On 07/05/2013 10:39 PM, Joseph Gwinn wrote:
Re: time-nuts Digest, Vol 108, Issue 28
Message: 2
Date: Fri, 05 Jul 2013 09:18:39 -0700
From: Jim Lux<[email protected]>
To: [email protected]
Subject: Re: [time-nuts] Speaking of Costas loops
Message-ID:<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
On 7/5/13 8:44 AM, Bob Stewart wrote:
Wouldn't a Cs or Rb clock in orbit be slow due to relativistic
effects? I'm pretty sure there is a relativistic correction to the
GPS clocks.
Bob - AE6RV
I believe that the original WAAS repurposed transponders intended for
other L-band satellite signals (e.g. Sirius/XM/LightSquared).
As noted earlier in the discussion, the new satellites might have a
specialized payload, which could have a purpose specific coherent
transponder, rather than a linear translator.
If it is purpose specific and single channel, then making it immune to
the local oscillator is straightforward.
I worked on a proposal for the original WAAS system. The WAAS signal
is not a timing signal in the sense that GPS signals from space are
timing signals. WAAS instead sends out a stream of correction data
that allows one to greatly improve the accuracy and reliability of GPS
signals.
So, unless things have changed greatly, the geostationary satellite
that broadcasts the WAAS signal need not have an atomic clock.
This is naturally still true, but we are into the level of "there's a
signal here, what can we use it for?". Doing a much simplified receiver
could serve some well enough, without going the full mounty. It's like
taking the color-carrier of analog TV broadcasts.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
