[hpsdr] coherent dual mercury receivers

[Glenn Thomas]

It's been awhile since I've looked, but I believe the original GPS 
system specification called for CA time accuracy of +/- 10 ns. Thus the 
calibration of the receiver clock needs to be at least this good - the 
clock correction factors falling out of the position solution.

Given this, it seems like receiver 1 pps accuracy of +/- 100 ns ought to 
be a piece of cake, assuming that the receiver design engineers paid 
much attention to accuracy. A small thing, but I think it has to be done 
at the design stage of a consumer GPS receiver. Simply dividing the raw 
receiver clock signal down to 1 pps will provide accuracy no better than 
the clock itself if no other clock correction factors are applied. 
Likewise, dividing the correlater clock down to 1 pps will still contain 
uncorrected errors due to doppler and various inconstant indexs of 
refraction along the signal path.

73 de Glenn wb6w

On 3/14/2011 10:47 AM, Scott Cowling wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Joe and Phil,
>
> Check out this link:
>
> http://www2.iee.or.jp/ver2/honbu/14-magazine/log/2005/2005_08c_08.pdf
>
>
> It seems to indicate that the absolute accuracy could be much greater 
> than several uSec.
>
> 73,
> Scotty WA2DFI



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