[time-nuts] Considerations When Using The SR620

Bob Camp lists at rtty.us
Sun Dec 2 20:12:34 UTC 2012


Some of the problem comes from the OCXO. Some of it also comes from the stability of the internal circuitry. They do some interesting things with delay lines and the like in the SR620. Best bet is to let it warm up for a while before you need it to perform at it's top level of performance. 


On Dec 2, 2012, at 2:45 PM, Paul DeStefano <paul.destefano at willamettealumni.com> wrote:

> All,
> 	The following comment appeared on this list recently and it scared me a little:
>> Though the SR620 TIC is a great instrument when hunting the pico seconds we have to realize, that it's a thermal design desaster (I have to apologize to all sr620 friends). I have to run it for at least 12 hoursif not 24 to be shure, that every single part is at a more or less stationary thermal state. Some (NERC) say "...never switch it off".
> I assume this instability is due to the instability of the internal frequency standard.  There are two options for the SR620: the standard oscillator and an ovenized oscillator.  In fact, in our measurements, we plan to use a Cesium frequency standard as the timebase to our SR620. Does this anecdotal warning apply generally to the instrument or mainly to the use of the internal standard oscillator?
> We are using the SR620 to measure the interval between 1PPS signals from two clocks.  One is the Septentrio PolaRx4 GPS receiver and the other is a Rubidium clock.
> Many Thanks,
> Paul
> -- 
> Paul DeStefano
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