[time-nuts] Z3805 initial behaviour after power up

Steve Rooke sar10538 at gmail.com
Wed Jun 17 05:03:11 EDT 2009


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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