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20010320: NOAAPORT SDI system at LSU (cont.)



>From: Denise Laitsch <address@hidden>
>Organization: SSEC
>Keywords: 200103201621.f2KGLNL13513 SDI IDD NOAAPORT

Denise,

Thanks for getting back to us quickly.

>The error messages indicates that the SDI card is not seeing clock.
>Someone should, or maybe someone has, put a scope at the PC end of the
>coax cable and look for clock.

To our knowledge, this has not been done yet.  We will contact Rob Leche
of LSU and get him to organize this.

>Let us know if you see it.

I would assume that the clock signal will be there for an extended
period, but disappears or is not detected by the SDI card ever several
(5 - 14) days.  The reason I say this is that the SDI ingestion locks
up after several days of functioning correctly.  If the clock was never
working, it doesn't seem like SDI card would ever work.  True?

>If you don't
>see clock here, you may have a bad connector or a demod problem.

Yes, this would be the easy case.

>If you do see clock, it may be the SDI card or PCI slot.

This is what we were led to believe given that the system runs for an
extended period of time before freezing.

It seems that we will need to get a recording scope setup to monitor the
clock to see if it stops and then causes the SDI card to lock.  Hopefully,
LSU will be able to organize this and has a technician that knows how to
set it up.

Do you (or SSEC EEs) have any information that would help troubleshoot
and interpret this problem?  I am looking for things like:

o is the clock detect on the SDI card triggered by a rising/falling edge
  or is actuated by signal level

o if the SDI clock detect is by level, what is it expecting to see and
  what are the tolerances for the signal

o do you know what the clock signal strength is supposed to be out of
  the demod

More questions not of a technical nature:

o can you tell us if other SDI sites have experienced failures of their:

  o demods
  o serial cables that connect the demod to the SDI card (presumably, this
    is a cable that is supplied by SSEC with the system)
  o SDI cards
  o PCI slots

o is there any possiblity that terrestial inteference could cause the
  problems that are being seen on the LSU SDI box

>Let me know what you find.

Will do.  It would really help the troubleshooting process if you or
someone else at SSEC could provide answers to the above questions.

Tom