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APRS - Automatic Position Reporting System
An increasing number of radio amateurs are using APRS to broadcast his or her current position, or to read that of other hams. APRS can be implemented rather easily and most of the components needed, can be obtained from the 2nd hand market. Generally speaking, the following components are required:
  • GPS antenna
  • GPS receiver
  • Mobile transceiver (2m or 70cm)
  • Modem (e.g. TinyTrack)

The first thing you need is a (free) rig that can be used exclusively for APRS (i.e. not used for phone at the same time). Museum Jan Corver is currently selling surplus Bosch KF161 mobile transceivers that are ideal for this application and are also very cheap. Please follow the link below to find out how you can obtain one of those rigs.

Next you need a modem capable of transmitting and receiving the required data in the standard AX25 protocol. This is the same protocol as is used for Packet Radio. One such modem is the famouse TinyTrack design, that is available as a DIY kit on the Internet (please follow the link below for more information),

Fixed stations (e.g. your home) are now more or less ready, as they can 'program' their fixed position in the modem. Mobile stations however, will need a suitable GPS receiver and GPS antenna, in order to obtain their position.
 
Mobile APRS
   This block diagram shows what is needed for an active APRS station. To the left is the GPS antenna that will receive signals from a number of statellites simultaneously. It is important that this antenna has a clear view, so that it can 'see' a larger number of satellites. The more satellites it sees, the more acurate it will calculate your position.
The (active) antenna amplifies the signals and passes them on to the GPS receiver. The receiver compares the various signals and calculates your position with a high accuracy. Once the position is calculated, it is passed on to the modem in the so called NMEA format. The modem then broadcasts the position in the 2m or 70cm band, unsing the AX25 protocol.
 
GPS antenna
When using a GPS receive you'll need, of course, a suitable antenna. Although it is perfectly possible to build your own (passive) antenna, it is advised to use a commercially available active one. Such active antennas are often quite small, can be mounted easily on the roof of your car, and feature a very high gain.
 
   Museum Jan Corver has a limited number of brand new Trimble GPS antennas available for sale, at a greatly reduced price.. These active antennas are fed by a 5V power supply over the thin coax that is molded to the unit. The Trimble antenna can be connected directly to e.g. the well known Lassen II receiver (see below).


 Price list
 
GPS receiver
Many suitable GPS receivers are available on the 2nd hand market. Some are smaller than others, and some need minor modifications before they can be used. One very suitable receiver is the Trimble Lassen-II that is available as a plug-in unit (often found as surplus part of a taxi meter). The module can be connected directly to the Trimble GPS antenna described above and the NMEA data is available on its RS232 port that can be connected directly to the modem (e.g. TinyTrack).
 
   This is an image of the Trimble Lassen-II receiver. In The Netherlands these could be found as surplus of the disposed taxi meters of TCA in Amsterdam.


 More information about the Trimble Lassen-II module
 A suitable Trimble active antenna for this unit
 General information about GPS
 Datasheet
 
Modem (TinyTrack)
A modem is used to link the GPS receiver to your 2m or 70cm transceiver. The digital information produced by the GPS receiver is converted by the modem into the well known AX25 protocol that is also used for Packet Radio.

TinyTrack is a very small APRS interface that can be build into most rigs without too much hassle. The modem is build around a PIC microcontroller and links the rig to the GPS receiver (and optionally a PC). Please note that TinyTrack is a very simple modem that only implements part of the AX25 protocol. For this reason, TinyTrack is only suitable for broadcasting your current position and not for the reception of the position of the position of other hams. In othe words: TinyTrack is uni-directional. If you want to receive APRS information, you'll need to find another solution (see below).


 MOre information about TinyTrak
 DOS configuration for TinyTrak
 Mac configuration for TinyTrak
 MIC-E version of TinyTrack

TinyTrack is available as a bare PCB, a DIY-kit or as a readily build unit. Museum Jan Corver is currently considering to make a TinyTrack compatible unit available as a DIY kit. If you are interested in such a DIY-kit, please drop u an e-mail at the address below.
 Yes, I am interested in a DIY-kit
 
Transceiver for APRS use
If you want to be able to receive and broadcast APRS data permanently, you are advised to make a 2m or 70cm rig exclusively available for this purpose. As the APRS frequencies are fixed for both amateur bands, you don't need any fancy features on the rig. Museum Jan Corver has some very suitable portable and mobile transceivers available for this purpose. In particular the 2nd hand Bosch KF161 is very suitable for this application and the museum has many of these units available that are already equipped with the correct cristal.
 Bosch KF161 APRS mobile transceiver
 AEG Teleport 9 portable transceiver
 
Receiving APRS through the sound card of your PC
If you have a PC with a suitable sound card available, you may be able to use it for the reception of APRS signals, using only a few external components. PA7PTT and PA7FL have created some guidlines that will help you to connect a Bosch KF161 to your PC in just 10 steps.


 Using the sound card of a PC for APRS reception
 
Internet
Special software is available to display the location of many APRS stations on your PC (see below). If you have access to the Internet, you might want to check the location of a known amateur at http://www.findu.com

Just as an example, you may want to click the following link to find the location of Museum Jan Corver in The Netherlands. Within a few seconds, a map will be displayed, showing the latest known position of the requested station. Such links can be added to your website easily, by creating a link to:
    http://www.findu.com/cgi-bin/find.cgi?pa0vyl
    
Replace the call-sign (pa0vyl in the example above) by your own call-sign. When a visitor on your website clicks the link, a request will be sent to the findu server (pronouce: find-you). The server will then try to locate the requested station for you.
 
Software
A lot of useful software is available if you want to display maps and APRS data on your PC. Which program is suitable for you, depends on the type of PC and the operating system you are using. Here are some links to help you find your way:
 PocketAPRS
 APRS/CE
 UI-View
 XASTIR
 
Maps
Many maps, suitable for APRS use, are available on the Internet. Please note that the file format of these maps can be different for the various operating systems around. So, before downloading files, please check first if they are suitable for your system and your software.


Generally speaking, two types of maps are available: bitmap images and vector images. The first kind (bitmap) is the most commonly used and will be suitable for most applications. THe graphical quality is reasonable good but, due to the nature of bitmaps, they are not suitable for zooming in and out. If you want to be able to zoom in and out at will, please look for vector images. With the latter, the entire map is recalculated and redrawn each time you zoom in or out, without loss of quality.
 Maps
 More maps
 
Interesting links


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