[time-nuts] OCXO sensitive to gravity

[Bruce Griffiths]

Some caution is in order as some ferrites used in RF transformer coils
may be permanently altered by application of a strong magnetic filed.
Testing at lower fields first would be safer.
Setupo a pair of Helmholtz coils and excite them with low frequency AC
and look for associated sidebands in the oscillator output.
NB a spectrum analyser is unlikely to be sensitive enough for this.

Bruce

Don Latham wrote:
> once again, a simple experiment would suffice. Got a refrigerator magnet
> handy?
> Don
>
> Lux, Jim (337C)
>   
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>>> Behalf Of Rick Karlquist
>>> Sent: Thursday, August 13, 2009 3:35 PM
>>> To: Discussion of precise time and frequency measurement
>>> Subject: Re: [time-nuts] OCXO sensitive to gravity
>>>
>>> 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.
>>>
>>>
>>>       
>> Hmm. We're investigating just this at work, in connection with things
>> destined to orbit Jupiter, where we expect to see a periodically varying
>> flux as the spacecraft spins.  The quartz is insensitive, but the mounting
>> isn't necessarily insensitive to magnetic fields, especially if any
>> magnetic materials (i.e. Kovar seems to be of interest) are used.
>>
>> If you have any circuits sensitive to DC offsets, then a varying magnetic
>> field can cause problems (e.g. the VCO input in a PLL).
>>
>> I suppose it depends on "how good" the oscillator is expected to be...
>>
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>
>
>