Been sick for a few days and haven't been on. Feeling better now, but going to bed soon.
Just thought I'd throw out some photos of the new APRS tracking box. It now integrates the Trimble SK8 GPS module I got, a small interface board, the TinyTrak II APRS modem, voltage regulators, etc.
Features are: onboard GPS module and APRS modem (hard wired together), antenna sharing circuitry to allow my Garmin eMap to share the external GPS antenna feeding the Trimble module, voltage regulation for the Garmin (3 volts) and the Trimble and TinyTrak (5 volts), -5 volt inverter and transistor to provide "true" RS-232 signal levels, jacks for an external computer (for photo map tracking), key switch to enable/disable APRS radio tracking (local navigation still powered), toggle to allow computer to connect to either the Trimble unit, or the Garmin (when attached), and so forth.
In the pictures below, the first picture is a front view. The light green board closest to the front is the TinyTrak II, the brown board in the middle is the voltage inverter/RS-232 interface and on the bottom of it is a 3 volt lithium battery "coin cell" that provides backup clock power to the GPS module. The dark green board towards the rear on the right is the Trimble SK8 GPS module. The four LED's, left to right are: power, VHF receive status, GPS lock status, and transmit status. The little circuit board sticking up in the back left is on the LM317 regulator and has bypass caps and a resistor to "program" it to 3.0 volts output. To the right of that is the 5 volt regulator. Both regulators are on heat sinks, and fastened to a copper clad board -- they run cool.
The next two photos show side views. Yes, it's still a bit sloppy and the breadboarding is casual, but it works and I'll clean it up after full testing is done.
The last picture shows the rear panel. Left to right the jacks are:
BNC - External antenna in (also supplies power to the external antenna)
BNC - Antenna signal out to the Garmin eMap
8 pin mini DIN - RS-232 interface to onboard laptop computer
empty hole - not used
Coaxial power jack - 12 volts in
5 pin DIN - Interface to VHF radio (same as TNC-2 and MFJ 1270/1274 types)
Coaxial power jack - 12 volts out to VHF radio
8 pin mini DIN - RS-232 and 3 volt power to Garmin eMap
When this passes any test and modification that needs to be done, I'll take it apart, spray it flat black, and remount it in the truck. Right now, the beige box looks a little out of place. The box is an old Panasonic industrial camera driver box. We don't use them anymore so I salvaged the enclosure to use for this.
Anyway, it's in the truck and running fine so far. More on this as I develop it. It's nice because the tracking system is totally self contained and doesn't require my eMap to function so I can take it handheld, put it in another vehicle when needed, etc.
As always you can track me at http://map.findu.com/n3elz-14