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Version: 26.10.1

TNF (Tracking Notch Filters)

Status

Status: Supported · Applies to: FlexRadio, Hermes-Lite 2 (experimental)

Tracking Notch Filters remove persistent interfering carriers from the audio passband. A notch stays on its frequency as you tune, so it keeps removing the same interferer.

Using TNFs​

Creating a TNF​

  • Right-click on the spectrum or waterfall → Add TNF at XX.XXX MHz
  • Or click +TNF in the panadapter's overlay menu (creates a TNF at the current frequency)
  • The TNF appears as a shaded region on the spectrum and waterfall

The Add TNF entry is absent on a radio with no notch engine, and once the radio has as many notches as it supports.

Managing TNFs​

Hover a TNF marker for a tooltip with its depth and whether it is permanent. Right-click it for a menu headed by its frequency and width.

Move and resize​

  • Drag the marker horizontally to move it
  • Drag vertically to change its width

Width and Depth​

  • Right-click → Width: 50, 100, 200 or 500 Hz (only the widths the radio can actually produce are listed)
  • Right-click → Depth: Normal, Deep or Very Deep (FlexRadio)

Extended TNF​

  • Right-click → Extended TNF extends every notch's band down through the waterfall, the way Extended Passband does for the slice filter. It is a display preference that applies to all notches.

Make Permanent​

  • Right-click → Make Permanent — the radio keeps the TNF across power cycles. Make Temporary reverses it.
  • Permanent TNFs display in green; temporary TNFs in yellow

Remove​

  • Right-click → Remove TNF

Hermes-Lite 2​

The Hermes-Lite 2 supports the same notch gestures: right-click to add, drag to move and resize, right-click to remove. Its notches run on the computer rather than in the radio and keep tracking as you tune. Because the HL2 has no place to store them and its notches are full nulls, the Depth and Make Permanent entries are not offered. A notch (or a very narrow CW filter) lengthens the receive filter slightly, which adds a little audio delay. See Hermes-Lite 2.

Reference​

Permanent vs temporary​

TypeColourSurvives rebootDefault
TemporaryYellowNoYes
PermanentGreenYesNo

TNF removal and permanent-state changes are applied straight away in the display; the radio does not send a status confirmation for these commands.

Troubleshooting​

Add TNF is missing from the menu​

The radio has no notch engine, or it already holds as many notches as it supports.

  1. Remove a notch you no longer need (right-click it → Remove TNF), then try again.
  2. If the entry never appears, your radio doesn't offer notches. TNFs work on FlexRadio and Hermes-Lite 2.

My notches disappeared after the radio restarted​

They were temporary (yellow). Temporary notches don't survive a power cycle.

  1. Add the notch again.
  2. Right-click it and choose Make Permanent. It turns green.

See also​