[time-nuts] 5370B on eBay, carrier phase tracking GPS receiver
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sun Feb 18 21:31:11 EST 2007
Didier Juges wrote:
> On a different subject, I just won a Novatel Superstar 2 GPS receiver
> advertised to do "carrier phase tracking". It's specification lists a
> timing accuracy of 50nS typical, which is not bad at all for a GPS that
> does not have an OCXO, I think.
> I remember seeing a number of postings on time-nuts (must have been
> Bruce) advocating the increased performance of carrier phase tracking,
> but I need to educate myself about what it is and what good it can do
> for me :-)
> Any feedback regarding whether I am getting something useful, or just
> another item to go in the junk box (I did not break the bank, it went
> for $0.99, and $10 shipping...)
> Didier KO4BB
Don't junk it, you can do very well with it if you have the version with
a carrier phase output, potentially much better than with a simple
Rather than timing errors of a 50ns from the timing output, the carrier
phase measurement hardware built into the receiver has a resolution of
around 1/1000 of the period of the 1575.42MHz carrier. If you don't have
the carrier phase output version then you'll have to write your own
firmware, not difficult according to Magnus.
To make use of this data you need to be able to make accurate
ionospheric delay corrections, perhaps using the technique Magnus is
But you need to make a minor modification.
The 10MHz input on the receiver needs to be connected to a 10MHz derived
from the frequency standard you are attempting to discipline rather than
the on board TCXO.
Once this is done one can log the carrier phase data and use software to
determine the frequency offset and stability of your 10MHz standard with
an Allan variance of around 1E-11 at 1s descending rather quickly to a
noise floor of around 5E-14 or so.
If you can get a whole bunch of working carrier phase output receivers
at that price they would be extremely useful for things like geodetic
surveying etc. One Australian university uses them in a wide area
If you want further details on the way to use the carrier phase data to
discipline your standard just ask.
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