Weekend project, do APRS with your KT8900 transceiver

 

This little cheap Chinese transceiver can be found on Ebay, or Aliexpress for 60$, supporting VHF/UHF, can Tx up to 25W. A complete description and testing page is available on G7EOB website

You plan to drive for a long way? broadcast your position on APRS Network, with some components you can build a small tracker. Arduino sketch is based from Trackuino, EA5HAV Javi

Trackuino is more intended to be used on ballon flights, but can work for APRS general purpose.

With some minor modifications, the tracker can send position depending of speed of the vehicle. Reading var gps_speed parser and set the APRS_PERIOD do the job.

Just bellow, is the schematic, D3 is used to generate the modulation, through the trimmer you can adjust the modulation level, D12 is used to saturate the transistor and do the PTT, GPS1 is GPS shield, but for my test i have used a old EM406. A0 is used to monitor the battery voltage with a resistor divider. 10k/3.3k, a temperature sensor LM60, is connected A1. All parameters, like callsign, Gps baudrate, pin assignation …. can be set into the config.h file

Sketch is here, need Arduino IDE v1.8 min

You need:

  • Arduino Nano , or Mini, i prefer Nano because it’s powered @5v, so no need external level shifter for the GPS connection.
  • GPS head, like EM406, or a GPS Board (Neo 7M) …
  • A temperature sensor LM60 (option)
  • Two resistors to monitor the battery voltage (option)
  • 7805 voltage regulator with two tantalum capacitor
  • A 2n2222 transistor to drive the PTT
  • A 10K trimmer with a 1uf cap
  • A short network RJ45 cable
  • Wire, pin header, veroboard

Yes, i need a little nice box