The diff shows internal implementation details of the SWR sweep feature (rendering code, helper methods) that was already documented in the current page. The catalog entry shows VfoPos struct with no controls. Neither introduces any new user-visible behaviour beyond what is already documented in the current page.

Understanding Slices and VFOs¶

In AetherSDR, a slice is an independent receiver within a panadapter. Each slice has its own VFO frequency, mode, filter, and audio settings. The FLEX-8600 supports up to eight simultaneous slices (labeled A through H), letting you monitor multiple frequencies at once within the same or different panadapters.

Before you start¶

AetherSDR must be connected to a FLEX-8600 radio. Slices only exist when a radio connection is active.
The RX Controls applet must be visible. If it is not, click the RX tray button on the right sidebar.

How slices work¶

Each slice is a fully independent receive channel. It has:

A VFO frequency — the center tuning frequency for that slice, shown in the Frequency label in the RX Controls applet.
A mode — USB, LSB, CW, AM, SAM, FM, NFM, DFM, DIGU, DIGL, or RTTY — set with the Mode combo.
A filter passband — adjustable via filter width presets or by dragging the Filter passband widget.
Its own AF gain, AGC, squelch, RIT, and XIT settings.
Assigned RX and TX antennas.

A slice is always bound to a panadapter. The panadapter shows the FFT spectrum for the slice's band segment, and the slice's VFO marker appears as a line on that spectrum.

Slices and the panadapter¶

The panadapter's Spectrum / waterfall display shows the slice's current VFO position. Clicking or dragging on the spectrum tunes the active slice. The panadapter title bar shows which slice is bound to it (for example, Slice A).

In multi-slice mode, each panadapter can contain one or more slice markers. Clicking the spectrum of a different panadapter activates that panadapter and its associated slice.

Switching between slices¶

The RX Controls applet shows a row of tabs labeled A through H (up to the radio's maximum slice count). Click a tab to bind the RX Controls applet to that slice. The Slice badge indicator in the applet updates to show the active slice letter, colored by slice identity.

The tab row is hidden when only one slice is in use.

The TX slice¶

Only one slice transmits at a time. The currently transmitting slice is the TX slice. To make a slice the TX slice, click its TX (badge) button in the RX Controls applet. This routes transmit through that slice's frequency, mode, and TX antenna.

RIT and XIT¶

RIT (Receive Incremental Tuning) offsets the receive frequency without moving the VFO. Enable it with the RIT button; adjust with the RIT offset spinbox (10 Hz steps); reset with RIT 0.

XIT (Transmit Incremental Tuning) offsets the transmit frequency without changing the receive frequency. Enable it with the XIT button; adjust with the XIT offset spinbox (10 Hz steps); reset with XIT 0.

Both are independent per slice.

Locking a slice¶

To prevent accidental retuning, click the 🔓 button in the RX Controls applet. The icon changes to 🔒 and the slice ignores frequency changes until unlocked.

SWR sweep overlay¶

V0.9.4 adds a SWR sweep overlay that draws SWR versus frequency data directly on the panadapter spectrum. When a sweep is active, each data point maps its frequency (in MHz) to a horizontal position on the spectrum and plots the corresponding SWR value as a line overlay. The overlay is drawn on both the GPU-accelerated and software-rendered painting paths.

The overlay has three states:

State	Description	Notes
No data	Overlay is not drawn. Call `clearSwrSweepPoints()` to return to this state.
Sweep in progress	Overlay is drawn and a cursor marks the current sweep frequency. Set `running = true` and supply `currentFreqMhz` when calling `setSwrSweepPoints()`.
Sweep complete	Overlay is drawn without a cursor marker. Set `running = false` when calling `setSwrSweepPoints()`.

An optional source label (for example, the name of the antenna tuner or analyser providing the data) can be passed via the sourceLabel parameter and is displayed on the overlay.

To update the overlay, call setSwrSweepPoints() with a vector of SwrSweepPoint values. Each point carries:

freqMhz — frequency of the measurement, in MHz (default 0.0).
swr — SWR value at that frequency (default 1.0).

Points with non-finite freqMhz or swr values are silently skipped. Points whose mapped x-coordinate falls outside the visible spectrum area are not drawn.

To remove the overlay, call clearSwrSweepPoints().

Tips¶

The Frequency label displays the VFO frequency with dotted grouping (for example, 14.225.000). Click it to enter edit mode and type a frequency in MHz, then press Enter to tune and re-center the panadapter.
The STEP spinbox controls how far the VFO moves per scroll-wheel click or per press of the < / > buttons. Step sizes are per-mode — for example, SSB steps are 1, 10, 50, 100, 500, 1000, 2000, or 3000 Hz; CW steps are 1, 5, 10, 50, 100, 200, or 400 Hz.
The default step size is 100 Hz (index 2 in the per-mode list).
Pressing Escape in the frequency edit field cancels the entry, restores the previous frequency, and dismisses the editor.