[time-nuts] Fwd: Re: Help needed with frequency standard

[Luiz Alberto Saba]

-------- Mensagem encaminhada --------
Assunto: 	Re: [time-nuts] Help needed with frequency standard
Data: 	Wed, 30 Sep 2020 09:10:07 -0300
De: 	Luiz Alberto Saba <las at intercat.com.br>
Para: 	Dana Whitlow <k8yumdoober at gmail.com>



Dana & Mark:

I have a PM-6685R counter and a CNT-90.
I "calibrated" the rubidium of thr 6685 the following way:
Use the output of 6685 to feed the timebase of CNT-90 and measure, using 
statistical mode, 1 measure/s, for 7200 sec the output of my thunderbolt 
in a "calm" period of the day. Then I adjust the rubidium utnil CNT-90 
reads 10.000.000.000.000 after 2 hours. Time consuming and a patience 
test, but I could not think in other way to calibrate my 6685 and CNT-90.
Well... Using the same CNT-90 with the same rubidium timebase from 6685 
to read the output of my PRS-10 connected to a 1 pps source, during the 
same 2 hours, the p-p variance of the reading was about 3 mHz. It's low? 
yes, but i was expecting much less. Something in the uHz range.
I did something wrong or that's it?

Em 29/09/2020 23:23, Dana Whitlow escreveu:
> Mark:
>
> I don't have a PPS syncable PRS-10 yet, but will probably be getting one
> within a
> year or so. My expectations are not great, however, because I already know
> that
> the received GPS time has diurnal wiggles to the tune of up to 10's of 
> nsec
> p-p.
> And I also know that the PRS-10 (and probably all others in its price
> class) make
> seemingly random frequency "adjustments" on a time scale of just a few
> hours.
> For a GPS disciplining loop to fix both, it would have to have a loop time
> constant
> long compared to a day on the one hand, yet a loop time constant of well
> under a
> day on the other. It's kind of tough to have one loop with both properties
> at once.
>
> Dana
>
>
> On Tue, Sep 29, 2020 at 1:22 PM Mark Spencer <mark at alignedsolutions.com>
> wrote:
>
>> I would be curious to hear from those who have a GPS disciplined PRS 
>> 10 in
>> their home time labs. I was never that impressed with the performance of
>> one of mine in that configuration from a 10 MHz ADEV perspective (I 
>> did try
>> making a few parameter changes.) I ended up essentially free running mine
>> but would occasionally apply a 1pps signal to mine as means of adjusting
>> its output frequency on an as needed basis.
>>
>> I may try this again with a different PRS10 (the 1pps output on the unit
>> in question failed a few years ago but I have a spare that has been
>> recently put into service.) Perhaps the second unit will work better.
>> Both units were obtained via the usual auction site.
>>
>> Mark Spencer
>> mark at alignedsolutions.com
>> 604 762 4099
>>
>>> On Sep 29, 2020, at 8:02 AM, Luiz Alberto Saba <las at intercat.com.br>
>> wrote:
>>> Hi guys
>>>
>>>
>>> I want a stable & reliable frequency standard.
>>>
>>> I do NOT have a cesium beam.
>>>
>>> I DO have a lot of gpsdos and some rubidiums.
>>>
>>> Since I have one PRS-10 and this device has a 1 pps input, you already
>> know what I'm thinking...
>>> What I have:
>>>
>>> Trimble Thunderbolt
>>>
>>> Trimble UCCM
>>>
>>> Symmetricom UCCM
>>>
>>> Samsung UCCM
>>>
>>> HP 58503A
>>>
>>> TruePosition
>>>
>>> Oscilloquartz Star 4+
>>>
>>> and a little board with a ublox LEA 5T and 1 pps output.
>>>
>>> Which device is more suitable for disciplining the PRS-10?
>>>
>>> My gps antenna setup is:
>>>
>>> Symmetricom 58532A on the top of the water tank of my building with a
>> very good sky view.
>>> A Raven Industries LA-21-1575-100-T. About 50 m of RG6.
>>>
>>> A Symmetricom antenna distributor (don't remember the code but is the 4
>> outputs one)
>>> By the way... Someone knows the delay of the inline amplifier and the
>> antenna distributor? (for Lady Heather)
>>> Mark Sims is out there reading this list? I'm having problems with LH
>> 6.14 and the UCCM units.
>>> Any help you can give me will be welcomed.
>>>
>>>
>>> Thanks
>>>
>>>
>>> Luiz Alberto Saba
>>>
>>> from Santos - São Paulo - Brazil
>>>
>>>
>>>
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