Enable APD to Linearise the Transmitter

APD (Adaptive Pre-Distortion) reduces transmitter non-linearity by applying a correction equaliser to the signal before it reaches the PA. Enable it to improve spectral purity, particularly on SSB and digital modes.

Before you start

• AetherSDR must be connected to the radio. APD is a radio-side function and requires an active connection.
• Open the TX Controls applet. If it is not visible, click the TX tray button on the right sidebar.

Steps

1. Locate the APD button at the bottom of the TX Controls applet.
2. Click APD to toggle adaptive pre-distortion on. The button background changes to green when enabled.
3. Watch the status indicators to the right of the button:
4. Cal lights green while the radio is collecting calibration data.
5. Avail lights green when a calibration is complete but not yet applied.
6. Active lights green when the equaliser is applied to the transmit signal.
7. To turn APD off, click APD again. The button returns to its unlit state and all three indicators go dim.

What each control does

Control	Kind	Behavior
APD	Toggle button	Enables or disables adaptive pre-distortion on the radio. Green when on, unlit when off.
Active	Indicator	Lit green when APD is on and the equaliser is actively applied to the signal.
Cal	Indicator	Lit green when APD is on and the radio is still calibrating.
Avail	Indicator	Lit green when APD is on and a calibration is available but not yet applied.

The normal progression after enabling APD is: Cal → Avail → Active.

Tips

• APD calibration takes place automatically after you enable it. You do not need to transmit manually to trigger it; wait for the indicators to step through Cal → Avail → Active.
• If you disable and re-enable APD, the calibration sequence restarts from Cal.

ATU button behaviour

The ATU button uses a per-frequency toggle that mirrors SmartSDR behaviour:

• First click (or any click after a frequency change): starts a new ATU tune cycle.
• Second click at the same frequency, when the ATU reports a successful match: switches the tuner to bypass.
• Click after any frequency change: always starts a fresh tune cycle, even if the previous status was successful.

The bypass state is cleared automatically when the transmit frequency changes, so the next click will start a new tune rather than bypassing. There is no change to the ATU button label or appearance; the Success, Byp, and Mem indicators below the button continue to reflect ATU status as before.

Indicator	Kind	Behavior
Success	Indicator	Lights green when the ATU reports a successful or OK match.
Byp	Indicator	Lights orange when the ATU is in bypass or manual bypass.
Mem	Indicator	Lights green when the ATU is using a stored memory.

ATU right-click menu

Right-click the ATU button to open a context menu with two actions:

Action	Behavior
Pre-tune bands…	Opens the ATU Pre-Tune dialog to sweep and store tuner settings across bands. Enabled only when MEM is on.
Clear ATU memories…	Clears all stored ATU memories on the radio. A confirmation dialog appears before clearing.

TUNE button behaviour

Click TUNE to start or stop a tune carrier. The button label changes to TUNING... with a red background while the carrier is active.

TUNE right-click menu

Right-click the TUNE button to choose the carrier shape for the next tune cycle:

Action	Behavior
Mono Tone	Sets the tune carrier to a single tone. Checked if this is the current mode.
Two Tone	Sets the tune carrier to two tones. Checked if this is the current mode.

The selection is a one-shot transient — the radio's tune mode reverts to single tone across power cycles. AetherSDR does not persist the choice in AppSettings.

RF Power / Tune Power sliders

Control	Kind	Behavior
RF Power	Slider	Sets the transmit RF power level as a percentage of maximum (0–100%). Default: 100%. During drag, displays the current value as "XX%" above the slider handle.
Tune Pwr	Slider	Sets the tune-carrier power level as a percentage of maximum (0–100%). Default: 10%. During drag, displays the current value as "XX%" above the slider handle.

TX Profile selector

Select a TX profile from the combo box to load it on the radio. Profiles are populated from the radio's profile list.

RF Pwr and SWR meters

Forward power is displayed as a horizontal bar gauge. The scale changes based on the radio model (barefoot 0–120 W, or Aurora 500W 0–600 W). The gauge turns red above 100 W (barefoot) or 500 W (Aurora).

PEP peak-hold: a peak reading is held for 2 seconds, then decays smoothly to the current value. The peak is cleared immediately when the transmitter unkeys to prevent lingering readings across overs.

SWR is displayed as a horizontal bar gauge. Range 1.0–3.0. The gauge turns red above 2.5.

MOX button and Quindar tones

Clicking MOX routes through the Quindar-tone coordinator rather than toggling the transmitter directly. This means:

• Engage (click MOX on): if Quindar is enabled in the Audio Channel Strip and the active TX slice is on a phone mode, the K-tone plays before the transmitter keys.
• Disengage (click MOX off): the BK-tone plays after the transmitter unkeys.
• If Quindar is disabled, or the active TX slice is not on a phone mode, MOX behaves as before and keys the transmitter immediately.

The button appearance is unchanged: the MOX button turns red while the transmitter is keyed and returns to its unlit state when the transmitter is off.

Control	Kind	Behavior
MOX	Toggle button	Toggles manual transmit. Routes through the Quindar-tone coordinator so K/BK tones play on PTT engage/disengage in phone modes when Quindan is enabled. Button goes red while TX is keyed.

ATU MEM button

Control	Kind	Behavior
MEM	Toggle button	Toggles ATU memory recall on/off. Disabled when TGXL is in OPERATE mode.

Theme support

Starting with v26.6.1, the TX Controls applet uses theme-aware colours for all controls and indicators. Slider fill, label colours, and indicator states adapt to the active theme. If you use a custom theme, these controls will respect the applet/tx scope in the theme definition.

Related

• TX Controls overview
• Run a Two-Tone Tune
• Set RF output power