Skip to content

Change the HP/LP filter family (Butterworth, Chebyshev, Bessel, Elliptic)

The Filter family selector controls the mathematics used for HP and LP filter bands in the client EQ. Changing it lets you trade off rolloff steepness, passband flatness, and phase linearity to suit your audio goals.

Before you start

Steps

  1. Open the floating editor for the path you want to change — double-click the EQ stage in the CHAIN widget on the TX or RX side. The window title will read "Aetherial Parametric EQ — TX" or "Aetherial Parametric EQ — RX".
  2. Locate the Filter family combo box in the editor header strip, to the right of the Peak Hold button.
  3. Click the combo box and select one of the four options: Butterworth, Chebyshev, Bessel, or Elliptic.
  4. The EQ curve on the canvas updates immediately. If HP or LP bands are present, their slopes will redraw to reflect the new family.

The selection is saved automatically. It is stored separately for each path: ClientEqTxFilterFamily for the TX editor and ClientEqRxFilterFamily for the RX editor.

What each control does

Control Default Valid values
Filter family (TX editor) Butterworth Butterworth, Chebyshev, Bessel, Elliptic
Filter family (RX editor) Butterworth Butterworth, Chebyshev, Bessel, Elliptic
Smoothing Off (1/96) Off (1/96) | 1/24 | 1/12 | ⅙ | ⅓
Peak Hold unchecked checked / unchecked
Filter-type icon row A row of 8 custom-painted icons (one per band slot) at the top of the editor canvas area. Each icon draws the current filter shape (peak bell, shelf ramp, HP/LP slope) in its band's palette colour. Click an icon to cycle through the filter types for that band; clicking also selects the band, highlighting its handle on the canvas and its column in the parameter row. Located in the floating editor only. Icons dim to 35 % opacity when the band is bypassed. Implemented by ClientEqIconRow.
Parameter text row A row of 8 text columns (one per band slot) below the canvas showing each band's Freq, Gain, and Q values. Values update live during canvas drags. Clicking a column selects that band. Right-click a column to open a context menu for numeric entry of Freq, Gain, or Q. Located in the floating editor only. Implemented by ClientEqParamRow.
Filter cutoff guide lines (TX / RX) Dashed yellow vertical lines overlaid on the canvas at the radio's current TX low/high filter cutoff (TX tile) or RX passband edges (RX tile). Hovering near a line changes the cursor to a horizontal-resize arrow. Dragging a line in the editor moves the radio's corresponding filter cutoff in real time. Dragging the TX cutoff guides emits cutoffsDragRequested(Tx, lo, hi), which MainWindow forwards to TransmitModel. Dragging the RX guides writes to the active SliceModel. Pass 0 for an edge to suppress that guide.
Output Fader 0 dB (linear 1.0) -36.0 to +12.0 dB
Reference curve Off Off | AT&T 1959 | Heil DX | Astatic D-104 | Shure 444 | Heil HC-5

Smoothing — Applies fractional-octave power-averaging to the analyzer trace for display — does not affect EQ math. Lower fraction = smoother (⅓ is most smoothed; 1/96 is effectively off). Shared between TX and RX editors. Tooltip: 'Fractional-octave smoothing applied to the analyzer trace. Lower fraction = smoother (⅓ = most, 1/96 = off). Affects display only — EQ math is unchanged.' Located in the editor header strip (floating editor only).

Peak Hold — When checked, the per-bin peak-hold trace in the analyzer stops decaying — every frequency's highest observed level is held until the button is toggled off. Located in the editor header strip (floating editor only, not the docked applet tile). Amber background when checked.

Output Fader — Vertical combined fader + level meter on the right edge of the floating editor. Drag to set post-EQ master gain; scroll wheel adjusts in 0.5 dB steps; double-click resets to 0 dB. The level bar behind the handle shows the smoothed post-EQ peak in real time with the same green-amber-red gradient as the Tube level meter. Click the dB readout at the bottom to enter a value directly via keyboard. Persisted separately per path: ClientEqTxMasterGain / ClientEqRxMasterGain. Tooltip: 'Output gain (dB). Drag to set, wheel for fine step, double-click to reset to 0 dB.' Gain range is linear 0.0 to ~4.0; the scale labels run from -40 to 0 dB. Located in the floating editor only — not in the docked applet tile.

Reference curve — Overlays a semi-transparent amber target curve on the EQ canvas, showing the frequency response of a classic microphone or recommended speech contour. Use this visual target as a guide when shaping your parametric EQ bands. Available in the floating editor header strip. Options: Off, AT&T 1959 (Bell Labs optimum transmission response for speech, +5 dB peak at 2.5 kHz), Heil DX (Bob Heil's recommended pile-up talk power curve, +6 dB at 2.7 kHz), Astatic D-104 (classic crystal lollipop mic response, peaky presence around 3 kHz), Shure 444 (classic broadcast desk mic, gentler presence boost), Heil HC-5 (modern dynamic SSB mic target, +6 dB at 2.5 kHz). The curve is for visual reference only — it does not apply any filtering to the audio. Stored in settings key ClientEqTxReferenceCurve / ClientEqRxReferenceCurve.

Butterworth — maximally flat passband; no ripple in the passband or stopband. The default choice for general use.

Chebyshev — steeper transition band than Butterworth, with 1 dB of ripple in the passband.

Bessel — linear phase response and the gentlest rolloff of the four families. Preserves transient shape.

Elliptic — steepest transition of all four options, with ripple in both the passband and the stopband.

These options apply only to HP and LP band types. Peak and shelf bands use their own fixed second-order topology regardless of this setting.

Tips

  • If you have no HP or LP bands in the current EQ, switching the filter family changes nothing audible. Add an HP or LP band first via the filter-type icon row.
  • The filter family is set independently for TX and RX. Changing it in the TX editor does not affect the RX editor, and vice versa.
  • Clicking Reset in the editor header strip resets the filter family back to Butterworth along with all band parameters.
  • To enter exact frequency, gain, or Q values for a band, right-click its column in the parameter text row and choose the parameter you want to edit from the context menu. After typing a value and pressing Enter, the change is saved and the EQ curve redraws immediately.
  • Use the Reference curve to visually match your parametric EQ to a classic microphone response. Select from the dropdown in the editor header strip. The overlay does not affect audio — it is a visual guide only.
  • The reference curve is stored separately for TX and RX. Change it independently for each path.

Troubleshooting

  • The Filter family combo is not visible — The combo is only present in the floating editor, not the docked applet tile. Double-click the EQ stage in the CHAIN widget to open the editor.
  • Changing the family has no effect on the curve — No HP or LP bands are active. The setting only affects HP and LP cascade math. Check each band's type using the filter-type icon row.
  • The parameter text row appears to overlap the band-plan strip — This was a display issue in versions before v0.9.7 where the row's dark background bled upward over the canvas. Update to v0.9.7 or later; the row is now transparent and its labels are bottom-aligned within each column.
  • The Output Fader dB readout doesn't accept typed values — Click the readout at the bottom of the fader to focus it, then type a value (e.g. "-6.5") and press Enter. Press Escape to cancel editing and revert to the previous value.
⚡ Athena AetherSDR Assistant
Hi! I'm Athena, the AetherSDR AI assistant. Ask me anything about installation, configuration, or troubleshooting.