GlobalSat BU-353-S4 GPS receiver not locking coordinates in UCL software on Windows 11

A solid red light on the BU-353-S4 means power is on, but satellite fix has NOT been acquired.

The LED must be blinking red for a valid GPS 3D fix.

Troubleshooting steps:

1. Move the antenna near an open window or terrace with a clear sky view. Thick concrete roofs block satellite signals.

2. In Device Manager → Ports (COM & LPT):

   • Verify the COM port number (e.g., COM3)
   • Set Baud Rate to 4800 (mandatory for UCL)

3. Windows 11 driver issue: Prolific PL2303 requires driver version 3.8.31.0 or older.

   • Newer drivers from Windows Update cause Error Code 10 (device cannot start).
   • Download the older driver from the Prolific official site.

Device Manager → Right-click COM port → Update driver
→ Browse my computer → Let me pick
→ Select v3.8.31.0

Before launching UCL, verify GPS reception with the GPSInfo.exe test utility (included with the BU-353-S4 package).

What to look for:

• At least 4 active green satellite bars must be visible in GPSInfo
• Accuracy should be below 10 meters

Once you see a valid fix in GPSInfo:

1. Close GPSInfo
2. Launch UCL client
3. GPS will sync within 30 seconds

If you're indoors, placing the dongle cable outside the window via a USB extension works well.