APRS project

The radio-amateurs of Sint-Truiden were asked to present their services to volunteers of 'Red Cross Flanders' (Belgium). This would take place during their training "cartography and communication" in November 2000 (province-level). This was a chance we couldn't let go by, so many initiatives were launched and cooperation was started between HAM operators throughout the province.

Here's a list on activities deployed:

• A general introduction to radio amateurism with many of its aspects (using a video presentation)
• A joyful acquaintance session to Morse code
• Practical tips on setting up and maintaining communication head quarters
• Advantages of digital communication (TCP/IP and APRS)
• Exchange of imagery (SSTV, ATV, attaching digital pictures to E-mails)
• Practical session, during which a military event was simulated

Some of these sessions were tightly integrated, especially ATV, APRS and the practical session.

Personally, I presented the digital communication session (of course). I told the story on how digital communication evolved from Morse, over RTTY, FEC and TOR to PSK31 and (high-speed) Packet Radio. I did the same for imagery: from fax over SSTV to ATV and TCP/IP. This evolution was illustrated by live demos and audio captures (letting them hear what imagery sounds like). The presentation (Dutch) is available on request. Naturally, a complete demo setup with a Linux TCP/IP server and 2 Windows-based workstations was presented to show the benefits of wireless Internet technology.

A premiere was presented too: I developed an APRS project, specifically for this training. Due to time constraints and limited equipment availability, I gathered the following devices to set up this project:

• A carrying case, which was typically used for camcorders.
• A 12VDC battery, which was also used with camcorders.
• An MCB-152 device (running KISS firmware).
• A Garmin GPS-55 device.
• An IPC@CHIP DK40 kit.
• A Kenwood TH-78E portable transceiver.

The IPC@CHIP device from Beck (http://www.beck-ipc.com/chip) is particularly interesting: it's a micro controller device, based on the Intel 80186 chip, equipped with 256kB FLASH (FAT-like format), 512kB RAM, MS-DOS compatible multitasking OS, TCP/IP stack (including web, FTP and telnet server), 10Mbps Ethernet port, 2 RS-232 serial ports, 8 programmable I/O lines and an I2C bus. This system fits in a 50mm x 45mm x 20mm box.

The project was compiled using a regular C++ compiler for MS-DOS (generating code for a 80186). I discovered the multitasking feature of the OS while in progress, so if I would do it again, I would take another approach:

• Write one application that waits for data from the GPS device on one serial port, and, when valid data is received, would update that data into a 'file' in the FLASH area.
• Write another application that would encapsulate the information from the updated GPS data-file at a configurable interval into an APRS-formatted AX.25 frame which is, in turn, encapsulated into an KISS frame, that can be sent to the other serial port.
• The OS semaphore primitives (actually software interrupts) would be used to define critical sections for reading/writing the GPS data-file, which is commonly used by the 2 applications.

Source code is also available on request.