FlexRadio FLEX-6700 firmware v4.2.20

Page 1 | Copyright 2026 FlexRadio, Inc. | SmartSDR v4.2.20 Release Notes | SmartSDR+ v4.2.20 Release Notes Version Release Date Release Theme/Title 4.2.20 2026-06-03 v4.2 new feature access for SmartSDR+ licensed radios.

SmartSDR Basic™ and SmartSDR+™ v4.2.20 is a SmartSDR+ Feature Access software and firmware release for Aurora™, FLEX-8000™, and FLEX-6000™ series SDRs, as well as Maestro™.

This version supersedes all previous SmartSDR releases and is available to all users.

Access to new features in this release is available to all SmartSDR+ feature license holders.

Important Release Information Before upgrading, please review all sections marked as IMPORTANT for upgrade prerequisites and other critical information.

There are multiple important notices associated with SmartSDR v4.2.20.

You should understand these changes before upgrading from a previous version of SmartSDR.

Please open a HelpDesk support ticket if you have questions.

Important Notice: If you are not running SmartSDR v4.2.18, it is highly recommended to uninstall all previous versions of SmartSDR before upgrading to SmartSDR v4.2.20.

If you are running SmartSDR v4.2.18, skip this notice.

Before installing SmartSDR v4.2.​20, it is strongly recommended that all previous versions of SmartSDR be completely uninstalled from your PC, including DAX and the FlexVSP driver.

SmartSDR v4.2.18 introduces a new software architecture that includes updated DAX and FlexVSP drivers.

Retaining older versions on your system may result in installation conflicts or degraded performance.

For best results, ensure all earlier SmartSDR versions (v4.1.5 and below) are fully removed before proceeding with the installation.

Refer to the HelpDesk article “How to Install SmartSDR v4.2.18” for detailed uninstallation and installation instructions.

Just bear in mind that you will be substituting v4.2.20 for v4.2.18 Important Notice: SmartSDR v4.2.20 is a Feature Access Release.

This version of SmartSDR activates the new features included in SmartSDR v4.2.18 for all radios that have a SmartSDR+ Feature license installed.

It also contains bug fixes; it is recommended that all users upgrade to SmartSDR v4.2.20.

For information regarding the new features introduced in SmartSDR v4.2.18, please refer to the SmartSDR v4.2.18 Release Notes.

Remember is it's “best practice” to read the SmartSDR Release Notes before installing a new version.

Important Notice: Upgraded DAX to a completely new audio transfer architecture.

Starting with SmartSDR v4.2.18, the DAX functionality has been completely re-architected and is now called DAXv2.

This update delivers significant architectural improvements, enhanced low-latency performance, and improved compatibility and stability with modern Windows systems.

DAXv2 is available for all users.

In addition, DAXv2 is available as a native x64 and ARM application.

The new DAX driver no longer relies on deferred procedure calls (DPCs) for transferring audio data from the radio to PC applications.

For a complete listing of changes, refer to the HelpDesk article DAX Version 2 - Improvements and Updates.

Important Notice: SmartSDR for Windows utilizes a Microsoft Installer (MSI)–based installation package.

Upgrading to an MSI installer architecture provides a standardized installation environment that can automatically detect and repair missing/corrupted components (“self-healing”) if files go missing.

It will install any needed .NET and system dependency software often without user interaction.

Page 2 | Copyright 2026 FlexRadio, Inc. | SmartSDR v4.2.20 Release Notes | SmartSDR+ v4.2.20 New SmartSDR+ Features: These are the new features introduced in the SmartSDR+ v4.2.18 Early Access release that are now available to all SmartSDR+ Feature License holders.

Feature Description Supported Radio Models

SMART-205

Band Plan/Band Edge Markers: SmartSDR now includes an integrated band plan display feature that provides a visual, color-coded representation of amateur radio frequency allocations based on IARU regional standards, including detailed sub- band information on the panadapter.

This feature gives operators a clear, at-a- glance understanding of band usage recommendations directly within SmartSDR, helping ensure compliant and efficient operation across different international band plans.

Band plans for IARU Region 1, Region 2, and Region 3 can be selected from the panadapter display menu, providing an optional context-aware display based on the selected or active region, showing clearly defined sub-band segments within each amateur band.

The default IARU region is based on the radio’s region setting.

Aurora

FLEX-8000

FLEX-6000

SMART-11334

User Configurable RX Filters: SmartSDR now includes mode-specific, user configurable receive filters, allowing operators to tailor receiver bandwidth characteristics independently for each operating mode.

This enhancement provides greater flexibility and precision in tailoring audio and signal response for different types of operation, such as SSB, CW, AM, FM, and digital modes.

Additional benefits include reducing the need to manually reconfigure filters when changing modes and allowing users to fine-tune receive filter characteristics for contesting, DXing, or digital operation.

Aurora

FLEX-8000

FLEX-6000

SMART-12046

Display TX Filter on Panadapter: SmartSDR now includes an optional feature that displays the transmit filter bandwidth directly on the panadapter, with an additional on-screen overlay indicator.

This allows for real-time tracking of transmit filter bandwidth changes as mode or bandw​idth settings are adjusted.

From an operational standpoint, this feature provides immediate visual confirmation of transmit signal bandwidth, helping operators ensure transmitted energy remains within the ham bands, which is particularly useful when operating near band edges.

Aurora

FLEX-8000

FLEX-6000

Page 3 | Copyright 2026 FlexRadio, Inc. | SmartSDR v4.2.20 Release Notes | SmartSDR Bug Fix Highlights: Below are the bug fixes highlights for SmartSDR v4.2.20.

Some bug fixes may be specific to radio hardware platforms and SmartSDR+ feature license holders.

Please refer to the SmartSDR v4 Changelog for a complete listing of all SmartSDR v4 software and firmware changes.

Feature/Defect Description SMART-12729 Fixed: FDX does not work with single SCU radios.

SMART-12734 Changed default CW Receive Filter presets to 50 Hz, 100 Hz, 250 Hz, 500 Hz, 1 kHz, and 3 kHz.

The 1 kHz and 3 kHz options are now pitch aware.

Reset factory settings after updating to v4.2.19 to expose new default values.

SMART-12738

Fixed receive audio going silent after 30 seconds to 2 minutes of connection to SSDR and Maestro in some setups SMART-12758 Changed default Digital Receive Filter presets to 100 Hz, 300 Hz, 600 Hz, 1 kHz, 3 kHz, 6 kHz. Reset factory settings after updating to v4.2.19 to expose new default values.

SMART-12780

• Fixed Maestro drops remote audio after ~3 min.
• SMART-12747 Mic Gain Slider now adjusts the PC Mic
• SMART-12735 Restored the Offset menu item in the Slice Flag DSP Menu when set to Digital modes

SMART-12536

Fixed an issue where the TGXL Tune command from SmartSDR and API was not triggering Tune

SMART-12748

Fixed an issue with 6000 Series Radios where receive audio would not come back promptly after keying CW with some setups. SMART-12772 XVTR output power now scales with the RF Power setting

SMART-12743

Fixed an issue where the Tune button didn't trigger Tune on some XVTR bands Page 4 | Copyright 2026 FlexRadio, Inc. | SmartSDR v4.2.20 Release Notes | Description of SmartSDR Basic, SmartSDR+, and SmartSDR+ Early Access Feature License Tiers: SmartSDR v4 Basic is available free of charge and includes all bug fixes and select minor feature enhancements for all radio models.

We strongly encourage all customers to upgrade to SmartSDR v4.

If you are currently licensed for SmartSDR v2 and upgrade to SmartSDR v4 Basic, you will receive all prior bug fixes and minor enhancements from a