Fun with 618,813 pulses...


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Message boards : SETI@home Staff Blog : Fun with 618,813 pulses...

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Profile Johnney Guinness
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Message 925505 - Posted: 12 Aug 2009, 5:02:56 UTC - in response to Message 877279.
Last modified: 12 Aug 2009, 5:14:30 UTC

Eric Korpela said:

Now all that's left in the short term is to port the algorithm to C++ and have it write the results back into the database. I'd also like to know what that splat is at an index of 70 and a DM of 300 is. But that's a story for another time...
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Eric,
I have read this message several times over the last few months, i waited until now to respond, i needed time think. This is one of the most interesting messages i have seen you post, it does contain a lot of science information and explains the RFI problem very well.

You can't stop the local airport in Arecibo from broadcasting or you can's stop commercial and military ships from sailing around the island of Arecibo, hence you can't get rid of RFI from the field of view of the Arecibo dish. I also think you will always be fighting RFI trying to remove it with more and more complex software programs.

It seems to me, the best way to remove the RFI is to remove it at source rather than from the recorded data. I think you should be looking at trying to source and electronic filter that should be physically fitted to the receiver. Remove the RFI electronically before the data gets recorded. This is also not a simple thing to do, but it is possible. A special electronic RFI filter fitted to the AlFA receiver. ALFA gets the signal from the field for view, you then filter the signal electronically, then you record to disk. The filtering becomes part of the signal processing.

John.
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Message 925521 - Posted: 12 Aug 2009, 8:41:36 UTC - in response to Message 925505.
Last modified: 12 Aug 2009, 8:42:03 UTC

It seems to me, the best way to remove the RFI is to remove it at source rather than from the recorded data. I think you should be looking at trying to source and electronic filter that should be physically fitted to the receiver. Remove the RFI electronically before the data gets recorded.

There are already such filters fitted to the receivers. When "switched in", s@h gets clean data.

However, other users require the filters to be switched out for their observations and that is when s@h suffers the RFI contaminated data. I guess the radar detector is only a partial help for marking sections of data as contaminated. There will still be a lot of very weak radar pulses in the data picked up from long range reflections off distant aircraft and possibly even rain clouds.

Quite a headache!


But still a good question is whether s@h can include their own dedicated filter in front of just their recorder...

Keep searchin',
Martin
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Message 925740 - Posted: 13 Aug 2009, 2:07:46 UTC - in response to Message 925505.

It seems to me, the best way to remove the RFI is to remove it at source rather than from the recorded data. I think you should be looking at trying to source and electronic filter that should be physically fitted to the receiver. Remove the RFI electronically before the data gets recorded. This is also not a simple thing to do, but it is possible. A special electronic RFI filter fitted to the AlFA receiver. ALFA gets the signal from the field for view, you then filter the signal electronically, then you record to disk. The filtering becomes part of the signal processing.

Would that it was that simple.

Another problem not already mentioned: a lot of these noise sources are broadband, and simply have a lot of energy that would be in the passband for any hypothetical filter you might want to add.

Between that and insertion loss, it'd probably hurt as much as help.

Easier to just ask ET to crank up their transmitter power.
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Message boards : SETI@home Staff Blog : Fun with 618,813 pulses...

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