Start a tune carrier to check SWR

Send a continuous carrier at reduced power to read SWR on your antenna system. Use this before a QSO or after changing antennas to confirm a good match.

Before you start

• AetherSDR must be connected to the radio. The TX Controls applet is only active with a live radio connection.
• Make sure you are clear to transmit on the frequency (the band must be open to your station legally).
• Set the tune power to a level appropriate for your antenna system. The default is 10; see Set tune-carrier power.

Steps

1. Click the TX tray button in the right sidebar to open the TX Controls applet if it is not already visible.
2. Check the Tune Pwr slider. The default is 10 (out of 100). Adjust if needed before transmitting.
3. Right-click the TUNE button to select the carrier shape for the next tune cycle. Choose Mono Tone or Two Tone from the context menu. The radio's tune mode is a transient one-shot — AetherSDR does not persist the choice.
4. Click TUNE.
5. The button label changes to TUNING... and the button background turns red while the carrier is active.
6. The SWR gauge updates in real time. The scale runs from 1.0 to 3.0; readings above 2.5 are shown in red.
7. The RF Pwr gauge shows forward power at the exciter output. A peak-hold bar tracks the peak envelope power (PEP) for 2 seconds, then decays toward the current reading.
8. Read the SWR value from the SWR gauge.
9. Click TUNE again to stop the carrier.
10. The button label returns to TUNE and the red background clears.

What each control does

Control	Kind	Default
TUNE	Push button	—
Tune Pwr	Slider	10
RF Pwr	Meter	—
SWR	Meter	—
RF Power	Slider	100
TX Profile	Combo box	—
MOX	Toggle button	—
ATU	Push button	—
MEM	Toggle button	—
APD	Toggle button	—
## Tips

• Keep Tune Pwr low (10 or less) when testing an unknown antenna system. Raise it only after confirming a reasonable SWR.
• The SWR gauge turns red above 2.5. If it pegs at 3.0, stop the carrier and check your feedline and antenna connections before continuing.
• To run the internal ATU instead of checking SWR manually, click ATU after the tune carrier confirms the antenna is usable. See Run the internal ATU.
• If you want to inhibit specific TX outputs (ACC TX, TX1, TX2, TX3) during tuning, configure them at Settings > Inhibit during TUNE.
• The peak-hold bar on the RF Pwr gauge resets to zero immediately when the transmitter un-keys, so a held PEP reading does not linger across overs.

ATU button behavior

Starting with v0.9.5.1, the ATU button behaves as a frequency-aware toggle rather than always starting a new tune cycle. The logic mirrors SmartSDR's per-frequency behavior:

• First click (or after a frequency change) — Starts a fresh ATU tune cycle.
• Second click at the same frequency — If the ATU has already reported a successful match (Success or Mem indicator lit) and the transmit frequency has not changed since that tune, clicking ATU switches the tuner to bypass instead of starting another cycle.
• After any frequency change — The saved tune frequency is cleared. The next ATU click always starts a fresh tune cycle, even if the previous result was successful.

When the ATU enters bypass, the tuned-frequency record is also cleared, so the next click will start a fresh tune regardless of frequency.

This change has no effect on the MEM button or the ATU status indicators (Success, Byp, Mem), which continue to behave as described below.

ATU right-click menu

Right-click the ATU button to access the following actions:

• Pre-tune bands… — Opens the Pre-Tune Bands dialog to run a sweep across selected bands. This action is only available when MEM is enabled (the MEM button must be engaged). If MEM is off, the menu item is disabled with a tooltip explaining that MEM must be enabled first.
• Clear ATU memories… — Prompts for confirmation and then clears all stored ATU memories.

This matches SmartSDR Windows's hidden right-click menu on the ATU button.

MOX and Quindar tones

Starting with v0.9.7, clicking MOX routes through the Quindar-tone coordinator rather than keying the transmitter directly. When the QUIN chip is enabled in the Audio Channel Strip and the active TX slice is on a phone mode, the K-tone plays on PTT engage and the BK-tone plays on PTT disengage. When Quindar is disabled or the active TX slice is not on a phone mode, the behavior is identical to previous versions.

This change affects only the MOX button in the TX Controls applet. Hardware PTT, VOX, and other PTT sources are not affected.

Slider value display

Starting with v26.5.3, when dragging the RF Pwr or Tune Pwr slider, the slider thumb displays the current value in percent (e.g., "50%") as a tooltip next to the thumb. This provides immediate visual feedback of the power level as you adjust the slider.

APD status indicators

The APD button cluster shows three indicators that track the adaptive pre-distortion state:

Indicator	Color when lit	Meaning
Cal	Green	APD is on and actively calibrating.
Avail	Green	APD is on and a calibration result is available but not yet applied.
Active	Green	APD is on and the equalizer is actively being applied.

The typical progression is: Cal (calibrating) → Avail (ready) → Active (applied). All indicators are dim when APD is off.

Troubleshooting

• TUNE button does nothing — The applet requires an active radio connection. Check that AetherSDR shows the radio as connected before attempting to transmit.
• SWR gauge does not move during TUNE — Forward power may be at or near zero. Verify the Tune Pwr slider is above 0 and that the correct antenna port is selected for the current band.
• Carrier does not stop — Click TUNE once more. If the button remains in TUNING... state, check the radio connection; a dropped connection can leave the transmit state unacknowledged.
• ATU button bypasses the tuner instead of retuning — This is expected behavior when the ATU already holds a successful match at the current frequency. Change frequency or wait for the tuner to clear its result, then click ATU again to start a fresh tune cycle.
• MOX keys the transmitter but no Quindar tones are heard — Confirm that the QUIN chip is enabled in the Audio Channel Strip and that the active TX slice is set to a phone mode (USB, LSB, AM, FM, or similar). Quindar tones do not play on CW or digital modes.
• Pre-tune bands menu item is grayed out — Enable MEM by clicking the MEM button in the TX Controls applet before right-clicking ATU.
• Peak-hold bar does not appear during tune — The peak-hold bar only tracks when the transmitter is keyed. The bar decays after 2 seconds of holding a peak, and resets to zero on un-key.

Related

• Set tune-carrier power
• Run the internal ATU
• Pre-tune bands
• Clear ATU memories
• Recall an ATU memory
• Set RF output power
• Toggle MOX to manually key the transmitter