What tests are being run?

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Tom Mazanec

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Message 1875706 - Posted: 29 Jun 2017, 17:47:19 UTC

I see the tests being flashed on the display as they are run, like "Pulse triplets" or "fast Fourier Transforms" or "Gaussian...something or other" But they are too fast for me to make out.
Can you list the tests and what they are doing?
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rob smithProject Donor
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Message 1875712 - Posted: 29 Jun 2017, 18:24:05 UTC

Fast Fourier Transform is a technique for moving data from the time domain into the frequency domain. The data coming from the telescope is in the form of energy (signal strength) plotted against time. It is easier to analyse such data as energy plotted against frequency - hence doing the transform.
The rest are looking at data in the frequency domain:
Triplet detection looks for a series of three peaks at equal frequency intervals.
Spikes are short, very narrow peaks
Gaussian signals are signals that are "bell shaped", having a Gaussian distribution about the centre frequency.
Doublets are similar to triplets, but only two such signals.
Each of these signal types may be indicative of a "purposeful" transmission. BUT most actually come from our own endevours when further analysed.
Then there is "auto-corelation", which is a sort of combination of Fast Fourier Transform and peak-shape detection. A bit hard to explain without several pages of maths, but can be very good at detecting potential data carrying signals that are too small for other techniques.
One day soon I expect to see another transform technique being deployed - "wavelets" - this technique can be faster and more sensitive than FFT, but one has to be VERY careful in selecting the "seed" used as the seed can have a significant impact on the outcome.
Bob Smith
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Message 1875714 - Posted: 29 Jun 2017, 18:48:40 UTC

Simple (I hope) summary of autocorrelation: The more information per time a signal carries, the more random-looking it becomes. Noise is a random signal, so the signal starts looking more like noise and thus can't be distinguished from the noise background.

Autocorrelation consists of repeating each block of the transmission at the sender end, then at the receiver end each repetition can be compared to the last one which will isolate the signal from the background noise.

Hope I got that right. :^)
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Message boards : SETI@home Science : What tests are being run?


 
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