"Alfred A. Aburto Jr." <aaburto@pacbell.net> wrote in message news:<8RIBb.69329$7r.38040@newssvr25.news.prodigy.com>...

"David Woolley" <david@djwhome.demon.co.uk> wrote in message

 news:T1070828218@djwhome.demon.co.uk...

In article <0Mtzb.32209$_g4.16482@newssvr29.news.prodigy.com>,
Alfred A. Aburto Jr. <aburto@sbcglobal.net> wrote:

Another point to be raised is that the SNR need not be so "high"
as shown in the FAQ. In fact, an SNR of 3 might be ok in many
cases. I note that Kraus in the Radio Astronomy reference, used

3:1 will produce totally unacceptable false positive rates.

I'm not sure it is "unacceptable" because I have seen FFT time histories
of the Project Phoenix's detection of the Pioneer Probe signal and it
was clearly detectable at low SNR ... there are also examples of the
the detection of low SNR (averaged) signals where during one scan
you could not distinguish the signal (target) but for multiple scans it
stands out very clearly ...

I don't have the logs from our old observing system here, but I think
Pioneer 10 usually registered as SNR ~ 6 to 10 in a single sample (.7
Hz x 1.4 sec) and when integrated for a few minutes was a strong
detection.

I think that the SNR threshold is something an individual user/system
should adjust for their own purposes.

The SNR and ultimately the PFA should be set by the overall goal of
the project.  In the case of Phoenix, where we do immediate follow-up
of candidate signals, we need to balance the use of the telescope for
follow-ups vs. covering new stars and frequencies. Our threshold for
CW signals is 8.5 times the mean noise.  For SERENDIP/SETI@Home, you
need a threshold that will generate some number of candidates that can
be reasonably checked in a day or two of dedicated observing about
once a year.  You can't afford to generate lots of false candidate
signals that will use up the limited dedicated telescope time needed
for confirmation observations.