The FLEX-8600M (and the 8000 series in general) eliminates the need for physical soundcards and hardware PTT cables. All audio and control signals are handled by SmartSDR DAX and SmartSDR CAT software.

1. Radio Settings (FLEX-8600M)

On the radio’s touchscreen or via SmartSDR for Windows, set up 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 you intend to use.
• RF Power: Set your desired operating power (e.g., 50W-100W).

2. DAX Control Panel Configuration

Open the SmartSDR DAX application on your PC. This must be running 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. We will fine-tune this later to ensure clean audio.

3. SmartSDR CAT (Virtual PTT)

VARA requires a dedicated COM port to trigger PTT.

1. Open the SmartSDR CAT application.
2. Click Add… to create a new virtual port.
3. Set Port Protocol to PTT.
4. Note the COM port number assigned (e.g., COM11). This is what Winlink will use to key the radio.

4. Winlink Express & VARA Settings

Because the Flex uses virtual “cables,” the soundcard selection in VARA must point to the DAX drivers.

VARA HF Soundcard Settings

Inside the VARA HF modem window, go to Settings > SoundCard:

• Input Device: DAX Audio RX 1 (FlexRadio Systems)
• Output Device: DAX Audio TX (FlexRadio Systems)

Winlink Radio Setup

In the Winlink Session window, navigate to Settings > Radio Setup:

• Radio Model: FlexRadio 6000 (This driver works perfectly for the 8000 series)
• I/P Address: 127.0.0.1 (Assuming Winlink is on the same PC as SmartSDR)
• PTT Port: Select the Virtual PTT Port you created in Step 3 (e.g., COM11).

5. Transmit Level & Adaptive Predistortion (APD)

The 8600M features Adaptive Predistortion, which makes your VARA signal exceptionally clean.

1. Monitor the Level: In SmartSDR, look at the TX Level Meter (in the DAX/TX panel).
2. Click 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 0dB point.
4. ALC Check: Unlike Yaesu/Icom, Flex handles ALC digitally. Ensure the “level” indicator in SmartSDR remains in the solid green zone. If it hits the red, you are over-driving the digital buffer.

Troubleshooting: “No TX Audio”

The Problem: The radio keys up (red TX light on), but no power is output. The Solution: 1. Check the DAX button on the SmartSDR transmit panel. It must be highlighted (active) for the radio to “listen” to the DAX TX stream. 2. Verify that the DAX Control Panel shows the TX stream as “Active” during the transmission.