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

Willis willis.hendley at gmail.com
Fri Mar 27 01:57:25 UTC 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:

https://www.u-blox.com/images/downloads/Product_Docs/Timing_AppNote_%28GPS.G6-X-11007%29.pdf

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?

-willis




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