When your APRS transmission is digipeated by the ISS, it can be received by other hams and iGates, which then upload the packets to the internet, allowing them to be displayed on aprs.fi and other tracking sites.

Frequencies for ISS APRS Packet Radio

• Worldwide Uplink & Downlink: 145.825 MHz FM
• Digipeater Alias: ARISS

Yaesu FT-5DR Configuration for ISS APRS

The Yaesu FT-5DR is an APRS-capable handheld transceiver that can be used for ISS APRS packet communication. Below are the step-by-step settings to configure your FT-5DR for APRS contacts via the ISS.

1. Setting Up Frequency and Mode

1. Press the [V/M] button to enter VFO mode.
2. Set frequency to 145.825 MHz FM (both TX and RX).
3. Ensure the mode is FM (not AM or digital modes).

2. Configuring APRS Settings

1. Press [F], then tap the [APRS] menu.
2. Select "APRS Type" and choose "1200 baud" (the ISS digipeater uses 1200 baud AFSK).
3. Set "Beacon TX Interval" to 1-2 minutes (avoid excessive transmissions).
4. Enter your callsign in the "My Callsign" field.
5. In "Unproto Path," enter:
   • CQ VIA ARISS
   • OR simply VIA ARISS

3. Enabling Packet Data Transmission

1. Press [F], then navigate to [APRS] → [DATA TX].
2. Select "TX Method" and set it to "AUTO" (automatically transmits beacons at preset intervals).
3. Set "APRS Filter" to ALL (ensures no APRS packets are ignored).
4. Confirm that "APRS Beacon" is enabled.

4. Adjusting Power Output

• Start with 5W power output and increase if needed.
• Higher power (>10W) is usually unnecessary, as the ISS has a sensitive receiver.

5. Monitoring Packet Traffic

1. Tune to 145.825 MHz FM and listen for packet bursts (digital chirping sounds).
2. If the ISS is in range, decoded packets will appear on your screen.
3. Your radio will alert you when a received APRS packet matches your station.

Using a Yaesu FT-5DR with an External TNC or Software Modem

If you prefer to use an external TNC (such as Mobilinkd TNC3 or a computer-based solution like DireWolf), follow these steps:

1. Connect your FT-5DR to the TNC using a 3.5mm TRRS cable (speaker/mic interface).
2. Set your radio frequency to 145.825 MHz FM.
3. Configure your TNC/software to use 1200 baud AFSK.
4. Set "Unproto Path" to VIA ARISS.
5. Use APRS software (such as PinPoint, YAAC, or APRSDroid) to send and receive packets.

Best Practices for Successful ISS APRS Contacts

✔ Use a ¼ Wave Ground Plane or Handheld Whip – Stock rubber duck antennas are often insufficient.
✔ Transmit When the ISS is Overhead – Use tracking software to time transmissions.
✔ Keep Messages Short – Avoid packet collisions by limiting message length.
✔ Check APRS Maps – See if your packets reached an iGate at aprs.fi.
✔ Monitor Packet Signals – If you hear packets but your messages don’t appear on the map, adjust TX timing and power.

Additional Resources for FT-5DR APRS Setup

• Yaesu FT-5DR APRS Guide: https://www.yaesu.com/
• "QRP to the ISS" (Building a Tape Measure Beam for ISS Contacts):
  • http://www.work-sat.com/Antennas_files/QRP-ISS.pdf
• AMSAT Beginner’s Guide: https://amsat-uk.org/beginners/
• ISS Tracking & Pass Predictions: https://www.heavens-above.com

Step 1:  Install JTDX from Sourceforge

I installed the 64bit Windows version with 32 bit audio, it seems to work well for me though the 16 bit audio is the recommended stable edition.

Step 2:  Delete JTDXLog File

Type “cmd.exe” in the Windows search bar. Hold down Ctrl + Shift while you press Enter. This will launch the command line interface with the administrative privileges needed to make the hardlink.

Navigate to JTDX directory:

cd C:\Users\<username>\AppData\Local\JTDX 

Delete the local log file:

del wsjtx_log.adi 

Step 3:  Create the Hardlink

mklink /H C:\Users\<username>\AppData\Local\JTDX\wsjtx_log.adi C:\Users\<username>\AppData\Local\WSJT-X\wsjtx_log.adi 

If you’ve successfully created the hardlink, you should see the following: 

Hardlink created for C:\Users\<username>\AppData\Local\JTDX\wsjtx_log.adi <<===>> C:\Users\<username>\AppData\Local\WSJT-X\wsjtx_log.adi 

All that’s left is to run JTDX and get yourself some QSOs!

-73