Re: [ldm-users] NOAAport carrier/noise down considerably since primary switchover

On Sat, 12 May 2012, Stonie R. Cooper wrote:


We are still over 15dB at our lab and operational downlink, with our lab
over 16dB most of the last hour.

Having said that, I would caution against calling or emailing NCF
because your dB is not as high as it was previously.  That is a single
measure of the ability to receive data, and not the whole picture.

While it is true that it is just one measure, having one car fall off
a train is not a trivial event, especially in satellite communication.
I'm seeing this across the board, and a lot of people aren't getting the 16 SNR they should be getting, anyway.

By illustration, the retransmit rate on the NWSTG channel since the 9th
has been very low - never getting above 5%.  In contrast, prior to the
6th, the retransmit rate on NWSTG bounced as high as 22%, and certainly
several instances over 10%.

And, as mentioned, I am getting no data loss as well. But my point was this: around the country, we generally have good enough weather for excellent reception of NOAAport, even with a marginal signal (it's *not* marginal, but it's now closer to it). Yes, you have storms in the southeastern U.S., but scattered. Again, my issue is that this lowers the C/N ratio so that as the weather deteriorates, we will see packet loss in less harsh conditions that we've seen before. Even with the last good CME from the sun that brought us "Northern Lights" shimmering north of my dish, the C/N went down to 10.5. Again, no packet loss, but now that it is down significantly, I can't be sure that the next time it happens, I won't lose data. And it looks like we have a good chance for more M-class and maybe even X-class solar flares in the next few days thanks to that active sunspot, so...

NCF will look at the stats of retransmit requests from the 160+ WFO and
RFCs and see they are low and tell you that you have a local issue if
you are losing data, and if you are not losing data, then, "what is the
problem?" will be the more likely response.

The problem is when atmospheric conditions (rain and clouds) get more active in the weeks to come over a wider area of the country. Then the signal may degrade to useless levels more easily than before.

I understand that it is vexing to see dB lower than what you feel it
should be, but I also want to prepare you for the likely response at
this given time considering NOAA is not seeing any data reception issues
at their downlinks, based upon retransmit requests.

I understand, too. But it may be a problem when the relatively tranquil
pattern (in general) across most of the country breaks down. Having said
that, you CC'd Jamie Casamento on this thread, and being the cool guy that
he is, he'll check it out anyway. :-) Again, this isn't a "oh my
goodness, everybody will lose data now" email, or I would have sent the
message much earlier this week. But, as the weather pattern becomes more
active, I think this could become more of an issue in the weeks to come.
I'll wait for Jamie to chime in to see what he says.


Gilbert Sebenste                                                     ********
(My opinions only!)                                                  ******
Staff Meteorologist, Northern Illinois University                      ****
E-mail: sebenste@xxxxxxxxxxxxxxxxxxxxx                                  ***
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