APRS BASICS AND TRACKING

Joe Foley

N1ZRN/TF

IRA Meeting 29/3/2012

What is APRS?

Automation of what we doRelay radio messages to their destination

Simplified AX.25 implementation for ease of use

Ad-hoc data infrastructure Cheap GPS location tracking Check weather station data

What is APRS NOT?

NOT a way to pass encrypted data from one place to another

NOT for streaming video or pictures NOT the internet

OK, this is a bit of a lie due to IGates like TF3RPG

I have a smartphone with GPS, why do I care?

Your cellphone has a maximum power of 100mW at ~1-3Ghz

Without Siminn/Vodaphone, you have an expensive brick

APRS can use higher power, higher gain, different frequencies

You get greater control over your data and who sees it.

What do I need to use APRS? You need three parts

Something to generate or process data○ GPS module, weather station, microcontroller

Something that understands AX.25 signalling○ Microcontroller, custom ASIC○ Terminal Node Controller

Something that can transmit/receive radio signals○ You know what this is...

A valid wireless license of course!

Generate or Process Data

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AX.25 ModemsPortable TNC

TinyTrak4 OpenTracker USB

http://www.byonics.com/tinytrak4/http://www.argentdata.com

AX.25 ModemStandard TNC

http://www.universal-radio.com/used/UW61lrg.jpg

http://wb0wao.net/images/tnc-x.jpg

AX.25 ModemArduino

Argent Radio Shield Trackuino Shield: Arduino is the TNC!

APRS-ready Transceivers

Kenwood TH-D72A Yaesu VX-8GR

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I bought the toys, now what?

<yourcallsign>-<SSID>

APRS Callsigns

-0 Primary -1..4 Generic -5 Other net -6 Special -7 Human -8 Boats/RV -9 Primary -10 Internet -11 Balloons -12 Trackers -13 Weather

-14 Truckers -15 Generic

Digipeater“Digital Repeater” Two kinds

WIDE1 (fill-in)WIDE2 (wide area)

Frequency: 144.800 MHz (Europe) You can use other frequencies too!

Digipeater Aliases

All respond to WIDE1 Only WIDE2 responde to WIDE2 If WIDE(n) where n>2,

WIDE2 respond, and relay WIDE(n-1)To prevent packets bouncing forever

Paths

APRS is simplified AX.25AX.25 allows long-range many hopsAPRS intended for local use

SuggestedMobiles: WIDE1-1,WIDE2-1Stations: <relay>,WIDE2-1Airborne: WIDE2-1 or WIDE2-2

○ Low altitude: WIDE1-1

Beaconing

Transmit “something” to every ARPS Station in earshot (usually location)

Set transmit rate according to speed>2 min for driving>20 min for stationary

Position comment“Emergency” will cause people to notice!

ObjectsHamfest, accident, meeting

http://20poorandfabulous.files.wordpress.com/2012/03/texting2.jpg

Sending Messages

You can broadcast or sendSpecific callsignGroupsALL in range

This message can have a position, so people can go there

Internet Gates (IGates)

If you can get to one, you can:Send emailReport position to webpage https://aprs.fiWHO-IS: Lookup info on a callsignCQ Server for APRS QSO

Questions?

Much of this material is from “APRS Beginner Guide 2011 by K9DCI”

There is interest at RU for APRS development

Joe Foley foley@ru.is N1ZRN/TF is an instructor of mechatronics and mechanical design at Reykjavik University