[time-nuts] 10MHz Rubidium reference source for frequency counter

Karen Tadevosyan ra3apw at mail.ru
Fri Oct 31 15:57:51 EDT 2014


Thanks All for your comments and clarifications.

The next OCXOs have been tested today:
	* Morion MV89A 10.000MHz  #1
	* Morion MV89A 10.000MHz  #2
	* Morion MV89A 10.000MHz  #3
	* Isotemp 131-191 10.000MHz #1
	* Pilot C3Z 10.000MHz 
	* Bliley NV26R891 100.000MHz
	* Giacint-M 5.000MHz 

Measurement set up:
	* Pendulum CNT-91 with TimeBase opt.19 and 10
	* Prologix GPIB-USB 
	* TimeLab V1.2 (x64)
	* Windows7 Pro (x64)  
	* PC i5 /3.4GHz / 16GB 

ADEV results https://dl.dropboxusercontent.com/u/21338179/hamradio/OCXO_Adev/ocxos_adev_test_20141031.jpg
TimeLab configuration https://dl.dropboxusercontent.com/u/21338179/hamradio/OCXO_Adev/timelab_adev_config.jpg
All OCXO's TimeLab TIM files can be download https://dl.dropboxusercontent.com/u/21338179/Hamradio/OCXO_Adev/OCXO_Adev.zip

> A good MV89A can be below 1E-12.
As you can see ADEV of all my tested OCXOs are not better than 4E(-10) for tau =1s.
Question: can I be more or less happy with this result or something wrong in my measurement?
Karen
 
> Date: Thu, 30 Oct 2014 23:32:48 +0100
> From: Adrian <rfnuts at arcor.de>
> 
> Karen,
> 
> as by the datasheet, the time interval resolution of your counter is 50 ps.
> This translates into an ADEV value of 5E-11 at tau = 1 sec, 5E-12 at 
> tau = 10 sec etc,  and represents the theoretical measurement limit of the counter.
> It can be measured by feeding the same signal into both inputs (start 
> and
> stop) at the same time. A short delay (additional length of coaxial
> cable) at the stop input keeps the counter from producing phase wraps 
> (jumping between a full input signal period and zero).
> 
> A good MV89A can be below 1E-12. For measuring two good MV89A's 
> against each other, a TI resolution of 50 ps is insufficient because 
> up to 100 sec, to the most part of it, the actual ADEV of the 
> oscillators can be below the measurement limit of the counter.
> 
> Adrian




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