On Wed, 08 Nov 2006 18:00:33 -0500, John Ackermann N8UR <[EMAIL PROTECTED]> wrote:
>Another way is to use an oscilloscope to watch the drift of the Z3801A >versus the Spectracom. You can set the scope up to show a Lissajous >display, or just use one signal to trigger the scope while viewing the >other. Either way will let you calculate the frequency offset by >measuring how quickly the Spectracom signal drifts some amount (e.g., 1 >cycle) away from the reference. Assuming you think the GPS reference is good, using an o'scope to compare phase is what I have done. Just the simple sine waves on two different channels to watch. If there is significant drift, adjust the one you are measuring to stop the drift. During that alignment you can put them in a known phase state. On some of the OCXO's I have played with, the adjustment is too coarse to ever set it properly. On a few others, I noticed a "jumpy" quality to the signal I was trying to set. Can't like those results. In spite of the good name-brand of those, they are now in my third string. On a few after syncing I was able to get what I thought was a good stability over a couple of days. If they are staying close, a stopwatch and measuremnent of drift over a period of time can give a relative stability measurment. Seeing bad things on several "good" by reputation OCXO's that I bought on the internet, I'd say, first look and see if it is really working as it should. After that and some tuning as described, you can then start looking at the finesse that this group cares about. This is my first-order approach. Having seen bad things from several, what I thought would be good, oscillators I would recommend you look at the actual signal and see if you can tame it and if it looks clean and good on the oscilloscope before you waste time on statistical analysis. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
