With SmartSDR v3.9 and above, FlexRadio introduces Serial Passthrough, a handy feature that lets you connect and control RS-232 serial devices—like antenna rotators or amplifiers—directly through your radio over the internet using SmartLink.
Whether you're running third-party software like PSTRotator or other Windows-based control apps, this guide walks you through setting up your FTDI RS232-USB cable, configuring SmartSDR, and getting everything talking seamlessly.
The hardware you are controlling must have an RS-232 connection.
Devices that use proprietary USB protocols (e.g. NOT serial/RS-232) do not work with this feature.
How to Configure Serial Passthrough in SmartSDR
Step 1: Connect the FTDI RS232-USB Cable
Plug your FTDI USB-to-RS232 cable (the one connected to your external device like a rotor controller or amp) into one of the USB ports on your FlexRadio. These cables are available from the FlexRadio store.
Step 2: Set Up the Cable in SmartSDR for Windows
- Open SmartSDR for Windows. SmartSDR must be v3.9 or greater.
- Go to Settings > USB Cables.
- In the USB CAble program window, locate the USB cable by serial number.
- Click Edit, then set the Type to Passthrough.
- Click OK or Apply to save the changes.
Step 3: Create a Passthrough Port in SmartSDR CAT
- Launch SmartSDR CAT.
- Click to Create a New Port, and choose Passthrough in the protocol selection.
- Select the same USB cable from Step 2 (matched by serial number).
Step 4: Use the Passthrough Port in Your Application
- In your third-party app (like PSTRotator or another device control program), choose the COM port that was just created in Step 3. (You can find the COM port name in SmartSDR CAT).
- Make sure your application is set to use that port for communication.
📝 Tip: Double-check in SmartSDR CAT that the Process is showing the name of the application you're using (like PSTRotator, PuTTY, etc.), which confirms the connection is active.