[time-nuts] LTE-Lite module

Poul-Henning Kamp phk at phk.freebsd.dk
Tue Oct 21 02:41:07 EDT 2014

In message <766D6811-F733-4AB2-8574-24E4606E45FA at aol.com>, Said Jackson via tim
e-nuts writes:
>Thats exactly right Bob.
>By the time your ocxo jumps to catch up to the efc voltage, you
>have oversteered,  then the process starts in reverse and the ocxo
>jumps in the opposite direction.

This is a well known PI effect called "windup".

The cause is a phase offset of opposite sign of the frequency offset.

The fix is simple:

Start running with only the P term, and engage the I term only after

1. The input phase offset changes sign


2a. The input phase offset levels off


2b. Some calibrated amount of time has passed.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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