[time-nuts] RE: phase locking Rb to GPS

Bill Hawkins bill at iaxs.net
Sun Oct 23 11:53:34 EDT 2005

Speaking as a process control engineer, it sounds like
too much gain. You can verify that it is the oven by 
warming up the device somehow. That should change the
period of oscillation. If it is still 7 minutes then
reduce the gain somehow.

You can elevate the temperature of the device by
putting it in a large cardboard box with a 60 or 100 watt
incandescent light. Monitor the temperature.

Bill Hawkins

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
Behalf Of Alberto di Bene
Sent: Sunday, October 23, 2005 10:30 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] RE: phase locking Rb to GPS

Richard H McCorkle wrote:

> [snip]
>     In interfacing an Isotemp mil spec version of the HP 10811B with a
> sensitivity of 9.7e-9/volt and a span of 4.85e-8 to the Shera controller
> even with  [snip]

  do you perhaps have any experience of using the Isotemp OCXO134-12 unit ?
I built a GPSDO using it, and it works rather well, were it not for a 
residual oscillation of the frequency of about +- 2E-11. i.e. +- 0.0002Hz
at 10MHz, with an oscillation period of about 7 minutes, which is too fast
to be corrected by the PI software loop.

I attributed it, lacking other explanations, to an imperfect temperature
control of the oven. Translated in temperature terms, that frequency
oscillation amounts to a change of about 0.18 degrees Celsius.

What you think about this ?  TNX

73  Alberto  I2PHD


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