[time-nuts] Z3801 Newbie Question

Artek Manuals Manuals at ArtekManuals.com
Thu Jan 28 16:49:02 UTC 2016


My Z3801A came out of mothballs after 15 years in controlled storage and 
appears to be behaving. now I am curious as to what I am seeing

First I am not truly a "time" nut ( I am semi retired and have not worn 
a watch since October 12th 2008 :-) ). I am probably more of "frequency" 
nut . I use the Z3801A as my 10MHz reference. Having a reference source 
that is good to .1Hz at 10MHz is more than adequate as a reference for 
my counters, signal generators and and spectrum analyzers. But like all 
engineers if you give me the numbers I an drawn to trying to figure out 
what they are telling me.

My Z3801A has been on for about 2 weeks now and typically reports 1PPS 
+/- 20ns readings 20 hours/day. Then all of a sudden once or twice a day 
it will go nuts and the variation increases to +/- 80ns for an hour or 
two before settling back down. Watching the 10mhz on a 10 digit counter 
shows no short term change in the frequency of the OCXO when the thing 
goes nuts there are slight changes in EFC but nothing dramatic vs any 
other hour to hour variation. The Allen and modified Allen deviation is 
around 2e-13 as it approaches 1e5 samples

Here is the setup
1) Z3801A
2) Symmetricom 58532A antenna, just above the roof, with 8 feet of RG213 
to the Z3801A
3) Running on a lab grade power supply at 48.5 volts (voltage variation 
over time is less .05 volts)
4) Lab runs at 73deg F +/- 2 degrees , humidity is NOT closely controlled
5) Running Z38xx software
6) Elevation cutoff on satellites is set for 15 degrees

And here is the question is the sudden jump in the pps deviation due to 
ionospheric and the satellite constellation change? IS there anything I 
can do to minimize it (or is it even necessary to worry/ wonder about)  
This behavior has going on since the beginning so it is not likely 
related to events earlier in the week. But that set me to wondering 
could I minimize it by say raising the elevation mask? Are there 
satellites in the constellation that are notorious for noise etc  that 
could be excluded from the tracking list ...etc etc


A man with a watch always knows what time it is
A man with two watches is never quite sure

Manuals at ArtekManuals.com

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