Slipping normally happens when the sync and data paths become misaligned leading to one being shorter, longer than the other. This would add noise and cause frequencies to move around.
Cheers Andrew On Mon, 2012-09-17 at 10:56 -0400, Jason Castro wrote: > Thank you all for your input. It's always nice to come into work on a > Monday and be able to hit the ground running! I loaded Jack's latest > tutorial 3 bof file and I got some interesting results. The spectrum > slips along the x axis 4 channels every 800ms or so. This slipping > event is also accompanied by about 10db of noise in the stop band of the > signal. Please see the following plots: > > ftp://ftp.cv.nrao.edu/NRAO-staff/jcastro/CASPER/Spectrometer/Tutorial_3_sliding_spectrum1.PNG > ftp://ftp.cv.nrao.edu/NRAO-staff/jcastro/CASPER/Spectrometer/Tutorial_3_sliding_spectrum2.PNG > > I'll dive into this and try to figure out what's going on, but extra > eyes are appreciated. > > Thanks, > > Jason Castro > NRAO > > > > On 9/17/2012 8:03 AM, Jason Manley wrote: > > On 17 Sep 2012, at 11:45, Jack Hickish wrote: > >> 2^27 isn't a valid sync period for tut3, which has an FFT ending in a 10th > >> order reorder (https://casper.berkeley.edu/memos/sync_memo_v1.pdf). > > Good catch! This is what I get for copy-pasting that design from another :-/ > > > > Tut3 has been in use in CASPER for over 3 years now and I think you're the > > first one to notice! > > > > Jason > >
