# [time-nuts] Frequency error -> Parabolic Time Error?

Tom Van Baak tvb at leapsecond.com
Sat Apr 9 18:57:26 EDT 2005

```Yes, you can assume df for a Cs or GPS is zero for all
but short time spans.

/tvb
----- Original Message -----
From: Brooke Clarke
To: Tom Van Baak ; Discussion of precise time and frequency measurement
Sent: Saturday, April 09, 2005 15:48
Subject: Re: [time-nuts] Frequency error -> Parabolic Time Error?

Hi Tom:

Now suppose the reference oscillator is a Cesium type, does that automatically mean that df is zero?

Have Fun,

Brooke

Tom Van Baak wrote:

Yes, the curve is described by a quadratic formula,
same as any parabola. The time, T, (phase) of a
reference oscillator is given by:

T = t0 + f0 * t + 1/2 * df * t^2.
-- where t0 is the initial time offset (phase),
-- and f0 is the initial frequency offset,
-- and df is the frequency drift per unit time.

This can give rise to several different looking shapes
depending on the initial conditions.

/tvb

----- Original Message -----
From: "Brooke Clarke" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Saturday, April 09, 2005 15:18
Subject: [time-nuts] Frequency error -> Parabolic Time Error?

Hi:

Suppose that my reference oscillator is offset from 10.0 MHz by some
small amount.  If I plot the time interval between the reference
oscillator and a GPS 1 PPS what will the plot look like over a long time
period, a parabola?

Have Fun,

Brooke

--
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w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
http://www.precisionclock.com

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```

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