[time-nuts] OCXO sensitive to gravity

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Aug 13 22:03:31 UTC 2009


Tom

Really?
What mechanism do you have in mind?

In practice the same effect is observed when the Earths magnetic field
is cancelled using a set (3 pairs) of Helmholtz coils (or equivalent) or
in a magnetically sheilded enclosure?

Bruce

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
> ----- Original Message ----- From: "John Green" <wpxs472 at gmail.com>
> To: <time-nuts at febo.com>
> Sent: Thursday, August 13, 2009 11:02 AM
> Subject: [time-nuts] OCXO sensitive to gravity
>
>
>> A while back there was some discussion about crystal oscillator's
>> changing
>> frequency due to the effects of gravity. Since I got my Z3801 up and
>> running
>> full time, I have been trying to characterize some OCXOs I had picked
>> off
>> eBay but had no specifications for. I was trying to fine tune one to the
>> '3801 and noticed that when I picked it up and tilted it to get to the
>> adjustment , the frequency changed. I started rotating it 90 degrees
>> at at
>> time and noticed that the frequency changed up or down depending on
>> which it
>> was oriented. The change was immediate and quite noticeable. It is
>> nice to
>> have something as stable as the Z3801 but now I realize all those
>> OCXOs I
>> thought were so great, aren't. I do see why the rubidium sources are
>> well
>> liked. They lock in a couple of minutes and that's pretty much it.
>> The ones
>> I bought off eBay were both off by about 1E-9. It occurred to me that
>> they
>> probably in equipment where they were locked to GPS and with nothing
>> connected to the frequency control input, they would naturally be a
>> little
>> off.
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>
>
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