APRS

[prerunner1982]

On the most recent Jeep Talkshow I did a Radio Comm Tech segment about APRS... Anal Pro... I mean Automatic Packet Report System.

You're probably saying what is a Packet and what does this have to do with Jeeping? Hang with me for a minute..

A Packet is data and in the case of APRS it is speed, direction, altitude, location, and a message which typically states what frequency you are monitoring. This packet is transmitted via a 2 meter ham radio on 144.39 MHz, so you have to be a licensed amateur radio operator to use APRS.

Your data packet is transmitted from your 2m radio and can be received and decoded directly by another APRS user or it can be picked up by a digital repeater (digipeater or digi) and rebroadcast. If another digi is within range of the first one it will also rebroadcast your packet. Two hops is the generally accepted standard setting. If you have a full featured APRS set up (as opposed to just a simple/dumb tracker) you can view the other stations packet info and see them on a map.

A digipeater may also be an Internet Gateway (Igate) which then copies your packet info to the net for sites such as APRS.fi and OpenAPRS.net. These sites map you and your packets. This allows for your friends and family to see where you are on your wheeling adventures.

APRS can be used for more than just tracking. You can send messages to other APRS users (as long as they have a full featured APRS set up), you can send text messages, and short emails (both text and emails require that you be within range of an IGate). The APRS system also allows you to see who is around you, their distance from you, and their direction from you.... as the system was designed for situational awareness.

This type of system would be good for a trail run event where you could see what trail each group was on and where on the trail they were. It would also be good if you were in search and rescue. Others could see where you had been and if every S&R group had an APRS beacon you could see where everyone had been and make sure the area had been covered accordingly.

The system could also be helpful if you were wheeling and someone broke down or sustained an injury. Other radio operators (if you used your Ham radio to call for help) or rescue personnel could use APRS.fi to locate you and provide GPS coordinates.

You may say SPOT can do the same/similar. Sure they do, but after the initial set up of an APRS transmitter it is free to use where the SPOT requires a subscription.

In future Radio Comm Techs I will discuss the hardware needed for APRS and my own set up. After those episodes air I will post up the info here as well.

Of course if you have any questions let me know.

You can listen to the segment here!
http://traffic.libsyn.com/tonymuckleroy/RCT_APRS_Part1_Final_01_01.mp3

[bluedragon436]

That's pretty cool explanation of what APRS is, and how it works... I've heard of it, or seen folks talk about it both on here and elsewhere with my researching to learn what I can about HAM operations, just never understood what it was or what the reasons were for running the setup.. So thank you for explaining what it is for the lay person (NEWB)...

[Mudderoy]

Jon, I know cell phone reception can be limited in off road areas, but do you know of a ARPS smart phone app that doesn't require HAM radio, or a HAM license?

Most phones have GPS and the ability to send and receive data on the Internet and an app could provide this positional information. People could try it out before getting the HAM license.

I've never looked for an app like this but reading your article made me think of the question.

The downsides, one I've already stated, the other would be using ARPS during time of emergency and the resources that provide Internet access may be down.

[prerunner1982]

I am not aware of any APRS app for a non amateur as info reported to the APRS-IS (Internet Service) has the ability to be gated to RF.

In an emergency where the Internet goes down you are correct the APRS info would not be gated to the APRS-IS (internet) however the info could still be digipeated (if a digi is still standing and active) and it could also be received via simplex by other APRS users.

With digipeaters I can see stations on my mobile APRS set up from a hundred(s) of miles away. So the internet is not necessary to make APRS a useful tool.

On Oct 5th I picked up a station from Topeka Kansas, 265.63 miles away.

Part of the set up for APRS is to set how many "hops" you want your packet to take. Hops are how many times the packet is digipeated. Standard acceptable is 2, however some choose 3 and you could do more. However the more hops you try to do the more chance that your packet will be corrupted by colliding with another packet. If your packet is being digipeated when another station is transmitting their packet neither packet will get received by anyone or another digi. It is like two people talking at the same time. Occasionally whoever has the strongest signal wins but with an APRS packet there is not error correction built in so if one little bit (sound) of the packet is messed up in any way the whole packet is trash.

In a emergency I would increase my hops to 3 or 4 in hopes that it can be digipeated far enough that someone may be able to call for assistance. Also with enough hops though the Igate (internet gateway) in your area may be down, an Igate 100+ miles away may be working.

[Mudderoy]

Well I did a little digging and no luck, then it dawned on me. If someone did create an Internet only APRS the non-HAMs data couldn't be transmitted on the HAM bands since they were not licensed. Damn, it was a great idea until I thought about it. :D

[prerunner1982]

And sometimes you get an anomaly like the packet I received yesterday that said the ham was 10,695 km (6600+ miles) east of me. In actuality he was about 20-25 miles south of me.

There has been a Moderate to High geomagnetic storm the last couple of days so that may have been the culprit.

BTW.. 6600 miles east of me would be Kovancilar Turkey.

[Mudderoy]

And sometimes you get an anomaly like the packet I received yesterday that said the ham was 10,695 km (6600+ miles) east of me. In actuality he was about 20-25 miles south of me.

There has been a Moderate to High geomagnetic storm the last couple of days so that may have been the culprit.

BTW.. 6600 miles east of me would be Kovancilar Turkey.

I bet that is why 20 meters is sucking in the mornings.

[prerunner1982]

Maybe..

[downsy]

There actually are full internet based APRS apps for both the apple and droid platforms. Infact I have one on my phone called OpenAPRS. There are also apps that you can use an audio patch cable to hook into something like a Baofengs mic jack from your apple or DROID's phone jack and use that to xmit APRS data over the air. You still have to be a HAM and register with a callsign for them to work work though even the non radio based apps.

The OpenAPRS app allows me to send and recieve text messages see other ect but again is totally dependant on my phone's cell connection.

I've only just began to meddle in APRS so I really haven't got past the iPhone app I have and using my phone hooked to my radio to xmit data with the cell service turned off.

[prerunner1982]

There actually are full internet based APRS apps for both the apple and droid platforms. ..... You still have to be a HAM

Exactly... but not for non-amateurs due to the possibility of their info being transmitted over RF.

[prerunner1982]

Figured it was time I added to this thread...

Hardware.. what do you need for an APRS set up.

As mentioned above you could take the easy way out and just download the APRS app for your phone (remember you have to be a licensed ham to use this) but if you want to go the RF route here is what you will need.

First off and most obvious, a radio. A radio that operates on the 2m band to be specific. There are some dual band radios that allow you to run APRS on one side and voice on the other, but most do not. Most dual band radios are dual receive but single transmit.
A dedicated single band (2 meter) radio would work fine. You can use a mobile or HT, the mobile would have more watts which may come in handy if you live in an area with sparsely placed digi-peaters. The radios that allow APRS and voice to be used at the same time also typically have the APRS hardware built in, these radios include the Kenwood TM-D710G (mobile), Yaesu FTM-400DR (mobile), Kenwood TH-D72A (HT) and Yaesu VX-8DR (HT).

GPS antenna/unit: If you want to have a dumb tracker where you just transmit your info and can not receive/look at other's info you will just need a GPS antenna. However if you want a full featured APRS set up with mapping capabilities you will want the GPS unit. The GPS unit provides the telemetry (location, speed, direction, etc) and well as mapping others info that is received. The most popular/sought after GPS unit is the Nuvi 350 though it is no longer in production it can be found used on Ebay. The Avmap Geosat 6 is an APRS specific GPS unit, but is pretty expensive. You may also use an Android tablet/smart phone with GPS and Bluetooth with a bluetooth TNC (see below).

You will also need a TNC or Terminal Node Controller. This device takes the digital info from the GPS and converts the digital info to audio tones to be transmitted by the radio and vise versa. Common TNCs are the Tiny Tracker and the Argent Date Open Tracker. These require the GPS be wired to them, and for them to be wired to the radio.
Another option is the Mobilinkd TNC that only connects to the radio with a wire, but connects to an Android tablet/smart phone via bluetooth. The phone/tablet would then need to have the APRSDroid loaded onto it. With this set up the radio/TNC can be hidden away under a seat or in a rear cubby and you would just have your phone/table on the dash with no cables running around the cab of the vehicle.

Lastly you would likely want an external antenna. If you are using an HT for APRS while hiking you could probably get away with a better HT antenna, however for mobile use you will want an external antenna.

I will also add that you can connect an Android smart phone directly to a Baofeng UV5R (perhaps other HTs as well though this is the one I see the most) without the TNC. This may work better for walking/hiking or if you have an extra phone to leave connected to the radio when mobile.


I am currently running a Baofeng UV5R+ HT with a Mobilinkd bluetooth TNC,an Asus 7 tablet and external 1/2 wave antenna. This set up works fairly well though the 4 watts output of the HT is marginal as the only two digipeaters around are 25 and 40 miles away and with the hilly terrain here a number of my packets do not make it into the digipeater (this could also be attributed to the packets colliding with other users packets). In the future I would like to upgrade to a mobile radio dedicated to APRS for the higher output, but for not this set up works quite well.

[prerunner1982]

The pictures I posted in the first post are from aprs.fi, these pictures are what I see on the display in my Jeep.

[prerunner1982]

Well I finally got tired of the Baofeng. Transmit was ok at best with 4 watts but the receive was poor unless I was fairly close to a digipeater which I am not usually.

I purchased a Yaesu FTM-3100R, it's a new radio on the market and was cheaper than the outdated FT-2900R. I made up my own cable to connect the Mobilinkd TNC to the mic and speaker jacks of the radio.

The new set up is working marvelous! Output is set to mid level of 30 watts (wish the radio had 4 power options instead of 3) and does better reaching the digipeaters (20-40 miles away). The receive is the biggest improvement, going from receiving 1 packet on my 45 min drive to/from work to receiving 30 stations and 60-90+ packets.

Yesterday and Today the VHF propagation has been good in the mornings. Yesterday I was picking up stations from Missouri and one from Iowa. Today I was picking up stations from Houston, one from Corpus Christi, and 1 from Louisiana. Now this isn't simplex, station to station, but using digipeaters. The digis though are communicating over long distances. Today using only 1 digipeater hop my signal was reaching Tulsa and Dallas from OKC.

[prerunner1982]

I have been using APRS for awhile for tracking, sending messages to other APRS uses, sending messages through the International Space Station...etc.
Recently I finally got around to playing with SMS Text and Email.

I was successful at sending both SMS and email through my radio. Just have to work on setting up Aliases so that my wife's # won't be blasted on the air waves, but only a title that I choose for her. muahaha

The SMS recipient can text back, but legally they should be a licensed ham to do so as their message is transmitted over RF.

You must be within a couple of hops of an I-Gate for the SMS or email to work.