[time-nuts] Speaking of Costas loops

bg at lysator.liu.se bg at lysator.liu.se
Wed Jul 3 15:13:03 EDT 2013


Attila,

> On Wed, 3 Jul 2013 08:29:02 -0400
> Bob Camp <lists at rtty.us> wrote:
>
>> There are two batches of GPS / WAAS sats up there:
>>
>> 1) The ones with numbers above 100 that are geosync and that only do
>> WAAS
>>
>> 2) The ones with numbers <= 32 that do nav. These are not geosync.
>>
>> I believe the only ones with corrected / high stab clocks on board are
>> those in the second group. The stuff in the first group aren't dedicated
>> sats, just leased transponders on conventional multipurpose geosync
>> birds.
>
> I don't know about WAAS, but AFAIK the EGNOS signals are generated on
> ground using Cs references and retransmitted by the satelites using
> a "bend pipe". Ie. the signals should be of time-nut quality even without
> high accuracy frequency standards in the birds themselves.
>
> (Sorry, i'm not able to find where i read about that, so no references
> today)
>
> 			Attila Kinali

WAAS is the US implementation of SBAS, EGNOS the European, MSAS the
Japanese, GAGAN the Indian, etc...

Here are some references.

http://egnos-portal.gsa.europa.eu/library/technical-documents
http://egnos-portal.gsa.europa.eu/sites/default/files/content/documents/egnos-user-guide_en.pdf

You could also check the WAAS site at Stanford.edu.

--

    Björn



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