Work an FM repeater with CTCSS tone and ± offset¶

Configure a slice for FM duplex operation with a repeater offset and a CTCSS access tone so you can both hear the repeater output and key it correctly on transmit.

Before you start¶

AetherSDR is connected to your FLEX-8600.
The RX Controls applet is visible in the right sidebar. If it is not, click the RX tray button on the right sidebar.
You know the repeater's output frequency, offset direction, offset magnitude, and CTCSS tone frequency.

Steps¶

In the RX Controls applet, click the Mode combo and select FM (or NFM for narrow FM).
Click the Frequency label to open the Frequency edit field. Type the repeater's output (receive) frequency in MHz and press Enter.
In the Offset (FM) spinbox, set the offset magnitude in MHz. Use the spinbox arrows or type a value directly. Valid range is 0.0–100.0 MHz in 0.1 MHz steps. The default is 0.0 MHz.
Set the offset direction by clicking one of the three toggle buttons:
− — TX frequency is below the RX frequency.
Simplex — TX frequency equals the RX frequency (default).
+ — TX frequency is above the RX frequency.
Click the Tone mode (FM) combo (default: Off) and select CTCSS TX.
Click the CTCSS tone value combo and select the tone frequency required by the repeater. The available tones include the standard EIA/TIA-603 tone set (67.0 Hz to 254.1 Hz), plus the non-standard 69.3 Hz, 159.8 Hz, 165.5 Hz, 171.3 Hz, 177.3 Hz, 183.5 Hz, 189.9 Hz, 196.6 Hz, and 199.5 Hz tones that some repeaters use.
Confirm the squelch is set appropriately for the band. See Turn on the squelch and set its threshold if needed.

What each control does¶

Control	Default	Valid range / options
Mode combo	Sets slice mode; reshapes filter and step presets for the new mode.	RADE option requires HAVE_RADE build flag. DSTR and FreeDV modes are filtered out when the model doesn't support them. Selecting a real radio mode tears down a running WFM software-demod overlay (WFM itself is toggled from the VFO-flag WFM button, not this combo).
Tone mode (FM)	Off	Off, CTCSS TX
CTCSS tone value	—	67.0 Hz – 254.1 Hz, including standard EIA/TIA-603 tones plus non-standard 69.3, 159.8, 165.5, 171.3, 177.3, 183.5, 189.9, 196.6, and 199.5 Hz tones
Offset (FM)	0.0 MHz	0.0 – 100.0 MHz, step 0.1
− (offset down)	—	toggle
Simplex	checked	toggle
+ (offset up)	—	toggle
REV / XFC	For FM repeater operation, REV inverts the TX offset sign to work a reversed repeater pair. On backends that support a transmit-frequency check, the button relabels to XFC: pressing it holds the transmit frequency check for the duration of the press, and while held it briefly forces the radio toward the transmit frequency to confirm coverage.	The button toggles REV (checkable) normally, or becomes a momentary XFC down-button when the connected radio backend advertises hasTransmitFrequencyCheck. The held XFC is released on hide, deactivate, capability change, or disconnect.
SQL / AUTO	Three-way cycle button: each click steps Off → SQL (manual threshold) → AUTO (algorithm tracks the noise floor) → Off. In AUTO mode the button shows amber 'AUTO'; in manual mode green 'SQL'. Disabled (and auto-turned off) in RTTY and digital modes (DIGU, DIGL) where squelch would notch out FSK characters (#2504).	Manual and Auto both turn the radio squelch on. The auto-squelch algorithm lives in the panadapter; the level is the dB margin above the measured noise floor. Mirrored by an identical button in the VFO panel's Audio tab.
Mute	🔊 (unmuted)	Toggle button. Single-click mutes/unmutes this slice; double-click mutes/unmutes all owned slices. Icon updates only when the radio acknowledges.

Tips¶

If you need to listen on the repeater's input frequency to check whether the channel is busy before transmitting, click REV to swap the offset direction temporarily.
FM family modes hide the filter width preset buttons. This is expected; filter width for FM is fixed by the mode itself.
Slice tab buttons and the slice badge are color-coded per slice using SliceColorManager (v0.9.3+). The colors persist across sessions and are reflected in the slice tabs, the slice badge, VFO widgets, and meter strips.
When the radio reports a different number of available slices than the tab row was built for, AetherSDR now tears down the existing slice tab buttons and rebuilds them for the new count before reconnecting click handlers (v0.9.5.1, #2254). This prevents stale buttons appearing after a reconnect or a change in hardware configuration.
Filter width presets are stored in the format lo:hi (passband edges in Hz) or as a plain width value, depending on whether the preset was saved with explicit edge positions. Both formats are read correctly when you reopen the applet or switch modes (#2259).
The filter width readout is shared with the VFO panel via RxApplet::formatFilterWidth(). In v0.9.8+, this method is now a public static function so both widgets produce identical, mode-aware formatting for SSB, digital, and AM modes (#2197).
The widen/narrow shortcuts (e.g. Ctrl+Shift+W, Ctrl+Shift+N) call stepFilterWidth(int direction), which walks the per-mode filter preset list to find the next valid width and applies it with correct edge geometry for the current mode (#2208). As of v26.8.4, CW mode detection uses a single shared isCwMode() helper across all CW variants (CW, CWL, CWU) rather than separate mode strings.
The slice badge now supports rich text formatting (HTML) for the slice letter display (#2606).
Antenna selection for both RX and TX now prioritizes the slice's own antenna list when available. The menu shows antenna labels with tooltips and status tips, with actual antenna data stored separately from display text. TX antenna menus filter out ports with the "RX" prefix and include only antennas matching patterns like "ANT", "TX", or "XVTR".
The mute button uses a deferred single-click mechanism to avoid conflicts with double-click actions. A single-click mutes or unmutes the current slice. A double-click mutes or unmutes all owned slices. The icon updates only when the radio acknowledges the mute state change, ensuring the displayed state always matches the radio's actual state. Per the Radio-Authoritative Settings Policy (#2489), mute state is not saved or restored on reconnect — the radio is the source of truth.
The AGC Threshold slider has a right-click context menu. Right-click the slider and select Calibrate AGC-T against noise floor… to open the AGC-T noise calibration panel. The tooltip also advertises this feature.
When entering a frequency in the Frequency edit field, AetherSDR uses FrequencyEntryParser to normalize the input. If you type a value above 54 MHz without being on an XVTR antenna, the parser checks whether it was entered as an explicit MHz value. If so, the maximum allowed frequency is raised to 50000 MHz, allowing entry of VHF/UHF frequencies above the normal 54 MHz limit without switching to an XVTR antenna first (e.g., typing 146.520 MHz on a non-XVTR antenna).
The offset direction buttons and REV button are part of an exclusive button group; selecting one automatically deselects the others.
The L/R pan slider now paints its fill from the centre outward. This provides a visual indication of the neutral (centre) position at a glance. The centre mark is a small dot painted on the groove.
The filter preset buttons and other styled buttons now use tokenised stylesheet colours through ThemeManager. This means the button appearance updates automatically when you switch themes, consistent with the rest of the UI (v26.6.1).
The RX antenna menu now includes virtual antenna tokens from the KiwiSDR when a KiwiSDR manager is active. Tokens are appended to the options list and are not duplicates of existing physical antennas. Selecting a virtual antenna triggers a kiwiRxAntennaSelected signal instead of calling setRxAntenna directly (#2781).
The RX antenna menu is rebuilt as a popup menu rather than an inline menu. The menu is deleted automatically when hidden (#2781).
Squelch threshold is radio-authoritative. The previous client-side persistence of the manual squelch level in LastManualSquelchLevel has been removed. The manual squelch level always comes from the radio, and the client-side fallback value is only used briefly when no slice is attached (v26.8.4, #4592).
The CTCSS tone list now includes the non-standard tones 69.3, 159.8, 165.5, 171.3, 177.3, 183.5, 189.9, 196.6, and 199.5 Hz. These are listed without EIA designations (showing only the frequency) to distinguish them from the standard 41-tone set.

Troubleshooting¶

Repeater does not respond to your transmissions — Confirm the CTCSS tone value matches what the repeater expects, and that Tone mode is set to CTCSS TX rather than Off.
TX frequency appears wrong — Check that the offset direction button (−, Simplex, or +) matches the repeater's published offset direction, and that the Offset (FM) value is set to the correct magnitude (e.g. 0.6 MHz for a typical 2 m repeater).
Tone mode and CTCSS controls are not visible — The slice mode must be FM, NFM, or DFM. These controls are hidden in all other modes.
Squelch controls are greyed out — Squelch is disabled automatically when the slice mode is DIGU, DIGL, NT, RTTY, CW, or CWL. Switch to an FM or SSB mode to enable the squelch controls.
Repeater requires a non-standard CTCSS tone — Check if the tone is one of the non-standard frequencies (69.3, 159.8, 165.5, 171.3, 177.3, 183.5, 189.9, 196.6, or 199.5 Hz). These are listed with only the frequency value in the CTCSS tone combo box, without an EIA designation.
Slice tab buttons appear incorrect after reconnecting — If the slice tab row shows the wrong number of buttons or a stale layout after the radio reconnects, disconnect and reconnect manually. In v0.9.5.1 this is corrected automatically: the applet calls clearSliceButtons() to remove the old buttons and restore the static slice badge before rebuilding the tab row for the new slice count (#2254).
Filter preset button does not change passband — If the current width is not a standard preset value, the widen/narrow step may not change the passband. This is expected behavior; click a specific filter preset button or type a frequency to change the passband, then the widen/narrow shortcuts will work from the new width.
Mute icon does not change on click — The mute icon is updated only when the radio acknowledges the mute state change. If the icon does not change, the radio may not have confirmed the new state. This is expected per the Radio-Authoritative Settings Policy (#2489).
Frequency edit field does not accept typed input — The frequency edit field now uses FreqLineEdit which provides a hint label "MHz" instead of placeholder text. Click the frequency label to enter edit mode, type the frequency in MHz, and press Enter to apply.
Manual squelch level is not remembered between sessions — As of v26.8.4, the manual squelch threshold is radio-authoritative and is not persisted client-side. The radio maintains the per-slice squelch level. When no slice is attached, the client uses a fallback value of 20.

NT mode and RTTY mode notes¶

The NT and RTTY modes are treated as digital modes in the RX Controls applet (v0.9.3+ for NT, v26.5.1 for RTTY). This has the following effects:

NT