Yaesu FT-991A + fldigi Setup Guide

Windows 11

1. CRITICAL: Unplug USB cable from computer before installing drivers
2. Download CP210x_VCP_Windows.zip from Silicon Labs VCP Drivers
3. Extract and run appropriate installer:
   • 64-bit: CP210xVCPInstaller_x64.exe
   • 32-bit: CP210xVCPInstaller_x86.exe
4. Restart computer
5. Plug radio into same USB port each time (do not use USB hubs)
6. Verify two COM ports appear in Device Manager (e.g., COM3 Enhanced, COM4 Standard)

macOS

1. Download Silicon Labs driver from Silicon Labs
2. Unplug radio USB before installation
3. Run installer and reboot
4. Radio will appear as /dev/tty.SLAB_USBtoUART

Linux

No driver installation required - cp210x driver is built into the Linux kernel.

Radio will appear as /dev/ttyUSB0. Grant permissions:

sudo usermod -a -G dialout $USER

Log out and back in for changes to take effect.

Essential Menu Settings

Key Point: CAT RATE (Menu 31) must match fldigi's CAT baud rate (38400)

Radio Mode Selection

1. Press MODE button on radio
2. Select D-U (DATA-USB mode)
3. Confirm with DATA-USB indicator on LCD

Step 1: Configure Audio Devices

1. Open fldigi → Configure → Sound Card
2. Set both Capture and Playback to USB Audio CODEC
3. Playback level: ~60 (avoid overdriving ALC)
4. Click OK

Critical: If no blue waterfall appears, audio input is not properly configured.

Step 2: Configure Rig Control (RigCAT)

1. fldigi → Configure → Rig → RigCAT tab
2. Enable: "Use RigCAT"
3. Rig Description File: FT-991.xml (or FT-991A.xml)
4. Device: COM3 (your Enhanced COM port)
5. Settings:
   • Retries: 2
   • Retry Interval: 10 ms
   • Baud Rate: 38400
   • Write Delay: 50 ms
   • Stop Bits: 1
6. Enable checkboxes:
   • "Commands are Echoed"
   • "CAT command for PTT" - Required for PTT
   • "RTS/CTS flow control"
   • "Restore Settings on Close"
7. Click OK

Alternative: Using flrig

If RigCAT gives issues, use flrig as a bridge:

1. Start flrig and configure for FT-991A @ COM3, 38400 baud
2. In fldigi: Configure → Rig → flrig tab
3. Enable: "Use flrig for rig control"
4. fldigi will communicate through flrig

Example command:

rigctl -m 135 -r /dev/ttyUSB0 -s 38400 -v

No Blue Waterfall / No Audio Input

• Verify USB Audio CODEC is selected in fldigi Sound Card config
• Check Device Manager - USB device must be present
• Lower computer sound card volume to ~20%
• Try different USB port (always same port going forward)
• Reinstall USB drivers completely

CAT Not Working / No Frequency Control

• Verify correct COM port (Enhanced port, not Standard)
• Verify baud rate = 38400 in both fldigi and radio menu 31
• Ensure menu 33 (CAT RTS) is enabled on radio
• Check "CAT command for PTT" and "RTS/CTS flow control" enabled
• Try using flrig as intermediary

Transmit Audio Too Hot (Over-Driven ALC)

• Lower fldigi Playback Level slider to 40-60
• Adjust radio menu 65 (AFt OUT Level) to 1500 Hz or lower
• Use USB cable with ferrite chokes
• Verify radio mode is DATA-USB

USB Connection Drops

• Do NOT use USB hubs - connect directly to computer
• Always use the same USB port
• Replace USB cable with high-quality shielded cable
• Ensure radio firmware is up-to-date