Beginners - APRS

This morning I was asked if I knew of a website that had a good general over view of APRS. As much as I would have liked to provide and answer. I could not. So with a little help from an old owners manual I'm going to try and give an overview here..

With APRS you will need 4 items.

1. Ham Radio Transceiver (Simplex 144.390 MHz)
2. TNC
3. GPS
4. APRS Software

If you are not a Ham or Amateur Radio Operator. A transceiver would be a radio transmit and receiving unit used to communicate with radio waves through the used of specific radio frequencies. Much like your cell phone.

A TNC, is a Terminal Node Controller. It converts packets to audio tones and audio tones into packets. It does this by using the AX.25 Protocol at the Data Link Layer of the Network OSI Model. This allows for a computer or a TNC capable radio to communicate over the radio waves. Much like the internet of the old days with a modem. You would use a modem to modulate an audio signal over the phone line. Another example would be a fax machine.

A Global Positioning System, or GPS is recommended, but not a required item. You should be able to manually set your GPS coordinates. Though if you are mobile with a vehicle, its suggested that you have a GPS. Again not required but recommended. Some radio / TNC systems will just need a GPS antenna. While other systems might actually need a full GPS for you to connect to your TNC / Radio. Best to read your owners manual for a more proper answer to your gear. I've recently discovered a device called Mobilinkd, which uses your cell phone and a GPS.

Software is where all the magic happens. In more recent times newer radios have their own version of software. It actually firmware because it is inside the radio. Any software that is embedded in hardware is always known as firmware. Since the OSI networking model is being used and the AX.25 protocol in place of the Data Link Layer. Its just a matter of knowing a few commands / responses. You could actually run an older TNC in terminal mode and do everything manully by hand with a command line in a terminal window.

The APRS software program and registered trademark of Bob Bruninga, WB4APR. He has made packet communications much more exciting than before.This program allows you to track mobile stations on a map which you recall on a computer screen. Imagine seeing one mobile station moving on the map which can be scaled from .5 to 2000 miles. You also may be tracked on the computer screen of another station. For stations to be tracked must transmit beacons at certain intervals.

BASIC APRS SETUP

Now that you have an APRS setup. What can you do... ?

I'll tell you what I"ve done in the past.. you can go from there..

I've used it to allow up to a few minutes update as to where I am in my vehicle. Someone I know has a habit of calling my cell phone every 20 - 30 minutes asking where I'm at. Now I just provide a link in email and refer them to it..

other uses..

Tracking shuttles during large volunteer events.
Tracking people (portable APRS)
Weather Stations reports to local hams.
Relay short text messages from one radio station to another.

If you search around on the internet, you'll see there are many tracking purposes, and you might come up with some ideas of your own..

I hope that this provides you with enough information to get you started with APRS.

73s

Tracy - KD6VZQ

APRS on Raspberry Pi or Android Tablet

Before getting started here. I would like to thank Scott WZØW for the resource and idea he presented. It provided some new and fresh ideas regarding APRS.

What is APRS?

I think Wikipedia explains it well.

"Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time tactical digital communications of information of immediate value in the local area. In addition, all such data are ingested into the APRS Internet System (APRS-IS) and distributed globally for ubiquitous and immediate access. Along with messages, alerts, announcements, and bulletins, the most visible aspect of APRS is its map display. Anyone may place any object or information on his or her map, and it is distributed to all maps of all users in the local RF network or monitoring the area via the Internet. Any station, radio, or object that has an attached GPS is automatically tracked. Other prominent map features are weather stations, alerts and objects and other map-related amateur radio volunteer activities including Search and Rescue and signal direction finding."

I have used APRS for all except direction finding.. I might have to try that some day.. :)


I first got started with text over Ham Radio by playing with TNCs (Terminal Node Controller). This allowed for me to send digital text information over the local radio waves. it was cool and easy for the novice techie to understand. It was a lot like the old BBS systems I used to visit with my computer. Just over Ham Radio.


For you young folks a BBS was pre-internet days of computer techies communicating and sharing information with each other. You used a modem and a phone line to connect to other systems. Most BBS have moved on to least costly activities with the internet. Not to mention being able to reach a broader audience. A blog site is a great example of an old BBS. However, a BBS did not have a graphic interface like we do here on the web. (BBS was short for Bulletin Board System) There are still a few around today. 

Moving on to APRS on tablet..

As per discovery from reading Scott's site. I got myself a Mobilinkd device, much like Scott did. I found this device handy for two reasons.

1. It using an HT
2. Connect with it via Bluetooh. (less wires)

I have an old Kenwood TM-D700 which is one of the first mobile radios that came with a TNC installed to allow for APRS. Other than being installed in a vehicle, it is rather bulky to carry, and battery is heavy. Not very practical. A HT and a Tablet or Phone is quite a bit easier to carry. Gotta love technology.

Mobilinkd does have a setup process that they have generally documented. Took me a few tries to understand what they were wanting for the hardware setup to be. Also they have DCD setup by default. In their documentation they state that it needs to be on. It was not working with my tablet. But once I turn it off, everything was working fine. Following directions is good. but sometimes you gotta think out of the box. 

On both my phone and tablet. I have used APRS Droid on and off during the last couple of years. I have found it to be one of the better apps for APRS.

For us who are fans of the Raspberry PI. You can install some software named Xastir for APRS. You'll also need some additional blue tooth hardware for your pi.  A little USB adapter $5 - $10 can be found at your local tech store or Amazon. Xastir did not work for me. But you can still give it a try. You can refer to Scott's page, on how to get Xastir installed.

After trying Xastir, I felt really disappointed with the software. Its about 6 years out of date and leaves you wanting some much needed functionality.

The maps are out of date. So much so that if you select the wrong map from the options, you'll be stuck for about 1 minute on your screen from map to map. I was only able to get two of the maps working out of the several that are listed.

The software attempts to reach locations on the internet that are no longer available. (For example http://mm.aprs.net)  The locations are where maps are / were stored. They are no longer there.

Once I was able to get my bluetooth TNC to work, software would still not transmit my packet information over the airwaves. I would hit the transmit now button, and nada! Receiving stations were just as bad. I would get garbage in the text, as if I had selected the incorrect baud rate for comms.

All in all, Xastir has a lot of catching up to do.

Xastir may have worked for other hams. But certainly not for my Raspberry Pi setup. My cellphone did much better than this.

Stepping back to Mobilinkd device. Of the three options I tried. There is only one device with any active GPS. Well, its not a real GPS, It simply gathers information from local systems to triangulate on your current position. So long as you stay within range of cell phone sites, your GPS function on your cell phone would work just fine. If you do manage to travel abroad and out into the boonies. The GPS on your phone will stop working the moment you loose your cell phone signal. Just something to keep in mind.

With a little trouble shooting. I'll have to say that the Mobilinkd device worked as expected. I feel its a good item to add to my Ham hardware collection.

73s for now..

Tracy - KD6VZQ

Why a Mesh Network

I have a working Mesh Network. What do I do now?

This seems to be the main question Hams have after getting a Mesh system working. I even had the question myself. I had the question because the information around the internet comes in bits and pieces. It was like being on the internet while participating in a scavenger hunt for pieces of a puzzle.

So here I’ll try and make it simple for you. A Mesh Network is created by changing the firmware on standard home internet routers. Once the firmware is change, you change on how the router works. It can only be bridge to extend a network (Mesh), or an Access Point connected to a Mesh Network.

That is demonstrated in my blog " Wireless Video Over Mesh Network "

If you are wanting a full and complete understanding on creating a mesh network. Be sure to read my other blogs on creating a Mesh Network.

Now for the answer you’ve been waiting for. A Mesh Network is a network that you build yourself. In essence it is its own internet network. Depending on what you would like to do with your network. You might need some additional hardware. Like a Server, or a Cloud system for file transfer.

To prove that mine worked, I chose to do streaming video through the Mesh Network. As demonstrated in my blog " Wireless Video Over Mesh Network ".

Now that you have that basic concept and understanding. Here is a list of some items that Hams have done with Mesh Networking.

• Text Chat
• Voice Chat
• VOIP (Voice Over Internet Protocol) Voip would be a phone system. Like Cisco phones at the office.
• Remote control link between house and Ham Shack.

There was a Ham Group in Texas that supported a marathon by using a wired camera through a mesh network. Which brings me to my next point. 

Why a Mesh Network? Hams have the license ability to use part of the WiFi frequencies. Because it falls within their license rights.

This allows for Hams to experiment with power output and Antenna systems. Legally extending the range of a Wifi Mesh network. In the case of the Ham Group in Texas. They extended the range between each router to 10 miles.

I hope this answers some of your questions about Mesh Networks. And maybe even give you some ideas of your own.

Thanks for reading.

Tracy

KD6VZQ