Re: [SpectrumLabUsers] Correlogram
- Hello Edgar,
Hi,The amplitude unit is quite arbitrary. Two sinewaves with 0 dBfs and same frequency will correlate with amplitude 1.0 at all time lags where they coincide. The unit is linear. I didn't care much about calibration when I tried the FFT-based correlator algorithm; so the amplitude units may be wrong. Consider them to be 'quite arbitrary' :)
I have been experimenting with the correlogram function in Spectrum Lab.
The signals in a band width of 2 kHz at ~383 kHz were recorded at Sydney (top) and Moonah (bottom), Australia.
The recordings were started at approximately the same time, 9:30 PM.
A signal from non directional beacon WU Wanganui NZL has been passed through a band pass filter.
The process works well.
To learn more about correlogram set-up I have the following questions.
1. How is the amplitude of the correlogram adjusted?
i.e. the range shown as -0.50 to 1.50.
2. In the correlogram waterfall display where do the horizontal bars come from?
Do they represent the coinciding of the signal cycles.
The blue horizontal bar is when the signal cycles match
and the spaces when the signal cycles do not match?
3. When working with the three panes what is the preferred method to select one to change the settings?
4. Are there any functions to return the values from the correlogram so they can be plotted?None .. the correlogram was more or less an experiment which was rarely used (at least afaik..)
The most impressive experiment which I used it for was to measure the distance between the walls in the living room (!), by filling the room with white noise from a loudspeaker, and feeding the signal from a microphone into both channels of the correlator (which effectively turned it into an autocorrelator). The peaks in the correlogram appeared at the distances between the walls, divided by the speed of sound. Oh well, the distance could have been measured much easier :o)
All the best,