Paul, I use MixW for most digital modes and SpectroGram for general
spectral estimation. I have found that I can readily see a 10 Hz change in
frequency on the waterfall under steady state conditions. When I get out to
the shack tonight, I try to do a rapid 10 Hz up and back down change and
see what shows up.
One critical factor to all this, of course, in addition to the soundcard
sampling rate is the waterfall speed. I speed up the normal MixW waterfall
by a factor of eight, and it is surprising how much more detail you can see
in a PSK31 signal. Virtually every keystroke from a slow enough operator
can be viewed.
So, the microchirp detection by waterfall should use the highest possible
sampling rate and the highest possible waterfall speed. I'll try all that
tonight and let you know how it works out here. YMMV . . .
72/73/oo, George W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
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Paul Christensen wrote:
> In theory, I believe that some of the sound card analysis programs can work,
> but I'm not sure if they sample fast enough to detect
> the change in pitch...although we're probably speaking of less than 50-100 mS
> for detecting the duration of a "microchirp." Seems
> like any PC should be fast enough, but I just don't know if enough will be
> captured to the screen. The PSK31 "waterfall" displays
> look like the trick because a pitch shift should be seen by a horizontally
> shifted waterfall line. However, I haven't seen anything
> out there that will give accurate results in a small enough pitch shift
> window like 10-50 Hz.
> I use a Fast Fourier Transform (FFT) program called SpectraPlus for my Hi-Fi
> SSB work. The resolution down at the low end of the
> audio spectrum is good but the FFT sample size at low frequencies must be
> very large in order to offer enough resolution to see
> small pitch changes. On the high end of the audio spectrum, the FFT size can
> be made smaller, but then resolution is lost because
> of the display's semi-log scale. I may experiment with it this weekend.
> -Paul, W9AC