[time-nuts] Speaking of Costas loops

[Bob Camp]

Hi

I believe the *code* is corrected, but the carrier frequency is not. Without correction it's plenty close enough for any receiver that can handle a normal GPS sat. The intended "product" is the code rather than the carrier. Even if you tried to correct for doppler, it would only work for a single point. Your velocity to every place else would be either to fast or to slow for the correction (the motion is in 3 dimensions …).

Bob

On Jul 4, 2013, at 5:23 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> On 07/03/2013 02:29 PM, Bob Camp wrote:
>> Hi
>> 
>> 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.
> 
> Correct. But the up-link station monitors the signal and makes corrects as I recall it. In fact, there is a whole array of monitoring stations to provide for ionospheric corrections.
> 
> The orbit is also known and corrected for.
> 
> WAAS/EGNOS has 100 baud data, using half-rate convolution code.
> 
> Cheers,
> Magnus
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