On Mon, Jan 5, 2009 at 12:13 PM, Lux, James P <[email protected]> wrote: > > >> -----Original Message----- >> From: [email protected] >> [mailto:[email protected]] 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
I don't think Allan Deviation is the right measure. First, standard Allan dev numbers won't take environmental differences into account. Also, isn't Allan Dev measured vs. a better reference? > 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. Unfortunately, post processing isn't possible in this app, since it is a real-time communications application. Thanks, Matt _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
