Re: [time-nuts] Tboltmon Serial Port Selection...??
I followed up a hunch after browsing through the sample code they supply for TBCHAT. John Miles wrote: Thanks! How'd you find that option? -- john, KE5FX -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Stephen Tompsett Sent: Friday, March 28, 2008 1:12 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Tboltmon Serial Port Selection...?? My version of Tboltmon (version 2.60)accepts a command line argument which bypasses the selection menu e.g. TBOLTMON.EXE -c1 This does not appear to be documented. ___ 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. -- Stephen Tompsett ___ 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] Another Trimble Tbolt question....
Hello, All-- Thanks to the collective savvy of this list and the patient assistance of Ken Winterling wa2lbi I was finally able to get my Tbolt to stop requiring me to configure the COM-4 channel every time I ran the monitoring software. So-- I had such good luck with that question, I'm going to pester the group with one more Tbolt question: In the Position area of the Tbolt monitoring display my altitude is given as 1.4 meters. The USGS topo map and a recent survey both say that the ground level at my house is 84 feet above MSL. The antenna for the T-bolt is on the top of my house 19 feet above the ground. If I open SETUP / POSITION and SET ACCURATE POSITION to, say: 28 meters and enter that value, the indicated altitude changes to 28 meters, but the next day or so, I always find that it has reverted to 1.4 meters. Admittedly, having a (relatively) accurate altitude display is of minor importance to me since my primary reason for having the Tbolt is for a decent 10MHz reference. However, as a matter of principle it would be nice to have the altitude display be a little closer! Any suggestions as to how to get the Tbolt to display a more correct altitude? Thanks! Mike Baker WA4HFR Micanopy, FL - ___ 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] Another Trimble Tbolt question....
Mike, A quick answer to this - two reasons why... 1) Your Thunderbolt is using WGS84 coordinate system and not USGS, and.. 2) The altitude fix is usually the most inaccurate parameter, as it is very unlikely that you have a GPS bird directly overhead. Think of your position fix as you sitting inside a sphere of probability. In the ideal world with perfect GPS geometry it would be a sphere, but in reality it is an ellipsoid due to less accuracy in the Z plane. Why, after setting (and assuming storing) a known accurate position it changes again, I don't know, unless the unit is reverting to a survey mode. I don't know this product intimately, so I'm sure others will proffer better suggestions. Rob Kimberley -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Baker Sent: 29 March 2008 12:50 To: time-nuts@febo.com Subject: [time-nuts] Another Trimble Tbolt question Hello, All-- Thanks to the collective savvy of this list and the patient assistance of Ken Winterling wa2lbi I was finally able to get my Tbolt to stop requiring me to configure the COM-4 channel every time I ran the monitoring software. So-- I had such good luck with that question, I'm going to pester the group with one more Tbolt question: In the Position area of the Tbolt monitoring display my altitude is given as 1.4 meters. The USGS topo map and a recent survey both say that the ground level at my house is 84 feet above MSL. The antenna for the T-bolt is on the top of my house 19 feet above the ground. If I open SETUP / POSITION and SET ACCURATE POSITION to, say: 28 meters and enter that value, the indicated altitude changes to 28 meters, but the next day or so, I always find that it has reverted to 1.4 meters. Admittedly, having a (relatively) accurate altitude display is of minor importance to me since my primary reason for having the Tbolt is for a decent 10MHz reference. However, as a matter of principle it would be nice to have the altitude display be a little closer! Any suggestions as to how to get the Tbolt to display a more correct altitude? Thanks! Mike Baker WA4HFR Micanopy, FL - ___ 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] Racal-Dana 1992 switches
This topic has been addressed earlier; though with some debate. I have proposed a simple heterodyne scheme for beating 2 stable sources against each other observing a 1KHz difference frequency to resolve 1uHz deltas. This is NOT a state-of-the-art scheme, but it will provide better than 1E-12 resolution in less than 10s. This scheme does require some non-standard items. 1. You need a stable synthesizer with external clock capability to yield 10.001 Mhz, phase locked to one of your sources. The HP3336C or a PTS040 work fine. 2. You need a 1KHz zero crossing detector to drive your counter input with low jitter. The ZCD requires 2 opamps a few passive parts, including 2 inductors you'll need to wind by hand. 3. You need a level 7 double balanced mixer to heterodyne the second source the 10.001Mhz signal. Mixers optimized as phase detectors, like the mini-circuits SYPD-1 work well for this. You also need a diplexer on the mixer output to separate the 1KHz beat signal from the other mixer products. The diplexer is 6 passive parts. The results are stable provide counter readings of 9 significant digits down to 1uHz with the leading 4 digits of frequency assumed from the mixing process. The counter gate time setting provides useful often necessary averaging of the readings; so a variable gate time counter is handy. I've used a H-P 5335A, don't know much about the Racal 199x series, but I suspect they would do just fine. Pete Rawson ___ 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] Racal-Dana 1992 switches
How do you pick the optimal difference frequency? I see that 1kHz has a nice numerical property where you can read the frequency directly off the counter, you just need to mentally prepend the first 4 digits. With computers it's not that important, the difference can easily be a strange number if it optimizes performance. I'm wondering what difference frequency optimizes the performance of the mixer thing or if it really matters? Do you worry about the phase-noise contribution of the 10.001MHz source? As I do the math, it seems that the phase noise of the mixing signal is subtracted out after the mixing, so it shouldn't mater that the 10.001Mhz source comes from a frac-N synthesizer and has a few random spurs. You say this isn't state of the art. Why not? Can't you run the timing collection for longer runs and get higher resolution results? jeff Pete wrote: This topic has been addressed earlier; though with some debate. I have proposed a simple heterodyne scheme for beating 2 stable sources against each other observing a 1KHz difference frequency to resolve 1uHz deltas. This is NOT a state-of-the-art scheme, but it will provide better than 1E-12 resolution in less than 10s. This scheme does require some non-standard items. 1. You need a stable synthesizer with external clock capability to yield 10.001 Mhz, phase locked to one of your sources. The HP3336C or a PTS040 work fine. 2. You need a 1KHz zero crossing detector to drive your counter input with low jitter. The ZCD requires 2 opamps a few passive parts, including 2 inductors you'll need to wind by hand. 3. You need a level 7 double balanced mixer to heterodyne the second source the 10.001Mhz signal. Mixers optimized as phase detectors, like the mini-circuits SYPD-1 work well for this. You also need a diplexer on the mixer output to separate the 1KHz beat signal from the other mixer products. The diplexer is 6 passive parts. The results are stable provide counter readings of 9 significant digits down to 1uHz with the leading 4 digits of frequency assumed from the mixing process. The counter gate time setting provides useful often necessary averaging of the readings; so a variable gate time counter is handy. I've used a H-P 5335A, don't know much about the Racal 199x series, but I suspect they would do just fine. Pete Rawson ___ 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] FS Trimble Ace-III Gps Receiver.
I have for sale Two Trimble Ace-III Gps receivers. Asking $30.00 each to include shipping to lower 48. Further information is available at: http://trl.trimble.com/docushare/dsweb/Get/Document-1883/ace%20iii.pdf If interested contact me off list at: [EMAIL PROTECTED] Bruce W1GBS ___ 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] Racal-Dana 1992 switches
Bill, I guess my reason for wanting to see beyond 0.001 Hz is the usual, I have reached a limit and wonder if the equipment I have is capable of more, if I just understood the more esoteric functions I seldom use. The Racal seems like my scientific calculator.. lots of shift functions that might be hiding some useful capabilities with a little coaching and study. Just saw Pete's answer, and I do have a PTS160 synthesizer. So the locked offset idea is do'able. Have mixers, phase detectors, but may need more info on the zero crossing detector opamp portion if you could point me in the right direction. From a GPS equipment standpoint more resolution might tell me if my GPS receivers are working good enough or marginally. I passive split the antenna line four ways. The Lucent units lock to it with about 34~45 C/N readings. But my Z3801A has some other issue now that I've replaced the UT+. It hasn't locked and gives recurring UTC receiver timeout messages on GPScon. The previous UT+ receiver was somewhat lightning damaged and would only lock to one or two satellites for a few hours a day, but at least it was communicating. It may just be a comm issue between the Z3801A motherboard and my present UT+, since the Z3801A motherboard does answer back with serial number etc to GPScon. So I know the baud rate at that level is communicating between PC and Z3801A. The UT+ is a used one from one of the Lucent RFTGm units. So maybe there's a difference in the way they were setup. The UT+'s are 2000 vintage Synergy R5122U1112 to Lucent with V2.2 firmware and no battery. I actually have collected enough damaged UT+ boards (from the lightning prone place I previously worked) that I should build up an NMEA test fixture to verify they work outside the systems they normally reside in, and that all the parameters are set correctly. Then I can try to resurrect a few. The M1501 LNA chips are usually what goes. And I have some ideas I want to try, to dead bug in a MMIC fix for that obsoleted LNA chip. Charles Osborne K4CSO, EM74wa Duluth, GA - Original Message - From: Bill Hawkins [EMAIL PROTECTED] To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Friday, March 28, 2008 9:09 PM Subject: Re: [time-nuts] Racal-Dana 1992 switches Charles S. Osborne said, in part, Now the real question is... is there a clever way to make the Racal 1992 readout the difference in µHz between two GPS disciplined oscillators? My only other counter, an HP5384A, is offscale at 10.000 000.000 MHz . I'm referencing the counter with one Lucent RFTG-m-XO and clocking a Lucent RFTGm-II-XO. Things are working well enough to be beyond my counter's ability to see any jitter. The Racal says nanosecond time interval counter, so I bet there's a way to subtract and increase the resolution similar to an HP53131? Haven't seen the answer on this list, so perhaps it occurred privately. The Racal 1992 is able to read the phase error between two 10 MHz signals (A and B) in degrees. I have done this with the outputs of two 3801s, which are the only pair of frequency sources that I have. This would be sub-nanosecond accuracy except that the display shows 3-10 degrees of jitter (difference between two successive readings). This, however, is only 10E-9. Most people on this list are investigating areas at least two orders of magnitude lower. I find that the phase method gives me comparative drift errors soon enough. An hour gets you near 10E-12. Others require measurement intervals much shorter than that, but the phase angle method is more than adequate for time errors that humans will notice. A drift of one second per year is on the order of 10E-8. It all depends on your reason for pursuing accurate time/frequency measurement. Bill Hawkins ___ 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] FS Trimble ACE-III GPS Receiver
I have for sale Two Trimble Ace-III Gps receivers. Asking $30.00 each to include shipping to lower 48. Further information is available at: http://trl.trimble.com/docushare/dsweb/Get/Document-1883/ace%20iii.pdf If interested contact me off list at: [EMAIL PROTECTED] Bruce W1GBS ___ 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] Racal-Dana 1992 switches
Jeff, There's nothing magic about 1KHz as the heterodyne frequency. I picked it to avoid power line pickup permit a tuned circuit to limit the noise bandwidth. But, any tuned circuit in the signal path will have temperature driven phase variations possibly signal level phase variations, as well. The opamps contribute some noise they also limit the output slew rate; yielding approx. 400ps rms jitter. Using rather stable L C components limits the total impact of these effects to less than +/-1E-9 @ 1KHz (equivalent to +/- 1E-13 @ 10MHz). These issues speak against extending this scheme to much longer times. The synthesizer PN does contribute to the counter measurements. But, even with 2s gate time you are averaging 1000 samples things quiet down nicely. Some synthesizers are better used at 9.999MHz as opposed to 10.001MHz, but I've no solid data on this. Either frequency is OK in this scheme. Pete Rawson ___ 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] Racal-Dana 1992 switches
Jeff Mock wrote: How do you pick the optimal difference frequency? I see that 1kHz has a nice numerical property where you can read the frequency directly off the counter, you just need to mentally prepend the first 4 digits. With computers it's not that important, the difference can easily be a strange number if it optimizes performance. I'm wondering what difference frequency optimizes the performance of the mixer thing or if it really matters? Do you worry about the phase-noise contribution of the 10.001MHz source? As I do the math, it seems that the phase noise of the mixing signal is subtracted out after the mixing, so it shouldn't mater that the 10.001Mhz source comes from a frac-N synthesizer and has a few random spurs. You say this isn't state of the art. Why not? Can't you run the timing collection for longer runs and get higher resolution results? jeff Jeff Whilst a naive analysis indicates that the phase noise of the offset oscillator isnt critical, in practice it is. The dependence on the offset oscillator phase arises because zero crossings of the 2 beat frequencies do not occur at the same time. The greater the time difference between the 2 zero crossings the more critical the phase noise of the offset oscillator becomes. Random spurs do matter, as JPL has found with their nominal 100Hz beat frequency system, performance is much better when the synthesizer is set for a 123Hz beat frequency. The optimum beat frequency is that which minimises the system noise. As the beat frequency is lowered the resolution, for a fixed accuracy in measuring the zero crossing times, increases. However as the beat frequency decreases the mixer output noise density increases. Thus a balance between increasing noise at low offset frequencies and increasing resolution at low offset frequencies has to be found. JPL currently uses 100MHz mixer input frequencies and a nominally 100Hz beat frequency. NIST have also moved from 10MHz mixer input frequencies with a 10Hz beat frequency to 100MHz mixer input frequencies and a 100Hz beat frequency. The system isnt state of the art because the zero crossing detector performance is far from state of the art. A diplexer isnt the optimum IF port termination for low noise at low ( 100kHz) beat frequencies. State of the art systems have a system noise level of around 1E-14/Tau or less. The use of tuned circuits in the zero crossing detector increases its phase shift tempco over that of a state of the art design. Thus as the averaging time increases ambient temperature variations will ultimately limit the system noise. In fact a similar performance to the proposed system is possible using an analog phase comparator if one takes a little care in the design. Bruce ___ 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.
