Martyn, The stability of timing systems depends on both the type of fundamental noise processes in a timing distribution system and how the various processes spectrally combined through processes that shape noise such as clock servo loops and measurements system. Consider the noise processes of an oscillator which is a fundamental building block. Oscillator noise can be modeled effectively as a sum of power-law noise processes. Power law noise has a fixed slope when observed on a log-log spectral plot. When the slope is zero, the nose is simply white noise. White noise is well behaved statistically and we can describe stability using strait-forward concepts like standard-deviation or variance. Unfortunately oscillators exhibit other power-law noise that is not well behaved. For example, flicker noise (1/f) is a non-stationary divergent process. One cannot associate a simple standard-deviation or variance metric to a flicker noise process. Allan variance metrics address this issue by providing a theoretically sound means of extracting and estimate of the type of power-law noise processes present as well as the intensity. On a log-log Allan Variance plot, the type of noise is identified by the slope in the region the noise dominates. The intensity of the noise is identified by the position of the line. Allan variance is not a single metric but rather a family of metrics. New members of the family have been adopted over the years to address new modeling needs. Including TVAR, TDEV, MTIE and minTDEV. minTDEV might be interesting for many people on this list since it is used to measure stability of sync in a packet network !! Let me know if that helps, -Jeremy B. PS. What products did your friend test :-) -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of time-nuts-request@febo.com Sent: Thursday, February 14, 2008 4:05 AM To: time-nuts@febo.com Subject: time-nuts Digest, Vol 43, Issue 33 Send time-nuts mailing list submissions to time-nuts@febo.com To subscribe or unsubscribe via the World Wide Web, visit https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts or, via email, send a message with subject or body 'help' to time-nuts-request@febo.com You can reach the person managing the list at time-nuts-owner@febo.com When replying, please edit your Subject line so it is more specific than "Re: Contents of time-nuts digest..." Today's Topics: 1. Re: gps timing antennas (WB6BNQ) 2. Z3801A schematics? (d.seiter@comcast.net) 3. Re: gps timing antennas (Brian Kirby) 4. Re: Trimble Thunderbolt Rs-232 Levels (Didier Juges) 5. Re: gps timing antennas (Didier Juges) 6. Re: GPS Locked and Unlocked Performance Comparison (Didier Juges) 7. Allan variance Vs Plain Old Accuracy (Martyn Smith) 8. Re: GPS Locked and Unlocked Performance Comparison (Luis Cupido) ---------------------------------------------------------------------- Message: 1 Date: Wed, 13 Feb 2008 18:57:46 -0800 From: WB6BNQ <wb6bnq@cox.net> Subject: Re: [time-nuts] gps timing antennas To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Message-ID: <47B3AE2A.A517EC43@cox.net> Content-Type: text/plain; charset=us-ascii Hi Brian, Have you ever published your efforts with making the choke ring out of pie plates ? If so do you have that available with, hopefully, pictures, deminsions and so forth ? I have one of the Timing 2000 antennas. Did you use the choke ring pie plate with it ? thanks, 73....Bill....WB6BNQ Brian Kirby wrote: > The Motorola Timing 2000 and 3000 antennas are patch antennas. They > have a pointed radome. The have very little ground plane, which > reduces reception near the ground, which is desirable because of multipath > effects. They also have quite a bit of filtering, so transmitting > antennas near the units, will not affect them. > > If you are not having a problem with multipath, a regular patch type > antenna probally from anybody should work well. > > If you are having multipath problems a timing antenna should help or a > choke ring assembly should help. I have built choke rings out of pie > plates, and Dr. Tom Clark made a basic choke assembly using a common > electric junction box. > > I had problems with multipath because of mountains about 3/5 around my > location. I changed the look angles so my receivers only receive > above 20 degrees above the horizon and I use timing antennas now. > > Brian KD4FM > > Matt Ettus wrote: > > Is there really anything in particular which is different about the > > antenna requirements of timing receivers as compared to ordinary > > high-quality receivers? The timing antennas seem to be in pointy > > radomes, so that tells me they are probably quad-helixes rather than > > patch antennas. How is that advantageous for timing in particular? > > > > Thanks, > > Matt > > > > _______________________________________________ > > 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. ------------------------------ Message: 2 Date: Thu, 14 Feb 2008 05:21:44 +0000 From: d.seiter@comcast.net Subject: [time-nuts] Z3801A schematics? To: <time-nuts@febo.com> Message-ID: <021420080521.8509.47B3CFE8000461080000213D22007456729D0A9B070A9CD20B@co mcast.net> Are any schematics available, especially for the power supply board? -Dave ------------------------------ Message: 3 Date: Wed, 13 Feb 2008 23:23:16 -0600 From: Brian Kirby <kirbybq@bellsouth.net> Subject: Re: [time-nuts] gps timing antennas To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Message-ID: <47B3D044.6050408@bellsouth.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed I put pictures out on the net years ago. I put two rulers in the pictures to show folks the dimensions. Back then we used the stock Motorola Antenna97, a patch antenna. I have a set of the antennas stored. When I get to the storage location this weekend, I will try to remember to shoot another set of pictures. As I recall, I found a common size aluminum cake pan set of 5 pans that came close to the needed choke ring dimensions. The smallest pan was turned over and some of the rim was removed and the antenna was glued to it with epoxies. Then then remaining pans were used face up and centered via a bolt. I used some square aluminum tubing on the bottom to attach pipe clamps, and it was mounted to a pipe mount. The other two sets that I have, are attached to adjustable laser level mounts, which is attached to surveying tripods. I did some carrier phase surveying using the Motorola Oncore VP gps receivers and in general had positioning repeatability of just under 3/4 of an inch. Of the bat, somewhere either NASA or NGS published data (on the web) on choke ring antennas back when choke rings first came out. They had photos and measured dimensions and some performance data on the electrical phase centers/error on these antennas. I believe the test were performed in Maryland, Virginia or DC area. Also, I do not remember if it was on this list or the earlier TAPR list, it was discussed using the choke ring assembly off of a 3.7-4.2 Ghz satellite TVRO feedhorn assembly. Choke rings can be wide bandwidth and low "Q" or narrow band and high "Q". If Dr. Clark is still on the list, he may be able to enlighten everybody. Brian KD4FM WB6BNQ wrote: > Hi Brian, > > Have you ever published your efforts with making the choke ring out of > pie plates ? If so do you have that available with, hopefully, > pictures, deminsions and so forth ? I have one of the Timing 2000 > antennas. Did you use the choke ring pie plate with it ? > > thanks, > > 73....Bill....WB6BNQ > > Brian Kirby wrote: > > >> The Motorola Timing 2000 and 3000 antennas are patch antennas. They >> have a pointed radome. The have very little ground plane, which >> reduces reception near the ground, which is desirable because of multipath >> effects. They also have quite a bit of filtering, so transmitting >> antennas near the units, will not affect them. >> >> If you are not having a problem with multipath, a regular patch type >> antenna probally from anybody should work well. >> >> If you are having multipath problems a timing antenna should help or >> a choke ring assembly should help. I have built choke rings out of >> pie plates, and Dr. Tom Clark made a basic choke assembly using a >> common electric junction box. >> >> I had problems with multipath because of mountains about 3/5 around >> my location. I changed the look angles so my receivers only receive >> above 20 degrees above the horizon and I use timing antennas now. >> >> Brian KD4FM >> >> Matt Ettus wrote: >> >>> Is there really anything in particular which is different about the >>> antenna requirements of timing receivers as compared to ordinary >>> high-quality receivers? The timing antennas seem to be in pointy >>> radomes, so that tells me they are probably quad-helixes rather than >>> patch antennas. How is that advantageous for timing in particular? >>> >>> Thanks, >>> Matt >>> >>> _______________________________________________ >>> 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. > > ------------------------------ Message: 4 Date: Thu, 14 Feb 2008 03:05:22 -0600 From: "Didier Juges" <didier@cox.net> Subject: Re: [time-nuts] Trimble Thunderbolt Rs-232 Levels To: "'Discussion of precise time and frequency measurement'" <time-nuts@febo.com> Message-ID: <009801c86ee8$bbd70c80$0a01a8c0@didierhp> Content-Type: text/plain; charset="windows-1250" RS-232 specs are just about totally obsolete, but at the time they meant anything, they required that RS-232 receivers work with as little as +/- 3V and that they accept +/- 18V at least before failing. Signals between +3V and -3V are unspecified and therefore may generate an undetermined state. However, most recent (<10 years old) computers will work with unipolar TTL levels because the receivers have a bias point set slightly positive. Didier KO4BB > -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of Hal Murray > Sent: Wednesday, February 13, 2008 12:05 AM > To: Darrell Robinson > Cc: time-nuts@febo.com > Subject: Re: [time-nuts] Trimble Thunderbolt Rs-232 Levels > > > > I think I will apply power to the module and measure the > levels from > > the port. If it is TTL out, I will need to do a level > shift anyway to > > give the computer proper voltages to run it's serial port. > > Most RS-232 level shifters also include an inverter. > > I'd just plug it in and see if it works. Especially if it has a DB-9. > > Ages ago, RS-232 specs called for 12 V. I think they updated it to > work at 6V. > > In practice TTL signals actually work, at least if you aren't using > long cables. All the receiver chips I've checked have had an input > threshold at roughly the TTL switching level - 2 diode drops above > ground. > > > > -- > These are my opinions, not necessarily my employer's. I hate spam. > > > > > _______________________________________________ > 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 incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.20.4/1275 - Release > Date: 2/12/2008 3:20 PM > > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.4/1277 - Release Date: 2/13/2008 8:00 PM ------------------------------ Message: 5 Date: Thu, 14 Feb 2008 03:08:40 -0600 From: "Didier Juges" <didier@cox.net> Subject: Re: [time-nuts] gps timing antennas To: "'Discussion of precise time and frequency measurement'" <time-nuts@febo.com> Message-ID: <009901c86ee9$312fca30$0a01a8c0@didierhp> Content-Type: text/plain; charset="windows-1250" > -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of Poul-Henning Kamp > Sent: Wednesday, February 13, 2008 5:07 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] gps timing antennas > > > I would suspect that the higher domes is a concession to weather: > when mounted on a building or tower, a steeper angle of the surface > will collect less snow and dirt. And don't forget the birds... Didier KO4BB No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.4/1277 - Release Date: 2/13/2008 8:00 PM ------------------------------ Message: 6 Date: Thu, 14 Feb 2008 04:01:50 -0600 From: "Didier Juges" <didier@cox.net> Subject: Re: [time-nuts] GPS Locked and Unlocked Performance Comparison To: "'Discussion of precise time and frequency measurement'" <time-nuts@febo.com> Message-ID: <009a01c86ef0$9ed143a0$0a01a8c0@didierhp> Content-Type: text/plain; charset="windows-1250" Said, What 24 bit DAC do you have in mind? I have been looking for a standalone 24 bit DAC in a small package and have not found anything I liked :-( Thanks Didier > -----Original Message----- > From: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] On Behalf Of SAIDJACK@aol.com > Sent: Wednesday, February 13, 2008 4:11 PM > To: tvb@leapsecond.com; time-nuts@febo.com > Subject: Re: [time-nuts] GPS Locked and Unlocked Performance > Comparison > > Hello Tom, > > Bruce mentioned there is a validity bit that can be checked for > holdover. I wonder if a small micro can be used to hold the EFC > voltage steady without much effort. Or maybe using Super-Caps in the > loop filter? > > Or maybe use one of those new 24 bit Sigma-Delta ADC/DAC chips to > capture a > 24 bit word (ADC) and feed that to the 24 bit DAC during holdover. > Kind of a > 24 bit high-precision sample-and-hold circuit. > No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.4/1277 - Release Date: 2/13/2008 8:00 PM ------------------------------ Message: 7 Date: Thu, 14 Feb 2008 11:00:32 -0000 From: "Martyn Smith" <martyn@ptsyst.com> Subject: [time-nuts] Allan variance Vs Plain Old Accuracy To: <time-nuts@febo.com> Message-ID: <9745B9B72C6C40C7BDE6DC25BCA184F6@MartynDesktop> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Hi All, This comment is bound to get you all going. Maybe I'm being stupid, but why does everyone use Allan Variance and not plan old accuracy? I am very familiar with David Allan's full article on Allan Variance. However Allan Variance isn't the same as accuracy. Accuracy is what is important to most people. And that's not RMS but peak to peak, e.g worse case. And not averaged over 24 hours but averaged over 1 second or less. Although I sell GPSDO using OXCO's, I don't find their accuracy as good as my rubidium disciplined oscillators. I have an article on my web site where I compare a OXCO based unit versus my rubidium's unit. I won't say what OXCO unit it is, but its one of the well known ones on the market that is talked about in this forum. www.ptsyst.com/AppNote2.pdf Also a friend of mine measured one of the current leading OXCO based units (from a very big manufacturer). He found its accuracy was +3.93E-10 and -4023E-10 over a 10.5 hour period. Over the same time the unit displayed a worse case error of 1.4E-12. It tended to drift in one direction for a long time and then drop. So its Allan Var was still very good, but its accuracy was poor. That's another one of my gripes. The frequency accuracy displayed by many units has little bearing on actual frequency accuracy. Rubidium's oscillators usually stay within 1E-10 accuracy, about five times better than any OXCO unit I've measured. And now that I can sell you a Rubidium with GPS locking built in for under $600.00 why buy an OXCO!!!!! Ok, I do need an order for > 5000 pieces. Best Regards Martyn ------------------------------ Message: 8 Date: Thu, 14 Feb 2008 12:03:55 +0000 From: Luis Cupido <cupido@mail.ua.pt> Subject: Re: [time-nuts] GPS Locked and Unlocked Performance Comparison To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Message-ID: <47B42E2B.9030101@mail.ua.pt> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hi, I got also a 10KHz version fit on a CPLD as per request of W7QX in early 2004 (for 100MHz etc) and later for N1JEZ and G6GXK (this time having also 10MHz). All is on my web pages since then but only if you look in detail in the configuration list files you find it... I must rearrange my web layout as some stuff is not so visible, sorry. on the other hand I suffer from extra queries about things I have there... ;-) Anyway, is is the the same old straightforward style of design (as the others) and has both XOR and FF outputs available. Unfortunately I do not have a Jupiter RX so I did not any real performance tests on it only some basic functional tests :-( ... I'm stuck to 1pps ;-) Luis Cupido. ct1dmk http://w3ref.cfn.ist.utl.pt/cupido/ Dave Brown wrote: > There's a published design very similar to James Millers from Andy > Talbot- > > http://www.frars.org.uk/cgi-bin/render.pl?pageid=1285 > > I think they were both published about the same time originally. > He uses a 4046 for the phase detector and suggests a decent OCXO but > otherwise very much the same. > > DaveB, NZ > > _______________________________________________ > 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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 43, Issue 33 *****************************************