[time-nuts] Some observations of the BG7T BL GPSDO (John Miles)

Willis willis.hendley at gmail.com
Thu Mar 26 21:57:25 EDT 2015

[Apologies if I've messed up this reply - my first posting to timenuts as a 
new nutlet]

> See performance plots, data files, and summary at
> http://www.ke5fx.com/gpscomp.htm .   Thanks to Bob, W7AVK for the loan of
> the unit for testing!  Would be curious to know if anyone else has
> encountered a similar frequency error, or if the issue I saw was unique to
> this particular example.

In looking through the ublox Timing Appnote on the ublox 6 GPS receivers:


aside from possible sources of error from antenna cable delay and multipath 
it also refers to quantization error of the timing pulse itself.

Is it possible that this also has a systematic offset or is this just 
contributing to the observed noise level around the mean? Being new to the 
concept of GPSDOs I have no idea how much these intrinsic errors in the GPS 
receiver itself bleed through to the performance of the output frequency 
from the OCXO - or is it all masked by the long time constants and filtering 
in the Software PLL loop?


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