[GPS_Standard] vcxo control averaging?

[Arie Dogterom]

Dr OM Bert,
I think I did not formulate the point correctly.
In fact I did all you suggested.
But my point is different: After a certain number of samples, albeit 50 or 
500 the difference counter can give any value between 0 and the holdover 
threshold, although the long term average is nearly or exactly zero. For 
example I see in a random case ( and this is not much different in the two 
modes) with a 500 sample period that after 498 samples the cumulative sum is 
0. After 499 it is -1 and at 500 it is -3. Well that results in a change of 
the dac output. But the real average deviation is very near to zero.
Or do I see this incorrectly??
73
Arie

----- Original Message ----- 
From: "Bert, VE2ZAZ" <ve2zaz at sympatico.ca>
To: "Arie Dogterom" <pa0ez at amsat.org>; <gps_standard at mailman.qth.net>
Sent: Thursday, January 25, 2007 1:20 PM
Subject: Re: [GPS_Standard] vcxo control averaging?


> 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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