APRS - GPS - Packet Radio - Ham Radio - Amateur Radio - Tripmate GPS - 2 Meter Radios

Please keep in mind that this modification will not allow you to use your Tripmate with the Street Atlas Software as it was originally designed. I do share plans on how to build an external Tripmate Adapter that will allow you to use your Tripmate with Street Atlas or you can connect it to a Tiny Trak 3 for use with APRS. Also, this modification will void any warranty if you still have one.

The DeLorme Tripmate GPS receiver can be modified to work with the Tiny Trak 3 APRS controller sold by Byon Garrabrant of Byonics. These Tripmate GPS units sell on ebay for around $50.00 and work reasonably well as the GPS receiver for your APRS tracking station. DO NOT buy a DeLorme EARTHMATE if you see it listed on ebay. If you have an Earthmate, you can purchase a converter from Byonics to work with your Tiny Trak. The Earthmate does not put out the NMEA 0183 signal that the Tiny Trak requires. Unfortunately, DeLorme has completely sold out and discontinued the Tripmate. 

I created this page because I followed some of the other web pages that described modifications for the Tiny Trak 2 only mine didn't work right off the bat for my Tiny Trak 3. The addition of the 10k ohm resistor in series with the GPS output to the serial connector and not to tie the brown and black wires together made the difference. I also pulled 12 volts through J7 on the Tiny Trak 3 and regulated it to 5 volts inside the Tripmate with the use of a 7805 voltage regulator.

Parts list for the modification are:

1-DeLorme Tripmate GPS receiver
1-7805 positive 5 volt regulator
1-10k ohm resistor - 1/8 watt
1-.01uf ceramic disc capacitor
1-10uf, 30 volt electrolytic capacitor 
A little bit of black plastic tape
Some short pieces of hook up wire from your junque box

Click any image for a larger image.

First after opening the unit I removed the AA battery holder and cut the red & black wires as close to the battery holder as possible. Unplug the small white connector from the GPS receiver and set it aside for the time being. I removed the three small screws that secured the metal plate to the top of the plastic GPS housing. Using my nibbler tool I nibbled a small passage way for the red wires to pass through from the 7805 voltage regulator. This 7805 will be mounted on the lower side of the metal plate opposite the GPS circuit board. If you do not have a nibbler tool you can drill a small hole where two wires will pass through.

After exposing the GPS circuit board I unsoldered the yellow, brown, black and red wires that come in from the serial cable. Do not remove the orange wire from the GPS circuit board that comes in from the serial cable. The orange wire is the ground wire. Tie off the yellow and brown wires because they will be abandoned and not be used for this modification.  Move the red wire that comes from the serial cable to the input of the 7805 voltage regulator. The 12 volts from the Tiny Trak 3 will be supplied through this red wire. Add a small piece of red wire from the output of the 7805 (photograph 1) to the third pad on the GPS circuit board (photograph 2). This red wire just turns the GPS receiver on and doesn't power the GPS. The 5 volt regulated power for the GPS receiver comes in through the small white connector with the black and red wires. To the right is a drawing of a 7805 voltage regulator and the pin out. I temporarily screwed the 7805 to the metal plate using one of the the original screws then soldered the center lead of the 7805 to the metal plate. This is the common lead that connects to the ground. I then soldered the red lead from the white power connector to the output of the 7805 along with one lead of a .01uf cap. The other lead of the .01uf cap was soldered to the metal plate or ground. Then solder the + lead of a 10uf electrolytic to the input side of the 7805 and the - lead to the metal plate or ground.

Photograph 1 (click for a larger image) shows the location of the 7805 5 volt regulator that supplies power to the GPS through the white connector red wire and another red wire going to pad 3 on the GPS circuit board. (See photo 2 below). The black wire from the white connector is soldered to the metal plate as ground. A little piece of black tape helps to insulate the connections from shorting out. I just discovered that the yellow wire you unsolder is sometimes a white wire on some Tripmates.

Photograph 2 (click for a larger image) shows the location of the GPS out to GPS in jumper (yellow wire), the +5 volt red wire that turns on the GPS receiver and the 10k ohm resistor that connects to the black wire GPS serial to the Tiny Trak 3. That black wire is sort of hard to see. The original yellow and brown wires from the serial connector cable has been abandoned and should be taped off. In my text I am calling the pad number 4 is where the orange wire is soldered (ground wire), pad number 3 is the red wire (+5 volts to turn on the GPS receiver), pad 2 is the lower point of the yellow jumper and pad number 1 is the other end of the yellow jumper and where the 10k ohm resistor is soldered. 

Here is another view of the 7805 voltage regulator and the 2 capacitors. The black tape helped to assure that the leads would not short out against the metal plate. The center or ground lead of the 7805 is soldered right to the metal plate along with the opposite leads of the capacitors. The small red wire is the +12 volts that comes in from the serial connector by means of J7 inside the Tiny Trak 3. The larger red wire goes to pad number 3 on the GPS circuit board and turns on the GPS receiver. The 3rd red wire exiting the top of the photograph goes to the white power connector and is soldered to the output of the 7805.
   
Above are a few more views of the GPS circuit board and a photograph of the finished GPS receiver. I painted it flat black because I felt the original bright yellow color drew too much attention to "that thing" up on the roof of my truck. I also fixed a magnet from an old CB antenna mag-mount to the bottom to hold it in place. Neither the paint or the magnet seems to effect the performance of the GPS receiver.

Remember to also solder bridge J7 on the bottom side of the Tiny Trak 3. This will provide a path for the +12 volts to get to the GPS receiver. Refer to the documentation available from Byonics concerning J7.

Also, the Tripmate takes a few minutes to acquire a lock on the satellites.  Don't get too impatient waiting for the green LED on the Tiny Trak 3 to quit flashing and stay on. All of the Tripmates that I am aware of always takes at least two minutes to acquire a signal. In addition, the Tripmate only works when it has a wide angle view of the sky. After finishing the modification you will need to go outside to test it. The Tripmate will not work inside on the work bench.

For the terminally curious

Because it's a bit of a pain to figure out, here are the connections from the Tripmate's DB9 female connector to the internal wiring within the GPS unit itself. You probably won't ever need this information, but it could be useful.

Note: All other pins are not connected to the Tripmate.

73's and hope to see you on APRS soon!

Jerry Karlovich, KD5OM
Email me and let me know if this has been helpful or if you have something different to share.
jerry@kd5om.com - Where is KD5OM-2 on Findu? - Back to my original page on modifying the Tripmate.

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