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[IDD #KUD-512290]: Backup NOAAPort source ?



Hi Rosie, Jerry, et. al,

re:
> Ok Tom. You should be able to get into both np1 and np2 as user ldm.

Thanks!  I have been poking around on np1 and np2 looking for anything
that might be amiss, but I see nothing obvious.

re:
> Also, Dave swapped in a spare LNB at 1523UTC today.
> So far I am not seeing a change.

Hmm... The marginal Carrier to Noises (C/N) being seen on both
of your Novra S300Ns that are connected to the signal from your
6.3m dish, about 9.2-9.4, are below what we consider to be useful
for NOAAPort ingest.  The fact that replacing the LNB resulted in
no change strongly suggests one of two things:

- the dish pointing is off

  Perhaps it is seeing a side lobe of the original signal?

- there is a problem in either a connector or the coax signal
  cable that goes from the LNB to the signal splitter to which
  your Novra S300Ns are connected

Since we were told a long time ago that the C/N being seen on
your S300Ns was in the high 16s dB and it is now down to below
10 dB, it would seem possible that some sort of electro-mechanical
connection (e.g., cable connector) has been degrading over time.
The problem with this conjecture is that there is no data to examine
it in any detail as the monitoring that is being done is only saving
signal strength information.  It is our experience that the signal
strength is not a good measure of true signal quality, so we don't
look at it much at all.  We and lots of other sites that are ingesting
NOAAPort have found that C/N provides a very good measure of signal
quality.  As I said in a previous email, the target C/N for NWS
WFOs is 17 dB.  Most sites known to be ingesting well (meaning 
having an acceptable number of Gaps/number of missed frames) have
C/Ns that are in the mid-15s dB or higher.  The only exception to
this "rule" that I know of is a Northrup Grumman office that is
located on the beltway in Northern Virginia.  Their C/N is
typically in the mid-11 dB range, but their ingest quality is
exceptional.  After extensive discussions with Stonie Cooper
of Planetary Data, Inc., our conclusion is that the "right" 
Novra S300N can extract good data even when there is "low"
C/N.

Musing:

- combining your comments about the performance of your NOAAPort
  ingesters with our experience here in UCAR, at LSU/SRCC, and
  at Northrup Grumman has led us to believe that the magic C/N
  below which one can not successfully ingest NOAAPort is around 10,
  AND this is only the case if one's S300N is "better than average".

Questions:

- do you have a spare piece of coax signal cable that can be used instead of
  the one that is in-place

  If the answer is yes, the test I would run is to connect the spare coax
  from the LNB directly to one of your Novra S300Ns and see what the
  indicated C/N is.

- the other question is if you are using a line amplifier in the signal
  path

  We are, and without it we are not able to get a usable signal.  I can't
  remember for sure, but I seem to recall that the indicated C/N when
  our line amp was removed was on the order of 10 dB at best.

Is it worthwhile to chat about your and my troubleshooting?  If yes, I should
be back in the office sometime after 3 MDT.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: KUD-512290
Department: Support NOAAPORT
Priority: Normal
Status: Closed


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