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Quietest SETI unit recorded? Some of these WUs must exist...



 
 
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  #1  
Old September 30th 05, 02:52 AM
Max Power
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Default Quietest SETI unit recorded? Some of these WUs must exist...

Quietest SETI unit recorded? Some of these WUs must exist...

General requirements for a quiescent WU:
1. No Gaussians
2. No Triplets
3. No 'spikes' of any kind that would show up on the meter
4. No 'Doppler effects in the signals
= I hope I have covered all the bases...



  #2  
Old October 1st 05, 12:18 AM
Eric
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"Max Power" wrote in message ...
Quietest SETI unit recorded? Some of these WUs must exist...

General requirements for a quiescent WU:
1. No Gaussians
2. No Triplets
3. No 'spikes' of any kind that would show up on the meter
4. No 'Doppler effects in the signals
= I hope I have covered all the bases..


"Quietest" WU is probably one put together from a session after someone
tripped over a receive waveguide...


  #3  
Old October 2nd 05, 09:39 PM
Bill Jillians
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Quietly we read , unable to
contain our credulity we realized that Max Power
said this:
Quietest SETI unit recorded? Some of these WUs must exist...

General requirements for a quiescent WU:
1. No Gaussians


You can fit a Gaussian to random noise, it just would be a very poor
fit. You would have to specify how poor for this post to make any
mathematical sense.

2. No Triplets
3. No 'spikes' of any kind that would show up on the meter


Unless all readings are identical you will also get spikes.

4. No 'Doppler effects in the signals
= I hope I have covered all the bases...


Having said the above I had a very flat WU that completed in 6 hours
when they normally take 12 or more on my computers. It had a very small
result.sah file. Wish I'd kept a copy.


--
Bill Jillians
  #4  
Old October 2nd 05, 10:10 PM
David Woolley
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In article ,
Bill Jillians wrote:

1. No Gaussians


You can fit a Gaussian to random noise, it just would be a very poor
fit. You would have to specify how poor for this post to make any


Not in S@H. It tries to fit so many gaussians to each work unit that
approximately one of them will be good enough to report to Berkeley.
That's true of all the detection modes; they are all calibrated for
the order of one false positive per work unit. What will stop gaussians
is an unacceptable angle range, that stops them being tested for.

Also note that there is no absolute amplitude information in the work
unit so connecting the feed to any noise source will produce similar
statistics.
  #5  
Old October 2nd 05, 11:33 PM
red
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David,
I must respectfully disagree. I don't know about Boinc, but in S@H
classic, there is a power threshold below which Gaussians will not be
reported, no matter what the "fit" may be. I believe that the Gaussians
must also be of the correct duration, to match the results of the Arecibo
antenna "sweeping" across a point radio source in the sky as Earth rotates.
I have run dozens of WUs that SETIspy clearly showed with no Gaussians at
all, just before I sent them in for the record. Spikes can certainly be
just noise, and the occurrence of spikes would be meaningless without
duplicating the results later; even then, it could be just a natural radio
source, such as a pulsar.
--
(Replies *will* bounce, unless you delete
the letter A from my email address)
Cheers,
Red

David Woolley wrote:

In article ,
Bill Jillians wrote:

1. No Gaussians


You can fit a Gaussian to random noise, it just would be a very poor
fit. You would have to specify how poor for this post to make any


Not in S@H. It tries to fit so many gaussians to each work unit that
approximately one of them will be good enough to report to Berkeley.
That's true of all the detection modes; they are all calibrated for
the order of one false positive per work unit. What will stop gaussians
is an unacceptable angle range, that stops them being tested for.

Also note that there is no absolute amplitude information in the work
unit so connecting the feed to any noise source will produce similar
statistics.

  #6  
Old October 3rd 05, 10:46 PM
David Woolley
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In article ,
red wrote:

I must respectfully disagree. I don't know about Boinc, but in S@H
classic, there is a power threshold below which Gaussians will not be
reported, no matter what the "fit" may be. I believe that the Gaussians


Having two degrees of freedom makes means that you can trade one against
the other in setting the threshold, but the fact still remains that if
the threshold weren't set to produce lots of false positives from noise
artefacts there ould only really two other possibilities, both of which
would have major consequences for SETI:

a) We're are seeing huge numbers of non-repeating genuine ETI signals; or

b) There are natural phenomena that produce much narrower band signals
than we had previously assumed.

The former would imply proof of ETI and the latter would indicate that the
search strategy is unworkable.

Incidentally, if I remember correctly, there is actually a technical
paper that discusses the threshold selection strategy for pulses.
 




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