Criswell-Robinson American Legion Post 71 115 North First St, Cabot, AR 72023.

They offer testing sessions after every meeting. Preregistration is not required unless you are upgrading to General or Extra.


That about wraps up this episode/post for the Everything Ham Radio Podcast. I would like to thank each of yall for listening to my podcast and/or reading this post. We are already on episode 6, barely a month after I started this podcast and I already have over 1200 downloads. Please continue to listen, like, share and subscribe. If you enjoyed this episode or any of the others, please go to ITunes and give me an honest Star rating and Review.

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Until next time…

73 de Curtis, K5CLM

Music provided by bensound.com

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  • Richard Slusher

    Great show, Curtis! There’s also an APRS app for your iPhone called OpenAPRS. You can create your object with a limited duration so it’s not broadcasting all the time. The app will refresh every 5 minutes and also has a messaging function though I’ve never played with that!

    • Thanks, still working out a few tweaks but it almost to the point where I think I like it 100%…thanks for listening!

  • K4CDN

    Another SUPER Low Cost way to delve into APRS is the Mobilinkd TNC2 that operates with an Android Device (burner phone/old tablet) and any 2m radio (re: Baofeng). If one lives in an area with a great deal of APRS coverage-it’s the perfect way to start…. http://store.mobilinkd.com/

    Out here in the country-Not So Much! I’ve also has some success with the Byonics TinyTrak4.

    73 Y’all K4CDN