[time-nuts] Motion effects on accuracy of GPS pps

Hal Murray hmurray at megapathdsl.net
Tue Jun 29 19:44:06 UTC 2010

> Thanks for the response Björn. Also thanks to Didier Juges for pointing  out
> that this has been covered on a previous thread. I'll go and find it  in the
> history.

Somebody setup a good oscillator on a pendulum.  They could measure the 
frequency shift as G changed slightly.

There have been several mentions of the change in frequency when you turn an 
oscillator over.  That's a 2G shift.

> Unfortunately the device will be used in urban areas so some multipath &
> obstruction of skyview is expected. I've just done some testing on my  OCXO
> and it has a maximum sensitivity of about 5 ppb / *g*, which is  notable,
> but shouldn't present a problem. I've yet to explore the  vibration effects
> - thanks for pointing my attention to the motion  effects on the OCXO
> itself, its an aspect I'd otherwise have overlooked. 

Somebody provided the URL for a good article on vibration, a PDF from a 

The problem they were working on was radar in helicopters.  The return signal 
is smeared by the noise bandwidth in the source signal.  That determines the 
minimal velocity that you can see if you filter out the ground clutter.  They 
were measuring acceleration and correcting via EFC.  It was a fun read.

Sorry, I don't have any URLs or subjects to search on, but the ideas might 
help if you are scanning the archives.

These are my opinions, not necessarily my employer's.  I hate spam.

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