[time-nuts] Speaking of Costas loops

[jmfranke at cox.net]

Valid concerns all. What I am building is a squaring circuit for recovering the carrier from a WAAS GPS satellite. Granted there is still some Doppler and other issues, but the accuracy would not be bad and it just looks like a fun thing to do. Plus, I can use my four foot diameter dish antenna to reduce the number of satellites seen, reduce thermal ground noise, and get some signal gain.

John  WA4WDL

---- "J. Forster" <jfor at quikus.com> wrote: 
> More on your question:
> 
> I'm prettyt sure that just sticking up an antenna and hooking up a simple,
> phase tracking receiver for GPS will yeild nothing useful, because there
> are always several birds in view, so you will get a superposition of their
> signals in the bandpass and each signal will be Dopplar shifted be a
> different amount- a time-varying amount.
> 
> You have to use a complete GPS receiver that can unravel it all.
> 
> -John
> 
> ================
> 
> 
> 
> 
> 
> 
> 
> 
> > Here we go again - the first send didn't seem to get through. This is
> > the second attempt.
> >
> > This talk of Costas loops reminded me of something I wanted to
> > investigate some day. I read somewhere a while back about
> > carrier-phase measurements, and various methods for recovering the
> > GPS carrier frequencies, including the Costas loop, and something
> > with carrier-squaring. Nothing I found showed actual examples or
> > detail of how this is done, only high-order mathematical descriptions.
> >
> > For my needs, I'm more of a frequency-nut - I usually don't care
> > about getting time info, but I'd like perfect 10 MHz for reference.
> > Can using only the carriers lead to simple ways to get the same (or
> > better) frequency stability as a conventional GPSDO, but without the
> > time and location info, or is it pointless to worry about it, and
> > just go with full GPS decoding of everything? Or, is carrier-phase
> > just an enhancement only if you already have the full GPS info?
> >
> > I know that the group could redesign the whole GPS system with tubes
> > if necessary, considering recent philosophical discussions on that,
> > so I think there's plenty of knowledge here about carrier-phase
> > related stuff too.
> >
> > Ed
> >
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> 
> 
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