[time-nuts] Re: A beginner's question.

[ordnit]

Hi Bob,
thank you for the clever suggestion. I jumped the "have a look with a 
good oscilloscope at what is going on ".

So, the point is: using the splitter, the voltage on the 50ohm line 
drops to 0.6V (peak). Triggering at 1V was a mist ake.

I managed run 5 times Timelab for 1000s with different trigger levels, 
from 0.1V to 0.5V.

1second ADEV  with increasing trigger level:
0.1V 6.88E-10	
0.2V 7.05E-10
0.3V 7.00E-10
0.4V 7.14E-10	
0.5V 7.28E-10

10seconds ADEV  with increasing trigger level:
0.1V 7.05E-11		
0.2V 7.07E-11	
0.3V 7.03E-11	
0.4V 6.89E-11	
0.5V 7.40E-11

Performances are best with high trigger level.

Let me attach a nice picture. Thank you for valuable help. I love to 
learn from my mistakes.


adelmo iz6cus


Il 14/05/2023 23:04, Bob Camp ha scritto:
> Hi
> 
> One suggestion:
> 
> While you have the counter sitting there, play with the trigger settings and input levels.
> You may find a way to improve things a little bit. No need to go to the 1000 second level.
> A 100 second run looking at 1 and 10 second data will tell you what you need to know.
> 
> Bob
> 
>> On May 14, 2023, at 1:21 PM, ordnit via time-nuts <time-nuts at lists.febo.com> wrote:
>>
>> Hi all,
>> I've been reading the ML for quite a long time. In the last weeks I managed to have some spare time to try some measurements, just to see how far is "reading" from "trying".
>>
>> My lab is made up of a pair of GPSDO (UCCM modules with an external antenna and good sky coverage), a 53131A and a pair of quartz oscillators that were ripped from some scrap instruments.
>>
>> Before trying to measure ADEV on a OCXO, I just wanted to see how deep is the noise floor with my setup. I read in old post (2012) that I could perform some tests using a the PPS output from the GPSDO, a power splitter and two coaxial cables of different lenght. So i put the counter in "t1 to T2" mode, auto-trigger on channel OFF and performed a very long ADEV analisys in TI mode.
>>
>> Results I found were, in some ways, encouraging (to me):
>> 1s	Sigma(tau) 	6.59E-10
>> 10s			6.96E-11
>> 100s			7.12E-12
>> 1000s			7.01E-13
>>
>> Tomorrow I'm going to perform more tests in fequency mode, by looping the 10MHz out of the counter, to its channel 1 input and performing ADEV analisys to. According to what I read, results should be quite different.
>>
>> My question is: am I going on the right way? Are the tests I performed somewhat meaningful?
>>
>> Thanks in advance.
>>
>> Best regards.
>>
>> adelmo
>>
>> References:
>> Best counter setting for ADEV? - Time-nuts ML Oct 1 2012
>> Recommended parameters for Timelab ADEV analysis - Time-nuts ML Nov 15 2012
>> Measuring ADEV for a beginner - Time-nuts ML Nov 1 2014
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at lists.febo.com
>> To unsubscribe send an email to time-nuts-leave at lists.febo.com
> 
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