APRSAutomatic Position Reporting System

By Nicolas - M1HOG

www.M1HOG.com

Introduction

• Disclaimer - Nothing in the talk is warranted as accurate, optimal or indeed sensible.

• Objectives • Introduction to APRS and what it can be used for.• Introduction to the Club project and what it can do.• Practical - High level talk and equipment walkthrough.

APRS Overview

Automatic Position Reporting System• Exchange information with other APRS equipped stations• Call sign• GPS Position (Altitude / Speed)• Status Messages• Comments• Show Who / What is nearby – Stations repeaters etc.• Send short Emails via gateways• Send Messages and Bulletins via APRS network• Receive or send Weather Reports• Produce Maps showing stations and messages.

History of APRS

• Based on Packet Radio, developed in the early 80’s• Small packets of data are transported over the AX.25

protocol using 1200 baud Bell 202 audio frequency-shift keying(AFSK) on a 2 meter FM Frequency

• KA9Q - Developed software for an early TNC – Terminal Node controller – Basically a Modem that uses radio instead of a phone line.

• KA9Q software was later modified to provide a TCP/IP stack and use a phone line modem. This enabled early IBM PC’s to access the Internet and was how I first accessed the Internet.

APRS • 2 meter FM Radio – 144.800• GPS • TNC – Radio Modem – PC required• Tracker/TNC – No PC required• Digipeater• IGate

Radio • 2 meter FM Radio - 144.800• Ideally with fixed low level audio input and output

for easy interfacing to a TNC• Most 2 meter FM radios can be easily adapted

GPS

• Global Positioning System • Position, speed and altitude• Typically connected to via a serial lead to a

Tracker…

Terminal Node Controller

• Terminal Node Controller - “Radio Modem”Traditional TNC Requires a PC

• Tiny Track (TNC + Can send position)• Open Tracker etc (TNC + Can send position)

• Radios with built in TNC + Tracker• Kenwood D7• Kenwood D700• Yaesu VX-8RA

Tracker

• TNC vs Tracker• Functions as a “Smart” TNC

Generates the contents of packets • Typically - GPS plot, Call sign, Messages

With out requiring a PC and separate TNC • Tiny Track • Open tracker etc• May include a display to show packets received

May have various other functions including..

Digipeaters

• A "digipeater" from "digital repeater", digipeaters receive a packet radio transmission (APRS packet) briefly store it and then retransmit it on the same frequency.

• Like voice repeaters, digipeaters are used to increase the distance a radio packet can travel

• Typically digipeaters enable packets to reach…

IGate

• Sends packets to APRS-IS (Automatic Packet Reporting System-Internet Service)

• Radio -> TNC -> PC -> Internet connection • PC Software - APRS4R many others are available• The APRS data is then be plotted on to maps by various

internet sites…

APRS.FI - M3NQG IGATE

Recent Tracks

G0LGJ

G0LGJ -> M3NQG

M3NQG - Stations Heard

M3NQG - Stations Heard

APRS Review

Automatic Position Reporting System• Exchange information with other APRS equipped stations• Call sign• GPS Position (Altitude / Speed)• Status Messages• Comments• Show Who / What is nearby – Stations repeaters etc.• Send short Emails via gateways• Send Messages and Bulletins via APRS network• Receive or send Weather Reports• Produce Maps showing stations and messages.

Club Project – Bluetooth TNC • Based on Open Source hardware and software.• Draws on Moblinkd, BeRTOS projects• Provides Tracker, TNC, GPS and iGate functions

APRS Station Comprises • 2 meter FM Radio – 144.800• Android App – APRSDroid• Bluetooth TNC – Our Project!

• Uses Radio to transmit data, not a connection to the Internet!

Radio • 2 meter FM Radio - 144.800• Ideally with fixed low level audio input and output

for easy interfacing to a TNC• Most 2 meter FM radios can be easily adapted

APRSDroid

APRSDroid

Mobilinkd ● A better user interface for mobile APRS● Low cost — much less expensive than

existing purpose-built APRS gear.● Battery powered and Bluetooth

connected.● Excellent performance.● Ready to go with minimal configuration

Mobilinkd TNC

Club Project – Bluetooth TNC

• Simplified version of Mobilinkd design and all leaded/plug components

• Atmel Micro processor, as used in the Arduino, and a few supporting parts

• Bluetooth board, to link with APRSDroid etc.• Can be constructed on Strip/Vero board• Firmware based on Mobilinkd project• Configuration and software updates from Android

app• May be possible to add other features – FT857 –

Freq change prior to TX, power from the radio.

What Next?

• Thoughts and feedback from you• Complete prototype hardware• Test and Demo • Kit and build!• Have more APRS / Packet Stations on the air.

Links

• APRS - http://www.aprs.org/• APRS.FI – aprs.FI• BeRTOS -

http://www.bertos.org/use/examples-projects/arduino-aprs

• Mobilinkd – www.mobilinkd.com• APRSDroid – aprsdroid.org

Thank you !

This presentation is available at

www.SADARS.org

Nicolas

www.M1HOG.com