[time-nuts] Common sky pps errors for any GPSDOs?

Lux, James P james.p.lux at jpl.nasa.gov
Mon Jan 5 15:13:00 EST 2009



> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Matt Ettus
> Sent: Monday, January 05, 2009 11:31 AM
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] Common sky pps errors for any GPSDOs?
>
> I am working with someone who needs to have time synchronized
> reception of signals in various locations which are separated
> by less than 100 km.  This is a situation similar to VLBI,
> but since the distances are shorter, the center frequencies
> are lower, and the integration times are much shorter, we
> probably don't need a Hydrogen Maser, and the application
> can't afford one.
>
> The real question is whether we can get away with a GPS
> disciplined OCXO or whether we would need to use a Rubidium.
> Does anyone have any data on the relative frequency and/or
> phase errors of the 10 MHz reference out, and relative PPS
> time errors of any commonly available GPSDOs?

Isn't that just the Allan Deviation data? Symmetricom has datasheets on their website for their various modules. They have a GPS discplined quartz oscillator in several flavors.
http://www.symmetricom.com/media/files/downloads/product-datasheets/ds%20XLi%20Options%202.pdf

Something else to consider is doing post processing.. Use a nice quiet 10MHz oscillator for your source/sampling clock, and record the 1PPS from the GPS receiver as well as your unknown, then figure out after the fact what the oscillator was doing.

Jim




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