Re: [time-nuts] TU60-D120-131 Specs....?
Sorry to be so dense on this but doesn't the unit just default to the Jupiter-T command set on power up. I should be able to just enter @@Cj and receive the (manufacturer name, model, serial number and software revision ) shouldn't I? -=Bryan=- > From: hol...@hotmail.com > To: time-nuts@febo.com > Date: Wed, 29 Jun 2016 02:42:50 + > Subject: [time-nuts] TU60-D120-131 Specs? > > "@ @ W b 0x01 cksum 0x0D 0x0A" will switch from Motorola mode to Zodiac > mode. The checksum is the XOR of all bytes after the @@ and before the cksum > byte. The 0x?? values represent binary bytes. The spaces are for clarity > and are not sent. > ___ > 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] How to properly characterize 32kHz oscillators manually and with a microcontroller?
On Tue, Jun 28, 2016 at 12:14 AM, Van Horn, David wrote: > > > p...@heypete.com said: >> I'm a little concerned about the speed at which the pulses need to be >> counted. The 32kHz pulses come in every ~30.5 microseconds, and handling an >> interrupt on an ATmega328 running at 16MHz takes about 5.125 microseconds[1] > > Huh? > > Instruction cycle time is 62.5nS for almost all instructions at that clock. > That’s a pretty long ISR by my standards. According to the "How long does it take to execute an ISR?" part of http://www.gammon.com.au/interrupts, it takes 82 cycles total to service an external interrupt (i.e. one triggered by an interrupt pin), including the time needed to enter the ISR and to leave it after it's done whatever you needed it to do. At 62.5nS for each clock cycle, that's 5.125uS just to process the interrupt. That doesn't include the time needed to execute whatever code you want it to do. > 1: Reserve a couple of registers for handling data inside ISRs, avoiding push > and pop. > 2: Reserve a register for holding SREG during the ISR. > > ISR:in STEMP,SREG > At this point you can fearlessly trash SREG and ITEMP and ITEMP2 > Do Stuff using ITEMP and ITEMP2. > Do as little as practical in the ISR, letting the non-isr code do the > heavy lifting. > Out SREG,STEMP > RETI > > Optionally, set a register (I usually call it "ZERO") to 0x00 to speed up 16 > bit operations. > Keep data you need FAST in registers in the low page, rather than in RAM. Thanks! I think that may be a bit beyond my ken for the time being, but I'll definitely keep it in mind for when I know more. Cheers! -Pete -- Pete Stephenson ___ 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] How to properly characterize 32kHz oscillators manually and with a microcontroller?
Hi > On Jun 29, 2016, at 5:08 AM, Pete Stephenson wrote: > > On Tue, Jun 28, 2016 at 12:14 AM, Van Horn, David > wrote: >> >> >> p...@heypete.com said: >>> I'm a little concerned about the speed at which the pulses need to be >>> counted. The 32kHz pulses come in every ~30.5 microseconds, and handling an >>> interrupt on an ATmega328 running at 16MHz takes about 5.125 microseconds[1] >> >> Huh? >> >> Instruction cycle time is 62.5nS for almost all instructions at that clock. >> That’s a pretty long ISR by my standards. > > According to the "How long does it take to execute an ISR?" part of > http://www.gammon.com.au/interrupts, it takes 82 cycles total to > service an external interrupt (i.e. one triggered by an interrupt > pin), including the time needed to enter the ISR and to leave it after > it's done whatever you needed it to do. At 62.5nS for each clock > cycle, that's 5.125uS just to process the interrupt. That doesn't > include the time needed to execute whatever code you want it to do. That all assumes you have turned interrupts off for some reason. Common reasons could be that you are in another interrupt service routine or that you are executing interrupt related code. Bob > >> 1: Reserve a couple of registers for handling data inside ISRs, avoiding >> push and pop. >> 2: Reserve a register for holding SREG during the ISR. >> >> ISR:in STEMP,SREG >>At this point you can fearlessly trash SREG and ITEMP and ITEMP2 >>Do Stuff using ITEMP and ITEMP2. >>Do as little as practical in the ISR, letting the non-isr code do the >> heavy lifting. >>Out SREG,STEMP >>RETI >> >> Optionally, set a register (I usually call it "ZERO") to 0x00 to speed up 16 >> bit operations. >> Keep data you need FAST in registers in the low page, rather than in RAM. > > Thanks! I think that may be a bit beyond my ken for the time being, > but I'll definitely keep it in mind for when I know more. > > Cheers! > -Pete > > -- > Pete Stephenson > ___ > 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] How to properly characterize 32kHz oscillators manually and with a microcontroller?
O M G.. So I followed the link and saw how they do it.Wow. They write interrupts like the DMV processes applications. I can only imagine what this looks like on the PIC, where every instruction takes 4x as many cycles. All of that pushing and popping is PRECISELY what you need to avoid. Pushing any register that the ISR does not actually change is totally insane. My average ISR is far shorter than their intro and outro code. "C" does not cooperate easily with this, but you can declare your interrupts "naked" and write them in assembler so as to avoid this insanity. I say this as someone who has been developing on the AVR platform for something like 20 years. My first application was on the 8515, and they didn't even have production silicon yet. My development was done on a chip with date code "ES" (Engineering Sample) ___ 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] buying a time interval counter
Hello there, I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. What model still distributed would you think is good for that at the moment ? Thanks & cheers Stephane ___ 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] How to properly characterize 32kHz oscillators manually and with a microcontroller?
>That all assumes you have turned interrupts off for some reason. Common >reasons could be that you are in another interrupt service routine or that >you are executing interrupt related code. > >Bob What I saw in their interrupt routine was a "full boat" implementation, pretty typical for C code, saving registers without regard for what happens in the ISR, but nothing about the interrupts being turned off. If you mean not having re-enabled ints during the ISR, then yes, and that is how I would urge anyone to write an ISR. The reason that you would re-enable ints during an ISR is that your ISR takes too long. Making the ISR take even longer isn't really a solution. Write faster ISRs. The key is to do absolutely as little housekeeping as needed, and have the ISR do as little as possible. I have had cases where I didn't even preserve SREG because what I was doing in the ISR didn't alter SREG. Don't blame the hardware for poor implementation of software. There really is no actual minimum code in an ISR. In one case, I had a useful ISR that had actually no code in it!. A very special case, but they happen. What I showed is my typical intro and outro code for probably 90% of what I write. I avoid pushing and popping because it wastes time. Copying SREG into a dedicated register is faster. Using dedicated ISR registers is faster than pushing and popping to free up registers. All this pushing and popping causes deep stack usage, which isn't even an option on some processors. When your stack collides with your data, you're toast. It is to your significant advantage to minimize stack usage. I will typically put a stack guard below where I expect the stack to live, and monitor that in the "sanity check" routine for any changes. The sanity check routine looks at this and other things that I know should never change, and if they are not the correct values, then the watchdog won't be reset. The sanity check routine is also the only place that the watchdog gets reset.WDRs scattered through the code are symptomatic of poorly written code. ___ 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] TU60-D120-131 Specs....?
may be this zip-file from James Miller helps to set up the Jupiter properly: http://www.jrmiller.demon.co.uk/projects/ministd/jupcom.zip Götz Am 29.06.2016 um 10:45 schrieb Bryan _: Sorry to be so dense on this but doesn't the unit just default to the Jupiter-T command set on power up. I should be able to just enter @@Cj and receive the (manufacturer name, model, serial number and software revision ) shouldn't I? -=Bryan=- From: hol...@hotmail.com To: time-nuts@febo.com Date: Wed, 29 Jun 2016 02:42:50 + Subject: [time-nuts] TU60-D120-131 Specs? "@ @ W b 0x01 cksum 0x0D 0x0A" will switch from Motorola mode to Zodiac mode. The checksum is the XOR of all bytes after the @@ and before the cksum byte. The 0x?? values represent binary bytes. The spaces are for clarity and are not sent. ___ 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. -- Götz Romahn ___ 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] TU60-D120-131 Specs....?
No, they are set up to default to Motorola command set. And all messages must have the proper checksum and CR LF sequence. When the receiver is in Zodiac binary mode, it wont take Motorola commands and vice versa. ___ 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] OCXO noise as they retrace
On Mon, 27 Jun 2016 21:55:55 + (UTC) Bob Stewart wrote: > I've had a specific GPSDO running for some time now, and I notice that > the noise at tau 1s has gotten worse as the retrace flattens out. > In this case, the ADEV was about 3.6E-11 a month or so ago, and has now > gone up to about 8.5E-11. (Measurements performed by a 5370A against a > PRS-45A Cs standard.) Is this normal as the startup drift settles out? > It's been on the same power supply module during this time, but I have been > using it to test new code, so the DAC has been cycled from midpoint to lock > numerous times. Another unit that's been running for some time has done > essentially the same thing. > > Weather? Environment? GPS demons? As the change is just about a factor of 2, my first guess would be that you see numerical effects due to the finite tuning resolution of the GPSDO. You can see it as a similar effect as in delta-sigma modulators. As long as the output value is changing, the noise power (which can be assumed to be constant for a first order approximation) will be spread over a wide frequency range. But, if you output a constant value, the noise power will get concentrated in a couple of spurs, which will then stick out quite a bit. A simple test for this hypothesis would be to send the GPSDO into hold-over mode and measure the ADEV of the OCXO again with constant EFC voltage. Another indication would be, if the ADEV increased only in a narrow range, while slightly decreasing overall (though, this is a much weaker argument as it can be confunded by other phenomena). Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] How to properly characterize 32kHz oscillators manually and with a microcontroller?
> > For more precise stuff timing, I have a Thunderbolt and other goodies. > (Speaking of which, I really need to figure out how to use the > Thunderbolt as an external clock source for my Arduinos.) > I don’t think you can do it for an Arduino without hardware changes. The CLKI pin is shared with XTAL1. But you can clock almost any AVR from an external clock source as long as the Vcc vs frequency “safe operating area” is respected (see the datasheet for your particular device). Note that if you fuse the device for an external clock source of any kind, that source must be present during (non-HV) programming as well as operation. I use a DC blocking cap and self-biased inverter nowadays as an input conditioner for external clock inputs. It allows me to accept sine as well as square inputs if necessary. My principle use for this is my Crazy Clock calibrator, which I clock from one of my GPSDOs. It’s not 100% reliable, and I’m not sure why. Every once in a while, the AVR will lock up, even with the watchdog turned on. The square wave on CLKI looks *perfect*. I can only guess that there’s a glitch every once in a while that screws something up, but I haven’t figured it out yet. ___ 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] buying a time interval counter
On 29 Jun 2016 17:02, "Stéphane Rey" wrote: > > Hello there, > > I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. It still looks available to me http://www.thinksrs.com/products/SR620.htm There is also a Keysight 53230A with a slightly better (20 ps vs 25 ps) single shot resolution. It looks more modern, but I don't know how well they compare. Dave. ___ 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] buying a time interval counter
On Wed, 29 Jun 2016 14:32:07 + Stéphane Rey wrote: > I'm planning to buy a such instrument in order to do some frequency > stability measurement at work. The SR620 seems to be discontinued. What > model still distributed would you think is good for that at the moment > ? The SR620 is still being sold: http://thinksrs.com/products/SR620.htm What kind of device you want to get highly depends on your requirements. Without knowing them, it's impossible to give good advice. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] buying a time interval counter
Hi Dave, Yep it looks like it's still available. I've seen discontinued on a distributor website which made me thinking the product wasn't available anymore. I'll look what is the price for the HP53230A for comparison. Cheers Stephane -- Message d'origine -- De : "Dr. David Kirkby (Kirkby Microwave Ltd)" À : "Discussion of precise time and frequency measurement" ; "Stéphane Rey" Envoyé 29/06/2016 18:22:50 Objet : Re: [time-nuts] buying a time interval counter On 29 Jun 2016 17:02, "Stéphane Rey" wrote: > > Hello there, > > I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. It still looks available to me http://www.thinksrs.com/products/SR620.htm There is also a Keysight 53230A with a slightly better (20 ps vs 25 ps) single shot resolution. It looks more modern, but I don't know how well they compare. Dave. ___ 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] How to properly characterize 32kHz oscillators manually and with a microcontroller?
Hi David: I built a number of clocks based on PIC uC and using interrupts. The idea is to use the output from a frequency standard as the heart beat of the clock. Depending on what the PIC was doing when interrupted the delay can different by one cycle and a simple test corrects that. Clock settable to 1ms and keeps perfect time. http://www.prc68.com/I/PRC68COM.shtml#07092006 I wrote this directly using the Microchip assembler. I'm not a fan of C. My first uC was the SWTP kit that came with no software. I learned to write directly in hex machine language. The problem with that is every time code is changed inside a loop the target address needs to be recomputed. Later I got a copy of the Motorola assembler and editor which was a big help. http://www.prc68.com/I/comp.shtml#SWTP -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message O M G.. So I followed the link and saw how they do it.Wow. They write interrupts like the DMV processes applications. I can only imagine what this looks like on the PIC, where every instruction takes 4x as many cycles. All of that pushing and popping is PRECISELY what you need to avoid. Pushing any register that the ISR does not actually change is totally insane. My average ISR is far shorter than their intro and outro code. "C" does not cooperate easily with this, but you can declare your interrupts "naked" and write them in assembler so as to avoid this insanity. I say this as someone who has been developing on the AVR platform for something like 20 years. My first application was on the 8515, and they didn't even have production silicon yet. My development was done on a chip with date code "ES" (Engineering Sample) ___ 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] buying a time interval counter
Hi Stephane: I traded my HP 53132A counter for an SR 620. The 53132 has what I'd call a user hostile interface, so if you are manually controlling the counter the SR 620 has a huge advantage. I also like the long display on the 620 which can be read from across the room. PS Stanford Research is a company founded by physicists and makes some really high quality stuff. In fact some of the products HP/Agilent/Keysight sells are repackaged SR instruments. http://www.prc68.com/I/TandFTE.shtml#SR620 The claim to fame for the HP 53132A is that it can make a frequency (not time interval) measurement to 1E12 in a second. Here's how to get that same result with the SR620: http://www.prc68.com/I/FTS4060.shtml#SR620Fast On the down side the printing functions on the 620 require an Epsom printer. Does anyone have a solution for that? PS SR also makes a 10 MHz crystal oscillator that has options trading stability for aging as well as the EFC tuning polarity and range so as to match other OCXOs. http://prc68.com/I/TandFTE.shtml#SC10 At one point they were looking into making a GPS time receiver where the cable length calibration would be built-in. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message Hello there, I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. What model still distributed would you think is good for that at the moment ? Thanks & cheers Stephane ___ 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] Datum Starloc II GPSDO issues
On 2016-06-29 10:00 AM, Mark Sims wrote: I don't think so. The day and year is there, only the month is 0. The guy selling them has them available in sealed factory case lots. They look new. They are in sealed anti-static bags. My guess is they came from somebody's product line closeout. I did notice that several of their messages make liberal use of fields that Trimble marks "reserved". Was yours in a sealed bag? Looking at the auctions, they're described as 'New in open bags' or 'may have been opened'. If I was the suspicious sort (oh wait, I am!) I'd suspect that there was a complete changeout of all units with fresh ones from the factory - perhaps due to one or more of the bugs you've found - and the ones being sold are the bad ones that were replaced and then junked. If there are any that are sealed, they might be leftover good units. If you look for pictures of the Starloc II, it's a box with, probably, two boards; this one and a power converter, similar to the 'retail' version of the Thunderbolt. It seems odd that a distributor would have a boxful of just this board. Ed ___ 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] OCXO noise as they retrace
Hi Attila et al, I think I've finally got a handle on the problem. A few months ago I posted that I was getting phase pops on my 5370A. At least I thought it was on the 5370. So, I bought another one on ebay, and the problem disappeared. Then it came back, and rapidly got worse. Unfortunately, the OCXO I had put into one of my GPSDOs was also bad. So, when I did a three-way comparison, no comparison looked good. Thus my conclusion that the new 5370 had somehow gone bad in the same way that the old one did. So, last night, I plugged in an older unit that had always tested good and let it cook overnight. This morning, comparing that to the PRS got me about 1E-10 --- not very good. Then I compared the old one to what I had considered the best of the new units I have on hand, and it's down in the 4E-11 or so range at 1 second. So, I swapped out the OCXO in the other unit I had been testing, and the ADEV at 1s is just under 4E-11, which is where I would expect with my test equipment. So, my conclusion is that the PRS was the cause of the popping I reported back around February, but it improved for awhile before getting worse: about 1E-10 at 1 second tau. At the same time, one of the units I was testing not only had a noisy OCXO, but the previous one I had in that unit was also bad. So, essentially this was a comedy of errors. I'm left with using one of my GPSDOs as a reference. But, the difference between good and bad seems to be large enough that I think it will be good enough, even if it eventually were to become noisy. I do use ebay OCXOs in my GPSDOs to keep the cost way down. This experience underlines how important it is to test them carefully before depending on them. Out of about 30 tested, I've had maybe 10 which are unacceptably noisy, which is more or less what I had planned on. Like Bob Camp says, you never know what you're getting when you get one of these Chinese "recycled" OCXOs. But, if you buy in some quantity, and carefully test them, enough are good to make them viable. Bob --- GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Attila Kinali To: Bob Stewart ; Discussion of precise time and frequency measurement Sent: Wednesday, June 29, 2016 10:49 AM Subject: Re: [time-nuts] OCXO noise as they retrace On Mon, 27 Jun 2016 21:55:55 + (UTC) Bob Stewart wrote: > I've had a specific GPSDO running for some time now, and I notice that > the noise at tau 1s has gotten worse as the retrace flattens out. > In this case, the ADEV was about 3.6E-11 a month or so ago, and has now > gone up to about 8.5E-11. (Measurements performed by a 5370A against a > PRS-45A Cs standard.) Is this normal as the startup drift settles out? > It's been on the same power supply module during this time, but I have been > using it to test new code, so the DAC has been cycled from midpoint to lock > numerous times. Another unit that's been running for some time has done > essentially the same thing. > > Weather? Environment? GPS demons? As the change is just about a factor of 2, my first guess would be that you see numerical effects due to the finite tuning resolution of the GPSDO. You can see it as a similar effect as in delta-sigma modulators. As long as the output value is changing, the noise power (which can be assumed to be constant for a first order approximation) will be spread over a wide frequency range. But, if you output a constant value, the noise power will get concentrated in a couple of spurs, which will then stick out quite a bit. A simple test for this hypothesis would be to send the GPSDO into hold-over mode and measure the ADEV of the OCXO again with constant EFC voltage. Another indication would be, if the ADEV increased only in a narrow range, while slightly decreasing overall (though, this is a much weaker argument as it can be confunded by other phenomena). Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] Cable length calibration
bro...@pacific.net said: > At one point they were looking into making a GPS time receiver where the > cable length calibration would be built-in. How would you do that? The obvious way is to compare the time you get with a known-good time, but if you had that, why would you want this new GPS with an unknown cable length. You might be able to do it by measuring the DC drop. Getting enough accuracy seems tough. -- These are my opinions. 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.
Re: [time-nuts] Cable length calibration
Hi Hal: I think the cal process is essentially a time domain reflection measure of cable length. The GPS receiver and the cable cal hardware would be in the antenna unit. The 1 PPS signal would be aligned at the output of the cable. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message bro...@pacific.net said: At one point they were looking into making a GPS time receiver where the cable length calibration would be built-in. How would you do that? The obvious way is to compare the time you get with a known-good time, but if you had that, why would you want this new GPS with an unknown cable length. You might be able to do it by measuring the DC drop. Getting enough accuracy seems tough. ___ 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] Cable length calibration
Yo Hal! On Wed, 29 Jun 2016 12:28:50 -0700 Hal Murray wrote: > bro...@pacific.net said: > > At one point they were looking into making a GPS time receiver > > where the cable length calibration would be built-in. > > How would you do that? TDR. The GPS already sends a voltage down the cable to power the antenna. Send a sharp down the cable and see when the reflection comes back. Even some of my cheap managed ethernet switches can do that. RGDS GARY --- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588 pgpfVp3cT8POs.pgp Description: OpenPGP digital signature ___ 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] Cable length calibration
We have a smart antenna where the receiver is in the antenna housing and the link to the timing receiver is digital over coax. On that, we can run a variant of DTI (DocSis Timing Interface) which calibrates the cable delay automagically. Not sure what the original question was but yes, it's possible. -Original Message- From: time-nuts [mailto:time-nuts-bounces+greg.dowd=microsemi@febo.com] On Behalf Of Hal Murray Sent: Wednesday, June 29, 2016 12:29 PM To: Discussion of precise time and frequency measurement Cc: hmur...@megapathdsl.net Subject: [time-nuts] Cable length calibration EXTERNAL EMAIL bro...@pacific.net said: > At one point they were looking into making a GPS time receiver where > the cable length calibration would be built-in. How would you do that? The obvious way is to compare the time you get with a known-good time, but if you had that, why would you want this new GPS with an unknown cable length. You might be able to do it by measuring the DC drop. Getting enough accuracy seems tough. -- These are my opinions. 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. ___ 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] Cable length calibration
In message <20160629192850.19c29406...@ip-64-139-1-69.sjc.megapath.net>, Hal Mu rray writes: >> At one point they were looking into making a GPS time receiver where the >> cable length calibration would be built-in. > >How would you do that? TDR ? If it wasn't behind a choke, the inrush current to the antenna preamp power filtering capacitor could be measured, but the choke ruins that. The trouble is how to do it without frying the antenna preamp... Seriously... GPS antennas and receivers are cheap, I would just use two GPS antennas with a known difference in cable-length. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Cable length calibration
Am Wed, 29 Jun 2016 12:28:50 -0700 schrieb Hal Murray : > > bro...@pacific.net said: > > At one point they were looking into making a GPS time receiver > > where the cable length calibration would be built-in. > > How would you do that? > > The obvious way is to compare the time you get with a known-good > time, but if you had that, why would you want this new GPS with an > unknown cable length. > > You might be able to do it by measuring the DC drop. Getting enough > accuracy seems tough. > Possibly a bit far-fetched, but Time-Domain Reflectometry might work out. It wouldn't directly yield the physical cable length but rather twice the propagation time, but as the time delay is what this all would be about, this seems a fair deal. I'm sure this could in principle be done, but haven't thought about it for long enough to have an idea on how to address some more or less obvious obstacles. Best regards, Florian ___ 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] buying a time interval counter
I will try to buy one of these SR620. I've some Standford & Research products like the 535 or the 30 MHz DDS generator. I do admit I'm not fan of the front panel interface as well but this is ok and usable. The SR620 would probably be PC controlled anyway to automate some measurements. The 10 MHz reference will come from a GPSDO which is broadcasted over optical fibers. However the optical SFPs have been tested to have 500fs RMS jitter which mich be pretty high for that. I've a Thunderbolt GPSDO sleeping in a box that will do the job otherwise. I plan to buy a Rb oscillator for reference for DTMD method and design a small circuit for the downmixing. To be continued. Thanks for the comments Stephane -- Message d'origine -- De : "Brooke Clarke" À : "Stéphane Rey" ; "Discussion of precise time and frequency measurement" Envoyé 29/06/2016 19:20:22 Objet : Re: [time-nuts] buying a time interval counter Hi Stephane: I traded my HP 53132A counter for an SR 620. The 53132 has what I'd call a user hostile interface, so if you are manually controlling the counter the SR 620 has a huge advantage. I also like the long display on the 620 which can be read from across the room. PS Stanford Research is a company founded by physicists and makes some really high quality stuff. In fact some of the products HP/Agilent/Keysight sells are repackaged SR instruments. http://www.prc68.com/I/TandFTE.shtml#SR620 The claim to fame for the HP 53132A is that it can make a frequency (not time interval) measurement to 1E12 in a second. Here's how to get that same result with the SR620: http://www.prc68.com/I/FTS4060.shtml#SR620Fast On the down side the printing functions on the 620 require an Epsom printer. Does anyone have a solution for that? PS SR also makes a 10 MHz crystal oscillator that has options trading stability for aging as well as the EFC tuning polarity and range so as to match other OCXOs. http://prc68.com/I/TandFTE.shtml#SC10 At one point they were looking into making a GPS time receiver where the cable length calibration would be built-in. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message Hello there, I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. What model still distributed would you think is good for that at the moment ? Thanks & cheers Stephane ___ 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. --- L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast. https://www.avast.com/antivirus ___ 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] Datum Starloc II GPSDO issues
I'm leaning toward Ed's bet. Having done sub contracting in the past, when we completed modification work ESD requirements were that the bags either sealed or closed with a static warning label. On Wed, Jun 29, 2016 at 10:09 AM, Ed Palmer wrote: > On 2016-06-29 10:00 AM, Mark Sims wrote: >> >> I don't think so. The day and year is there, only the month is 0. The >> guy selling them has them available in sealed factory case lots. They look >> new. They are in sealed anti-static bags. My guess is they came from >> somebody's product line closeout. >> I did notice that several of their messages make liberal use of fields >> that Trimble marks "reserved". > > > Was yours in a sealed bag? Looking at the auctions, they're described as > 'New in open bags' or 'may have been opened'. If I was the suspicious sort > (oh wait, I am!) I'd suspect that there was a complete changeout of all > units with fresh ones from the factory - perhaps due to one or more of the > bugs you've found - and the ones being sold are the bad ones that were > replaced and then junked. If there are any that are sealed, they might be > leftover good units. If you look for pictures of the Starloc II, it's a box > with, probably, two boards; this one and a power converter, similar to the > 'retail' version of the Thunderbolt. It seems odd that a distributor would > have a boxful of just this board. > > Ed > > > > ___ > 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] Datum Starloc II GPSDO issues
It appears that they are brand new... no signs of ever being handled or installed. The anti-static bag is sealed with a yellow warning sticker. The date codes in the firmware/software ID message indicates year 2000. The manufacture date message returns 0's in all the fields. They have a DC-DC converter module soldered to the PCB. The second board in the stack is the Motorola timing receiver. These are OEM boards like the gold boxed Thunderbolts, not the metal boxed "retail" units like the Trimble "red box" Thunderbolts. The connectors are a match to the Trimble units, except the RS-232 connector is a male and requires a null modem cable/adapter. And for your viewing pleasure, a few more warty warts... a couple of times an hour the UTC offset field reports 0 even though the receiver has a proper UTC offset value. In the TSIP binary protocol any 0x10 bytes must be sent as 0x10 0x10. The end-of-message flag is 0x10 0x03. If a message contains more than one 0x10 byte, there is a very good chance that the Starloc will send 0x10 0x10 as the end-of-message flag instead of 0x10 0x03! This causes the next message to be merged with the previous one, and it will not be decoded. The satellite health message (0x59) should have a info type byte followed by 32 bytes of info flags (one for each possible satellite). Our fiends, the intrepid Starloc coders, send an info type byte of 00 (invalid, should be 3 or 6) followed by 31 bytes of 0's. Ahh, the ephemeris status message (0x5B) should have 16 bytes of data in it. Starloc gives you 15 bytes of zeroes. The tracked satellite list message (0x6D) has a byte that says how many bytes of satellite ID numbers follow it... good ole' Starloc sends however many bytes if ID's it wants to. The count byte is pretty much useless and if the two don't match, well, the message is bogus. The satellite solutions message (8F:A7) should have lots of useful info in it like per-satellite clock bias. Well Starloc sends a message with just 13 bytes of who know what... I don't... it ain't nuthin' like what Trimble documents... ___ 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] GNSS antenna delays
The discussion about antenna cable delays made me think of the issue of the antenna delay. An antenna typically has a bandpass filter and amplifier so there clearly is some non-negligible delay associated with this. The issue is usually sidestepped by calibrating the delay of receiver+antenna (against what? A calibrated receiver + antenna from the BIPM of course...) But sometimes, after calibration, an antenna in the field has to be replaced with a different antenna and the original calibration is invalidated. It then becomes necessary to expand the uncertainty of the delay. I did read a NIST paper where they described measuring the delay by physically disassembling the antenna so that they could feed signals directly to the electronics. Delays like 30 ns were measured, I think. Myself, when changing antennas I have seen steps like 10 ns. Does anyone have any data points to add to this ? Cheers Michael ___ 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] Cable length calibration
On Wed, 29 Jun 2016 20:18:49 + "Poul-Henning Kamp" wrote: > If it wasn't behind a choke, the inrush current to the antenna > preamp power filtering capacitor could be measured, but the choke > ruins that. > > The trouble is how to do it without frying the antenna preamp... That's rather "simple". The impedance of the LNA is anything but constant over frequency, said capacitor with the choke are one of those things that make it different than 50 Ohm. You only need to find one frequency at which the impedance is close to a short or to an open and then send down a sine at that frequency and measure the reflection. This is probably easier than doing TDR, but unfortunately it is still quite involved. Another way would be to send down a sine at a known frequency, couple it out at the LNA and inject sharp pulses into the antenna, at the rate of the sine. This way the whole path through the antenna and the LNA down to the receiver can be measured. It even makes it possible to measure the phase differences between different frequencies (think L1, L2). But this would require a custom receiver. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] Cable length calibration
Am 29.06.2016 um 22:07 schrieb Gary E. Miller: TDR. The GPS already sends a voltage down the cable to power the antenna. Send a sharp down the cable and see when the reflection comes back. Even some of my cheap managed ethernet switches can do that. What reflection? If the antenna preamp has at least a somewhat decent S22 (output return loss) there will be exactly nothing that comes back. And the cable attenuation counts twice; GPS antennas have high gain to accommodate a lot of attenuation. regards, Gerhard ___ 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] Cable length calibration
Some of the cheap gigabit network cards can and with surprising accuracy On 29 Jun 2016 22:02, "Gary E. Miller" wrote: > Yo Hal! > > On Wed, 29 Jun 2016 12:28:50 -0700 > Hal Murray wrote: > > > bro...@pacific.net said: > > > At one point they were looking into making a GPS time receiver > > > where the cable length calibration would be built-in. > > > > How would you do that? > > TDR. The GPS already sends a voltage down the cable to power the > antenna. Send a sharp down the cable and see when the reflection comes > back. > > Even some of my cheap managed ethernet switches can do that. > > RGDS > GARY > --- > Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 > g...@rellim.com Tel:+1 541 382 8588 > > ___ > 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] buying a time interval counter
On 6/29/2016 10:20 AM, Brooke Clarke wrote: PS Stanford Research is a company founded by physicists and makes some really high quality stuff. In fact some of the products HP/Agilent/Keysight sells are repackaged SR instruments. http://www.prc68.com/I/TandFTE.shtml#SR620 In the old days, HP/Agilent made microwave frequency counters. One of the main competitors was EIP, which was located a few miles away. A key R&D manager defected to EIP and eventually Agilent stopped making microwave counters and instead resold EIP counters. I'm not surprised to hear the same thing is going on with SRS, also a few miles away. Rick ___ 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] buying a time interval counter
On 6/29/2016 9:22 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: There is also a Keysight 53230A with a slightly better (20 ps vs 25 ps) single shot resolution. It looks more modern, but I don't know how well they compare. Dave. The 53230A does not offer a 10811 option, but instead offers some greatly inferior OCXO. Don't waste your money on this oscillator. If you're reading time-nuts, you probably already have a 10811 or equivalent anyway. The counter itself has the interesting feature of being able to display Allan deviation using its own internal math engine. What I have found is that Hadamard deviation is a lot more useful for screening oscillators, but all you get with the 53230 is Allan. If you're reading time-nuts, you can probably figure out how to calculate the DEV du jour. (There are actually many flavors, as we know). Given the price of the 53230A, I just don't see a value proposition there. Rick N6RK ___ 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] GNSS antenna delays
Hi There are a lot of variables in all this. If you have a good antenna, it’s got a filter ahead of the preamp. It may also have a filter after the preamp. Just how wide these filters are … that depends. If you grab a bunch of SAW filter data sheets, you see numbers in the 10 to 25 ns range. Older ceramic resonator filters are a bit hard to pin down. Bob > On Jun 29, 2016, at 5:46 PM, Michael Wouters > wrote: > > The discussion about antenna cable delays made me think of the issue of the > antenna delay. An antenna typically has a bandpass filter and amplifier so > there clearly is some non-negligible delay associated with this. > > The issue is usually sidestepped by calibrating the delay of > receiver+antenna (against what? A calibrated receiver + antenna from > the BIPM of course...) > > But sometimes, after calibration, an antenna in the field has to be > replaced with a different antenna and the original calibration is > invalidated. It then becomes necessary to expand the uncertainty of the > delay. > > I did read a NIST paper where they described measuring the delay by > physically disassembling the antenna so that they could feed signals > directly to the electronics. Delays like 30 ns were measured, I think. > Myself, when changing antennas I have seen steps like 10 ns. > > Does anyone have any data points to add to this ? > > Cheers > Michael > ___ > 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] Cable length calibration
Yo Poul-Henning! On Wed, 29 Jun 2016 22:57:30 + "Poul-Henning Kamp" wrote: > Most GPS antenna preamps will croak before you get up to 10V. The Fluke TDR is 4V max: http://www.flukenetworks.com/datacom-cabling/installation-tools/ts100-pro-cable-fault-finder-powerbt-bridge-tap RGDS GARY --- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588 pgpLgPLKlHCud.pgp Description: OpenPGP digital signature ___ 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] Cable length calibration
In message <20160629151528.543f4...@spidey.rellim.com>, "Gary E. Miller" writes : >It works on live ethernet cables, so it can't be too harsh. Ethernet is incredibly robust, to the tune of a couple hundred volts pretty much any way you can connect it. Most GPS antenna preamps will croak before you get up to 10V. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Cable length calibration
Yo Poul-Henning! On Wed, 29 Jun 2016 20:18:49 + "Poul-Henning Kamp" wrote: > >How would you do that? > > TDR ? > > If it wasn't behind a choke, the inrush current to the antenna > preamp power filtering capacitor could be measured, but the choke > ruins that. > > The trouble is how to do it without frying the antenna preamp... The TDR would only put the same voltage on the cable that it already does. So nothing gets fried. If you are worried about the antenna, disconnect it before doing the TDR. It works on live ethernet cables, so it can't be too harsh. A real good TDR can shouw you every tight bend in a cable. Or buy a tape measure. RGDS GARY --- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588 pgp5xEdXqVJLC.pgp Description: OpenPGP digital signature ___ 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] GNSS antenna delays
Ublox timing receivers let you specify the RF delay of your antenna / amplifier / receiver electronics independent of the cable delay. They are the only low cost receivers that seem to have this feature. ___ 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.
