APRS v1 Page 4

From whuckaba
Jump to: navigation, search

Back to APRS


http://www.whuckaba.com/aprsproject/small/DSC01202.JPG Take one Street Finder GPS for PALM III unit
http://www.whuckaba.com/aprsproject/small/DSC01203.JPG Expose it's inner workings
http://www.whuckaba.com/aprsproject/small/DSC01204.JPG Remove it from the casing.
http://www.whuckaba.com/aprsproject/small/DSC01205.JPG Remove the lith-ion battery pack
http://www.whuckaba.com/aprsproject/small/DSC01206.JPG
Remove the GPS board from the interface card. This is a bulk-commercial gps decoding card. It is capable of 12 satellite tracking, and is as accurate as any other GPS on the market. The nice thing is it is plain-jane. The only downside to this board is the on-board battery on the GPS board itself was not installed for this unit, so it is ALWAYS a cold-start.
http://www.whuckaba.com/aprsproject/small/DSC01207.JPG
The modification is fairly simple. Usually the interface board tells the gps unit when to go active, and when to be in a stand-by state. Basically you have to short a jumper to turn the NMEA out on power-up, and change out a jumper with a capacitor (Which was originally on the interface board to change it's state). Here the board can be seen with the Positive 4-16volts in, ground, and serial out. (It also has serial in for telling the GPS where it is and other details to allow for a warmer boot up.
http://www.whuckaba.com/aprsproject/small/DSC01208.JPG It is attached to a stereo-phone style connector.
http://www.whuckaba.com/aprsproject/small/DSC01209.JPG
And it works (here is TT3 the 3rd attempt. Green light shows it is getting good NMEA data in. Red light is power indication. The Cyanacyrlate glue did its usual stick to anywhere I touched and left oils bit.
http://www.whuckaba.com/aprsproject/small/DSC01210.JPG
Ahh... Altoids to the rescue. :) I'm saving this poor GPS board from RF over-load. I think its sad that it doesn't have very much RF protection in it's original state. But Oh well. Will need to protect the antenna better later. Currently just tack-soldered in place. :) Need to get some double-sided tape, and then eventually find some RF-passing material to completely encapsulate the antenna.
http://www.whuckaba.com/aprsproject/small/DSC01211.JPG
Matching Altoids. Hmm... you'd think I did this on purpose. Serial connection is to the HT. The RCA connection is power (9volt battery in this case). And the right stereo connector is the GPS in.
http://www.whuckaba.com/aprsproject/small/DSC01213.JPG Almost a professional job, sides the scary wiring for the temp power. :)
http://www.whuckaba.com/aprsproject/location.JPG
The first 4 test packets