With SmartSDR v3.9.18 and above, FlexRadio introduces Serial Pass-Through, a new capability of the SmartSDR USB Cable feature that allows you to connect and control RS-232 serial devices, such as antenna rotators and amplifiers, directly through your radio. This feature works locally and over the internet using SmartLink.
Whether you're running third-party software like PSTRotator or other Windows-based control applications, this guide walks you through setting up your FTDI RS-232 USB serial cable with your radio and configuring SmartSDR to enable the feature.
The hardware you are controlling must have an RS-232 serial interface.
Devices that use proprietary USB protocols (e.g., NOT serial/RS-232) are not supported.
Below is a diagram showing the RS-232 serial communications signal path between the PC running the device control application (utility) and the remote device over a SmartLink connection.
How to Configure Serial Passthrough in SmartSDR
Step 1: Connect the FTDI RS232-USB Cable Between the Radio and Your Serial Controlled Device
- Plug your FTDI USB-to-RS232 cable (the one connected to your external device, such as 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 USB Cable Using SmartSDR for Windows
- Open SmartSDR for Windows. SmartSDR must be v3.9 or greater
- Go to Settings -> USB Cables.
- You should find your USB cable in the list, identified by its serial number.
- Click Edit, then set the Type to Passthrough.
- Click OK or Apply to save the changes.
- Click Edit, then set the Type to Passthrough.
- Double-click on the USB Cable to edit the settings
- Click on Advanced
- Set the Baud rate of the device.
- Exit
- Connect the serial cable to your external device’s RS-232 port (antenna rotators, amplifiers, etc)
Step 3: Create a Passthrough Port in SmartSDR CAT
The Passthrough CAT port will be used to connect to your serial application running on your PC.
- 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.
- Configure your application to use the SmartSDR CAT port number for external device communications.
đź“ť 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.