[time-nuts] Z3805 initial behaviour after power up

Steve Rooke sar10538 at gmail.com
Wed Jun 17 05:28:59 EDT 2009


Ulrich,

I must have lost the plot here but I thought that was only for HPIB
data. How are you collecting the data?

73,
Steve

2009/6/17 Ulrich Bangert <df6jb at ulrich-bangert.de>:
> 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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>> > and follow the instructions there.
>> >
>>
>>
>>
>> --
>> 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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>
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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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