Re: [ldm-users] NEXRAD3 Again ... part III

On Sun, 31 Jul 2011, Bryan C. Hahn wrote:

I find it strange that there are so many retransmits to begin with.  It
makes one wonder if there is an NWS site somewhere that is having
particularly bad reception problems.


One of the odd things I have noticed is how low the carrier to noise ratio is at most sites. The standard is 16:1. Mine hovers around 14. UNIDATA gets 16, but they are in one of the strongest signal areas coming from the satellite. Some people I see getting signal strengths of 80+ are seeing C/N's of 10. Something is still not right, and I suspect the power coming from the bird is 3 dB or more too low for what is needed. Yes, that's speculation on my part, but boy, it would sure improve the link budget when it rains.

I expect a lot more retransmits in the summer, but not like this. As it is, the signal is ~5 dB less than the digital video signals (free to air and encrypted) sent on the SES-1 satellite. SES-1 is pretty much the latest geosynchronous bird up there, with some amazing technology behind it's not the fault of the satellite. The last one (AMC-2) was so old I was amazed it did as well as it did.

All that said, the weekly switching to various uplinks indicates there are serious issues they're quietly resolving. And if the duplicates stop this morning at 13:15Z as they switch to a backup uplink site, you know where one of the issues is at.

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