Receiving APRS Packet

Owned by Rio Liu
Last updated: Apr 11, 2022
2 min read

APRS Transmitter

The BigRedBee transmitter can be configured with the 70cm and 2meter APRS Transmitter utility at https://shop.bigredbee.com/pages/documentation-and-programming-utilities (direct link https://cdn.shopify.com/s/files/1/0062/3919/1158/files/BeeLineGPS.066a_1.zip?10068239033136361787). The 70cm 100mw APRS Transmitter document at the same page (direct link https://cdn.shopify.com/s/files/1/0062/3919/1158/files/beelineGPS_19.pdf?17310379549075783602) explains how to configure it in detail. Essentially, you start the configuration utility on the computer and connect the radio transmitter to the computer using its ICSP to USB adapter. Power up the board, select the correct COM port, and click the “Read” button before the board enters charging mode, change the configurations in the utility, then click the “Write” button.

(Their program kinda sucks)

Right now we’re using 431.000 MHz to transmit the packets.

The setup was tested with the following configurations:

Last Tested Conguration

 

Getting Software

The setup uses Dire Wolf as software TNC to decode audio input, and APRSISCE/32 to display the position on the map.

  1. Get direwolf from https://github.com/wb2osz/direwolf/releases/tag/1.6

  2. Extract the zip somewhere (on the team laptop I put it on Desktop)

  3. Get APRSISCE/32 from http://aprsisce.wikidot.com/downloads

  4. Extract the exe in zip into an empty folder (on the team laptop I put it in Desktop\APRSIS32)

Running Software

  1. Connect the FT-4X tranceiver to microphone jack using an aux line.

    1. If the computer only has TRRS combo jack (like the team laptop), use a splitter cable to split out TRS microphone line and connect using that.

    2. If the computer doesn’t appear to be receiving audio with splitter cable, try unplug the aux line from the splitter first, plug the splitter into the computer, then plug the aux line back to the splitter.

  2. Turn on the tranceiver and set the frequency to 431.000MHz (or whatever frequency the transmitter is configured to).

  3. Start direwolf.exe

    1. If the transmitter is on and has a fix, it should send a packet every 5 seconds. Direwolf should be able to decode them and print them out.

    2. If there are warnings about signal level, adjust the volume of the tranceiver.

  4. Run APRSIS32.exe

    1. When starting the program for the first time, it’ll asking for a call sign. We’re not using it to transmit anything so it should be fine to put anything (like NOCALLL).

    2. Once the program is started, uncheck these options:

      1. Uncheck Enable → APRS-IS Enabled - we don’t need to send the position to the internet

      2. Uncheck Enable → Beaconing Enabled - doesn’t really matter since we’re only receiving packets, but unchecking it reduces useless messages in the program.

    3. Go to Configure → Ports → New Port
      Type: AGW
      Name: direwolf

    4. In the next popup
      Select TCP/IP
      IP or DNS: 127.0.0.1
      Port: 8000
      Uncheck everything else

    5. Once the port is added, check Enables → Ports → direwolf

    6. If everything is working properly, the position of the APRS transmitter should now be shown on the map