Feature request: manual notch filters #11
Description
Following Russ's example, add manual notch filters as an alternative to autonotch:
https://groups.io/g/SoftwareControlledHamRadio/message/35544
The notch button could cycle through three options: no notch, autonotch, and manual notch. In manual notch, a line would be displayed on the audio spectrum showing the location of the notch. The location of the notch would be changed by turning the filter knob.