[GPS_Standard] vcxo control averaging?

[Bert, VE2ZAZ]

Hello Arie,

You seem to have left your parameters to the initialisation mode. Once the
FLL has reached equilibrium, you must set your parameters for a much longer
averaging period. As a minimum, perform two things:

Your Ageraging Sample size (S) is set too small. 10 samples are not enough.
To really try to measure to a better accuracy, you must set your S parameter
to something, say, more than 100. A one hour long period is a good start.
Set S to 225.

Also, to decrease the impact of one "way off" sample, set your FLL Sampling
mode (M) to Voting.

Please read my website and the user manual. I explain all of this in more
detail in there.

Regards,

Bert, VE2ZAZ

----- Original Message -----
From: "Arie Dogterom" <pa0ez at amsat.org>
To: <gps_standard at mailman.qth.net>
Sent: Thursday, January 25, 2007 6:55 AM
Subject: [GPS_Standard] vcxo control averaging?


Hello,
I have built the gps controlled standard and am very impressed by the
intelligent control and monitoring software.
But one question remains:
Say one sets a period of 10*16 seconds to average out the "noise"on the one
sec impulses. If the vcxo is about correct on frequency the result of the
counter jumps around 0 but I see deviations of +-4 at times. The PC
programme statistics picture indicates gradually an average which goes down
and reaches values around 10^-11. But at the end of the averaging period it
is possible that just at that moment the result of the 16 sec measurement
indicates not 0 but + or - 3. In that case, although the frequency is almost
correct, the control voltage suddenly is changed and the measuring period
starts again. But now it is possible that the vcxo is slightly set away from
the correct figure.
I would think a better solution would be that not the momentary deviation
but the long time average is used to set the control voltage.
Or do I see this incorrectly?.
Arie

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