ATU Pre-Tune overview¶
Run an automatic sweep across selected HF and 6m bands, triggering the radio's built-in ATU (Antenna Tuning Unit) at each center frequency. This ensures your tuner has a valid tuning solution stored for every band you plan to use, reducing the chance of high SWR when you change frequencies during an operating session.
How it works¶
The ATU Pre-Tune feature steps the active TX slice through a calculated set of center frequencies across the bands you select. At each frequency, AetherSDR sends an atu start command to the radio and waits for the radio to report completion (via atuStateChanged) before moving to the next point. Band edges are taken from the active region's band plan so the sweep stays within legal and practical frequency limits.
Before you start¶
- A radio must be connected. The Pre-Tune dialog requires an active radio connection to send ATU commands.
- The radio must have an internal or external ATU available and functional.
Opening the dialog¶
- Menu path:
Settings > TX Band Settings...then select the ATU Pre-Tune tab. - Alternative: Right-click the Tuner applet in the Applet Panel and choose ATU Pre-Tune from the context menu.
What each control does¶
| Control | Type | Behavior |
|---|---|---|
| Band selection | Combo box | Selects which HF/6m bands to include in the pre-tune sweep. Band edges follow the active region's band plan. |
| Start Sweep | Push button | Begins the ATU pre-tune sweep. Steps through each selected band's center frequencies and triggers ATU tuning at each point. |
| Mode: | Combo box | Selects Step mode (per-point confirmation via Tune/Skip buttons) or Auto mode (unattended sweep through all points). New in v26.5.2.1 (#2624). Auto mode triggers additional warnings for high power and high point counts. |
| License class: | Combo box | Data-driven from active bandplan's optional license_classes block. Filters out sub-bands the operator's class does not authorise. Hidden when the active plan has no class structure. Setting key: OperatorLicenseClass. New in v26.5.3 (#2649 #8). Includes 'All classes (no filter)' safety floor. ARRL US bandplan ships with {T, G, E} classes. |
| Band selection checkboxes | Per-band checkboxes to include bands in the sweep (160m through 6m). Band edges follow the active region's band plan. | New in v26.5.2.1 (#2624). Per-band info labels show point count, low/high frequency range, and license class filter status. |
| Disclaimer | Rich-text operator-responsibility warning: transmissions must not interfere with other traffic; operator is responsible for license compliance and local regulations. | Always visible in config page. Orange background (#2a1a10). |
| Cancel | Push button | Closes the dialog without starting a sweep. |
| START | Push button | Begins the ATU pre-tune sweep. In Auto mode, shows max-points warning if >100 points are planned and high-power warning if tune power exceeds 20 W. Steps through each selected band's center frequencies and triggers ATU tuning at each point. Sends atuStart commands to the radio's TransmitModel and waits for atuStateChanged. 30 s per-point timeout with audible beep. 3 consecutive fail-bypass on a band triggers per-band early exit (#3063). Max-points soft cap at 100 (#2649 #4). High-power warning at 20 W (#2649 #5). |
| Tune this frequency | Push button | Step mode only: triggers ATU tuning at the current sweep point. |
| Skip | Push button | Step mode only: skips the current point and moves to the next. |
| Continue | Push button | After a TUNE_FAIL_BYPASS result, allows continuing the sweep instead of aborting. Hidden by default. New in v26.5.3. |
| ABORT / Close | Push button | During sweep: aborts the current sweep. After sweep completes or aborts: closes the dialog. Label changes to 'Close' when sweep finishes. |
| Sweep status / progress / result | Indicator | Live status text showing current band, frequency, progress, and per-point SWR result. Post-sweep shows summary: success/fail/abort counts and per-band early-exit notes. |
| ## Theme support |
Starting with v26.6.1, all text labels in the ATU Pre-Tune dialog use theme-aware color tokens. Colors adapt automatically to the selected theme, replacing previous hardcoded hex values. The dialog container uses the theme key dialog/atuPreTune.
Troubleshooting¶
- Sweep does not start — Ensure a radio is connected and the active TX slice exists. The dialog requires an active radio connection.
- ATU fails on some frequencies — The radio's ATU may be unable to find a match on certain bands or antenna configurations. Verify your antenna is resonating reasonably on the chosen bands.