[time-nuts] DC Voltage Ramp?

Magnus Danielson cfmd at bredband.net
Sun Sep 4 14:48:33 EDT 2005

From: Brooke Clarke <brooke at pacific.net>
Subject: Re: [time-nuts] DC Voltage Ramp?
Date: Sun, 04 Sep 2005 11:26:50 -0700
Message-ID: <431B3C6A.9000808 at pacific.net>

> Hi Tom & Robert:
> I think what this is saying is that if the control voltage to the OCXO 
> is fixed, then during the 10,000 (or more) seconds needed for GPS the 
> OCXO has drifted about 5E-11/day * 10,000/86400 = 6E-12 seconds which 
> exceeds what we are trying to accomplish.
> BUT, if instead of using a fixed control voltage, a Ramp is used then 
> this will not happen.  Now instead of using GPS to control a fixed 
> voltage it's used to control the slope of the ramp.
> What am I missing?

You need to come up with the ramp/parabolic which will compensate your
oscillators linear frequency error and frequency drift and the only way to do
that properly is to compare it to something which is better. So, you need to
compare against a Cesium or GPS, and then calculate the parameters, and then
redo this. In order to handle other perturbations such as random phase jumps
and result of mechanical chock, you need to do this on a regular basis.
What you now have is a control-loop of some sort, wherein a PLL is really just
one perticular class.


More information about the time-nuts mailing list