What problem can occur when using an automatic notch filter (ANF) to remove interfering carriers while receiving CW signals?

An Automatic Notch Filter (ANF) uses digital signal processing algorithms to identify and eliminate steady, continuous tones (carriers) that appear in the receiver's passband. This is incredibly useful for suppressing annoying heterodyne squeals during voice (SSB) communications. However, Continuous Wave (CW) signals are essentially just intermittent continuous carriers. If the ANF is active while you are listening to Morse code, the algorithm may misidentify the steady tone of the desired CW signal as an interfering carrier. As a result, the ANF will quickly attempt to "notch out" or suppress the very CW signal you are trying to copy, making it disappear along with the noise. Because of this, ANF should generally be turned off when operating CW.