Getting Into APRS

by kc0vcu

What do I need to do to start working APRS?

 

You can do anything from an APRS beacon letting the world know where you are, adding APRS to an in-car navigation system, message passing via APRS, monitoring where APRS users are located, through building infrastructure to handle APRS traffic and gateway it to the Internet.

You can get hardware that provides all the APRS functionality minus the GPS receiver, on down to building your own APRS tracker.

As far as the basics of APRS goes, a Tracker, or aprs sending device takes a collection of information from a gps receiver, formats it into a packet, then sends it to a device that can transmit it. A full capability APRS system will both transmit information, as well as listen for APRS information that others have transmited.

A gateway primarily receives aprs packets via a radio receiver, and reformats those packets to be distributed on the Internet. It may also be listening on the Internet for APRS packets to be re-transmitted into the local APRS network. This can enable a user to send or receive APRS messages to other APRS users who are not local. That said the implementation of such a gateway is a bit beyond the scope of this blog.

Currently both the Kenwood TM-D710E Mobile and the Kenwood TH-D7AG HT radios allow you to simply attach a gps reciever, and configure them directly to be an APRS system. On the assumption that you already have a radio that you would like to use, or consider one of these radios to be too expensive on their own, there are a lot of other alternatives.

Many radios include a mini-din port that allows you to plug a TNC into the radio. This is part of their ability to act as a packet radio. APRS effectivly is a dedicated packet radio system, where the traffic involved is gps, or weather related information. (or messages.) If your radio provides this capability, you can use any TNC, with a computer or custom ASIC (pic, basic stamp, whatever) based computer and a gps receiver to work as your APRS system.

Ok, so somewhat like me, you have a radio or two, without a port to accept a TNC. You are not left out. There are a couple of software applications out there that allow you to use a sound card in a pc, along with one of the leads on either a com port, or a printer port to toggle transmit, to send data, including aprs packets, via a radio that does not have a port for a TNC adapter. Likewise if you are looking to simply monitor APRS traffic, you can simply use a scanner or other radio that can listen to the appropriate frequency, and feed the audio into a PC sound card and, using the same software as above, simply monitor.

If you don't want to add the expense of a TNC, and a computer to your setup, and already have a usable GPS receiver, you may choose to take the route I took towards getting into APRS. I use a TinyTracker3 to connect between a GPS receiver, and a HT that acts as a transmiter. TinyTracker3 can be bought either assembled (and tested) or as a kit to build on your own. As an alternative OpenTracker can also be built or bought pre-assembled, and has the potential advantage of allowing you to re-write the software involved on your own. This may be more of a software development project than you are interested in, but serious software developers may find it an additional incentive to take this route.

Some further links you may wish to persue regarding APRS.

APRS software for your PC:
A excelent program APRSIS http://aprsisce.wikidot.com/start/ I use this mobile when out of range of a I-Gate "Paul G0HWC" http://www.truckcam.tv

Trackers:
OpenTracker http://n1vg.net/opentracker/
TinyTracker http://www.byonics.com/tinytrak (USA) or http://www.ekradio.co.uk/mb7usk/html/tinytrak.html (UK Supplier)

Radios:
Kenwood http://www.kenwood-electronics.co.uk/products/comms/amateur/vhf_uhf/TM-D710E/
Other manufacturers do have radios with built in TNCs, ports, etc. Check with the manufacturer's web sites, or representatives.

Frequency:
general local aprs frequency UK 144.800 mhz.
general local aprs frequency USA 144.390 mhz.
hf frequency http://www.aprs.net/vm/DOS/HF.HTM

The current SSID recommendations to use:
-0 Home Station, Home Station running IGate.
-1 Digipeater, Home Station running a Wide1-1 Digi, Wx Digipeater
-2 Digipeater [#2 or] on 70CM
-3 Digipeater [#3]
-4 HF to VHF Gateway
-5 IGate (Not home station)
-6 is for Operations via Satellite
-7 Kenwood D7 HH
-8 is for boats, sailboats and ships (maybe 802.11 in the future)
-9 is for Mobiles
-10 is for operation via The internet only
-11 is for APRStouch-tone users (and the occasional Balloons)
-12 Portable Units such as Laptops, Camp Sites etc.
-13 not used as yet
-14 is for Truckers
-15 is for HF

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