Packet Radio - GPS - Tripmate GPS - APRS - Ham Radio - Amateur Radio

Seems that I have the bug on these little Tripmate GPS units. I have modified several already to work with Byonics' Tiny Trak 3 APRS controller available through their web site at: www.byonics.com . 

I purchased my first Tripmate GPS with the Street Atlas software back in 1996 while vacationing through Colorado. For the next 7 or more years that little GPS unit sat on the shelf. Early in 2003, many of the fellows in our local Go to the internal modification page.

The following is how to build the external "Tripmate Adapter". 

Parts List:

1-Tripmate GPS Receiver
1-7805 Voltage Regulator
1-TO-220 heat sink
1-10k ohm 1/8 watt resistor
1-.01uf capacitor ceramic disc.
1-10uf / 35 volt capacitor
small pieces of hook up wire
Some small heat shrink tubing
1-Female DB-9 connector
1-Male DB-9 connector
1-Double Ended DB-9 hood
1-Battery Connector Jumper or Diode (see text)
1-Set of Jack-Sockets for the DB-9 to the GPS

The schematic is very simple and the entire unit should not take more than an hour to assemble and test. I have already built several of these adapters and I seem to get better at it every time. The only error I have made was switching the male and female DB-9s. We need to keep track of that.

The first thing I found out to do is attached the Jack-Sockets to the male DB-9 connector. It is difficult trying to get those little washers, nuts and screws together when you can not maneuver the DB-9 around. Remember to attach them to the MALE DB-9. 

All of this can fit snuggly inside a double DB-9 hood. I use the solder type of DB-9 connectors. I measured 37 mm from pin to pin. The ground wire is straight through from pin 5 to pin 5. Then I bend one end of the resistor in a little U shaped hook to work also as the jumper between pins 2 & 3 on the male DB-9. Then I cut it 37 mm in length from the start of the hook to the opposite end. Slip a piece of heat shrink over the resistor and solder the opposite end.

Position the hole of the 7805 about 1/4th the way from the Tiny Trak 3 end (female DB-9) and drill the hole. Now I choose to use a small TO-220 heat sink because the 7805 gets just a little bit warm. Not hot to the touch but you can tell it's warmer than the other parts. I measured about 130ma current draw on the input. I can see why a set of AA batteries only last about 5 to 6 hours! My first adapter that I built doesn't have a heat sink in it and everything is fine without a heat sink. Secure the 7805 in place inside the hood with a small screw, lock washer and nut. Using short pieces of hook up wire I attached the rest of the connections and the capacitors. 

Here is maybe the hard part of doing this modification without actually modifying the Tripmate. My latest Tripmate came with an external power cord and this little jumper for the power connector. Notice that it jumpers the first two pins. Different than the AA battery connector. It is the same connector found on the batteries of many cordless phones. There is a work around using a diode if you can not find a connector.

My local Radio Shack has a cordless telephone battery (part number 23-284) that they are discontinuing. This is normally a $12.00 battery and they sold 4 to me for $1.97 each. I wacked the connectors off and saved the NiCads for a future project.

There is a local company that rebuilds battery packs and I was able to purchase parts to build 30 connector jumpers. If you're in a city that has such a company you might try there. 

If you know of a good source for these little connectors please email me so I can share it here for others to know.

The diode jumper below also works just fine and you can still use your Tripmate with your Street Atlas software. However, the diode will void any warranty if you still have one.

If you can not find a connector to make a jumper like in the picture above, you can add a 1N4001 diode soldered in the position in the photograph to the left. Pay attention to the correct polarity position of the diode. This will allow you to use your adapter with your Tiny Trak 3. You could also continue to use your Tripmate with your Street Atlas software connected directly to your laptop by re-installing the batteries and reconnecting the original battery connector. Click here for a larger image.

Before closing up the hood you need to perform some tests. First re-examine all of your work making sure that you soldered to the correct pins of the DB-9s. Make sure you don't have anything shorting out. It is very cramped inside there. Apply 12 volts to pins 4 & 5 on the female DB-9. Positive to pin 4 and negative to pin 5. Smell smoke? If so disconnect immediately! Re-examine again find out why you were getting smoke signals. 

If there were no smoke measure the voltage across pins 4 & 5 on the male DB-9 connector. It should be about 5 volts. Also measure between pins 5 & 9 of the male DB-9 connector. Once again it should be about 5 volts. OK? 

Now you're ready to plug into the Tiny Trak 3. Before you do, have you solder bridged the J7 jumper on the bottom side of the Tiny Trak 3? This is important because this is how the Tripmate is to be powered. Review the documentation inside the Tiny Trak 3 instructions. 

Make sure you have attached the jumper connector inside the Tripmate or you performed the diode modification. Attach the Tripmate to the male DB-9 and the Tiny Trak 3 to the female DB-9. Apply power to the Tiny Trak and you should see the flashing LED sequence. Then the green LED should begin flashing. 

Don't close the cover on the adapter yet!

If you are indoors your Tripmate probably will not get a strong enough signal from the satellites to obtain a lock and the green LED will continue to flash. Carefully carry everything out to the patio table where you have a clear wide angle view of the sky. After about two or three minutes the green LED will cease flashing and stay lit indicating you have a lock on the satellites. Yea!

Now hook your Tiny Trak 3 up to a radio (after you have configured the Tiny Trak 3 of course). If you have the ability to monitor the APRS traffic or UI-View you should see yourself appear on the map. The VHF frequency for APRS is 144.390 MHz simplex, no CTCSS tone.

APRS path settings 

To find the wiring diagram or to buy the ready made cables to interface your Tiny Trak 3 to your radio go to: http://www.packetradio.com/tnc2rad.htm#KANTRONICS The Tiny Trak 3 uses the same interface cable as a Kantronics TNC.

If there is an Internet gateway station nearby you can go to:
http://www.findu.com/cgi-bin/find.cgi?call=YOURCALL
Where you see YOURCALL enter the call sign you configured your Tiny Trak 3 for. 
In my case it would be: 
http://www.findu.com/cgi-bin/find.cgi?call=KD5OM-2

If all is working you can go ahead and close the cover on the DB-9 hood. I suggest you make sure everything is working well before closing the covers because it is a bear getting that thing apart!!