Array Operations Questions

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Clint Coon Posts: 3	We have experienced a peculiar noise pattern going through our array... We have experienced a peculiar noise pattern going through our array. The signal ramps up for approx 15 minutes, disappears for about 10 minutes and then resumes by ramping back down for the final 15 minutes. The signal appears to travel from sight to sight through the array. We have switched out many components including the digitizer, sensor and cables yet the signal continued unchanged. It also appears to occur on a 24 hour cycle with slight changes. For these reasons we believe it to be external, possibly RF but we are unable to identify the source of such a signal or a means of blocking it. 02-27-2003 12:11 PM Click the image below to see a larger version
Manohar Lal Posts: 1	Clint Coon has shown the abnormal changes in the record on 12 Nov. This period is close to the Leonid meteors shower. Our record also shows some abnormal variation. We are measuring pressure variation at low latitude northern hemisphere (8.7 deg N, 77.8 deg E). Is that these changes have some relevances with the meteor shower?. Some more station observations would be helpful in validation. 03-10-2003 6:01 PM
Michael Hedlin Posts: 1	We have concluded that this problem must have an electronic source. The noise is not observed on all channels in the array at the same time. When it does occur, it does not coincide with any known activity in the atmosphere. We know of no atmospheric phenomenon that would cause air pressure to vary as seen in this figure. Furthermore we believe the signal could be man-made in origin. It usually lasts for approximately 1 month, during this time 1 to 3 signals will appear a day and each will re-occur in 24 hours +/- approximately 20min. We have not found any correlations with sunrise/sunset or temperature. Thanks for the ideas! 03-11-2003 9:17 PM
Jeong-Soo Jeon Posts: 1	We had operated the temporary seismo-acoustic stations Nov. 2003 in South Korea. In our case, we also got very similar waveforms more than 10 times during one month. I found left lamp is strong in local night time but reverse in local day time. Also it was very strange we could not find these signals at a adjacent station (500m apart). We exchanged the acoustic sensor between two sites, but results was same. We couldn't find the reason or origin. 02-27-2004 12:33 AM
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