[time-nuts] LPRO-101 with Brooks Shera's GPS locking circuit

bg at lysator.liu.se bg at lysator.liu.se
Fri Dec 15 01:42:22 EST 2006


On Fri, December 15, 2006 0:55, Dr Bruce Griffiths said:
>
> Björn
>
> You will need a dual frequency receiver to more accurately correct for the
> ionospheric delay.

Sure, that is an improvement. But how large is really the time rate of
change of the ionosphere? (Depends on the solar activity naturally)

> Currently non approved users do not have access to the codes required to
> use the L2 frequency signals in an optimum way.

I do not think the kludges are not impacting GPS use on a good stationary
antenna location that much.

> Multipath effects become even more critical as one attempts subnanosecond
> timing performance.

MP is the big remaining problem. What correlator types are really used in
OEM timing GPS receivers today? How "narrow" correlators do the different
receivers in the Oncore family use?

> One may have to use either a choke ring ground plane antenna (as used in
> geodetic receivers) or resort to phased array techniques.

Chokering antennas for a few hundred dollars are available on ebay, so
thats  not outside the reach.

> There is at least one commercially available GPS disciplined OCXO system
> that uses carrier phase measurement techniques to discipline a crystal
> oscillator.

:-)

--

   Björn




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