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WinLink (via VARA HF) with FLEX-8600M

Published: Aug 16, 2026

The FLEX-8600M (and the entire FlexRadio 6000/8000 series) eliminates the need for physical soundcards and hardware PTT cables. All audio routing and CAT control are handled entirely over the network via virtual audio (DAX) and virtual control channels on both Windows and macOS.

1. Radio Settings (FLEX-8600M)

On the radio’s touchscreen or via your client interface, configure your slice for digital operation:

  • Mode: DIGU (Digital Upper Sideband)
  • Filter Width: Set to 3.0 kHz (or wider) to accommodate VARA Wide.
  • DAX: Enable DAX Channel 1 on the slice assigned to digital data.
  • RF Power: Set your desired operating power (e.g., 50 W – 100 W).

2. macOS Setup (Native Path via MacWinlink & SmartSDR for Mac)

For macOS, MacWinlink provides a streamlined, native client that transparently manages the VARA modem backend without requiring a dedicated Windows VM.

Virtual Audio & CAT on macOS (xDAX / xCAT)

  1. Ensure SmartSDR for Mac (Marcus Roskosch) or the standalone xDAX / xCAT tools are running to expose the FlexRadio network streams as macOS CoreAudio devices and virtual serial ports.
  2. In xDAX, activate DAX RX Channel 1 and the DAX TX Stream.
  3. In xCAT, create a dedicated TCP CAT or virtual PTT port pointing to your slice.

Audio & Rig Configuration in MacWinlink

  • Audio Input: Select the virtual DAX RX 1 device.
  • Audio Output: Select the virtual DAX TX device.
  • Rig Model: FlexRadio 6000/8000 (or network IP/TCP control via SmartSDR backend).
  • PTT Mode: Network PTT / CAT or mapped virtual serial device.

3. Windows Setup (SmartSDR DAX & CAT)

If operating under Windows, use the standard FlexRadio desktop suite:

DAX Control Panel Configuration

Open the SmartSDR DAX application (must remain active in the background):

  • RX Streams: Ensure Channel 1 is turned ON (Blue).
  • TX Stream: Ensure the TX button is turned ON (Red).
  • TX Gain: Start with this at 50 for baseline alignment.

SmartSDR CAT (Virtual PTT)

  1. Open SmartSDR CAT.
  2. Click Add… to create a new virtual port.
  3. Set Port Protocol to PTT.
  4. Note the assigned port number (e.g., COM11).

Winlink Express & VARA Settings

  • VARA HF SoundCard Settings:
    • Input Device: DAX Audio RX 1 (FlexRadio Systems)
    • Output Device: DAX Audio TX (FlexRadio Systems)
  • Winlink Session Radio Setup:
    • Radio Model: FlexRadio 6000 (Fully compatible with 8000-series models)
    • I/P Address: 127.0.0.1 (When Winlink and SmartSDR run on the same PC)
    • PTT Port: Select the virtual PTT COM port created in SmartSDR CAT (e.g., COM11).

4. Transmit Level & Adaptive Predistortion (APD)

The FLEX-8600M features Adaptive Predistortion (APD), resulting in an exceptionally clean, low-IMD VARA signal.

  1. Monitor the Meter: In your SmartSDR interface, observe the TX Level Meter (DAX/TX panel).
  2. Tune: In VARA HF, click the red Tune button.
  3. Adjust Drive: Adjust the VARA Drive Level until the level in SmartSDR stays just below the 0 dB digital clipping threshold.
  4. Digital Level Check: Keep the level indicator in the solid green zone. Avoid hitting red, which indicates digital buffer overflow.

Troubleshooting: “No TX Audio”

  • The Problem: The radio keys up (red TX indicator turns on), but no RF power is output.
  • The Solution:
    1. Verify the DAX button on the SmartSDR transmit control panel is enabled/highlighted. If inactive, the transmitter will key but ignore the incoming DAX TX audio stream.
    2. Confirm that the DAX audio control panel (DAX on Windows, xDAX on Mac) shows the TX stream actively streaming packets during transmission.
    3. Ensure the active slice has DAX Channel 1 explicitly selected on the slice flag.