The orientation change is due more to the earth's magnetic flux effect on
the oscillator, and less so from gravity.
Tom
Tom Duckworth
tomd...@comcast.net
----- Original Message -----
From: "John Green" <wpxs...@gmail.com>
To: <time-nuts@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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