[time-nuts] 58503A VS SR625

Bob kb8tq kb8tq at n1k.org
Mon May 28 10:17:21 EDT 2018


If you are seeing 0.3 ppb delta between various HP GPSDO’s the first question would be “on for how long? / under what conditions?".  The HP devices take a *long* time 
to settle in ( like weeks ) to their final best performance loop settings. To fully settle, they need to be locked the whole time. Staying locked means an antenna that has a 
good satellite view and the unit having a solid survey location. If they are dropping out of lock from time to time, they will never really settle. 

Once settled, you still have a noise process. ADEV is one way to plot this sort of noise. Your results will still depend on the gate time on your counter(s) since that impacts 
how you “see” the noise.  A very short gate will give you more variation than a longer gate. Put another way, “tau” is part of any frequency measurement, even if ADEV is 
not being calculated. 


> On May 28, 2018, at 8:25 AM, Anton Moehammad via time-nuts <time-nuts at febo.com> wrote:
> Hi All, I have 5 pcs 58503A with various firmware and 3 of them have 8 channel recv and 2 have 6 channel receiver all is working but I found none of 5 has same result I mean when I compare it with my SR625 use SR620 or my CNT-90 use timelab there is a variation in the output.the variation about 3 E-9 Hz. yes use same cable and same antenna, I also monitor the temp and I sure the temp variation is very minimal.any one has explanation about this ?Thank YouAnton
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