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PIC 16F84A APRS Tracker : GPS Encoder

The Schematic & Technical Information presented here generates an APRS signal with very little effort. It’s a TinyTrak type of tracker hardware with small changes, where all functions are controlled by PIC16F84A.

The position data in NMEA format ( $GPRMC ) delivered from a GPS is decoded and a 1200 bps packet radio signal is generated from it. This can be fed directly into a Radio Transmitter without the need of an expensive TNC. Because of not having enough program memory left on PIC & to make hardware simple, circuit does not decode received APRS signals.

This APRS interface has a serial interface for connecting to the GPS and for configuration of user parameters into PIC’s memory.

The main new features compared to TinyTrak (Byonics) besides some hardware variations is, speed dependable beacon rates and beacon transmissions at major course changes.

Suitable Firmware for this type of hardware is developed by many radio amateurs. One tested in this project is by DK7IN who has also made a nice Linux based configuration utility to write user parameters in PIC. However, TinyTrak's windows configuration utility may also be used for the same purpose. A Linux version is available for download.

Other firmware, developed by PE1RXQ may also be used with added operational benefits. However, this was not tried by me on first proto board. There is also a way to convert this tracker into a Data Tracker, please visit the links provided below, where more information may be found.

In addition to above basic hardware & pre-programmed PIC supplied with kits, my main intention is to make available economical APRS tracker hardware/PCBs to Radio amateurs, who wish to further develop their own type of APRS Trackers.

Since FoxTrak may be configured for various firmware, you may update FoxTrak with a better & smarter Firmware & if necessary, change the PIC, to 16F628A. The Basic hardware remains the same.

Like TinyTrak 3+, this tracker also uses larger 5V regulator to supply GPS power. With suitable header installations, you may supply GPS with either 12V or 5V.

FoxTrak also includes an Instant Transmit Push Button.

FoxTrak is designed on a Double Sided PTH PCB & measures only 7cm x 4.5cm. I am using standard right angle D9F & M connectors.

FoxTrak also comes with Null Modem Adaptor. This adaptor uses two R/A D9F connectors, PTH PCB and has possibility to use RS232 Driver such as MAX232. Null-Modem gets its power from FoxTrak and if no MAX232 is installed, no power is required.

Both FoxTrak D9 Sockets, Radio side & RS232/GPS side, have exactly the same connection plan as used with TinyTrak & Open tracker

Completed FoxTrak:

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