Hello Bert, What is the cyan-colored trace seen in these screen shots? And is "1 ppt" the same as 1E-12 (just to be sure)?
Are these from LH? Thanks, Dana On Tue, Oct 2, 2018 at 1:46 PM ew via time-nuts <time-nuts@lists.febo.com> wrote: > We see the glitches all the time, they exist and with proper equipment are > very visible. These are telecom timing devices and the way they correct the > 1 pps is by changing the frequency. Even LH shows it and it is very visible > when you eliminate the other traces.What we call the Tbolt 2, the nicely > packaged Trimle that also was part of the fraud listing does the correction > once an hour. It is exact an hour function of when you powered it up.In my > case night time spikes where mostly negative Air conditioner. Recovery is a > function of the accumulated error. Standing next to it in front of my 19 > year old M300 it did effect the recovery since my legs where within a > foot. One picture shows the analog trace to.Original Tbolt does it > constantly. We have spend a couple of years on this, hoping to optimize a > clean up loop.so far no good results.Bert Kehren > In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time, > tsho...@gmail.com writes: > > Dana, the short term few-ns jitter of the two phases, I think in a digital > instrument is most likely data acquisition glitches. > > Even on a good old analog scope, jitter in the trigger circuit or jitter in > amplitudes (with resulting changes in harmonic content and thus the shape > of the curves) can cause the apparent zoomed in zero crossing to shift very > similarly. > > In days of old the telco standards for frequency stability also included > requirements for amplitude stability noise, directly related to making > repeatable measurements using scopes. I'm gonna see if I can find some of > those. I remember some crazy looking telco standard that required measuring > amplitude noise on time scales measured in weeks. > > Tim N3QE > > On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <k8yumdoo...@gmail.com> wrote: > > > I cheered when I saw Dave B's "silly question", for > > then I realized that I'm not the only one who likes > > to measure things with an o'scope. > > > > I had purchased a GPSDO a few weeks before and > > had been observing its behavior relative to a free- > > running Rb by watching 10 MHz sinewaves drift with > > respect to each other as an aid in setting the Rb's > > frequency. However, I was seeing enough fairly > > rapid random drift to limit the usefulness of this kind > > of observation. It dawned on me that I was sometimes > > seeing drifts of several ns over the course of just > > several seconds, thus implying that sometimes the > > relative frequency error between the two sources was > > reaching as high as roughly 1E-9. I wanted to be able > > to capture and plot a somewhat extended run of data > > so I could try to understand this behavior better. > > > > Being TIC-less, I decided to see what I could do with > > my o'scope, which is a Chinese-made 2-channel DSO > > with synchronous sampling by the two channels and > > with a respectable trace memory depth (28 MSA per > > channel). > > > > I began this effort in earnest a couple of days before I > > saw Dave's question, and have only now brought it to > > a sufficient state of completion to feel justified in reporting > > some results. > > > > I am presently able to record about 45 minute's worth of > > data as limited by the 'scope's trace memory, but my XP > > computer's RAM space limits me to processing only about > > 35 minutes of that in a seamless run. Over that time > > span I've seen a peak relative frequency discrepancy of > > about 1.4E-9, with a handful reaching or exceeding 1E-9. > > I've also measured average frequency differences between > > the source's a a few parts in 10E11. > > > > Most of the effort went into developing a C program to do > > the processing and then correctly scaling and displaying > > the results in a form which I considered useful to me. This > > processing of course had to deal with an off-frequency and > > drifting 'scope timebase, which is *horrible* compared to the > > quantities under measurement (as expected from the outset). > > > > Present indications are that at this level of GPSDO mis- > > behavior, the results I'm viewing are about 20 dB higher > > than the basic floor, which I am still characterizing. I > > believe that the floor is limited primarily by uncorrelated > > sampling jitter between the two 'scope channels. > > > > If there is an expression of interest in this technique, I'll > > publish a detailed description of the technique and some > > plots showing results, probably in the form of an attachment > > in pdf format. > > > > Dana > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.