[time-nuts] OCXO sensitive to gravity

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Thu Aug 13 23:34:39 UTC 2009


> 
> Date: Thu, 13 Aug 2009 15:34:43 -0700 (PDT)
> From: "Rick Karlquist" <richard at karlquist.com>
> Subject: Re: [time-nuts] OCXO sensitive to gravity
> To: "Discussion of precise time and frequency measurement"
>     <time-nuts at febo.com>
> Message-ID:
>     <c537a80798ce331ab1effbc1f05db353.squirrel at webmail.sonic.net>
> Content-Type: text/plain;charset=iso-8859-1
> 
> Tom Duckworth wrote:
> > The orientation change is due more to the earth's magnetic flux
> effect on
> > the oscillator, and less so from gravity.
> >
> > Tom
> > Tom Duckworth
> > tomduck at comcast.net
> 
> Sorry, this is simply incorrect.  Magnetic flux from the
> earth has no effect on quartz oscillators.  There is no
> mechanism there.  Acceleration definitely affects quartz.
> 
> Magnetic flux could have an effect on atomic standards,
> but they normally have magnetic shielding to mitigate
> this effect.  Orientation (or at least acceleration)
> can affect cesium beam standards because the atoms
> are flying.  Len Cutler put in a fix to mitigate against
> this in the 5071A CBT.  AFAIK, orientation doesn't affect
> Rb standards.
> 

One of the papers I looked at mentioned that Rb standards are also affected by magnetic fields, but differently. The Rb standard on Huygens apparently had some sort of magnetic compensation circuit in it.  Just like for other obsessively good sources, this is at the 1E-13 kind of levels. Googling "Rb Ultra Stable Oscillator magnetic field sensitivity" would probably turn up the paper (since I just glanced at it, saw it wasn't about quartz, and moved on"  Cryogenic Sapphire is also affected by magnetic fields.

There's just no getting away from an infinite capacity to obsess...



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