[time-nuts] 1 pps correction

[Azelio Boriani]

Oh, well, I have the original PRS10 manual as we (that is, the company)
bought a new PRS10 one month ago. I was enquiring wether or not it can be
scanned and sent to you. Now it no longer matters.

On Mon, Apr 2, 2012 at 11:35 AM, Stijn Nestra <stijn at pe1rks.nl> wrote:

> The PRS10 schematics are available on line from Didier.
> See the following link:
> http://www.ko4bb.com/manuals/**index.php?dir=05%29_GPS_**Timing/SRS<http://www.ko4bb.com/manuals/index.php?dir=05%29_GPS_Timing/SRS>
>
> Sincerely,
>
> Stijn
>
> Op 02-04-12 09:48, Azelio Boriani schreef:
>
>> OK, thank you. I'll collect the documentation you suggest to study it.
>> Yes,
>> the PRS10 manual available online has no schematic. The paper one does
>> have. Does this means that Stanford Research want it not to be
>> disseminated?
>>
>> On Mon, Apr 2, 2012 at 5:06 AM, Said Jackson<saidjack at aol.com>  wrote:
>>
>>  Hi Azelio,
>>>
>>> its a dual slope interpolator, much like the HP 5334A counter. In fact
>>> the
>>> 5334A service manual is very nice to go through to get lectured on how
>>> this
>>> works. The capture hardware is similar to the Linear Tech app note
>>> written
>>> by Jim Williams (mentioned in the time nuts archives). Basically its a
>>> very
>>> fast constant current source, and a high quality capacitor. Except Jim
>>> charges the cap, then uses an analog to digital converter to capture the
>>> time difference. We use a micro controller to capture the time difference
>>> on the cap, then capture how long it takes to discharge the cap with
>>> about
>>> ~1000x slower current than the charge current. Hence we get ~1000x to 1
>>> time dilution, which means the underlying 16.66ns counter resolution
>>> becomes a ~16.7ps resolution. While I have never seen the PRS-10 Rubidium
>>> schematics (anyone have them in PDF format?) I gather from the
>>> description
>>> in the service manual that they do something similar to this. The
>>> Wavecrest
>>> DTS user manuals floating around on the internet also explain how this
>>> works. So in short, all that is required to build a unit like this is a
>>> bunch of fast analog charge hardware, and an analog comparator that can
>>> trigger a counter capture event, and some software for calibration and
>>> control...
>>>
>>> bye,
>>> Said
>>>
>>> Sent from my iPad
>>>
>>> On Apr 1, 2012, at 4:07, Azelio Boriani<azelio.boriani at screen.**it<azelio.boriani at screen.it>>
>>>  wrote:
>>>
>>>  Said,
>>>> how complex is your 20pS time interval counter? Is it analog, FPGA,
>>>> something else (if you can disclose some info, of course)?
>>>>
>>>> On Sat, Mar 31, 2012 at 11:44 PM, Hal Murray<hmurray at megapathdsl.net
>>>> wrote:
>>>>
>>>>
>>>>> martyn at ptsyst.com said:
>>>>>
>>>>>> I’ve seen that the peak to peak jitter is reduced from something like
>>>>>>
>>>>> 27
>>>
>>>> ns
>>>>>
>>>>>> to<  10 ns.
>>>>>>
>>>>>
>>>>>  Is this a reduction of just the jitter, or is the actual accuracy to
>>>>>>
>>>>> UTC
>>>
>>>> also improved by this amount.
>>>>>>
>>>>>
>>>>> Have you read the hanging-bridges paper?
>>>>> Tom Clark and Rick Hambly: Timing for VLBI
>>>>> http://gpstime.com/files/tow-**time2009.pdf<http://gpstime.com/files/tow-time2009.pdf>
>>>>> I think that is the key to understanding this area.
>>>>>
>>>>> If you could average over many sawtooth cycles, you should get an
>>>>>
>>>> accurate
>>>
>>>> answer.
>>>>>
>>>>> The problem is that you don't get to pick how many cycles fit into your
>>>>> averaging time.  The sawtooth pattern is the beat between two
>>>>>
>>>> frequencies.
>>>
>>>> One of them is drifting with time/temperature.  If you are unlucky, the
>>>>> beat
>>>>> frequency can be very very low.
>>>>>
>>>>> The sawtooth correction lets you correct on a cycle-by-cycle basis.
>>>>>  You
>>>>> don't need to average over many samples.
>>>>>
>>>>>
>>>>> --
>>>>> These are my opinions, not necessarily my employer's.  I hate spam.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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