[time-nuts] Time keeping Netherlands beter readable

EJ Kroon ejkroon at hetnet.nl
Mon Aug 8 15:06:52 EDT 2005

Hereby some information how we keep time in the Netherlands. We use four cs 5071A high stability clocks in an electro magnetic shielded laboratory.
The temperature is 23 degrees Celsius +/- 0.1 degrees. Relative humidity is between 45% and 55%. The frequency output of the clocks is coupled 
via micro phase steppers to correct the output frequency of the cs (steering resolution 3x10E-19). The clocks are compared using Stanford research  
interval counters (SR630). The signal are compared to TV signals, DCF77, GPS (Topcon, 3S navigation and others),Glonass (Topcon, 3S) for our customers. 
Our time UTC(VSL) is compared to PTB via Two Way Satellite Time and Frequency Transfer (TWSTFT) by special PRN modems (Mitrex and Satre). 
This is send on the Ku band using 2.4 double optics offset dish. We have developed a special satellite simulator to measure our delay of our system. 
The TWSTFT is preformed 4 times a day to several laboratories; PTB, NPL, OP, UNSO, NIST and others. 
The absolute timing uncertainty is about a 4 ns. Also we have a link to Asia (TL). Our uncertainty of frequency is better 2E-14 for 24 hrs. 
This is in brief our system in the Netherlands.


Erik Kroon

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