Originally Posted by auv-ee
However, I should point out that an uncertain frequency is one problem that can be aided with improved signal processing. In the traditional detector one would make the filter bandwidth wide enough to be sure to include the maximum drift of the signal, thereby including more noise. With DSP techniques, it's easier to simultaneously track multiple narrow bands to find one that has a signal. This is likely part of RR_NDB's point.
The problem with the short ping time is you cannot get the bandwidth down very far or you attenuate signal energy along with noise energy. The signal energy is coherent and the noise energy is not. So increased averaging times decreases your ability to detect the signal once you hit the threshold. Filter ringing, as it is called, screws you if you try really narrow bandwidths.
Um, and the oscillator chirp and drift mean you cannot use coherency tricks.
{^_^}