Re: [time-nuts] GPSDO - Does it work?
Bobble ? On Jul 15, 2013 6:09 PM, "Tim Shoppa" wrote: > Unless your frequency counter has some anti-bobble tricks, you will always > see +/-1 bobble in the last digit. Of course with longer gates, this last > +/-1 becomes a smaller fraction of total count. > > I personally do not trust a digital meter or counter that doesn't have > bobble. I naturally think it's stuck unless it bobbles. > > Googling "anti bobble" turns up a lot of references to something to do with > fabric and nothing to do with counters and gates :-). > > Tim N3QE > > > On Mon, Jul 15, 2013 at 4:46 PM, Bob Stewart wrote: > > > Hi Mark, > > > > I just tried a10 second gate, and it's still the same, though the > > 4.999 happens less often. Could it be related to the fact that this > is > > a TTL signal? If I don't set the 50 ohm Z button it counts double - i.e. > > 10MHz. > > > > bob > > > > > > > > > > > > > > > > From: Mark C. Stephens > > >To: Discussion of precise time and frequency measurement < > > time-nuts@febo.com> > > >Sent: Monday, July 15, 2013 3:06 PM > > >Subject: Re: [time-nuts] GPSDO - Does it work? > > > > > > > > >Slow the Gate time down. > > > > > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
On Mon, Jul 15, 2013 at 8:09 AM, Bob Stewart wrote: > I expected either to see a solid 5.000, or to see it wandering > between 4.999 and 5.001. You'd expect only a one count ambiguity but you question is why 4. and not 5.1? I'm betting it is because of the fixed phase of the 5MHz signal relative to the gate timing. If the counter is counting the number of positive transitions inside a gate time, it might less the last one but would never see an extra. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
Unless your frequency counter has some anti-bobble tricks, you will always see +/-1 bobble in the last digit. Of course with longer gates, this last +/-1 becomes a smaller fraction of total count. I personally do not trust a digital meter or counter that doesn't have bobble. I naturally think it's stuck unless it bobbles. Googling "anti bobble" turns up a lot of references to something to do with fabric and nothing to do with counters and gates :-). Tim N3QE On Mon, Jul 15, 2013 at 4:46 PM, Bob Stewart wrote: > Hi Mark, > > I just tried a10 second gate, and it's still the same, though the > 4.999 happens less often. Could it be related to the fact that this is > a TTL signal? If I don't set the 50 ohm Z button it counts double - i.e. > 10MHz. > > bob > > > > > > > > > From: Mark C. Stephens > >To: Discussion of precise time and frequency measurement < > time-nuts@febo.com> > >Sent: Monday, July 15, 2013 3:06 PM > >Subject: Re: [time-nuts] GPSDO - Does it work? > > > > > >Slow the Gate time down. > > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
Without terminating the cable in 50 ohms, you're getting reflections that the counter sees as additional peaks in time. To see much at all one needs 12 digits of resolution. Brian On 7/15/2013 20:46, Bob Stewart wrote: Hi Mark, I just tried a10 second gate, and it's still the same, though the 4.999 happens less often. Could it be related to the fact that this is a TTL signal? If I don't set the 50 ohm Z button it counts double - i.e. 10MHz. bob From: Mark C. Stephens To: Discussion of precise time and frequency measurement Sent: Monday, July 15, 2013 3:06 PM Subject: Re: [time-nuts] GPSDO - Does it work? Slow the Gate time down. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5992 - Release Date: 07/15/13 - No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2242 / Virus Database: 3204/5992 - Release Date: 07/15/13 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
Hi Mark, I just tried a10 second gate, and it's still the same, though the 4.999 happens less often. Could it be related to the fact that this is a TTL signal? If I don't set the 50 ohm Z button it counts double - i.e. 10MHz. bob > > From: Mark C. Stephens >To: Discussion of precise time and frequency measurement >Sent: Monday, July 15, 2013 3:06 PM >Subject: Re: [time-nuts] GPSDO - Does it work? > > >Slow the Gate time down. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
Slow the Gate time down. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul Sent: Monday, 15 July 2013 11:27 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPSDO - Does it work? On Mon, Jul 15, 2013 at 3:51 AM, wrote: > So, I did the obvious, and perhaps naively expected to see a steady 5.000 > on the 5334B.? Instead, it bounces back and forth between 4.999 and > 5.000. You'll need a standard to determine the "truth". My recently "tweaked" 5335A (w/ OCXO) is +- 2 in the LSD when counting my various 10MHz sources. What I'd do: 1) make/buy another and pick one at not quite random to be right. 2) shorten the gate time (round off the count) until happy. In my case my two GPSDOs agree to the resolution of the 5335 so I believe them and and assume I need to adjust my Rb. Of course since I'm just fooling around a few nanoseconds* don't matter so much. *A nanosecond here a nanosecond there, pretty soon you're talking real time. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
OK, I'll buy that. Thanks! > > From: Tom Van Baak (lab) >To: Bob Stewart ; Discussion of precise time and frequency >measurement >Sent: Monday, July 15, 2013 11:02 AM >Subject: Re: [time-nuts] GPSDO - Does it work? > > >It's mathematical in both frequency, and in phase (clock and channel input >timing). Depending on relative cable lengths I suspect you can get lucky and >see it always wander 1 count above 5 MHz instead of 1 count below 5 MHz. But >you should not expect it to do both; that would be 2 counts; your counter is >better than that. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
It's mathematical in both frequency, and in phase (clock and channel input timing). Depending on relative cable lengths I suspect you can get lucky and see it always wander 1 count above 5 MHz instead of 1 count below 5 MHz. But you should not expect it to do both; that would be 2 counts; your counter is better than that. /tvb (iPhone4) On Jul 15, 2013, at 8:09 AM, Bob Stewart wrote: > In this case, I was using the 10MHz output from the GPSDO as the reference > and measuring the 5MHz output from the GPSDO. So, even if the GPSDO is off > in frequency, the relationship between the 10MHz reference and the 5MHz > signal are mathematically fixed. It just seemed strange to me that under > such a circumstance the final count would wander only in the minus direction. > I expected either to see a solid 5.000, or to see it wandering between > 4.999 and 5.001. > > Bob > > > > > >> >> From: Azelio Boriani >> To: Discussion of precise time and frequency measurement >> >> Sent: Monday, July 15, 2013 4:47 AM >> Subject: Re: [time-nuts] GPSDO - Does it work? >> >> >> It is normal for a counter to have a +/- 1 count of wander. Then you >> have to consider the reference for that counter. When you connect a >> GPSDO on the input of a counter with its internal reference used as a >> timing source, you are measuring that internal reference accuracy and >> stability, not the GPSDO's one. To verify a new GPSDO it is necessary >> to have another (know good) GPSDO or a Cs reference. Missing that, you >> can use the PPS output of the GPS receiver but then an average process >> is needed: say, a digital 'scope with the display persistence function >> and... wait a lot of time (or use a high resolution TI counter and the >> TimeLab software). >> >> >> > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
On 7/15/2013 10:09 AM, Bob Stewart wrote: > In this case, I was using the 10MHz output from the GPSDO as the reference > and measuring the 5MHz output from the GPSDO. So, even if the GPSDO is off > in frequency, the relationship between the 10MHz reference and the 5MHz > signal are mathematically fixed. It just seemed strange to me that under > such a circumstance the final count would wander only in the minus direction. > I expected either to see a solid 5.000, or to see it wandering between > 4.999 and 5.001. > > Bob If it is counting events, that means it never rounds up. So half the time starting with a 4 and half the time starting with a 5 means that you are in the window between (5 + delta) and (5 - delta) for a very small delta. If all you ever saw was 5.000... then your little window is somewhere in between 5.000...0 and 5.000...1 Is that really where you want to be? 4.... is your friend. Chris w0ep ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
Just 1 count: either you see -1, 0 or 0, +1. From -1 to +1 there are 2 counts and, unless the clock is affected by a really bad jitter, it is hard to see more than 1 count of wander in a setup like you did. Anyway, you need a trusted reference, feeding the counter with a 10MHz and counting the same 10MHz divided by 2, doesn't tell you anything. On Mon, Jul 15, 2013 at 5:09 PM, Bob Stewart wrote: > In this case, I was using the 10MHz output from the GPSDO as the reference > and measuring the 5MHz output from the GPSDO. So, even if the GPSDO is off > in frequency, the relationship between the 10MHz reference and the 5MHz > signal are mathematically fixed. It just seemed strange to me that under > such a circumstance the final count would wander only in the minus direction. > I expected either to see a solid 5.000, or to see it wandering between > 4.999 and 5.001. > > Bob > > > > > >> >> From: Azelio Boriani >>To: Discussion of precise time and frequency measurement >>Sent: Monday, July 15, 2013 4:47 AM >>Subject: Re: [time-nuts] GPSDO - Does it work? >> >> >>It is normal for a counter to have a +/- 1 count of wander. Then you >>have to consider the reference for that counter. When you connect a >>GPSDO on the input of a counter with its internal reference used as a >>timing source, you are measuring that internal reference accuracy and >>stability, not the GPSDO's one. To verify a new GPSDO it is necessary >>to have another (know good) GPSDO or a Cs reference. Missing that, you >>can use the PPS output of the GPS receiver but then an average process >>is needed: say, a digital 'scope with the display persistence function >>and... wait a lot of time (or use a high resolution TI counter and the >>TimeLab software). >> >> >> > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
In this case, I was using the 10MHz output from the GPSDO as the reference and measuring the 5MHz output from the GPSDO. So, even if the GPSDO is off in frequency, the relationship between the 10MHz reference and the 5MHz signal are mathematically fixed. It just seemed strange to me that under such a circumstance the final count would wander only in the minus direction. I expected either to see a solid 5.000, or to see it wandering between 4.999 and 5.001. Bob > > From: Azelio Boriani >To: Discussion of precise time and frequency measurement >Sent: Monday, July 15, 2013 4:47 AM >Subject: Re: [time-nuts] GPSDO - Does it work? > > >It is normal for a counter to have a +/- 1 count of wander. Then you >have to consider the reference for that counter. When you connect a >GPSDO on the input of a counter with its internal reference used as a >timing source, you are measuring that internal reference accuracy and >stability, not the GPSDO's one. To verify a new GPSDO it is necessary >to have another (know good) GPSDO or a Cs reference. Missing that, you >can use the PPS output of the GPS receiver but then an average process >is needed: say, a digital 'scope with the display persistence function >and... wait a lot of time (or use a high resolution TI counter and the >TimeLab software). > > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
On Mon, Jul 15, 2013 at 3:51 AM, wrote: > So, I did the obvious, and perhaps naively expected to see a steady 5.000 > on the 5334B.? Instead, it bounces back and forth between 4.999 and > 5.000. You'll need a standard to determine the "truth". My recently "tweaked" 5335A (w/ OCXO) is +- 2 in the LSD when counting my various 10MHz sources. What I'd do: 1) make/buy another and pick one at not quite random to be right. 2) shorten the gate time (round off the count) until happy. In my case my two GPSDOs agree to the resolution of the 5335 so I believe them and and assume I need to adjust my Rb. Of course since I'm just fooling around a few nanoseconds* don't matter so much. *A nanosecond here a nanosecond there, pretty soon you're talking real time. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO - Does it work?
It is normal for a counter to have a +/- 1 count of wander. Then you have to consider the reference for that counter. When you connect a GPSDO on the input of a counter with its internal reference used as a timing source, you are measuring that internal reference accuracy and stability, not the GPSDO's one. To verify a new GPSDO it is necessary to have another (know good) GPSDO or a Cs reference. Missing that, you can use the PPS output of the GPS receiver but then an average process is needed: say, a digital 'scope with the display persistence function and... wait a lot of time (or use a high resolution TI counter and the TimeLab software). On Mon, Jul 15, 2013 at 4:38 AM, Bob Stewart wrote: > OK, I finally decided to plug my new GPSDO into my 5334B and give it a try. > I made mine with 2 outputs: 10MHz and 5MHz. So, I did the obvious, and > perhaps naively expected to see a steady 5.000 on the 5334B. Instead, it > bounces back and forth between 4.999 and 5.000. Ummm? Yeah, it's > way more accurate than anything I can imagine needing, but it looks like I > still have two clocks? > > Bob - AE6RV > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPSDO - Does it work?
OK, I finally decided to plug my new GPSDO into my 5334B and give it a try. I made mine with 2 outputs: 10MHz and 5MHz. So, I did the obvious, and perhaps naively expected to see a steady 5.000 on the 5334B. Instead, it bounces back and forth between 4.999 and 5.000. Ummm? Yeah, it's way more accurate than anything I can imagine needing, but it looks like I still have two clocks? Bob - AE6RV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
