[time-nuts] Z3801 Newbie Question

Tom Van Baak tvb at leapsecond.com
Thu Jan 28 12:25:04 EST 2016


Dave,

Plot the #SV tracked and signal strength(s) over a couple of days. See if your once or twice a day glitches correlate to periods of low reception.

To see what the reception of other z3801a owners look like:

http://www.realhamradio.com/GPS_websites_list.htm

You may even want to try a lower mask instead of a higher mask. It's a trade-off between fewer SV with solid reception and more SV with possibly spotty reception. 

Easy experiment: try 0 degrees for two days, then 15 degrees, then 30 degrees.

What I do is issue a syst:stat? command every 30 seconds. It's easy then to go back to the log files and check things like constellation changes and elevation, or brief or prolonged periods of holdover, etc.

/tvb

> On Jan 28, 2016, at 8:49 AM, Artek Manuals <Manuals at ArtekManuals.com> wrote:
> 
> OK
> 
> 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
> 
> Dave
> NR1DX
> ArtekManuals.com
> 
> A man with a watch always knows what time it is
> A man with two watches is never quite sure
> 
> -- 
> Dave
> Manuals at ArtekManuals.com
> www.ArtekManuals.com
> 
> 
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