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FFT Graph

FREQUENCY-TIME-POWER GRAPH

Here is where you can observe the graphical representation of the fast fourier transforms as they are calculated. Frequency runs along the horizontal x-axis, power along the vertical y-axis and time along the in/out z-axis. Here you may note the difference between the different frequency resolution FFT's. For a resolution of 0.075 Hz you will notice that we only do 8 FFT's to cover our 107 seconds of data. This will look different than the 0.14 Hz resolution where we do 16 FFT's. Everytime we reduce the frequency resolution by 1/2 (doubling the bandwidth) we get twice the time resolution (we do twice the number of FFT's). At the final resolution of 1200 Hz, we get a time resolution of 0.008192 seconds which also means that we do a total of 131,072 FFT's just for this one graph! This allows detection of fairly short pulses, but the frequency measurement cannot be as precise, and the sensitivity to find continuous signals is reduced.

The colors you see in the graph signify absolutely nothing. They were used only for aesthetic purposes. We hope you enjoy them as much as we do.

A significant extraterrestrial signal may not be visible in this graph as it may be masked by all the natural noise around it. So, if you see something, don't get overly excited, it's probably just a strong source somewhere local, or a satellite passing overhead. On the average we look at the same part of the sky every 3 to 6 months, so it will get re-checked at that time for the same strong signal.

See the section on RFI (Radio Frequency Interference ) for more details.


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