[time-nuts] How do I know my GPS stabilized oscillatoris working?

Sat Aug 12 12:50:48 EDT 2006

Thank you Ulrich, I will certainly give it a test drive and let you know
what I think.
I wanted to present a free analysis tool that would work with TIC232  for
young time-nuts that weren't aware of any options besides "doing AD by hand"
and I was familiar with AlaVar. Perhaps it will be your plotter program that
I
recommend to others in the future. Thanks for providing another option to
evaluate for use with TIC232. .

Sincerely,
Richard H McCorkle

----- Original Message ----- 
From: "Ulrich Bangert" <df6jb at ulrich-bangert.de>
To: "'Richard H McCorkle'" <mccorkle at ptialaska.net>; "'Discussion of precise
time and frequency measurement'" <time-nuts at febo.com>
Sent: Saturday, August 12, 2006 12:33 AM
Subject: AW: [time-nuts] How do I know my GPS stabilized oscillatoris
working?

Hi Richard,

> and feed the data into an Allan deviation calculator. A true
> Time-Nut would use Stable32 for detailed data analysis but at
> $395 this is not low cost. The free AlaVar calculator
> (http://www.alamath.com/alavar.html) can remove any time
> offset, scale the readings, has a built-in phase to frequency
> function to convert the time data, and generates an Allan
> deviation chart (be sure to set Tau for the sample period
> selected) that shows the stability of the GPSDO over time.

i have used ALAVAR a number of times and yes, compared to the $395
Stable 32 (that i also own and admire) every FREE tool that works
correct does indeed a good job. However, when it comes to easy data
manipulation, outlier extraction and the like, even Stable32 lacks some
features that i needed. That is the reason why i wrote me a tool of my
own. It es free, comes by the name "plotter" and you may download it
from

http://www.ulrich-bangert.de/html/downloads.html

It does everything that Alavar does plus some more and i hope that it
does everything a bit better and smoother than Alavar. There is only one
aspect in that it may seem inferior to Alavar: Reading multi-column data
is slower with my tool than with Alavar because in my concept ALL data
columns are read at the same time while in Alavar you have to decide for
a SINGLE data column.

Because it was you to suggest Alavar in this group and you seem to be
well acquainted to it, i thought you were a good test person for my
tool.

Best regards
Ulrich Bangert

> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Richard H McCorkle
> Gesendet: Freitag, 11. August 2006 20:52
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] How do I know my GPS stabilized
> oscillatoris working?
>
>
> A very low cost way to test your GPSDO is to generate 1Hz
> from the GPSDO with the TVB divider compare it to the GPS
> 1PPS with the Simple Time Interval Counter with RS-232
> Output(http://www.piclist.com/tehref/member/RHM-SSS-SC4/TIC232
> .htm), log the difference readings over time on a computer,
> and feed the data into an Allan deviation calculator. A true
> Time-Nut would use Stable32 for detailed data analysis but at
> $395 this is not low cost. The free AlaVar calculator
> (http://www.alamath.com/alavar.html) can remove any time
> offset, scale the readings, has a built-in phase to frequency
> function to convert the time data, and generates an Allan
> deviation chart (be sure to set Tau for the sample period
> selected) that shows the stability of the GPSDO over time.
> This provides a complete test system using 5-IC's for less
> than the cost of the box it's mounted in.
>      The Simple Time Interval Counter uses a Phillips HC4046
> phase detector, a 16F688 PIC, a 16M XO, and a MAX232 for
> RS-232 output. The low cost XO "dithers" the TMR1 clock to
> provide good averaging, but a high stability OCXO can be used
> for the TMR1 clock for high accuracy testing. Insure the TMR1
> clock and the DUT are from different sources for proper
> averaging. Adding an offset by inverting the DUT 1Hz to the
> TIC improves operation where the inputs are closely aligned.
> My test box uses a 14-pin 16F630 TVB divider with a 5M/10M
> frequency select pin and the arm and frequency select pins
> are driven from the TIC to allow arming and frequency
> selection by serial port command. An inverted 1Hz output is
> provided for the TIC, and a 1PPS with 100us duration aligned
> with UTC provides the DUT 1PPS output. (Thanks TVB for making
> this so easy!)
>
> ----- Original Message ----- 
> From: "Didier Juges" <didier at cox.net>
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> Sent: Sunday, July 30, 2006 11:04 AM
> Subject: Re: [time-nuts] How do I know my GPS stabilized
> oscillator is working?
>
>
> > Along those lines, I have a question.
> >
> > I am planning to (finally) finish my GPS stabilized OCXO using a
> > Jupiter receiver and an HP 10811-60102 OCXO recovered from
> a defunct
> > HP 8672A.
> >
> > The question that comes up is: how do I know my GPSDSO is
> working and
> > how do I evaluate its stability?
> >
> > I understand I could measure the control voltage from the phase
> > detector to the OCXO and plot it on the computer easily enough, but
> > that will only tell me the error between GPS and OCXO, which can be
> > significant in the short term, and that won't tell me who is right
> > (even though in theory, if the OCXO is any good, it should
> be the GPS,
> > then within a few hours or half a day, the GPS should take over).
> >
> > I have a Takeda Riken (Advantest) counter TR5823H that has the high
> > stability oscillator option (not as good as the HP OCXO)
> also and Time
> > Difference capability but no GPIB port, so I cannot get the
> output to
> > a computer. If anyone has the schematics for that counter, I may be
> > able to jury rig something to get the display to a computer.
> >
> > I have a couple of HP generators that have their own OCXO,
> I believe
> > they are also 10811 (a HP 8673M synthesizer and a HP 3586A
> with high
> > stability option). I also have another HP 8672A (on loan
> for now, but
> > I can get it back if needed) and I have an EIP 371 counter with an
> > OVENAIR OCXO (part number unreadable until I remove the
> OCXO from the
> > chassis, and I do not have the spec for it). Finally, I have a Tek
> > 494P with the excellent OCXO Tek has put in it (I do not know who
> > makes it). So any of these instruments could be used as a reference
> > against which I could measure my GPSDSO, but how do I know who is
> > right?
> >
> > Aside from the fact that some instruments specify the stability in
> > days and others in year does not help determine the best
> oscillator,
> > which should I use and how should I interpret the results? For
> > instance, is the Tek 494P at 1x10-7/year better than the HP
> 8673M at
> > 5x10-10/day? Since the HP 3586 uses a 10811 OCXO at 2x10-7/year vs.
> > 1x10-7/year for the Tek, it seems the Tek has better long
> term spec,
> > but what does it mean for short term stability?
> >
> > Should I go out and by an HP counter with time difference and GPIB?
> >
> > Is there another alternative that will not require another
> piece of HP
> > gear in my lab?
> >
> > Here are the specs I found for the oscillators I have:
> >
> > Tek 494P       1x10-7/year (after initial 6 months)
> > HP 8673M     5x10-10/day (after 10 day warmup)
> > HP 8672A      5x10-10/day (after 30 day !!! warmup)
> > HP 3586A      2x10-7/year
> > TR 5823H      5x10-8/day
> >
> > Thanks in advance for any suggestion or comment.
> >
> > Didier KO4BB
> >
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>
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