[time-nuts] Common-View GPS Network
Jim Lux
jimlux at earthlink.net
Tue Apr 16 06:00:49 UTC 2013
On 4/15/13 10:40 PM, bg wrote:
> Chris,
>
> Chokering is not needed. Measured quality antennas are listed at
>
> http://www.ngs.noaa.gov/ANTCAL/
>
> Or at
>
> http://www.geopp.de/index.php?sprachauswahl=en&bereich=0&kategorie=34&artikel=62
>
> /Björn
>
>
>
A lot of the antennas on that list are choke ring type. If you are
doing geodetic work, millimeter scale changes in phase center are
important. For time transfer, maybe not.. 1mm is 3 ps, after all.
A ratty old patch antenna has a phase center variation of a few cm at
most, and that's 30-50 ps.
the effect of a strong multipath (which is what the choke ring
suppresses) would be a LOT bigger than that..
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