[time-nuts] Z3805 initial behaviour after power up

Ulrich Bangert df6jb at ulrich-bangert.de
Wed Jun 17 05:07:32 EDT 2009


Steve,

my PLOTTER utility. I thought you did already try it out?

73s Ulrich, DF6JB

> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Steve Rooke
> Gesendet: Mittwoch, 17. Juni 2009 11:03
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] Z3805 initial behaviour after power up
> 
> 
> Ulrich,
> 
> What are you using to produce the graph you attached please?
> 
> 73,
> Steve
> 
> 2009/6/17 Ulrich Bangert <df6jb at ulrich-bangert.de>:
> > Gents,
> >
> > yesterday I received the Z3805 that I had bought from 
> fluke.I on eBay 
> > and immediately put it to work. I recorded the EFC value as well as 
> > the PPS TI value over about 20 hours. Attached is the graph of thes 
> > two values.
> >
> > I interprete this graph in this way:
> >
> > 1) Immediately after power up (perhaps up to the end of the site 
> > survey) the regulation loop seems to work with a very short time 
> > constant which is able to bring the PPS TI close to zero 
> although the 
> > OCXO has lots of drift at this time.
> >
> > 2) Then the loop time constant seems to switch to a 
> significant higher 
> > value which does not keep up with the oscillator's drift, 
> which leads 
> > to the negative excursion of nearly 500 ns.
> >
> > 3) This seems to be too much for the regulation which leads to 
> > switching back to the short time constant and to bring the 
> PPS TI back 
> > to near zero and to return to the longer time constant again...
> >
> > 4) ...which lets the procedure repeat again and again: 
> Drift to -500 
> > ns and pullback.
> >
> > 5) Note that I thought it was a kind of malfunction and send a 
> > :system:preset command to the device after the last negative PPS TI 
> > spike. The result was, that the total procedure repeated: About 2 
> > hours of PPS TI close to zero then again the drift and pullback 
> > procedure however with a reduced drift rate.
> >
> > 6) After 11 hours or so the regulation loop's time constant 
> seems to 
> > match the OCXO's drift and a "real" lock of the pll seems to take 
> > place. (The lock led had been on already hours ago...)
> >
> > Since I do not have an manual for the Z3805: Can any of you Z3801 
> > owners second this behaviour to be normal or would you 
> think that it 
> > is kind of special for the Z3805 or even a real malfunction (in the 
> > sense that the OCXO's drift is above the specs in the beginning)?
> >
> > Best regards
> > Ulrich Bangert
> >
> > Ulrich Bangert
> > www.ulrich-bangert.de
> > Ortholzer Weg 1
> > 27243 Gross Ippener
> >
> > _______________________________________________
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> >
> 
> 
> 
> -- 
> Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
> A man with one clock knows what time it is;
> A man with two clocks is never quite sure.
> 
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