Tait T2000 APRS Board

Please note that this page is still a work in progress.

Tait APRS Tracker fitted inside a Tait T2000 series 1 radio

This project is designed to be a PCB that will fit inside the Tait T2000 radio as an option board to add APRS capabilities to the radio. The modification is as easy as removing the top cover, plugging in the two board connectors, fitting 3 screws and replacing the cover. The APRS board fits with the standard radio connectors just as you’d expect of a genuine Tait module.

An early prototype of the Tait APRS Tracker Board fitted inside a T2000 series 1

The GPS antenna is connected to an SMA antenna which is visible through the D-sub socket hole in the back case.

The GPS antenna socket protrudes from the D-sub socket hole in the case of the T2000

If programmed for momentary action inside the Tait software, the ‘AUX’ button on the front panel will cause a location packet to be transmitted.


Tait T2000 APRS Schematic

Build Notes

The under-side of the Tait T2000 APRS tracker
  • Do not fit R18.
  • Be careful crimping the plugs P1a and P2a on to the ribbon, as they have a protruding pin.

Bill of Materials

Please note that this section is still at work in progress. Although the components are correct and the project will work with the following part codes, the component series’ are mixed, and the aesthetic of the board will be slightly inferior.

CategoryQuantityOrder CodeValue
M11eBayNEO GPS Module (NEO-6M, NEO-7M)
C11RS 841-07582u2
C2-C3, C7-C95RS 538-1310100n
C4-C52RS 852-332422p
C61RS 475-90091u
R11RS 135-95422kΩ
R21RS 125-115310kΩ
R31RS 135-982100kΩ
R41RS 683-40828.2kΩ (used in DAC)
R51RS 477-8117 4.02kΩ (used in DAC)
R61RS 683-34302kΩ (used in DAC)
R71RS 683-31651kΩ ( used in DAC)
R8, R102RS 125-11501kΩ
R14-R174RS 901-36821kΩ – SMT 0805 (for LEDS, D1-D4)
R91RS 135-97647kΩ
R11-R133RS 136-0581MΩ
R181DNFReserved for special use (do not fit)
U11RS 623-0320PIC16F648A (Firmware: aprstracker-0.12-16f648.hex, see below)
Q1-Q44RS 739-02242N7000
D11RS 497-4804Red LED (TX) – SMT 0805 (optional)
D21RS 691-0442Blue LED (GPS) – SMT 0805 (optional, recommended)
D31RS 700-7904Orange LED (CD) – SMT 0805 (optional)
D41RS 694-2786Green LED (PWR) – SMT 0805 (optional)
J11RS 681-24926-pin SIL 0.1″ vertical pins (PICKIT ISP)
J21RS 360-64373-pin SIL 0.1″ right angle pins (PROG)
J31Share J22-pin SIL 0.1″ right angle pins (GPS DATA Jumper)
P11RS 301-8054Micro-MaTcH 12-pin PCB Mount (P13)
P1a2RS 680-4993Micro-MaTcH 12-pin Ribbon Mount
P21RS 745-5365Micro-MaTcH 16-pin PCB Mount (P14)
P2a2RS 680-4990Micro-MaTcH 16-pin Ribbon Mount
X11RS 852-486010 MHz crystal
MISC1RS 289-987416-way ribbon cable for P1/P2

Programming the Board

Programming the PIC microcontroller

Use a PIC programmer to program the board externally, or an in-circuit programmer, such as the Mircochip PICKit, attached to J1. The board should be programmed before connecting to the radio, since programming voltages may damage the radio and cause problems programming.

The aprstracker firmware version 0.12 (supporting 9600 baud GPS) by PE1ICQ and PE1RXQ can be downloaded here: aprstracker-0.12.tar.gz

Programming the tracker information

The tracker can be programmed with any program compatible with the PE1ICQ and PE1RXQ software. The aprstracker-0.12 software includes a Linux program to configure the tracker, which in a terminal looks like below:

The APRSTracker Configure software by Jedrzej SQ2DK, which can be downloaded from here, and allows for easy programming via Windows. I have found the Linux software to give better results on a new device. Set “Beacon interval” to 0 to enable smart beaconing.

Programming is done with an FTDI USB-TTL-Serial interface connected to J2. This can be done when the board is connected into the radio and powered. To program, J3 (GPS link) must be removed, as it uses the same UART (data input on the PIC) for programming and GPS input.

An FTDI cable connected to J2 (PROG) connector for programming callsign and timings.

To run the tracker J3 must be linked. The GPS LED will flicker with GPS frames.

Known Issues

GPS Data Corrupts Configuration

With time, I have found that the GPS data-stream can corrupt the EEPROM configuration. Essentially, the GPS starts outputting data before the PIC is out of reset, which means the PIC starts listening to the UART stream in the middle of a GPS sentence, interpreting the first few characters received as control characters – occasionally, these are valid instructions and the PIC randomly overwrites some of it’s configuration as if instructed to by the PC software.

This is easily fixed by adding a delay to the GPS power up. In my initial testing and board bring up, I added a BSP250 P-channel MOSFET with an RC time constant circuit set to 2 seconds. This ensures the PIC is operational before the GPS is powered. The picture below shows a hacked together test.

Future boards will incorporate a similar fix.

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