Re: [time-nuts] They're baaaack!
Are LightSquared still trying to get some value from their contributions? Of course they are. Lightsquared (LS) bought low-valued spectrum at fire-sale prices, speculating that with rule changes and waivers they could use it for a terrestrial broadband network, in which case its value would increase by a factor of 100, 1k, or 1M. If there is any chance whatsoever to still reap that windfall, LS will press it. The spectrum LS bought is allocated to the Mobile Satellite Service (MSS). Until relatively recently, this spectrum could only be used for satellite networks. Because mobile satellite service has never caught on due to the high cost of the space segment and some technical limitations of delivering good broadband performance by satellite, the value of MSS spectrum has been much lower than the Commercial Mobile Radio Service spectrum now used for mobile broadband services (pennies on the dollar, or less). The FCC is convinced that the US will founder as a backwater and will be unable to climb out of the recession if it doesn't have more mobile broadband spectrum, and soon. (I believe this is a faulty notion at best, trending toward absurd, and have articulated my reasons here a number of times, so I won't repeat them now. Check the archives if you are interested.) So, the FCC is racing to make more spectrum available for mobile broadband service. It thought that the relative wasteland of underutilized MSS spectrum would be low-hanging fruit, so it indicated in its National Broadband Plan and some later decisions and Orders that terrestrial use of the spectrum should be considered. Seeing the opportunity to buy cheap MSS spectrum (including buying some MSS companies out of bankruptcy) and convert it to a much, much more valuable use, thereby reaping a windfall, LS did just that. However, as we have seen, the technical problems surrounding repurposing satellite spectrum have thrown a spanner in the works of the initial plan. As I have commented here before, how the FCC and whoever did the LS due diligence all missed the obvious problems with putting powerful terrestrial transmitters adjacent to receivers listening to satellites is beyond me, particularly when the issue of SDARS (satellite radio) ancillary terrestrial transmitters interfering with mobile networks should have been fresh in everyone's minds. To summarize -- LS bought cheap spectrum that nobody much wanted because of the difficulty of providing MSS services. The spectrum is still worth about what LS paid for it, *as MSS spectrum.* But LS apparently feels entitled to receive not just the value of the spectrum *as MSS spectrum,* but rather the value it would have *if it could be used for mobile broadband service.* Put another way, they want their speculative gamble covered. By whom? Well, that would be us, the folks who are still in the middle of bailing out the speculators of the last decade. LS now wants to swap its spectrum for government spectrum that would be useful for mobile broadband service. Now, on the one hand, I think having available the wholesale only service LS says it wants to provide would be a Good Thing. On the other hand, I do not think we, the people, should subsidize it. LS took a gamble, and lost. That should be the end of it. But there any number of politicians who, like the FCC, are panicked that the US is behind in the mobile broadband race and think more mobile broadband will restart the economy (again, I say, Dream On). So, LS has allies that want to cover its bet for their own reasons. Only time will tell how it works out. If you want to have input into the process, at this point lobbying your congressional delegation and the appropriate House and Senate committee members appears to be your best bet. Best regards, Charles ___ 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] They're baaaack!
There is also a proposal to pay commercial TV stations to move together as a cluster, then chop off part of the TV band for wireless. The current market simply will never fill the allotted DTV spectrum. [Cable/satellite/internet-streaming filled the void.] It is a bit nauseating to pay the broadcasts for spectrum that they never paid for in the first place. While I don't favor paying the broadcasters, I like everything else about this approach. Further, I'd get rid of VHF DTV all together. In the transition period, we did just fine when they were all on UHF. Save VHF for public service. I'd even grant the old VHF users an extra site/channel or two to make up for lost range. Currently the wireless companies in the US, at least the two major GSM providers, are dumping the 2G service to recover that spectrum. It is probably cheaper to migrate the 2G customers to 3G, then convert the old spectrum to LTE, than to buy new spectrum for LTE. As I have stated here before, there is already a satellite mobile service with ground transmitters, namely XM and Sirius. That system works today, and one of the bands is completely redundant after the merger. Let Light Squared pay off Sirius XM if they need a functional band. They could use the money. ___ 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] They're baaaack!
And I will not pay telephone prices for wideband data service. Pfui. Don gary There is also a proposal to pay commercial TV stations to move together as a cluster, then chop off part of the TV band for wireless. The current market simply will never fill the allotted DTV spectrum. [Cable/satellite/internet-streaming filled the void.] It is a bit nauseating to pay the broadcasts for spectrum that they never paid for in the first place. While I don't favor paying the broadcasters, I like everything else about this approach. Further, I'd get rid of VHF DTV all together. In the transition period, we did just fine when they were all on UHF. Save VHF for public service. I'd even grant the old VHF users an extra site/channel or two to make up for lost range. Currently the wireless companies in the US, at least the two major GSM providers, are dumping the 2G service to recover that spectrum. It is probably cheaper to migrate the 2G customers to 3G, then convert the old spectrum to LTE, than to buy new spectrum for LTE. As I have stated here before, there is already a satellite mobile service with ground transmitters, namely XM and Sirius. That system works today, and one of the bands is completely redundant after the merger. Let Light Squared pay off Sirius XM if they need a functional band. They could use the money. ___ 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ 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] RFX GPSDO - Anybody played with one of these?
Hi The OCXO probably isn't going to do very well with the outdoor temperature swings… Bob On Oct 2, 2012, at 12:12 AM, Raj vu2...@gmail.com wrote: Just saw this mentioned in Circuit Cellar, just wonding if it really exists, how much they are asking, and if anyone has played with one yet? http://www.rfx.co.uk/pdfs/GPS_OCXO_1300_10_module.pdf It is small enough to incorporate in the external antenna ! Raj ___ 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] Best counter setting for ADEV?
correction: HP53132A timeok Il 2012-10-02 13:29 Timeok ha scritto: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano -- ___ 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] RFX GPSDO - Anybody played with one of these?
Yes, I agree. On Tue, Oct 2, 2012 at 1:29 PM, Bob Camp li...@rtty.us wrote: Hi The OCXO probably isn't going to do very well with the outdoor temperature swings… Bob On Oct 2, 2012, at 12:12 AM, Raj vu2...@gmail.com wrote: Just saw this mentioned in Circuit Cellar, just wonding if it really exists, how much they are asking, and if anyone has played with one yet? http://www.rfx.co.uk/pdfs/GPS_OCXO_1300_10_module.pdf It is small enough to incorporate in the external antenna ! Raj ___ 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] Counters for ADEV measurements
Whilst considering the best settings for ADEV measurements, could I ask for views regarding the venerable HP 5345A counter/timer? I like this counter, particularly regarding its ability to operate up to 40GHz - with a suitable plug-in of course, and that I have two of them! Thanks Geoff ___ 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] Best counter setting for ADEV?
Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. On Tue, Oct 2, 2012 at 1:50 PM, Timeok tim...@timeok.it wrote: correction: HP53132A timeok Il 2012-10-02 13:29 Timeok ha scritto: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano -- __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Counters for ADEV measurements
I'm also interested in this. I've got one of these and a 53131A and am still learning the ins and outs of ADEV measurements with timelab. I was not aware of the 5/10MHz shortcomings of the 53131A that were discussed this weekend.. Brent On Tue, Oct 2, 2012 at 8:11 AM, Geoff Blake ge...@palaemon.co.uk wrote: Whilst considering the best settings for ADEV measurements, could I ask for views regarding the venerable HP 5345A counter/timer? I like this counter, particularly regarding its ability to operate up to 40GHz - with a suitable plug-in of course, and that I have two of them! Thanks Geoff ___ 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] Best counter setting for ADEV?
Luciano, For TI mode, I have recommended the Wavecrest DTS time interval counters here in the past. Can be 1/2 price of an HP 53132A ($600 or so) on ebay, has 800 femtoseconds resolution, and around 3ps SD typically. Goes to 800Mhz or twice that depending on model. That blows the 53132A out of the water. Useless in frequency mode though, one must calculate frequency by fast time interval measurement on the 10MHz for example using Stable 32 etc. Heavy, large, and power hungry, but quite solid. Said On Oct 2, 2012, at 4:29, Timeok tim...@timeok.it wrote: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano TIvs Freq mode1.jpg ___ 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] Counters for ADEV measurements
Searchin for the best clock characterization gear, the first parameter is the ability to sense the smallest time movement beetween clock edges. When you buy your top multimeter, you first decide about the resolution: 6 1/2 digits (for example) is better than 5 1/2. Here it is the same: the one-shot time interval resolution is the key parameter. On Tue, Oct 2, 2012 at 2:11 PM, Geoff Blake ge...@palaemon.co.uk wrote: Whilst considering the best settings for ADEV measurements, could I ask for views regarding the venerable HP 5345A counter/timer? I like this counter, particularly regarding its ability to operate up to 40GHz - with a suitable plug-in of course, and that I have two of them! Thanks Geoff ___ 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] Best counter setting for ADEV?
Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian ___ 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] Counters for ADEV measurements
Then you need a stable clock as a reference, OK, but the first move is towards the smallest one-shot resolution. It is the same as your multimeter: it is useless to have 6 1/2 digits resolution and a voltage reference that wipens out the last 2 digits. The HP5345A has a resolution of 10E-10 (page 2 of the datasheet) so it is not the best available for precision timing measurements. On Tue, Oct 2, 2012 at 2:40 PM, Azelio Boriani azelio.bori...@screen.itwrote: Searchin for the best clock characterization gear, the first parameter is the ability to sense the smallest time movement beetween clock edges. When you buy your top multimeter, you first decide about the resolution: 6 1/2 digits (for example) is better than 5 1/2. Here it is the same: the one-shot time interval resolution is the key parameter. On Tue, Oct 2, 2012 at 2:11 PM, Geoff Blake ge...@palaemon.co.uk wrote: Whilst considering the best settings for ADEV measurements, could I ask for views regarding the venerable HP 5345A counter/timer? I like this counter, particularly regarding its ability to operate up to 40GHz - with a suitable plug-in of course, and that I have two of them! Thanks Geoff ___ 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] Best counter setting for ADEV?
Wavecrest DTS for $600? Interesting... On Tue, Oct 2, 2012 at 2:43 PM, Adrian rfn...@arcor.de wrote: Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Best counter setting for ADEV?
No matter how much averaging takes place inside the counter, in TI mode the output resolution is limited to +/- 200ps (53132A) or +/- 500ps (53131A) which appears to translate directly into the measurement limit / noise floor. Adrian Azelio Boriani schrieb: Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. On Tue, Oct 2, 2012 at 1:50 PM, Timeok tim...@timeok.it wrote: correction: HP53132A timeok Il 2012-10-02 13:29 Timeok ha scritto: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano -- __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Best counter setting for ADEV?
Yes, and why the 10 seconds frequency mode sigma is apparently better than the 10 seconds TI mode sigma? Because between the two there are 200 averages taken by the frequency mode processing. This is possible also because the input frequency in frequency mode is 10MHz or 5MHz and in TI mode a 1Hz signal is used. On Tue, Oct 2, 2012 at 2:51 PM, Adrian rfn...@arcor.de wrote: No matter how much averaging takes place inside the counter, in TI mode the output resolution is limited to +/- 200ps (53132A) or +/- 500ps (53131A) which appears to translate directly into the measurement limit / noise floor. Adrian Azelio Boriani schrieb: Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. On Tue, Oct 2, 2012 at 1:50 PM, Timeok tim...@timeok.it wrote: correction: HP53132A timeok Il 2012-10-02 13:29 Timeok ha scritto: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshtt**ps://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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-nutshttps://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-nutshttps://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] RFX GPSDO - Anybody played with one of these?
Raj, JLT just sent out a press release some days ago on the LC_XO sub 1 inch square GPSDO that is smaller and higher performance than the RFX unit, runs from only 3.3V, and it can be soldered into a 100 mil standard breadboard, and consumes only about 0.5W (RFX unit is probably 1W). http://www.marketwire.com/press-release/jackson-labs-technologies-inc-delivers-lc_xo-complete-gpsdo-reference-sub-1-x-1-inch-1707006.htm bye, Said On Oct 1, 2012, at 21:12, Raj vu2...@gmail.com wrote: Just saw this mentioned in Circuit Cellar, just wonding if it really exists, how much they are asking, and if anyone has played with one yet? http://www.rfx.co.uk/pdfs/GPS_OCXO_1300_10_module.pdf It is small enough to incorporate in the external antenna ! Raj ___ 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] RFX GPSDO - Anybody played with one of these?
On 10/2/12 5:08 AM, Azelio Boriani wrote: Yes, I agree. On Tue, Oct 2, 2012 at 1:29 PM, Bob Camp li...@rtty.us wrote: Hi The OCXO probably isn't going to do very well with the outdoor temperature swings… Bob Why not.. granted it's easier with large mass and large insulation, but ultimately, it's all about the closed loop gain of the temperature control loop. With small mass, the time lag effects will be small, at least. ___ 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] Best counter setting for ADEV?
There are two on ebay now, $600 and $700... Buy it now.. I would ask the seller to connect the 100MHz ref output to both inputs one at a time and to measure jitter to make sure they work before buying though.. Dts-2075 recommended due to higher performance. On Oct 2, 2012, at 5:49, Azelio Boriani azelio.bori...@screen.it wrote: Wavecrest DTS for $600? Interesting... On Tue, Oct 2, 2012 at 2:43 PM, Adrian rfn...@arcor.de wrote: Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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.
[time-nuts] Z38XX parameters
Maybe a dumb question. Just got my new oscillator hooked up to my Fury board. Using the z38xx program of Ulrichs. Can someone help me wrap my head around the pps TI /s? It seems to be confusing me. May dovetail into the counter thread. Doc KX0O Sent from mobile ___ 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] Best counter setting for ADEV?
Hi Said, I have bought the HP53132A from HP several years ago when WWW and ebay was not invented! hi! I agree with you about the wavecrest luciano Il 2012-10-02 14:40 Said Jackson ha scritto: Luciano, For TI mode, I have recommended the Wavecrest DTS time interval counters here in the past. Can be 1/2 price of an HP 53132A ($600 or so) on ebay, has 800 femtoseconds resolution, and around 3ps SD typically. Goes to 800Mhz or twice that depending on model. That blows the 53132A out of the water. Useless in frequency mode though, one must calculate frequency by fast time interval measurement on the 10MHz for example using Stable 32 etc. Heavy, large, and power hungry, but quite solid. Said On Oct 2, 2012, at 4:29, Timeok tim...@timeok.it wrote: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano TIvs Freq mode1.jpg ___ 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. -- timeok ___ 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] Best counter setting for ADEV?
Hi Adrian, I had the Tracor and I say the instability is normal. Every decade multiplication is affected by noise introduced by the circuit it self. I think is a good, fast approach to evaluate the oscillators or adjust the frequency but not so affordabe for precision measurements Luciano Il 2012-10-02 14:43 Adrian ha scritto: Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian ___ 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. -- timeok ___ 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] RFX GPSDO - Anybody played with one of these?
Wonder what the cost is? Love the size and footprint. Something I can solder to. Regards Paul WB8TSL On Tue, Oct 2, 2012 at 9:03 AM, Jim Lux jim...@earthlink.net wrote: On 10/2/12 5:08 AM, Azelio Boriani wrote: Yes, I agree. On Tue, Oct 2, 2012 at 1:29 PM, Bob Camp li...@rtty.us wrote: Hi The OCXO probably isn't going to do very well with the outdoor temperature swings… Bob Why not.. granted it's easier with large mass and large insulation, but ultimately, it's all about the closed loop gain of the temperature control loop. With small mass, the time lag effects will be small, at least. __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] RFX GPSDO - Anybody played with one of these?
Don, Check out the JLT GPSTCXO eval board, plug and play no pcb layout required, very good performance if shielded from airflow, delivery from stock less than 1week, much lower power, gpstcxo itself w/o eval board is similar size. Supports WAAS, Egnos and Msas too. Supported by Ulrichs excellent Z38xx, and GPSCon. $300 time nuts special pricing plus usps shipping, tax in CA, comes with usb cable and GPS antenna, just a PC is needed or 5V supply. Bye, Said On Oct 1, 2012, at 9:27, Don Latham d...@montana.com wrote: Hello Hal and all: Here's the answer I got: Don, A single unit would set you back $465.00 and delivery would be in the region of 6 weeks. Best Regards Steven Wilson (#21490;#24093;#25991;) Technical Director RFX Limited Unit 11A, Oakbank Park, Livingston, West Lothian, Scotland,EH53 0TH, U.K. Tel - +44 (0)1506 439222, Fax - +44 (0)1506 439333 email/skype: steven.wil...@rfx.co.uk www.rfx.co.u Perhaps time-nuts would be interested in a group purchase? Don Latham Hal Murray t...@westwood-tech.com said: information appeared to be non-existent. IMHO for pretty much *everything* that is for sale, if you have to ask for the price it is a scam. Yes, when it says call for pricing, I usually drop interest. But I wouldn't say scam. How about not targeted at my corner of the market? I can think of several reasons for not publishing a price. 1) The product doesn't really exist yet. They have done the research but haven't finished up and handed off to manufacturing. They are looking for initial customers so they can tune things to fit what customers really need (and are willing to pay for). You want the tall skinny version? Fine, we'll make that first. How tall? 2) The product is tricky to use. They want to make sure it will work well in your application. 3) The product has lots of interacting options/parameters. They only stock a few combinations. If you want to buy more than a handful, you can get a better price by picking the right options. -- 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ 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] Best counter setting for ADEV?
Hi Luciano, Have a bunch of 53132as too, nice and small and convenient for frequency measurements. In the absence of Johns' Timepod, or if you need to measure 30MHz then I think the DTS are the best bang for the buck.. From there, its either 3048a or TSC5110... But those are $$$ Said On Oct 2, 2012, at 6:06, Timeok tim...@timeok.it wrote: Hi Said, I have bought the HP53132A from HP several years ago when WWW and ebay was not invented! hi! I agree with you about the wavecrest luciano Il 2012-10-02 14:40 Said Jackson ha scritto: Luciano, For TI mode, I have recommended the Wavecrest DTS time interval counters here in the past. Can be 1/2 price of an HP 53132A ($600 or so) on ebay, has 800 femtoseconds resolution, and around 3ps SD typically. Goes to 800Mhz or twice that depending on model. That blows the 53132A out of the water. Useless in frequency mode though, one must calculate frequency by fast time interval measurement on the 10MHz for example using Stable 32 etc. Heavy, large, and power hungry, but quite solid. Said On Oct 2, 2012, at 4:29, Timeok tim...@timeok.it wrote: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano TIvs Freq mode1.jpg ___ 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. -- timeok ___ 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] Best counter setting for ADEV?
Azelio, In frequency average mode the 53132A makes something like 200,000 measurements per second, according to the manual. This is why the instrument does so well as a smoothed frequency counter. The resolution gain is some fraction of sqrt(20), subject to the normal caveats like the need for independent samples. That's why these counters have reduced resolution when the input frequency is too close a multiple/fraction of the timebase. Details on this technique (used also in the Pendulum CNT-9x counters): New frequency counting principle improves resolution http://tycho.usno.navy.mil/ptti/ptti2005/paper67.pdf See also this fine presentation by Staffan Johansson: http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf Or, google for: continuous time-stamping frequency counter /tvb - Original Message - From: Azelio Boriani azelio.bori...@screen.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 5:30 AM Subject: Re: [time-nuts] Best counter setting for ADEV? Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. ___ 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] Counters for ADEV measurements
I'm also interested in this. I've got one of these and a 53131A and am still learning the ins and outs of ADEV measurements with timelab. I was not aware of the 5/10MHz shortcomings of the 53131A that were discussed this weekend.. Brent To be fair, HP/Agilent did not hide this fact, but I agree it is buried rather deep in the 53131A/53132A manual. The new series (e.g., 53230A) has a similar issue. There's a wonderful paper by Robert Leiby about this design artifact: ... Frequency Error near the Reference Frequency Harmonics http://cp.literature.agilent.com/litweb/pdf/5990-9189EN.pdf This is no reason not to use a frequency counter in the lab. It simply explains why this class of counter works amazingly well at arbitrary frequencies and not quite as well right around magic numbers like 5 or 10 MHz. /tvb ___ 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] Z38XX parameters
The TI (time interval) is the measure of the stability/accuracy of your clock: TI is always the same figure - clock is stable, TI is always 0 - stable and accurate. On Tue, Oct 2, 2012 at 3:12 PM, Bill Dailey docdai...@gmail.com wrote: Maybe a dumb question. Just got my new oscillator hooked up to my Fury board. Using the z38xx program of Ulrichs. Can someone help me wrap my head around the pps TI /s? It seems to be confusing me. May dovetail into the counter thread. Doc KX0O Sent from mobile ___ 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] Best counter setting for ADEV?
OK, got the papers. I'm still trying to figure out if a minimum resolution can be determined for the TI measurement OCXO_PPS/GPS_PPS. That is, if the GPS has a 25nS random wondering, is it worth having 25pS measurement resolution? At first yes, I can use the negative sawtooth but I'm not convinced. Then, I'm using a simple average over 100 or 1000 seconds but my OCXO moves menawhile: the simple average is not the ideal tool and I'm still investigating what magical statistic can I use. On Tue, Oct 2, 2012 at 3:39 PM, Tom Van Baak t...@leapsecond.com wrote: Azelio, In frequency average mode the 53132A makes something like 200,000 measurements per second, according to the manual. This is why the instrument does so well as a smoothed frequency counter. The resolution gain is some fraction of sqrt(20), subject to the normal caveats like the need for independent samples. That's why these counters have reduced resolution when the input frequency is too close a multiple/fraction of the timebase. Details on this technique (used also in the Pendulum CNT-9x counters): New frequency counting principle improves resolution http://tycho.usno.navy.mil/ptti/ptti2005/paper67.pdf See also this fine presentation by Staffan Johansson: http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf Or, google for: continuous time-stamping frequency counter /tvb - Original Message - From: Azelio Boriani azelio.bori...@screen.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 5:30 AM Subject: Re: [time-nuts] Best counter setting for ADEV? Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. ___ 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] Best counter setting for ADEV?
Azelio, Correct, all GPS timing receiver boards have jitter, sawtooth, or random wandering of some sort, on the order of tens of nanoseconds. This is normal. And so if you use a counter to compare the OCXO 1 Hz with the GPS 1PPS, a TIC resolution of 1 ns or 500ps is sufficient. I would say 25 ps is overkill. In many cases (e.g., Motorola Oncore series) the sawtooth correction message itself has a granularity of 1 ns. So again, a 25 ps measurement is especially overkill given a correction granularity of 1 ns. Depending on the receiver applying the correction will improve the average timing performance by, say, a factor of 3. See: http://www.leapsecond.com/pages/m12-adev/ As for your averaging question, yes, the OCXO will move during the average. This is normal. That's why too long an averaging interval is problematic. Depends on the quality of the OCXO. And if the averaging interval is too short, you pick up too much GPS jitter. Depends on the quality of the GPS receiver. There is no perfect answer; instead you choose something between too short and too long. /tvb - Original Message - From: Azelio Boriani azelio.bori...@screen.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 8:18 AM Subject: Re: [time-nuts] Best counter setting for ADEV? OK, got the papers. I'm still trying to figure out if a minimum resolution can be determined for the TI measurement OCXO_PPS/GPS_PPS. That is, if the GPS has a 25nS random wondering, is it worth having 25pS measurement resolution? At first yes, I can use the negative sawtooth but I'm not convinced. Then, I'm using a simple average over 100 or 1000 seconds but my OCXO moves menawhile: the simple average is not the ideal tool and I'm still investigating what magical statistic can I use. ___ 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] RFX GPSDO - Anybody played with one of these?
Hi The rated temperature stability of the OCXO is not super good. You will see more frequency shift on it than say the TBolt OCXO, far more than a DOCXO. That's not at all saying it's a bad part. For Time Nut duty, I would try to keep it in a fairly benign ambient situation. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Tuesday, October 02, 2012 9:04 AM To: time-nuts@febo.com Subject: Re: [time-nuts] RFX GPSDO - Anybody played with one of these? On 10/2/12 5:08 AM, Azelio Boriani wrote: Yes, I agree. On Tue, Oct 2, 2012 at 1:29 PM, Bob Camp li...@rtty.us wrote: Hi The OCXO probably isn't going to do very well with the outdoor temperature swings. Bob Why not.. granted it's easier with large mass and large insulation, but ultimately, it's all about the closed loop gain of the temperature control loop. With small mass, the time lag effects will be small, at least. ___ 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] Best counter setting for ADEV?
Hi So to do things the same way, start your time measurement at something less than 1 ms and do the math to get to 1 second and beyond. One advantage over the frequency reading would be that you will know what math has been done. The math *does* very much matter Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Tuesday, October 02, 2012 9:39 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? Azelio, In frequency average mode the 53132A makes something like 200,000 measurements per second, according to the manual. This is why the instrument does so well as a smoothed frequency counter. The resolution gain is some fraction of sqrt(20), subject to the normal caveats like the need for independent samples. That's why these counters have reduced resolution when the input frequency is too close a multiple/fraction of the timebase. Details on this technique (used also in the Pendulum CNT-9x counters): New frequency counting principle improves resolution http://tycho.usno.navy.mil/ptti/ptti2005/paper67.pdf See also this fine presentation by Staffan Johansson: http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf Or, google for: continuous time-stamping frequency counter /tvb - Original Message - From: Azelio Boriani azelio.bori...@screen.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 5:30 AM Subject: Re: [time-nuts] Best counter setting for ADEV? Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. ___ 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] Best counter setting for ADEV?
OK, so my 2.5nS resolution is OK. Now I have to determine what level of average is best for the combination MV201/M12M and LPFRS/M12M. On Tue, Oct 2, 2012 at 6:33 PM, Bob Camp li...@rtty.us wrote: Hi So to do things the same way, start your time measurement at something less than 1 ms and do the math to get to 1 second and beyond. One advantage over the frequency reading would be that you will know what math has been done. The math *does* very much matter Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Tuesday, October 02, 2012 9:39 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? Azelio, In frequency average mode the 53132A makes something like 200,000 measurements per second, according to the manual. This is why the instrument does so well as a smoothed frequency counter. The resolution gain is some fraction of sqrt(20), subject to the normal caveats like the need for independent samples. That's why these counters have reduced resolution when the input frequency is too close a multiple/fraction of the timebase. Details on this technique (used also in the Pendulum CNT-9x counters): New frequency counting principle improves resolution http://tycho.usno.navy.mil/ptti/ptti2005/paper67.pdf See also this fine presentation by Staffan Johansson: http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf Or, google for: continuous time-stamping frequency counter /tvb - Original Message - From: Azelio Boriani azelio.bori...@screen.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 5:30 AM Subject: Re: [time-nuts] Best counter setting for ADEV? Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. ___ 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] Best counter setting for ADEV?
Hi By far the easiest way to do it with the combinations you describe is to do a single mixer approach. Offset one oscillator by a few Hz and run the counter on the beat note. You will need a mixer and a limiter, but the total cost should be well below $100. If you have a pile of parts sitting around, the cost could easily be $0. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani Sent: Tuesday, October 02, 2012 12:52 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? OK, so my 2.5nS resolution is OK. Now I have to determine what level of average is best for the combination MV201/M12M and LPFRS/M12M. On Tue, Oct 2, 2012 at 6:33 PM, Bob Camp li...@rtty.us wrote: Hi So to do things the same way, start your time measurement at something less than 1 ms and do the math to get to 1 second and beyond. One advantage over the frequency reading would be that you will know what math has been done. The math *does* very much matter Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Tuesday, October 02, 2012 9:39 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? Azelio, In frequency average mode the 53132A makes something like 200,000 measurements per second, according to the manual. This is why the instrument does so well as a smoothed frequency counter. The resolution gain is some fraction of sqrt(20), subject to the normal caveats like the need for independent samples. That's why these counters have reduced resolution when the input frequency is too close a multiple/fraction of the timebase. Details on this technique (used also in the Pendulum CNT-9x counters): New frequency counting principle improves resolution http://tycho.usno.navy.mil/ptti/ptti2005/paper67.pdf See also this fine presentation by Staffan Johansson: http://www.npl.co.uk/upload/pdf/20060209_t-f_johansson_1.pdf Or, google for: continuous time-stamping frequency counter /tvb - Original Message - From: Azelio Boriani azelio.bori...@screen.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 5:30 AM Subject: Re: [time-nuts] Best counter setting for ADEV? Hmm, the frequency mode sigma is the same as the TI mode sigma for 200*tau. That is if I take the sigma at 200*tau from the TI mode I have the same figure of the frequency mode. Maybe the frequency mode 2 seconds sample time uses 100 averages per second. ___ 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. ___ 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] Best counter setting for ADEV?
Is there a list of GPS timing receivers that provide the sawtooth correction message or implement sawtooth correction internally? I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. On Tue, 2 Oct 2012 09:18:35 -0700, Tom Van Baak t...@leapsecond.com wrote: Correct, all GPS timing receiver boards have jitter, sawtooth, or random wandering of some sort, on the order of tens of nanoseconds. This is normal. And so if you use a counter to compare the OCXO 1 Hz with the GPS 1PPS, a TIC resolution of 1 ns or 500ps is sufficient. I would say 25 ps is overkill. In many cases (e.g., Motorola Oncore series) the sawtooth correction message itself has a granularity of 1 ns. So again, a 25 ps measurement is especially overkill given a correction granularity of 1 ns. Depending on the receiver applying the correction will improve the average timing performance by, say, a factor of 3. See: http://www.leapsecond.com/pages/m12-adev/ As for your averaging question, yes, the OCXO will move during the average. This is normal. That's why too long an averaging interval is problematic. Depends on the quality of the OCXO. And if the averaging interval is too short, you pick up too much GPS jitter. Depends on the quality of the GPS receiver. There is no perfect answer; instead you choose something between too short and too long. ___ 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] Best counter setting for ADEV?
Hi Almost any receiver that's labeled timing receiver will put out some sort of saw tooth correction. The saw tooth is a result of the math, so no there's not a cheap way to get rid of it. By the time you do a receiver that does the phase lock thing, you have pretty much built a GPSDO. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Sent: Tuesday, October 02, 2012 1:04 PM To: Tom Van Baak; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? Is there a list of GPS timing receivers that provide the sawtooth correction message or implement sawtooth correction internally? I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. On Tue, 2 Oct 2012 09:18:35 -0700, Tom Van Baak t...@leapsecond.com wrote: Correct, all GPS timing receiver boards have jitter, sawtooth, or random wandering of some sort, on the order of tens of nanoseconds. This is normal. And so if you use a counter to compare the OCXO 1 Hz with the GPS 1PPS, a TIC resolution of 1 ns or 500ps is sufficient. I would say 25 ps is overkill. In many cases (e.g., Motorola Oncore series) the sawtooth correction message itself has a granularity of 1 ns. So again, a 25 ps measurement is especially overkill given a correction granularity of 1 ns. Depending on the receiver applying the correction will improve the average timing performance by, say, a factor of 3. See: http://www.leapsecond.com/pages/m12-adev/ As for your averaging question, yes, the OCXO will move during the average. This is normal. That's why too long an averaging interval is problematic. Depends on the quality of the OCXO. And if the averaging interval is too short, you pick up too much GPS jitter. Depends on the quality of the GPS receiver. There is no perfect answer; instead you choose something between too short and too long. ___ 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] Counters for ADEV measurements
I also would love to get some hints/tips/secrets on ADEV measurement with my Phillips PM6680 - Clocked by a Tbolt. According to the Specs it should have : 250 ps single-shot time interval resolution 100 ps averaged time interval resolution Does anyone know if it suffers from the same 5/10Mhz issues as the HP's , the paper john presented wasn't clear about the pendulum models ? I'm also using timelab , to do the measurements. TIA CFO - Tnut beginner Denmark ___ 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] Best counter setting for ADEV?
In the case of just the sawtooth error, I thought it was caused by the limited resolution of the counter generating the output pulse. If the counter clock was 100 MHz and not phase locked to GPS time, then depending on how far off it is in frequency, the output pulse would wander an additional but predictable 10ns. On the other hand if it was phase locked, then the output pulse could be stuck at one offset which could not be average out which might be even worse. On Tue, 2 Oct 2012 13:10:04 -0400, Bob Camp li...@rtty.us wrote: Hi Almost any receiver that's labeled timing receiver will put out some sort of saw tooth correction. The saw tooth is a result of the math, so no there's not a cheap way to get rid of it. By the time you do a receiver that does the phase lock thing, you have pretty much built a GPSDO. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Sent: Tuesday, October 02, 2012 1:04 PM To: Tom Van Baak; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? Is there a list of GPS timing receivers that provide the sawtooth correction message or implement sawtooth correction internally? I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. On Tue, 2 Oct 2012 09:18:35 -0700, Tom Van Baak t...@leapsecond.com wrote: Correct, all GPS timing receiver boards have jitter, sawtooth, or random wandering of some sort, on the order of tens of nanoseconds. This is normal. And so if you use a counter to compare the OCXO 1 Hz with the GPS 1PPS, a TIC resolution of 1 ns or 500ps is sufficient. I would say 25 ps is overkill. In many cases (e.g., Motorola Oncore series) the sawtooth correction message itself has a granularity of 1 ns. So again, a 25 ps measurement is especially overkill given a correction granularity of 1 ns. Depending on the receiver applying the correction will improve the average timing performance by, say, a factor of 3. See: http://www.leapsecond.com/pages/m12-adev/ As for your averaging question, yes, the OCXO will move during the average. This is normal. That's why too long an averaging interval is problematic. Depends on the quality of the OCXO. And if the averaging interval is too short, you pick up too much GPS jitter. Depends on the quality of the GPS receiver. There is no perfect answer; instead you choose something between too short and too long. ___ 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] RFX GPSDO - Anybody played with one of these?
Said I was looking and did not see the eval kit on the sight??? Thanks Paul WB8TSL On Tue, Oct 2, 2012 at 12:29 PM, Bob Camp li...@rtty.us wrote: Hi The rated temperature stability of the OCXO is not super good. You will see more frequency shift on it than say the TBolt OCXO, far more than a DOCXO. That's not at all saying it's a bad part. For Time Nut duty, I would try to keep it in a fairly benign ambient situation. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Tuesday, October 02, 2012 9:04 AM To: time-nuts@febo.com Subject: Re: [time-nuts] RFX GPSDO - Anybody played with one of these? On 10/2/12 5:08 AM, Azelio Boriani wrote: Yes, I agree. On Tue, Oct 2, 2012 at 1:29 PM, Bob Camp li...@rtty.us wrote: Hi The OCXO probably isn't going to do very well with the outdoor temperature swings. Bob Why not.. granted it's easier with large mass and large insulation, but ultimately, it's all about the closed loop gain of the temperature control loop. With small mass, the time lag effects will be small, at least. ___ 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] Best counter setting for ADEV?
Are these easily calibrated? I contacted Wavecrest earlier today and they want $750 for the annual calibration. Not exactly 'hobby' friendly :-) jerry -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Said Jackson Sent: Tuesday, October 02, 2012 9:06 AM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? There are two on ebay now, $600 and $700... Buy it now.. I would ask the seller to connect the 100MHz ref output to both inputs one at a time and to measure jitter to make sure they work before buying though.. Dts-2075 recommended due to higher performance. On Oct 2, 2012, at 5:49, Azelio Boriani azelio.bori...@screen.it wrote: Wavecrest DTS for $600? Interesting... On Tue, Oct 2, 2012 at 2:43 PM, Adrian rfn...@arcor.de wrote: Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listi nfo/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. ___ 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] Best counter setting for ADEV?
Yes, very easy: 1) calibrate the internal 100MHz vectron OCXO using a small screwdriver, this is not really critical though as the unit does not really function as a frequency counter. 2) Calibrate the power supplies for proper voltages if necessary with same screwdriver, I found that is really not necessary usually 3) Auto-calibrate all the timing circuits using the built-in calibration feature and two external SMA cables, and two SMA shorts. The button to do that is on the front panel, and the unit does not have to be opened for this. You can also use their VISI application to do some more intensive long-term-averaging calibrations that are started via GPIB commands. There are user/service manuals floating around the web. Item 3) above is really the only thing that needs to be done from time to time I think. bye, Said In a message dated 10/2/2012 12:30:34 Pacific Daylight Time, jster...@att.net writes: Are these easily calibrated? I contacted Wavecrest earlier today and they want $750 for the annual calibration. Not exactly 'hobby' friendly :-) jerry -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Said Jackson Sent: Tuesday, October 02, 2012 9:06 AM To: Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? There are two on ebay now, $600 and $700... Buy it now.. I would ask the seller to connect the 100MHz ref output to both inputs one at a time and to measure jitter to make sure they work before buying though.. Dts-2075 recommended due to higher performance. On Oct 2, 2012, at 5:49, Azelio Boriani azelio.bori...@screen.it wrote: Wavecrest DTS for $600? Interesting... On Tue, Oct 2, 2012 at 2:43 PM, Adrian rfn...@arcor.de wrote: Timeok schrieb: test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano Hi Luciano, interesting. So, the 53132A gains a lot more by this method than my 53131A. As Magnus pointed to, there might be pitfalls. So, it would be interesting to have comparative measurements from a non questionable test setup. In the meantime I tried a Tracor 527A which greatly improved the dynamic range, but appears to suffer from serious instability that might or might not be normal. Adrian __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listi nfo/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. ___ 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] Best counter setting for ADEV?
Hi Mark, When you operate the 5370A in that configuration you are essentially just measuring the RMS sum of jitter of the 5087A output, 5370A input circuitry (ZCD), interpolators, and reference clock. I haven't measured this myself but I would expect jitter in the 5370A reference 10811 would have the same effect as jitter in the 5087A 10811. In other words, you can't tell which one is better; all you can tell is the RMS sum of their instabilities. This may be a lot to ask but try swapping the 10811's in the 5087A and 5370A and re-run the test to see if it's symmetrical. Bruce may also have some insights into the jitter contribution of the reference clock vs. the input clock(s). On your simultaneous measurements -- yes, this is a good thing to do. I run my house 5 MHz this way; using two high-end TIC's to inter-compare three high-end standards. Note if your samples are time-synced close enough you can create three data sets from any two: namely 1050 vs PRS10, PRS10 vs Fury, 1050 vs Fury. For added confidence measure all three pair with TI counters, and see how good the closure is if each one of the three counters didn't actually exist. Make sense, or shall I explain more? /tvb - Original Message - From: Mark Spencer mspencer12...@yahoo.ca To: time-nuts@febo.com Sent: Tuesday, October 02, 2012 10:19 AM Subject: Re: [time-nuts] Best counter setting for ADEV? On a somewhat related note over the weekend I spent a few hours characterizing the performance of two of my HP5370B's for making ADEV measurements by feeding the stop and start inputs with identical 10 Mhz signals from a HP5087a distribution amp. Not surprisingly they perform somewhat differently. More surprisingly the results vary depending on the oscillators used for the clock source for the HP5370B's. (I was under the impression the built in 10811's were more than adequate enough for this application.) I've also found that when trying to characterize the performance of an oscillator (in this case a disciplined PRS10 Rb unit) making two simultaneous measurements using different references and overlaying the results can provide some additional confidence as to their accuracy. (I suppose if I had an H maser I probably wouldn't need to use both an OCXO and GPSDO at the same time to have confidence in the measurements (: ) Looking at the phase differences in this case gives me a reasonable degree of confidence that the OCXO has not significantly drifted during the first 20,000 seconds or so and that the HP5370B's are providing valid data. ___ 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] Best counter setting for ADEV?
No, the Thunderbolt does it and it works beatutifully. The GPS receiver clock is derived from the 10 MHz oscillator. Voila, no messy sawtooth corrections to deal with. The Thunderbolt is a VERY user/hacker friendly design. Even if I were silly enough to build my own GPSDO, I'd still use a Thunderbolt as a base. It has the EFC dac, phase comparator, and temperature monitoring already implemented. Plus no sawtooth correction crap to handle. You can control the DAC manually and implement your own control loop. Opps, siilly me, been there, done that. Lady Heather does have an implementation of an alternate disciplining algorithm in it. -- I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. ___ 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] Best counter setting for ADEV?
On 10/02/2012 03:27 PM, Said Jackson wrote: Hi Luciano, Have a bunch of 53132as too, nice and small and convenient for frequency measurements. I have never got along very well with the 53132A. I just don't like it, it seems. The user interface isn't directly what I like, and I have never got PPS-triggered measurements to run stable. While the Wavecrest might be confusing, I like it better than the 53132A. Cheers, Magnus ___ 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] Best counter setting for ADEV?
Mark, All GPSDO remove that contribution to timing error by virtue of the quartz fly-wheel. I think David was asking about GPS timing receivers, not full-blown GPSDO. Yes, I agree the Thunderbolt is a very nice GPSDO. /tvb - Original Message - From: Mark Sims hol...@hotmail.com To: time-nuts@febo.com Sent: Tuesday, October 02, 2012 12:50 PM Subject: [time-nuts] Best counter setting for ADEV? No, the Thunderbolt does it and it works beatutifully. The GPS receiver clock is derived from the 10 MHz oscillator. Voila, no messy sawtooth corrections to deal with. The Thunderbolt is a VERY user/hacker friendly design. Even if I were silly enough to build my own GPSDO, I'd still use a Thunderbolt as a base. It has the EFC dac, phase comparator, and temperature monitoring already implemented. Plus no sawtooth correction crap to handle. You can control the DAC manually and implement your own control loop. Opps, siilly me, been there, done that. Lady Heather does have an implementation of an alternate disciplining algorithm in it. -- I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. ___ 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] Best counter setting for ADEV?
Magnus, Tell me more; I hope I can help. I use 53132A all the time, including for my cesium time scale. A wonderful instrument; totally reliable sub-nanosecond TIC; easy RS232/GPIB talk-only or full SCPI control. /tvb I have never got along very well with the 53132A. I just don't like it, it seems. The user interface isn't directly what I like, and I have never got PPS-triggered measurements to run stable. While the Wavecrest might be confusing, I like it better than the 53132A. Cheers, Magnus ___ 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] Best counter setting for ADEV?
On 10/02/2012 07:19 PM, Mark Spencer wrote: On a somewhat related note over the weekend I spent a few hours characterizing the performance of two of my HP5370B's for making ADEV measurements by feeding the stop and start inputs with identical 10 Mhz signals from a HP5087a distribution amp. Not surprisingly they perform somewhat differently.More surprisingly the results vary depending on the oscillators used for the clock source for the HP5370B's. (I was under the impression the built in 10811's were more than adequate enough for this application.) Did you disable the wide-band 5 MHz comb-generator of the 5370s? I did it to mine. Cheers, Magnus I've also found that when trying to characterize the performance of an oscillator (in this case a disciplined PRS10 Rb unit) making two simultaneous measurements using different references and overlaying the results can provide some additional confidence as to their accuracy. (I suppose if I had an H maser I probably wouldn't need to use both an OCXO and GPSDO at the same time to have confidence in the measurements (: ) Looking at the phase differences in this case gives me a reasonable degree of confidence that the OCXO has not significantly drifted during the first 20,000 seconds or so and that the HP5370B's are providing valid data. --- On Tue, 10/2/12, time-nuts-requ...@febo.comtime-nuts-requ...@febo.com wrote: Message: 1 Date: Tue, 02 Oct 2012 13:29:11 +0200 From: Timeoktim...@timeok.it To:time-nuts@febo.com Subject: Re: [time-nuts] Best counter setting for ADEV? Message-ID:8b1628eaf26d33f1dd95b380fbed8...@www.timeok.it Content-Type: text/plain; charset=utf-8; Format=flowed test using HP53123A: The pink line is the noise floor using the TI mode The blue line is the noise floor using the Frequency mode (gate 2 sec) The other two line are the same oscillator, an HP105B tested with both the modes. As you can see the range between 1 and 200 sec is totally compromised by the system noise floor using the TI method. The approximation using the freq mode can be anyway usefull to make a comparatinon between two source. I suppose to have right measurements, without any restriction we have to use the Timepod or other high level instruments than this kind of counters. Luciano -- next part -- A non-text attachment was scrubbed... Name: TIvs Freq mode1.jpg Type: image/jpeg Size: 85509 bytes Desc: not available URL:http://www.febo.com/pipermail/time-nuts/attachments/20121002/5b9a6f3b/attachment.jpg -- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 99, Issue 7 ___ 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] Best counter setting for ADEV?
On 10/02/2012 10:04 PM, Tom Van Baak wrote: Magnus, Tell me more; I hope I can help. I use 53132A all the time, including for my cesium time scale. A wonderful instrument; totally reliable sub-nanosecond TIC; easy RS232/GPIB talk-only or full SCPI control. I'll try to rig it up again at work tomorrow. Don't have one at home as I never got friendly with the one at work. I rather bring a SR620 to work for *real* stuff. Next time the TimePod will come with me. Cheers, Magnus ___ 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] Best counter setting for ADEV?
I am sorry if my question was not clear. Why not phase lock the clock that the pulse per second output is derived from to GPS time so that the pulse per second output does not display sawtooth jitter. I assume this is not done because it is cheaper to report the sawtooth correction for those who can use it rather than change the GPS receiver hardware. On Tue, 2 Oct 2012 12:57:15 -0700, Tom Van Baak t...@leapsecond.com wrote: Mark, All GPSDO remove that contribution to timing error by virtue of the quartz fly-wheel. I think David was asking about GPS timing receivers, not full-blown GPSDO. Yes, I agree the Thunderbolt is a very nice GPSDO. /tvb - Original Message - From: Mark Sims hol...@hotmail.com To: time-nuts@febo.com Sent: Tuesday, October 02, 2012 12:50 PM Subject: [time-nuts] Best counter setting for ADEV? No, the Thunderbolt does it and it works beatutifully. The GPS receiver clock is derived from the 10 MHz oscillator. Voila, no messy sawtooth corrections to deal with. The Thunderbolt is a VERY user/hacker friendly design. Even if I were silly enough to build my own GPSDO, I'd still use a Thunderbolt as a base. It has the EFC dac, phase comparator, and temperature monitoring already implemented. Plus no sawtooth correction crap to handle. You can control the DAC manually and implement your own control loop. Opps, siilly me, been there, done that. Lady Heather does have an implementation of an alternate disciplining algorithm in it. -- I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. ___ 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] GPS Jammer
Take a look at the specs of this unit: http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? -John ___ 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] Best counter setting for ADEV?
On 10/02/2012 10:45 PM, David wrote: I am sorry if my question was not clear. Why not phase lock the clock that the pulse per second output is derived from to GPS time so that the pulse per second output does not display sawtooth jitter. I assume this is not done because it is cheaper to report the sawtooth correction for those who can use it rather than change the GPS receiver hardware. You could do that. There are GPS receivers which can do that. It is a little more expensive as you need a steerable TCXO and some components to drive the VC input, the software algorithms for it is fairly trivial. Oh, the Thunderbolt is built that way. The real reason is that few users of GPS receivers care about details like that. Cheers, Magnus ___ 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] GPS Jammer
It also says output power +10 dBm. 3 hour Li battery life. Only for legal use :) Much does not make sense with this. Forward a copy to the commission? Regards - Original Message - From: J. Forster j...@quikus.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 02, 2012 4:43 PM Subject: [time-nuts] GPS Jammer Take a look at the specs of this unit: http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? -John ___ 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] GPS Jammer
On 10/02/2012 10:43 PM, J. Forster wrote: Take a look at the specs of this unit: http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? For a 500 mW jammer your jamming range should be much better. That's wrong. Cheers, Magnus ___ 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] Best counter setting for ADEV?
Hi All the signals into the GPS are Doppler shifted. The satellites are all moving and thus you get a variety of carrier frequencies. There is no one carrier to lock to. Each one gets a separate mathematical solution relative to the sampling clock. Yes, you can steer the LO towards the center of the solution. At that point you have a GPSDO. Much easier / cheaper to simply report the output of the math... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Sent: Tuesday, October 02, 2012 4:45 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best counter setting for ADEV? I am sorry if my question was not clear. Why not phase lock the clock that the pulse per second output is derived from to GPS time so that the pulse per second output does not display sawtooth jitter. I assume this is not done because it is cheaper to report the sawtooth correction for those who can use it rather than change the GPS receiver hardware. On Tue, 2 Oct 2012 12:57:15 -0700, Tom Van Baak t...@leapsecond.com wrote: Mark, All GPSDO remove that contribution to timing error by virtue of the quartz fly-wheel. I think David was asking about GPS timing receivers, not full-blown GPSDO. Yes, I agree the Thunderbolt is a very nice GPSDO. /tvb - Original Message - From: Mark Sims hol...@hotmail.com To: time-nuts@febo.com Sent: Tuesday, October 02, 2012 12:50 PM Subject: [time-nuts] Best counter setting for ADEV? No, the Thunderbolt does it and it works beatutifully. The GPS receiver clock is derived from the 10 MHz oscillator. Voila, no messy sawtooth corrections to deal with. The Thunderbolt is a VERY user/hacker friendly design. Even if I were silly enough to build my own GPSDO, I'd still use a Thunderbolt as a base. It has the EFC dac, phase comparator, and temperature monitoring already implemented. Plus no sawtooth correction crap to handle. You can control the DAC manually and implement your own control loop. Opps, siilly me, been there, done that. Lady Heather does have an implementation of an alternate disciplining algorithm in it. -- I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. ___ 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] GPS Jammer
The 0.5 W and + 10 dBm numbers in the specs don't work out. +10 dBm is 10 mW. I suspect that the 1/2 watt is really the DC input power. And, I'd agree about the range. +10 dBm into a dipole at 10 meters gets you about -44 dBm at the receiver antenna in a free-space model. That's really loud compared to the nominal -130 to -140 dBm you'd hear from the satellites. -John -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, October 02, 2012 4:02 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Jammer On 10/02/2012 10:43 PM, J. Forster wrote: Take a look at the specs of this unit: http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? For a 500 mW jammer your jamming range should be much better. That's wrong. Cheers, Magnus ___ 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] RFX GPSDO - Anybody played with one of these?
Said I have to say I was looking through the list of modules that are available. I guess a couple of things really jump out. The low power consumption and what you get in terms of behaviors. It is pretty amazing actually. Though I have my power sucking Tbolt and 3801. But I could easily see for a Amateur radio operator just getting into time nuttery that these might be a nice way to go. I guess that would open an interesting debate. Getting the used RBs at Hamfest of questionable quality for $200 or far less. Or something modern and simply works. Regards Paul. On Tue, Oct 2, 2012 at 3:34 PM, saidj...@aol.com wrote: Hi Paul, yes, it's a promotional tool, we did not put it on the website yet. We did put the GPSOCXO/GPSTCXO page on there though, and the GPSTCXO is used on that eval kit. Even though it is only a very high-end TCXO, it's performance is quite good, especially when encased in a small plastic bag etc to keep airflow away from it. TVB has done some measurements on this board, and I think he may have a page with the results on his website somewhere. Here is the GPSTCXO eval board photo, the user manual is too big to be posted to this list, let me know if you want me to send it off-list to you. The eval board has a 10MHz LVCMOS output on the BNC connector, supports a USB connection for power, NMEA, SCPI, and 1PPS interface, and has a solder point for the LVCMOS 1PPS output. It also has a connector for optional exernal 4V to 8V power supplies, and comes with an antenna, a USB cable, a CD with software an manuals, and a quick-start instruction sheet. Hope that helps, Said In a message dated 10/2/2012 12:24:29 Pacific Daylight Time, paulsw...@gmail.com writes: Said I was looking and did not see the eval kit on the sight??? Thanks Paul WB8TSL On Tue, Oct 2, 2012 at 12:29 PM, Bob Camp li...@rtty.us wrote: Hi The rated temperature stability of the OCXO is not super good. You will see more frequency shift on it than say the TBolt OCXO, far more than a DOCXO. That's not at all saying it's a bad part. For Time Nut duty, I would try to keep it in a fairly benign ambient situation. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Tuesday, October 02, 2012 9:04 AM To: time-nuts@febo.com Subject: Re: [time-nuts] RFX GPSDO - Anybody played with one of these? On 10/2/12 5:08 AM, Azelio Boriani wrote: Yes, I agree. On Tue, Oct 2, 2012 at 1:29 PM, Bob Camp li...@rtty.us wrote: Hi The OCXO probably isn't going to do very well with the outdoor temperature swings. Bob Why not.. granted it's easier with large mass and large insulation, but ultimately, it's all about the closed loop gain of the temperature control loop. With small mass, the time lag effects will be small, at least. ___ 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. ___ 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] GPS Jammer
On Tue, 02 Oct 2012 23:01:45 +0200, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 10/02/2012 10:43 PM, J. Forster wrote: Take a look at the specs of this unit: http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? For a 500 mW jammer your jamming range should be much better. That's wrong. Cheers, Magnus That is what I was thinking but I am too lazy to work out the math right now and I do not have a 1.5GHz source for testing at the moment anyway. A lot depends on antenna geometry since the jammer may need to be concealed and is unlikely to be in the high gain portion of the receiver's antenna pattern. ___ 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] RFX GPSDO - Anybody played with one of these?
Well Said, it looks like you have been busy! Congrats for an amazing product. Didier Sent from my Droid Razr 4G LTE wireless tracker. -Original Message- From: Said Jackson saidj...@aol.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: swith...@alum.mit.edu swith...@alum.mit.edu, Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tue, 02 Oct 2012 8:00 AM Subject: Re: [time-nuts] RFX GPSDO - Anybody played with one of these? Raj, JLT just sent out a press release some days ago on the LC_XO sub 1 inch square GPSDO that is smaller and higher performance than the RFX unit, runs from only 3.3V, and it can be soldered into a 100 mil standard breadboard, and consumes only about 0.5W (RFX unit is probably 1W). http://www.marketwire.com/press-release/jackson-labs-technologies-inc-delivers-lc_xo-complete-gpsdo-reference-sub-1-x-1-inch-1707006.htm bye, Said On Oct 1, 2012, at 21:12, Raj vu2...@gmail.com wrote: Just saw this mentioned in Circuit Cellar, just wonding if it really exists, how much they are asking, and if anyone has played with one yet? http://www.rfx.co.uk/pdfs/GPS_OCXO_1300_10_module.pdf It is small enough to incorporate in the external antenna ! Raj ___ 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] GPS Jammer
On 10/02/2012 11:05 PM, John Lofgren wrote: The 0.5 W and + 10 dBm numbers in the specs don't work out. +10 dBm is 10 mW. I suspect that the 1/2 watt is really the DC input power. Now, that makes sense. And, I'd agree about the range. +10 dBm into a dipole at 10 meters gets you about -44 dBm at the receiver antenna in a free-space model. That's really loud compared to the nominal -130 to -140 dBm you'd hear from the satellites. Indeed. Even for 10 mW it was not reasonable. No wonders that 1-10 m jammers cause such grief to DHS. Serious overkill. Cheers, Magnus ___ 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] RFX GPSDO - Anybody played with one of these?
Thanks much Didier! Those are kind words for the JLT team :) bye, Said In a message dated 10/2/2012 14:28:13 Pacific Daylight Time, shali...@gmail.com writes: Well Said, it looks like you have been busy! Congrats for an amazing product. Didier Sent from my Droid Razr 4G LTE wireless tracker. ___ 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] RFX GPSDO - Anybody played with one of these?
Hello Paul, thanks much for the feedback! Yes, we think we have identified a nice combination of oscillators, GPS, and firmware that seems to work pretty well. The GPSTCXO units cannot be compared to a lower cost $150 Thunderbolt in terms of phase noise or stability of course, and they have CMOS 10MHz outputs, but then the TB's cost around $1500 new I guess. We think the GPSTCXO's and LC_XO type units will work quite well wherever standard OCXO's are used today, and power/size/weight are an issue. Bye, Said In a message dated 10/2/2012 14:21:47 Pacific Daylight Time, paulsw...@gmail.com writes: Said I have to say I was looking through the list of modules that are available. I guess a couple of things really jump out. The low power consumption and what you get in terms of behaviors. It is pretty amazing actually. Though I have my power sucking Tbolt and 3801. But I could easily see for a Amateur radio operator just getting into time nuttery that these might be a nice way to go. I guess that would open an interesting debate. Getting the used RBs at Hamfest of questionable quality for $200 or far less. Or something modern and simply works. Regards Paul. ___ 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] Re Best Counter Setting for Adev
No, I didn't modify either of the 5370B's. Now that you mention it I recall seeing a reference to this mod in the past in the archives. I'm curious how much of a difference did the mod make on yours ? Regards Mark S On 10/02/2012 07:19 PM, Mark Spencer wrote: On a somewhat related note over the weekend I spent a few hours characterizing the performance of two of my HP5370B's for making ADEV measurements by feeding the stop and start inputs with identical 10 Mhz signals from a HP5087a distribution amp. Not surprisingly they perform somewhat differently. More surprisingly the results vary depending on the oscillators used for the clock source for the HP5370B's. (I was under the impression the built in 10811's were more than adequate enough for this application.) Did you disable the wide-band 5 MHz comb-generator of the 5370s? I did it to mine. Cheers, Magnus ___ 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] GPS Jammer
The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? I'd expect a much greater range with a 0.5 W jammer. But note that 0.5 W is the total output power -- the transmit power is only 10 dBm (0.01 W). Whatever those terms mean. (Does total output power include far IR and heat?) Note that The item is for Legal Use only! Best regards, Charles ___ 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] GPS Jammer
HI At least from here, the link no longer works. Bob On Oct 2, 2012, at 7:48 PM, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? I'd expect a much greater range with a 0.5 W jammer. But note that 0.5 W is the total output power -- the transmit power is only 10 dBm (0.01 W). Whatever those terms mean. (Does total output power include far IR and heat?) Note that The item is for Legal Use only! Best regards, Charles ___ 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] RFX GPSDO - Anybody played with one of these?
Shameless plug for JLT, but they helped me with a special application need in my day-job and it worked like a charm! One happy customer. -Brian, WA1ZMS (sent from my over-priced iPad3) On Oct 2, 2012, at 5:36 PM, saidj...@aol.com wrote: Hello Paul, thanks much for the feedback! Yes, we think we have identified a nice combination of oscillators, GPS, and firmware that seems to work pretty well. The GPSTCXO units cannot be compared to a lower cost $150 Thunderbolt in terms of phase noise or stability of course, and they have CMOS 10MHz outputs, but then the TB's cost around $1500 new I guess. We think the GPSTCXO's and LC_XO type units will work quite well wherever standard OCXO's are used today, and power/size/weight are an issue. Bye, Said In a message dated 10/2/2012 14:21:47 Pacific Daylight Time, paulsw...@gmail.com writes: Said I have to say I was looking through the list of modules that are available. I guess a couple of things really jump out. The low power consumption and what you get in terms of behaviors. It is pretty amazing actually. Though I have my power sucking Tbolt and 3801. But I could easily see for a Amateur radio operator just getting into time nuttery that these might be a nice way to go. I guess that would open an interesting debate. Getting the used RBs at Hamfest of questionable quality for $200 or far less. Or something modern and simply works. Regards Paul. ___ 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] Google's Spanner uses GPS and atomic time
In case anyone here hasn't seen this article: http://www.wired.com/wiredenterprise/2012/09/google-spanner/all/ Google is using GPS and atomic time synchronization across its data centers to ensure database consistency in innovative ways. Apparently there's a paper out on the system now but I haven't read it (yet). I wonder what happens if someone parks a truck outside a data center with a GPS spoofing device. -- Anthony ___ 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] Google's Spanner uses GPS and atomic time
Seems like a good reason to have LORAN-C or some other backup/sanity check. -John In case anyone here hasn't seen this article: http://www.wired.com/wiredenterprise/2012/09/google-spanner/all/ Google is using GPS and atomic time synchronization across its data centers to ensure database consistency in innovative ways. Apparently there's a paper out on the system now but I haven't read it (yet). I wonder what happens if someone parks a truck outside a data center with a GPS spoofing device. -- Anthony ___ 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] Google's Spanner uses GPS and atomic time
John writes: Seems like a good reason to have LORAN-C or some other backup/sanity check. What LORAN? I thought the U.S. had shut down all LORAN transmissions in order to enhance the vulnerability of navigation systems in the U.S. (?). -- Anthony ___ 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] Google's Spanner uses GPS and atomic time
The US, foolishly IMO, has killed LORAN-C and is killing WWVB. Hence my comment. Essentially, GPS is soon going to be the sole source of a standard of time interval. It is going to take a disaster of some kind to return sanity. -John === John writes: Seems like a good reason to have LORAN-C or some other backup/sanity check. What LORAN? I thought the U.S. had shut down all LORAN transmissions in order to enhance the vulnerability of navigation systems in the U.S. (?). -- Anthony ___ 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] Best counter setting for ADEV?
The Thunderbolt is a special case that does not provide sawtooth correction because it does not need it. It uses the OCXO as the clock for the processor while disciplining it to GPS so there is no nominal timing error between where the 1PPS is versus where it should be. The processor is able to bring the PPS edge exactly where it wants it, instead of the typical 25 to 40 ns granularity of most other GPS receivers that operate on a separate clock. Pretty simple and elegant solution. Didier KO4BB Sent from my Droid Razr 4G LTE wireless tracker. -Original Message- From: David davidwh...@gmail.com To: Tom Van Baak t...@leapsecond.com, Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tue, 02 Oct 2012 12:04 PM Subject: Re: [time-nuts] Best counter setting for ADEV? Is there a list of GPS timing receivers that provide the sawtooth correction message or implement sawtooth correction internally? I assume there is a design compromise that prevents economically phase locking the GPS receiver clock to the GPS signal to remove that contribution to timing error. On Tue, 2 Oct 2012 09:18:35 -0700, Tom Van Baak t...@leapsecond.com wrote: Correct, all GPS timing receiver boards have jitter, sawtooth, or random wandering of some sort, on the order of tens of nanoseconds. This is normal. And so if you use a counter to compare the OCXO 1 Hz with the GPS 1PPS, a TIC resolution of 1 ns or 500ps is sufficient. I would say 25 ps is overkill. In many cases (e.g., Motorola Oncore series) the sawtooth correction message itself has a granularity of 1 ns. So again, a 25 ps measurement is especially overkill given a correction granularity of 1 ns. Depending on the receiver applying the correction will improve the average timing performance by, say, a factor of 3. See: http://www.leapsecond.com/pages/m12-adev/ As for your averaging question, yes, the OCXO will move during the average. This is normal. That's why too long an averaging interval is problematic. Depends on the quality of the OCXO. And if the averaging interval is too short, you pick up too much GPS jitter. Depends on the quality of the GPS receiver. There is no perfect answer; instead you choose something between too short and too long. ___ 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] GPS Modulation and 10 MHz Delay Lock
On 10/2/12 3:39 PM, johncr...@aol.com wrote: Hello All - Here is a link that describes the GPS modulation. You do not need the 1 pps to lock the 10 MHz oscillator to the atomic clock in the satellites. http://www.kowoma.de/en/gps/signals.htm If you look at the block diagram you see PN code modulates the carrier at the 1.023 MHz chip rate. This is done by BPSK modulation of the carrier with the PN code. It can be done simply with a double balanced mixer. This spreads the signal with PSK at the chip( i.e. code clock) rate. Note also the modulo - 2 addition of the data to the code sequence. This called code inversion modulation. After de-spread of the code in the receiver - the signal is then simple BPSK and may be demodulated by a Costas or Squaring Loop to get at the data message. The obtain precision frequency needed I believe the T bolt simply locks to the chipping rate using some form of Delay Lock Loop. It is NOT at PLL. There is no need what ever to deal with the 1 pps using this method. The internal 10 MHz oscillator is controlled by this locking circuit and is part of the code correlation loop. That's not quite how it works.. It would work for terrestrial links where there is no Doppler, but in the GPS case, there is significant Doppler shift on all the signals. Since the carrier and the chips are generated from a common source on the spacecraft (the carrier frequency is a multiple of the chip rate, in fact), you can recover carrier and chips at the same time. But.. most receivers these days don't actually have an analog tracking loop at all. They digitize the input signal (1 bit quantizer) at a rate that makes the carrier alias down to something convenient (a few hundred kHz is typical.. you want it far enough away from zero that Doppler never makes it go negative). In the experimental receiver in SCaN Testbed flying on ISS it's about 39 MHz sample rate. Once you've got your one bit samples, you do some sort of combined Doppler/Code phase acquisition (these days, often using an FFT), then track both together digitally using some form of NCO. The tracking loops for all the satellite signals aren't necessarily independent and might be part of a Kalman filter that estimates all the observables together. Finally, from all that, you have an estimate of your local clock offset and timing offset, and from that you can generate your 1pps, typically with another NCO (with granularity of your clock rate). Since it's unlikely that your clock is EXACTLY an even number of cycles per second, at each second, a bit of error accumulates, until you have an whole cycle's worth leading to the familiar sawtooth error. That sawtooth error is predictable, of course, so you can generate a time error estimate for each 1pps pulse (or, even, control a variable delay to line it up). The important thing is that in modern receivers, nowhere is there a signal at the GPS carrier frequency, nor is there a signal at the chip rate. There *is* probably a signal (with low precision) at the code epoch (every millisecond), but it's different for each satellite signal, of course. ___ 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] GPS Jammer
On 10/2/12 4:48 PM, Charles P. Steinmetz wrote: The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters. Anybody think there is something wrong? I'd expect a much greater range with a 0.5 W jammer. But note that 0.5 W is the total output power -- the transmit power is only 10 dBm (0.01 W). Whatever those terms mean. (Does total output power include far IR and heat?) maybe it has some real bright LEDs to indicate it's on? ___ 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] GPS Jammer
In considering the effect of a simple jammer on a GPS receiver, a simple link analysis is insufficient. What must also be considered is the anti-jam capability of the receiver which due to spread spectrum processing gain will reject any simple jamming signal even though is it 10's of dB stronger than the desired signal. 73 -john k6iql ___ 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] Best counter setting for ADEV?
On 10/2/12 7:00 PM, shali...@gmail.com wrote: The Thunderbolt is a special case that does not provide sawtooth correction because it does not need it. It uses the OCXO as the clock for the processor while disciplining it to GPS so there is no nominal timing error between where the 1PPS is versus where it should be. The processor is able to bring the PPS edge exactly where it wants it, instead of the typical 25 to 40 ns granularity of most other GPS receivers that operate on a separate clock. Pretty simple and elegant solution. But it does depend on having a good oscillator that can be shoved around. That costs money and power. ___ 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] Centering ocxo
I am ok for awhile but how do you center the efc of an ocxo? I understand there is something (screw) to adjust the ocxo so it is approximately on freq with 2.5v efc. Specific oscillator datum-c. I have he datasheet but doesn't say coarse frequency adjust this screw or some such. Doc KX0O Sent from my iPad ___ 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] GPS Jammer
On 10/2/12 7:33 PM, johncr...@aol.com wrote: In considering the effect of a simple jammer on a GPS receiver, a simple link analysis is insufficient. What must also be considered is the anti-jam capability of the receiver which due to spread spectrum processing gain will reject any simple jamming signal even though is it 10's of dB stronger than the desired signal. not most simple GPS receivers which have very little AJ capability. They have a single bit quantizer (or maybe a 1.5 or 2 bit) after the LNA. If the LNA doesn't saturate, then the quantizer is captured by the strong CW carrier. This is a classic problem with DSSS receivers and led to a lot of research in the 80s on things like adaptive excisers to remove CW carriers. If you built a linear receiver with a lot of dynamic range, then, yes, the process gain will suppress the CW tone, but you still have to acquire the code, and as Dixon says (paraphrasing) acquisition is the secret sauce in spread spectrum systems. Back when I was doing this kind of thing seriously (mid to late 80s), acquisition, particularly robust techniques, were literally SECRET (in the DoD sense). There have been a nice series of articles in GPS World over the past few months about the variety of inexpensive GPS jammers out there. (and the problems they cause). ___ 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] Google's Spanner uses GPS and atomic time
And yes thank god we are cutting funding to those pesky satellites. Seems we can't afford them anymore. But fortunately other countries are filling our gap slow but surely. There was an article this month in GNSS about the funding cuts. Regards Paul WB8TSL On Tue, Oct 2, 2012 at 9:11 PM, J. Forster j...@quikus.com wrote: The US, foolishly IMO, has killed LORAN-C and is killing WWVB. Hence my comment. Essentially, GPS is soon going to be the sole source of a standard of time interval. It is going to take a disaster of some kind to return sanity. -John === John writes: Seems like a good reason to have LORAN-C or some other backup/sanity check. What LORAN? I thought the U.S. had shut down all LORAN transmissions in order to enhance the vulnerability of navigation systems in the U.S. (?). -- Anthony ___ 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] GPS Jammer
We don't know that they modulate the jamming signal some what. I bet 10 mW would do a good bit of harm to GPS systems even a block away. - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Tuesday, October 02, 2012 10:45 PM Subject: Re: [time-nuts] GPS Jammer On 10/2/12 7:33 PM, johncr...@aol.com wrote: In considering the effect of a simple jammer on a GPS receiver, a simple link analysis is insufficient. What must also be considered is the anti-jam capability of the receiver which due to spread spectrum processing gain will reject any simple jamming signal even though is it 10's of dB stronger than the desired signal. not most simple GPS receivers which have very little AJ capability. They have a single bit quantizer (or maybe a 1.5 or 2 bit) after the LNA. If the LNA doesn't saturate, then the quantizer is captured by the strong CW carrier. This is a classic problem with DSSS receivers and led to a lot of research in the 80s on things like adaptive excisers to remove CW carriers. If you built a linear receiver with a lot of dynamic range, then, yes, the process gain will suppress the CW tone, but you still have to acquire the code, and as Dixon says (paraphrasing) acquisition is the secret sauce in spread spectrum systems. Back when I was doing this kind of thing seriously (mid to late 80s), acquisition, particularly robust techniques, were literally SECRET (in the DoD sense). There have been a nice series of articles in GPS World over the past few months about the variety of inexpensive GPS jammers out there. (and the problems they cause). ___ 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] GPS Jammer
John, Coherent reproduction of the spread PRN standard positioning signal (SPS) signal gives ~30dB of A/J protection, the GPS signal level, as received at the GPS receiver is on the order of -160 dBW (L1-CA). If the jammer outputs half a Watt, and is anywhere nearby, the receiver will not maintain lock on the civilian code as the jammer would overwhelm the receiver front end. A commercial GPS receiver has a maximum of 20 dB power bandwidth. If the jammer is present prior to initial acquisition then the receiver would certainly never acquire lock. My experience is that the civil signal (SPS) is very easy to jam, where the precise positioning signal (PPS), using the P(Y) code adds significantly more protection. All values are round numbers and the individual receivers signal strategy can make some difference, as well as GPS aiding (especially a good clock, known position, velocity and so forth). Michael, K7HIL On Tue, Oct 2, 2012 at 7:33 PM, johncr...@aol.com wrote: In considering the effect of a simple jammer on a GPS receiver, a simple link analysis is insufficient. What must also be considered is the anti-jam capability of the receiver which due to spread spectrum processing gain will reject any simple jamming signal even though is it 10's of dB stronger than the desired signal. 73 -john k6iql __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] GPS Jammer
I talked to the GPS jamming group at Nellis a few years ago. They use broadband noise to jam GPSs. If somebody is going to the Nellis Aviation Nation coming up in November, the jammer group always has a static display. They have some Soviet jammer gear they acquired. http://www.nellis.af.mil/aviationnation/ ___ 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] GPS Modulation and 10 MHz Delay Lock (Jim Lux)
Hi Jim - Thanks for the update on the modern GPS receivers. I was aware that the modern ones do not have a classical analog tracking loop, much less a bunch of them. However it is a useful concept for purposes of explanation that you do not need the 1 pps to lock up the 10 MHz VCXO - which was my main point. The Tbolt block diagram in the manual Figure 5-10 shows the 10 MHz VCXO output going to the receiver and also to the output. The 1 pps comes from the cpu and support circuit. While the diagram is clearly simplistic - it implies that the Receiver circuitry first locks up the 10 MHz oscillator and the the 1 pps is derived from that. My only point was that it is possible and perhaps even better to discipline an oscillator using a code correlator (however implemented) rather than steering using the 1 pps. I believe this is why the T bolts work so well. For one thing the loop should work better and faster if the input is at the chipping rate rather than at 1 pps as the information rate is higher. On doppler - I believe that since the spread spectrum sidebands are coherent with the suppressed carrier, their relationship to it is unchanged by doppler and thus it should be possible to achieve a code correlation on a doppler shifted signal. The recovered carrier would be shifted in frequency by the doppler but it would still be recovered - at least by a classical IF correlator. - On jamming - maybe so, but the effect of the receiving correlator is to spread the energy of a CW interferer and concentrate the energy of the signal with the matching PN modulation is it not good fun anyway! -73 john k6iql -Original Message- From: time-nuts-request time-nuts-requ...@febo.com To: time-nuts time-nuts@febo.com Sent: Tue, Oct 2, 2012 9:53 pm Subject: time-nuts Digest, Vol 99, Issue 19 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-requ...@febo.com You can reach the person managing the list at time-nuts-ow...@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 Modulation and 10 MHz Delay Lock (Jim Lux) 2. Re: GPS Jammer (Jim Lux) 3. Re: GPS Jammer (johncr...@aol.com) 4. Re: Best counter setting for ADEV? (Jim Lux) 5. Re: RFX GPSDO - Anybody played with one of these? (Jim Lux) 6. Centering ocxo (Bill Dailey) 7. Re: GPS Jammer (Jim Lux) 8. Re: Google's Spanner uses GPS and atomic time (paul swed) -- Message: 1 Date: Tue, 02 Oct 2012 19:30:20 -0700 From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Modulation and 10 MHz Delay Lock Message-ID: 506ba33c.1010...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 10/2/12 3:39 PM, johncr...@aol.com wrote: Hello All - Here is a link that describes the GPS modulation. You do not need the 1 pps to lock the 10 MHz oscillator to the atomic clock in the satellites. http://www.kowoma.de/en/gps/signals.htm If you look at the block diagram you see PN code modulates the carrier at the 1.023 MHz chip rate. This is done by BPSK modulation of the carrier with the PN code. It can be done simply with a double balanced mixer. This spreads the signal with PSK at the chip( i.e. code clock) rate. Note also the modulo - 2 addition of the data to the code sequence. This called code inversion modulation. After de-spread of the code in the receiver - the signal is then simple BPSK and may be demodulated by a Costas or Squaring Loop to get at the data message. The obtain precision frequency needed I believe the T bolt simply locks to the chipping rate using some form of Delay Lock Loop. It is NOT at PLL. There is no need what ever to deal with the 1 pps using this method. The internal 10 MHz oscillator is controlled by this locking circuit and is part of the code correlation loop. That's not quite how it works.. It would work for terrestrial links where there is no Doppler, but in the GPS case, there is significant Doppler shift on all the signals. Since the carrier and the chips are generated from a common source on the spacecraft (the carrier frequency is a multiple of the chip rate, in fact), you can recover carrier and chips at the same time. But.. most receivers these days don't actually have an analog tracking loop at all. They digitize the input signal (1 bit quantizer) at a rate that makes the carrier alias down to something convenient (a few hundred kHz is typical.. you want it far enough away from zero that Doppler never makes it go negative). In the experimental receiver in SCaN Testbed flying on ISS it's about 39 MHz sample rate.
Re: [time-nuts] RFX GPSDO - Anybody played with one of these?
On 10/02/2012 10:37 PM, Jim Lux wrote: Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO? (7km/s) The total Doppler isn't usually the issue (the GPS satellites are moving faster, after all), but the receiver may not work for high velocities, high altitudes? GPS receivers that function above 60,000 feet altitude and at 1,000 knots velocity or greater are classified as munitions under ITAR. This doesn't make them illegal to possess or use as far as I know, but exporting them from the US is troublesome so civilian receivers will cease functioning under those conditions. Whether that's 60k feet and 1000 knots simultaneously or separately, is up for debate and probably depends on the manufacturer's interpretation. ___ 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] GPS Jammer
Hi: Other than a terrorist, who would want to jam GPS? Ron -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, October 02, 2012 2:28 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Jammer On 10/02/2012 11:05 PM, John Lofgren wrote: The 0.5 W and + 10 dBm numbers in the specs don't work out. +10 dBm is 10 mW. I suspect that the 1/2 watt is really the DC input power. Now, that makes sense. And, I'd agree about the range. +10 dBm into a dipole at 10 meters gets you about -44 dBm at the receiver antenna in a free-space model. That's really loud compared to the nominal -130 to -140 dBm you'd hear from the satellites. Indeed. Even for 10 mW it was not reasonable. No wonders that 1-10 m jammers cause such grief to DHS. Serious overkill. Cheers, Magnus ___ 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] GPS Jammer
Many folks. The paranoid tinfoil hat crowd Folks who are concerned that law enforcement has placed a GPS tracker on their car. Truckers avoiding log enforcement Truckers who want to sleep rather than drive. Ambulance drivers who want to sleep but claim to have been held up at hospital. Emergency services personnel (fire,ems,law enforcement) who want to take the company vehicle where they are not supposed to. Just a few of the many I can think of! On Oct 3, 2012, at 0:40, Ron Ward n6idl...@comcast.net wrote: Hi: Other than a terrorist, who would want to jam GPS? Ron -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, October 02, 2012 2:28 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPS Jammer On 10/02/2012 11:05 PM, John Lofgren wrote: The 0.5 W and + 10 dBm numbers in the specs don't work out. +10 dBm is 10 mW. I suspect that the 1/2 watt is really the DC input power. Now, that makes sense. And, I'd agree about the range. +10 dBm into a dipole at 10 meters gets you about -44 dBm at the receiver antenna in a free-space model. That's really loud compared to the nominal -130 to -140 dBm you'd hear from the satellites. Indeed. Even for 10 mW it was not reasonable. No wonders that 1-10 m jammers cause such grief to DHS. Serious overkill. Cheers, Magnus ___ 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] Centering ocxo
docdai...@gmail.com said: I am ok for awhile but how do you center the efc of an ocxo? I understand there is something (screw) to adjust the ocxo so it is approximately on freq with 2.5v efc. Specific oscillator datum-c. I have he datasheet but doesn't say coarse frequency adjust this screw or some such. There may not be a coarse adjustment. If the tuning range is big enough to cover the aging over your design life, you don't need one. There is a tradeoff between adjustment range and the number of bits you need in a DAC to get a required accuracy. Suppose I have an adjustment range of 1 Hz (peak to peak) on a 10 MHz oscillator. That's 1 part is 10^7. If I have a 10 bit DAC, I can adjust to 1 part is 10^10. A 20 bit DAC can get to 1 part is 10^13. But if the tuning range is 10 Hz, the same 20 bit DAC setup only gets you to 1 part is 10^12. -- 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] GPS Jammer
Other than a terrorist, who would want to jam GPS? Generic bad guys who don't want the FBI tracking them. The civil liberties types are suing the FBI to make sure the get a court document before they install GPS trackers on suspects cars. Truckers who don't want their boss to know what they are actually doing. The FAA test in NJ had troubles because of truckers using GPS jammers on the nearby NJ Turnpike. There is also jamming from broken gear, perhaps broken by (mis)design. The classic is a TV repeater on a boat that wiped out Monterrey Bay. GPS World used to have a good article on-line, but the URL I had bookmarked is now 404. Anybody got a working URL? The Hunt for RFI Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 -- 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] GPS Jammer
Hi all: Thanks for your response to my question. I had no idea! Ron -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Tuesday, October 02, 2012 10:07 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS Jammer Other than a terrorist, who would want to jam GPS? Generic bad guys who don't want the FBI tracking them. The civil liberties types are suing the FBI to make sure the get a court document before they install GPS trackers on suspects cars. Truckers who don't want their boss to know what they are actually doing. The FAA test in NJ had troubles because of truckers using GPS jammers on the nearby NJ Turnpike. There is also jamming from broken gear, perhaps broken by (mis)design. The classic is a TV repeater on a boat that wiped out Monterrey Bay. GPS World used to have a good article on-line, but the URL I had bookmarked is now 404. Anybody got a working URL? The Hunt for RFI Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 -- 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] RFX GPSDO - Anybody played with one of these?
On 10/2/12 2:36 PM, saidj...@aol.com wrote: Hello Paul, thanks much for the feedback! Yes, we think we have identified a nice combination of oscillators, GPS, and firmware that seems to work pretty well. The GPSTCXO units cannot be compared to a lower cost $150 Thunderbolt in terms of phase noise or stability of course, and they have CMOS 10MHz outputs, but then the TB's cost around $1500 new I guess. We think the GPSTCXO's and LC_XO type units will work quite well wherever standard OCXO's are used today, and power/size/weight are an issue. Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO? (7km/s) The total Doppler isn't usually the issue (the GPS satellites are moving faster, after all), but the receiver may not work for high velocities, high altitudes? GPS SVs moves at around 4km/s, but nevertheless there are still COCOM limits implemented in nearly all receivers (never break both 504m/s and 18km height) -- Björn ___ 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.
