[time-nuts] New GPS Signals

Magnus Danielson magnus at rubidium.dyndns.org
Wed Mar 25 20:53:09 UTC 2009


brooke at pacific.net skrev:
> Hi Magnus:
> The reason F0 = 1.023 MHz is that it's also used as the basis for the data
> bit rates.  The L1C/A code is 1 ms long @ F0 rate.
> The L2CM (Moderate) code will be 20 ms long @ F0/2
> The L2CL (Long) code will be 1.5 sec long @ F0/2,
> so maybe F0 should be 511.5 kpbs?

In that case you should be using 50 Hz... since that is the rate of the
C/A data modulation. But your reasoning is broken... you are attempting
to find even multiplication rates, but this is not the way to get the
fundamental frequency. ICD-200 clearly indicates 10,23 MHz.

The basic rate of GPS is 10,23 MHz for the P-code. The flimsy C/A code
is a 10th of that rate... and L2CM and L2CL is a further division by 2...

> I discovered that the Trimble p/n 16768-80 Trimpack GPS receiver has a
> graphics capability, which none of the others have, and wanted to know
> why.  So I'm in the process of reverse engineering and repairing it. 
> There's still a power supply problem that's making the LCD extreamly hard
> to read, but now I know the reason for the graphics is to switch between
> English and Arabic for all the displays.
> http://www.prc68.com/I/Trimpack.shtml#GraphicsTP
> My interest in the GPS Link frequencies and codes is related to the
> Polaris Guide (civilian version of the current military DAGR GPS receiver)
> and possible firmware upgrades.  I've just got off the phone with Rockwell
> and they say the Polaris guide only has L1 capability (I was expecting
> that it also had L2 since the DAGR has L2).
> http://www.prc68.com/I/DAGR.shtml#Pol

Kind of expected. It is only lately that we got any L2C coverage to be 
meaningfull. Codeless P-code tracking of some sort is still king for 
civilian uses. Especially with GLONASS added.

> I'm in the process of adding a LF differential beacon receiver interface
> to the Polaris Guide.  Also have the connector on order to add Have Quick
> time fill to the O-1814 Rb Time and Frequency standard.
> http://www.prc68.com/I/O1814.shtml


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