Re: [time-nuts] Low SNR GPS reception and cheap LNAs
On Fri, 25 Apr 2014 20:19:42 +0200 Björn Gabrielsson b...@lysator.liu.se wrote: On Fri, 25 Apr 2014 12:21:04 -0400 (EDT) gandal...@aol.com wrote: Coincidentally, I came across this earlier today when looking for some MMIC data, perhaps it might be worth a look?... http://lna4all.blogspot.co.uk/ Now that's almost perfect! Only two modifications and it does what i need it to do! Thanks a lot! Next time I will try a ZX60-P162LN+ from Mini-Circuits. http://217.34.103.131/pages/s-params/ZX60-P162LN+_GRAPHS.pdf only $54 for a boxed unit. Bias-T needed to. -- Björn Aren't these DC to daylight low noise amps fiction? I was told it is really hard to design a LNA that is optimal for more than an octave or so. http://www.datasheets360.com/pdf/-5223408218466592358 That minicircuits looks like a good match for 1090 mode-s. Probably good enough at GPS frequencies too. The input VSWR is good at GPS frequencies and the output VSWR is OK, maybe a little higher than you would like. It looks they tuned it for 1GHz. And yes, amplified noise is amplified noise. But it is a matter of the noise figure of your receiver. If you are using a crappy DVB-T which has a noise figure around 5db, you would appreciate the 0.5dB of the minicircuits. The front end determines the overall noise figure in a good design. With a gain of 20dB, the noise of the DVB-T is not the determining factor. But antenna gain is always better than amplifier gain. Regarding the GPS application, you would need to know the noise figure off the receiver. All this said, I think an amplified GPS antenna is cheaper in the long run. ___ 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] Low SNR GPS reception and cheap LNAs
On 04/25/2014 06:04 PM, Attila Kinali wrote: On Fri, 25 Apr 2014 08:42:16 -0700 Chris Albertson albertson.ch...@gmail.com wrote: You best bet is to change out the antenna. You can buy them with a higher built-in gain up to about 40dB. Buying a better antenna is also on the list. But i would still like to have an LNA, even if it's just to see that it doesn't help :-) My understanding is that designing a GOOD LNA is not so easy as little things like the exact layout of the PCB and how the PCB transitions to connectors matters a lot. Well, the idea is to use one of the monolitic types like the TQP3M9036 [1] which basicall only need power on the output. These should work quite well without a PCB. Though i'm really thinking about getting a small PCB run, both for my bias tee and the LNA, but that will incure a minimum cost of around 100EUR (same price whether i buy 1 or 10, though) But you can buy these ready made for cheap. I've seen complete LNAs in an enclosure with connectors at good prices on eBay.The user manuals I have say using 75R cables with compression type F connects is OK.I doubt the cheaper type f-connectors would work well. I looked at the ones available on ebay, but they were either made for sat solutions and require 12V, which would complicate the whole power supply system. Or are 100USD. Given that i can get a cheap LNA chip for 1USD or an expensive one like the TQP3M9036 for 4, then i can build one myself for less than 20USD that should do the job just as well. I have a good high quality Tremble in-line amplifier with N-connector and the ability to pass DC. In my experiment I place the antenna indoor and use amplifier and then outdoors with no amplifier. I get MUCH better results with my 26dB gain antenna on the roof and 25 feet of cable than with indoor amplified antenna with short cable. My un-scientific conclusion was that amplified noise is still noise. Well, GPS signal is mostly noise anyways ;-) The idea would be to place the LNA close to the antenna, in order to need less amplification in the bladeRF. And also to compensate for the longer cable i plan to use (getting the antenna to a better location) The indoor antenna would see the noise of the house 290-300 K rather than the background noise of the sky 3 K. The signal will also be attenuated when indoor. If you have a passive antenna, put a LNA right at the antenna, since any cable damping will cause the S/N to go down. Also, if you put an aditional amplifier in line, your want that too up at the antenna. Then, low-loss cable should be natural. 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] Low SNR GPS reception and cheap LNAs
On 04/25/2014 06:21 PM, gandal...@aol.com wrote: Coincidentally, I came across this earlier today when looking for some MMIC data, perhaps it might be worth a look?... http://lna4all.blogspot.co.uk/ This is the 0,5 dB NF amplifier from Minicircuits and I think it is an interesting alternative. I just haven't come around to order some. Fairly cheap alternative than to roll your own from the same chip, which was what I was considering. 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] Low SNR GPS reception and cheap LNAs
On 04/25/2014 08:19 PM, Björn Gabrielsson wrote: On Fri, 25 Apr 2014 12:21:04 -0400 (EDT) gandal...@aol.com wrote: Coincidentally, I came across this earlier today when looking for some MMIC data, perhaps it might be worth a look?... http://lna4all.blogspot.co.uk/ Now that's almost perfect! Only two modifications and it does what i need it to do! Thanks a lot! Next time I will try a ZX60-P162LN+ from Mini-Circuits. http://217.34.103.131/pages/s-params/ZX60-P162LN+_GRAPHS.pdf only $54 for a boxed unit. Bias-T needed to. The lna4all has a later and quieter chip and can be modified not to need bias-T at all. 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] Low SNR GPS reception and cheap LNAs
On Sat, 26 Apr 2014 12:25:11 +0200 Magnus Danielson mag...@rubidium.dyndns.org wrote: If you have a passive antenna, put a LNA right at the antenna, since any cable damping will cause the S/N to go down. Also, if you put an aditional amplifier in line, your want that too up at the antenna. Then, low-loss cable should be natural. My current antenna is an cheap patch antenna. It has an LNA, but aparently it's not enough. I talked with a few gnuradio people and they basically told me that the GNSS-SDR software needs a strong signal for acquisition. Ie. i realy need to put the antenna somewhere with good skyview. I ordered 4 of those lna4all, so that problem should be solved. I'm also getting a better antenna and we'll see how much signal i can get out of this place. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] Low SNR GPS reception and cheap LNAs
Hi The ability of these receivers to handle noisy signals depends on a lot of things. The good stuff seems to have a massive number of correlators. Going from a 1.3 to a 0.3 db nf amp likely only helps you by 1 db. The low correlateor GPS’s are / were 10 to 20 db less sensitive than the newer stuff. Bob On Apr 26, 2014, at 6:52 AM, Attila Kinali att...@kinali.ch wrote: On Sat, 26 Apr 2014 12:25:11 +0200 Magnus Danielson mag...@rubidium.dyndns.org wrote: If you have a passive antenna, put a LNA right at the antenna, since any cable damping will cause the S/N to go down. Also, if you put an aditional amplifier in line, your want that too up at the antenna. Then, low-loss cable should be natural. My current antenna is an cheap patch antenna. It has an LNA, but aparently it's not enough. I talked with a few gnuradio people and they basically told me that the GNSS-SDR software needs a strong signal for acquisition. Ie. i realy need to put the antenna somewhere with good skyview. I ordered 4 of those lna4all, so that problem should be solved. I'm also getting a better antenna and we'll see how much signal i can get out of this place. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] Low SNR GPS reception and cheap LNAs
On Sat, 26 Apr 2014 08:20:47 -0400 Bob Camp li...@rtty.us wrote: The ability of these receivers to handle noisy signals depends on a lot of things. The good stuff seems to have a massive number of correlators. Going from a 1.3 to a 0.3 db nf amp likely only helps you by 1 db. The low correlateor GPS’s are / were 10 to 20 db less sensitive than the newer stuff Yes, the sub-optimal correlation system in GNSS-SDR seems to be one of the problems. But still, the LNA will help with two things: It will enable me to put the antenna in a better spot while compensating for the cable loss (i need about 20m of additional cable, which is about 6dB of loss) and a stronger signal at the bladeRF such that less gain is needed in the radio chip there. My current goal is to get a feeling how GNSS-SDR works. After i get an understanding for the code, i will try to improve on the correlators in order to improve reception. Attila Kinali -- I pity people who can't find laughter or at least some bit of amusement in the little doings of the day. I believe I could find something ridiculous even in the saddest moment, if necessary. It has nothing to do with being superficial. It's a matter of joy in life. -- Sophie Scholl ___ 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] Low SNR GPS reception and cheap LNAs
Attila, On 04/26/2014 12:52 PM, Attila Kinali wrote: On Sat, 26 Apr 2014 12:25:11 +0200 Magnus Danielson mag...@rubidium.dyndns.org wrote: If you have a passive antenna, put a LNA right at the antenna, since any cable damping will cause the S/N to go down. Also, if you put an aditional amplifier in line, your want that too up at the antenna. Then, low-loss cable should be natural. My current antenna is an cheap patch antenna. It has an LNA, but aparently it's not enough. I talked with a few gnuradio people and they basically told me that the GNSS-SDR software needs a strong signal for acquisition. Ie. i realy need to put the antenna somewhere with good skyview. I ordered 4 of those lna4all, so that problem should be solved. I'm also getting a better antenna and we'll see how much signal i can get out of this place. I'm just about to put my double-frequency choke-ring antenna on the top of the antenna-pole, with support-lines, and then LMR-400 cables to go into the lab/shaft/mancave. I hope that will beat the old setup. I intend to rebuild one of my single-frequency antennas with a new element and suitable LNAs, and the lna4all looks very interesting. 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] Low SNR GPS reception and cheap LNAs
On 04/26/2014 02:59 PM, Attila Kinali wrote: On Sat, 26 Apr 2014 08:20:47 -0400 Bob Camp li...@rtty.us wrote: The ability of these receivers to handle noisy signals depends on a lot of things. The good stuff seems to have a massive number of correlators. Going from a 1.3 to a 0.3 db nf amp likely only helps you by 1 db. The low correlateor GPS’s are / were 10 to 20 db less sensitive than the newer stuff Yes, the sub-optimal correlation system in GNSS-SDR seems to be one of the problems. But still, the LNA will help with two things: It will enable me to put the antenna in a better spot while compensating for the cable loss (i need about 20m of additional cable, which is about 6dB of loss) and a stronger signal at the bladeRF such that less gain is needed in the radio chip there. My current goal is to get a feeling how GNSS-SDR works. After i get an understanding for the code, i will try to improve on the correlators in order to improve reception. You probably want to move from the Tong-search (traditional channel search) to FFT based cross-correlation search. Once the FFT has determined coarse phase and doppler frequency, you can setup the normal correlation channel with that and lock into the signal. You can also do a secondary FFT in order to get higher dopper frequency resolution once you have the phase. With both phase and doppler found, channel lockin becomes much quicker as you leave it very near the actual balance-points and that way you can allow the PLL bandwidth to be much smaller and thus suppress noise better. I've toyed with FFT phase correlation and hand-over to the channel, and for my case it worked really well without too much of code. 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] Rb vs.Crystal OCXO
Shane, The trade off for most applications is as follows: Rb has much faster stabilization time after power on. Ocxos suffer from retrace, that can take hours to days to get rid off. Retrace could cause a frequency shift of several ppb or more from say 15 minutes after power on compared to 10 hours after power on Retrace on a good Rb is very low, turn on a PRS-10 and after 10 minutes or so it will be stable and drift much less than 1ppb over the next days typically. 10x to 50x less retrace than on a good ocxo Is possible. This is important when you do not have a GPS to remove retrace error from the ocxo. If you run without gps (holdover) the best docxo will start to drift more and more after a day. Rb will stay stable for months or years. Important for base station applications where the amount of drift determines how much time can pass before a repair crew has to be sent. They do not want to send crews over the weekend for example because it could cost double overtime pay. Because the loop BW of a Rb is larger than a GPSDO (say 10Hz vs 0.001Hz) a typical Rb will have higher ADEV noise close in than a really good GPSDO due to the loop steering noise being additive to the ocxo noise. This is why a GPSDO can have significantly lower phase noise below 10Hz. But it depends on the Rb. For example the CSAC which works on the Rb vapor cell principle actually improves noise close in as Rick explained because it has a fairly low cost tcxo and the vapor cell thus is more stable than the tcxo by itself. On a PRS-10 one can see a steering hump below 1 Hz (around 20s or so depending on the selected loop time constant) that probably would not be there without the loop steering.. Most of the time Rbs are used because they require much less calibration, have much less g (tilt) sensitivity and much less initial retrace/warmup error. In the case of the CSAC they also have more than an order of magnitude less power consumption than a good Ocxo (0.12W vs 1.7W on a typical docxo) Bye, Said Sent From iPhone On Apr 25, 2014, at 15:40, Bob Camp li...@rtty.us wrote: Hi At least on the Rb I have seen, the phase noise (in to 1 Hz) is generally better if the Rb loop is narrower rather than wider. That of course assumes that the internal OCXO has pretty good phase noise to start. Maybe I’ve been slumming it …. Bob On Apr 25, 2014, at 6:29 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: My understanding is that a really good Rb standard use a fairly wide bandwidth loop to control its own internal XO, and therefore improve its close in phase noise to be better than you can get with quartz alone. The Rb standard is able to do this because the S/N ratio of its rubidium vapor frequency reference (RVFR) is fairly high, and in any event considerably better than the S/N out of a CBT. Also, Rb standards have much smaller frequency jumps, if any, than quartz. Phase noise specs conveniently don't include the effects of jumps. Newer laser diode pumped Rb standards may make the comparison even more lopsided. Rick On 4/25/2014 9:12 AM, Shane Kirkbride wrote: Hi Everyone, I'm newer to this forum but I really enjoy reading the discussions. I have a pretty basic question. I'm wondering why one would chose an Rb Oscillator over a traditional OCXO? It does not immediately appear there is a phase noise advantage in the Rb.. Thanks, ~Shane On Fri, Apr 25, 2014 at 10:00 AM, time-nuts-requ...@febo.com wrote: 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. Low SNR GPS reception and cheap LNAs (Attila Kinali) 2. Re: Symmetricom chip scale atomic clock (Tom Knox) 3. Re: How to accurately measure an oscillator's temperature. (Didier Juges) 4. Re: Low SNR GPS reception and cheap LNAs (Chris Albertson) -- Message: 1 Date: Fri, 25 Apr 2014 15:28:22 +0200 From: Attila Kinali att...@kinali.ch To: time-nuts@febo.com Subject: [time-nuts] Low SNR GPS reception and cheap LNAs Message-ID: 20140425152822.203775c003a761042e269...@kinali.ch Content-Type: text/plain; charset=US-ASCII Hi, I recently bought a bladeRF[1] to experiment a bit with GPS decoding. I tried to get GNSS-SDR[2] which seems quite good, but has its flaws. One of the things was that i cannot seem to get a fix in my environment. One of the problems seems that my antenna position is far from optimal. Aparently, GNSS-SDR uses only a very
Re: [time-nuts] Rb vs.Crystal OCXO
On 04/26/2014 06:34 PM, Said Jackson wrote: Shane, The trade off for most applications is as follows: Rb has much faster stabilization time after power on. Ocxos suffer from retrace, that can take hours to days to get rid off. Retrace could cause a frequency shift of several ppb or more from say 15 minutes after power on compared to 10 hours after power on Retrace on a good Rb is very low, turn on a PRS-10 and after 10 minutes or so it will be stable and drift much less than 1ppb over the next days typically. 10x to 50x less retrace than on a good ocxo Is possible. This is important when you do not have a GPS to remove retrace error from the ocxo. If you run without gps (holdover) the best docxo will start to drift more and more after a day. Rb will stay stable for months or years. Important for base station applications where the amount of drift determines how much time can pass before a repair crew has to be sent. They do not want to send crews over the weekend for example because it could cost double overtime pay. Because the loop BW of a Rb is larger than a GPSDO (say 10Hz vs 0.001Hz) a typical Rb will have higher ADEV noise close in than a really good GPSDO due to the loop steering noise being additive to the ocxo noise. This is why a GPSDO can have significantly lower phase noise below 10Hz. But it depends on the Rb. For example the CSAC which works on the Rb vapor cell principle actually improves noise close in as Rick explained because it has a fairly low cost tcxo and the vapor cell thus is more stable than the tcxo by itself. On a PRS-10 one can see a steering hump below 1 Hz (around 20s or so depending on the selected loop time constant) that probably would not be there without the loop steering.. Most of the time Rbs are used because they require much less calibration, have much less g (tilt) sensitivity and much less initial retrace/warmup error. In the case of the CSAC they also have more than an order of magnitude less power consumption than a good Ocxo (0.12W vs 1.7W on a typical docxo) The PRS-10 have a nice little trick in it, it stores the previous OCXO steering value, so on power-up it sets the OCXO to this and that gives it about the right frequency and only once the rubidium have heated up it locks to it. That gives a relatively quick stable signal for starters, which is quite quick. 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] Low SNR GPS reception and cheap LNAs
On Sat, 26 Apr 2014 12:28:20 +0200 Magnus Danielson mag...@rubidium.dyndns.org wrote: On 04/25/2014 06:21 PM, gandal...@aol.com wrote: Coincidentally, I came across this earlier today when looking for some MMIC data, perhaps it might be worth a look?... http://lna4all.blogspot.co.uk/ This is the 0,5 dB NF amplifier from Minicircuits and I think it is an interesting alternative. I just haven't come around to order some. Fairly cheap alternative than to roll your own from the same chip, which was what I was considering. Cheers, Magnus For a packaged unit, the Mini-Circuits is cheaper. I guess it is a matter of how much noise will be generated in the vicinity of your amp. In my case, I have a DC/DC brick, so I would have to box the amp anyway. ___ 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] SatStat on Windows 7
I just tried to run SatStat for the HP Z3801A on my new Windows 7 64-bit computer and it reported it would not run under that OS. What are folks using? -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ 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] SatStat on Windows 7
Old W98 or W2k machines work for me. From Tom Holmes On Apr 26, 2014, at 1:29 PM, Larry McDavid lmcda...@lmceng.com wrote: I just tried to run SatStat for the HP Z3801A on my new Windows 7 64-bit computer and it reported it would not run under that OS. What are folks using? -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ 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] SatStat on Windows 7
winxp On Sat, Apr 26, 2014 at 1:35 PM, Tommy phone thol...@woh.rr.com wrote: Old W98 or W2k machines work for me. From Tom Holmes On Apr 26, 2014, at 1:29 PM, Larry McDavid lmcda...@lmceng.com wrote: I just tried to run SatStat for the HP Z3801A on my new Windows 7 64-bit computer and it reported it would not run under that OS. What are folks using? -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ 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] Rb vs.Crystal OCXO
Magnus wrote: The PRS-10 have a nice little trick in it, it stores the previous OCXO steering value, so on power-up it sets the OCXO to this The PRS-10 has quite a number of nice tricks, in addition to particularly good engineering and high-quality construction of the basic physics package and support circuitry. The OP (and others) should not expect the same level of performance from $30-$100 ebay Rubidiums (LPRO, FRS, FE-56xx, etc., etc.). Very good to excellent OCXOs are available readily for $5 to $50. IMO, those should be the standard of comparison for any aspiring time nut. I'm not aware of any economy Rubidium that has close-in phase noise or low-to-medium-tau AVAR nearly as good as one of these very good OCXOs. As mentioned by others, some Ru may do better than a TCXO close in and at low tau. But so what? The TCXO should not be a time nut's standard of comparison as far as a lab standard is concerned. One quickly concludes that a good GPSDO, which includes a good OCXO, is the optimal solution for most time nuts. The OCXO has excellent stability with respect to close-in phase noise and low-to-medium-tau AVAR, and is disciplined by the GPS for excellent stability at longer tau. Probably the best turn-key solution is a Trimble Thunderbolt (although prices have risen in the last few years, so they are not the bargain they once were). Other, less expensive Trimble units that are also supported by the Lady Heather monitoring program are available on ebay, and are probably the best bet today for bargain-hunters. While I applaud the recent efforts to build simple DIY GPSDOs using inexpensive microcontrollers, from what I have seen so far most of them do not yet have the programming sophistication, particularly in the PLL loop filter and the houskeeping functions, to rival a good off-the-shelf GPSDO from a quality manufacturer. Final thought for specifying/designing/buying a GPSDO for time nuts purposes: Do not settle for a low-quality crystal oscillator (and especially not a TCXO). You will never achieve best performance at tau about 100 seconds that way. Insist on a 10811-quality OCXO (one of the many nice things about the Thunderbolt is that it has a very good OCXO). 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] SatStat on Windows 7
Hi Upgrade to a Win 7 version that has XP support in it. Bob On Apr 26, 2014, at 1:29 PM, Larry McDavid lmcda...@lmceng.com wrote: I just tried to run SatStat for the HP Z3801A on my new Windows 7 64-bit computer and it reported it would not run under that OS. What are folks using? -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO and holdover
I mentioned to Tom that I had seen the xgps program duplicate a lot of its satellites when I missed a PPS. I noticed my GPSDO go into holdover so I quickly brought up xgsp and noticed it happening again. This screen showed a few times intermixed with a normal screen. I have no idea whether it's a bug in xgps or due to something coming from the Adafruit, but it's interesting, nonetheless. http://www.evoria.net/Adafruit/Holdover.png Bob - AE6RV From: Paul tic-...@bodosom.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, April 25, 2014 1:20 PM Subject: Re: [time-nuts] GPSDO and holdover On Tue, Apr 22, 2014 at 9:57 PM, Tom Van Baak t...@leapsecond.com wrote: I have noticed skipped 1PPS on the Adafruit GPS also. I've always assumed this could happen but as a result of RF signal loss not a glitch in the gps. So I've started recording event timestamp deltas using the Linux kernel PPS interface. I read assert events (e.g. 1398449188.001000242#1741672) and compute timestamp and event deltas. If the t delta is .9 something horrible must have happened and if it's 1 some didn't happen assuming the event count delta is always 1. I wonder if this is a reasonable approach or if I'm being lazily optimistic. I just started (and I haven't added a join with the valid fix indicator yet) but I've had two missing pulses in the last 24 hours. ___ 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] SatStat on Windows 7
On Sat, 26 Apr 2014 13:52:47 -0400 Bob Camp li...@rtty.us wrote: Hi Upgrade to a Win 7 version that has XP support in it. Bob There is some confusion about XP support in win7. One way is to set the property of the file to be more XP compatible. The other means is to download a virtual machine from Microsoft that some versions of Win 7 are allowed to download and install. So you upgrade Win 7, then do another download. That said, I have managed to get XP programs going without the virtual machine if it is only a matter of finding the right DLLs. Win 7 Pro can use the XP VM from MS. Obviously Win 7 Ultimate can too. The only really useful thing in win 7 ultimate is the native NFS support, which you can painfully add to Win 7 pro in a few ways. So I wouldn't pay the premium to upgrade beyond win 7 pro. Now with another that said, since win XP is now history, is there a legit source to get an old copy and just run it in a VM? I'm sure it is pirated, but you would want a clean/safe version. The odds of getting hacked with XP in a VM is low, especially if you don't put email on it or browse from it. ___ 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] SatStat on Windows 7
WinXP. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Larry McDavid Sent: Saturday, April 26, 2014 12:29 PM To: Time-Nuts Mail List Subject: [time-nuts] SatStat on Windows 7 I just tried to run SatStat for the HP Z3801A on my new Windows 7 64-bit computer and it reported it would not run under that OS. What are folks using? -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ 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] Linux TSC clocksource on multi-core systems
Hi time-nuts, I've been reading the list for a while and I realize most of the discussion is a lot lower level than this, but I'm not sure where else to ask. I probably don't have a complete understanding of the problem, and maybe I just need a nudge in the right direction. My goal is nothing more than to experiment and learn. Goal: I want to use the 'best' clock source to keep the operating system clock as accurate as possible, as well as maximize the resolution of the clock. On modern general purpose computers like what most of us are using, this is the CPU Time Stamp Counter. I'm using Linux but insights with other software are also useful. The problem as I understand it: Operating systems like Linux use a system clock loop to satisfy gettimeofday calls and that is what NTP ultimately tries to make accurate. If the system clock is always slow or always fast, this is easy, but if the counter that's used for reference goes backwards or is otherwise unreliable then it can only get so close. The operating system can use things like the ACPI power management timer, the HPET, PIT, or any other hardware specific counter that is available. The precision and resolution of the system clock depend on the resolution of the counter backing it (please correct me if I misunderstood this). A 3Ghz processor's TSC provides more resolution than the 1.19Mhz PIT so you can make finer adjustments to get your time more accurate. The processor's TSC - Time Stamp Counter, is the highest resolution one usually available, and it also appears to be the lowest overhead to measure, so it's preferred to use this when possible. Sometimes (most of the time?) the TSC is not reli able in that it doesn't run at a constant speed, or that it may stop completely in certain power saving modes. Linux at least tries to test for this and will report tsc unstable messages to the user. The problem is worse with multiple cores or multiple CPU packages since the counters might not be synchronized, but today you'd be hard pressed to find an end-user computer that doesn't have multiple logical CPUs. What I'm interested in is if it's possible to work around the various TSC problems and make it usable. For example, turning off the power management (C-states, enhanced speed step, etc) can work around the problem of the frequency changing or the counter stopping. Is it possible to fix the multi-processor problems by synchronizing the counters somehow, or can the kernel always read the same CPU's counter? I know that the newest Intel CPUs like the E5s have a lot of these problems addressed and are advertised as having invariant counters, but what about all the stuff that's not the latest and greatest? I have an Intel Atom based system and I was able to make the TSC usable for time keeping by booting linux with nosmp so that it's only using one CPU core. It would be better if I could somehow make it so the other cores are usable while keeping the high resolution clock source. My other test system is a fairly old server using 2x Intel Xeon E5430 quad core processors. After turning off the CPU power management features in the BIOS, linux started using the TSC as the clock source, but it's keeping very poor time which I think might be due to poor synchronization of the counters. I'm going to try with nosmp and I expect that to work like it did on the Atom, but it would be nice if I could use the other CPUs. How is everyone dealing with this problem? It's fine to disable the additional cores/cpus on a dedicated NTP machine, but I wonder if there is a solution that allows both the TSC and all the cores to be used at the same time. Is it even possible to completely sync the counters across CPUs (not just get close)? It doesn't seem like it, but maybe someone knows better. Thanks, Laszlo ___ 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] SatStat on Windows 7
Take a look at Ulrich's Z38xx application, run it in Windows XP compatibility mode.. Sent From iPhone On Apr 26, 2014, at 10:35, Tommy phone thol...@woh.rr.com wrote: Old W98 or W2k machines work for me. From Tom Holmes On Apr 26, 2014, at 1:29 PM, Larry McDavid lmcda...@lmceng.com wrote: I just tried to run SatStat for the HP Z3801A on my new Windows 7 64-bit computer and it reported it would not run under that OS. What are folks using? -- Best wishes, Larry McDavid W6FUB Anaheim, California (SE of Los Angeles, near Disneyland) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPSDO and holdover
I have noticed skipped 1PPS on the Adafruit GPS also. I've always assumed this could happen but as a result of RF signal loss not a glitch in the gps. So I've started recording event timestamp deltas To be clear, we are not talking about a system-wide GPS problem here; the satellites are fine. All my other GPS receivers are fine. It's just one particular GPS receiver board that Bob, and now Bob and I, are questioning. using the Linux kernel PPS interface. I read assert events (e.g. 1398449188.001000242#1741672) and compute timestamp and event deltas. If the t delta is .9 something horrible must have happened and if it's 1 some didn't happen assuming the event count delta is always 1. I wonder if this is a reasonable approach or if I'm being lazily optimistic. I just started (and I haven't added a join with the valid fix indicator yet) but I've had two missing pulses in the last 24 hours. Sure, that's reasonable. I'm using a 53132 TIC to compare my house atomic 1PPS (start) against the Adafruit GPS 1PPS (stop) and so no timestamping is even necessary: the readings themselves tell you if there is a missed pulse. For example, you get TI readings like 0.000nn for hours or days and then once in a while you get a 1.000nn or 2.000nn, indicating a missed pulse. After Bob Stewart's first mention of the Adafruit Ultimate GPS board, I dug out mine and collected 30 days of data to see if I could duplicate or understand his measurements. As usual, a simple and quick test has turned into something more complicated and perplexing. I'll share some results maybe next week. The test is now multiple GPS boards, antennas, and counters. /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] Linux TSC clocksource on multi-core systems
On 04/26/2014 02:27 PM, Laszlo Hanyecz wrote: It's fine to disable the additional cores/cpus on a dedicated NTP machine, but I wonder if there is a solution that allows both the TSC and all the cores to be used at the same time. Is it even possible to completely sync the counters across CPUs (not just get close)? You could try pinning ntpd to a single CPU using the taskset command. It wouldn't give all the applications the benefit of a perfectly synchronized clock, but if you just want ntpd to be happy then it ought to work as well as turning SMP off. ___ 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] Fwd: Red Pitaya
An interesting piece of hardware. Reasonable for its capabilities/ Don Begin forwarded message: From: The Red Pitaya Team sa...@redpitaya.com Subject: Red Pitaya pre order notification Date: April 24, 2014 9:10:14 AM MDT To: d...@montana.com d...@montana.com Reply-To: The Red Pitaya Team sa...@redpitaya.com Use this area to offer a short preview of your email's content. View this email in your browser Dear Future Red Pitaya Team Member, Red Pitaya is now nearly here following our recent exclusive distributor agreement with RS Components Ltd (Europe and APAC) and Allied Electronics Inc (United States and Canada), the trading brands of Electrocomponents plc., the world's leading high service distributor of electronics and maintenance products. Manufacturing is now underway, with an initial delivery to RS expected during May. Due to the high levels of interest received for the instrument, it is anticipated that this product will sell quickly and demand may exceed initial stock holding. Therefore, as a valued customer who registered interest in this product, we would like to give you the opportunity to go and place your order today before sales to the general public open onMonday 28th April. Thank you for your interest in our product. We look forward to seeing how you and Red Pitaya work together to transform Test and Measurement applications. Don’t forget to revisit www.redpitaya.com to observe fresh ideas and new developments and visitDesignSpark to share your Red Pitaya experiences. Best regards, The Red Pitaya Team unsubscribe from this listupdate subscription preferences This email was sent to d...@montana.com why did I get this?unsubscribe from this listupdate subscription preferences Red Pitaya d.o.o. · Velika pot 22 · Solkan 5250 · Slovenia ___ 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] New timing receivers?
I'm reading though the manual for my recently acquired M12+T which I'm looking forward to using. I notice that the manual is dated 09FEB05. So the M12+T has been around for about a decade. Are there more recent timing receivers available now or has the ubiquity of the consumer GPS market distracted all investment from timing receivers except at the high end? Thanks Jim AB3CV ___ 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] New timing receivers?
Hi There are a number of timing receivers on the market. They still are a very small percentage of the total units sold. A lot of people play with the uBlox parts. Bob On Apr 26, 2014, at 7:59 PM, Jim Miller j...@jtmiller.com wrote: I'm reading though the manual for my recently acquired M12+T which I'm looking forward to using. I notice that the manual is dated 09FEB05. So the M12+T has been around for about a decade. Are there more recent timing receivers available now or has the ubiquity of the consumer GPS market distracted all investment from timing receivers except at the high end? Thanks Jim AB3CV ___ 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] New timing receivers?
Have a look for Navsync CW12-TIM. We'll be using these for various timing applications including a simulcast radio repeater system over IP. They're about US$89 from SemiconductorStore.com. Many thanks! On Sun, Apr 27, 2014 at 9:59 AM, Jim Miller j...@jtmiller.com wrote: I'm reading though the manual for my recently acquired M12+T which I'm looking forward to using. I notice that the manual is dated 09FEB05. So the M12+T has been around for about a decade. Are there more recent timing receivers available now or has the ubiquity of the consumer GPS market distracted all investment from timing receivers except at the high end? Thanks Jim AB3CV ___ 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] New timing receivers?
Given the state of the GPS chip, would it really take that big an investment to just add in the firmware to do timing? Or have the manufacturers just made a marketing decision to keep that a high end market as long as they can? Bob From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, April 26, 2014 7:27 PM Subject: Re: [time-nuts] New timing receivers? Hi There are a number of timing receivers on the market. They still are a very small percentage of the total units sold. A lot of people play with the uBlox parts. Bob ___ 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] New timing receivers?
Hi The ratios are pretty staggering. The timing market is 1% of the total chip market. Any mass market is *always* about price. If timing adds a few percent to the mass market parts, there’s no way anybody will do it. Bob On Apr 26, 2014, at 8:37 PM, Bob Stewart b...@evoria.net wrote: Given the state of the GPS chip, would it really take that big an investment to just add in the firmware to do timing? Or have the manufacturers just made a marketing decision to keep that a high end market as long as they can? Bob From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, April 26, 2014 7:27 PM Subject: Re: [time-nuts] New timing receivers? Hi There are a number of timing receivers on the market. They still are a very small percentage of the total units sold. A lot of people play with the uBlox parts. Bob ___ 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] Rb vs.Crystal OCXO
The thunderbolt is one of the best timing devices but not for frequency, if you want high resolution. Over time it is ok but high resolution short gate times and you see the frequency changes. They use the OCXO to correct for timing error and if you have a Tracor 527E you can see it. Also how else do you think they control the 1 pps. Bert Kehren In a message dated 4/26/2014 1:52:10 P.M. Eastern Daylight Time, csteinm...@yandex.com writes: Magnus wrote: The PRS-10 have a nice little trick in it, it stores the previous OCXO steering value, so on power-up it sets the OCXO to this The PRS-10 has quite a number of nice tricks, in addition to particularly good engineering and high-quality construction of the basic physics package and support circuitry. The OP (and others) should not expect the same level of performance from $30-$100 ebay Rubidiums (LPRO, FRS, FE-56xx, etc., etc.). Very good to excellent OCXOs are available readily for $5 to $50. IMO, those should be the standard of comparison for any aspiring time nut. I'm not aware of any economy Rubidium that has close-in phase noise or low-to-medium-tau AVAR nearly as good as one of these very good OCXOs. As mentioned by others, some Ru may do better than a TCXO close in and at low tau. But so what? The TCXO should not be a time nut's standard of comparison as far as a lab standard is concerned. One quickly concludes that a good GPSDO, which includes a good OCXO, is the optimal solution for most time nuts. The OCXO has excellent stability with respect to close-in phase noise and low-to-medium-tau AVAR, and is disciplined by the GPS for excellent stability at longer tau. Probably the best turn-key solution is a Trimble Thunderbolt (although prices have risen in the last few years, so they are not the bargain they once were). Other, less expensive Trimble units that are also supported by the Lady Heather monitoring program are available on ebay, and are probably the best bet today for bargain-hunters. While I applaud the recent efforts to build simple DIY GPSDOs using inexpensive microcontrollers, from what I have seen so far most of them do not yet have the programming sophistication, particularly in the PLL loop filter and the houskeeping functions, to rival a good off-the-shelf GPSDO from a quality manufacturer. Final thought for specifying/designing/buying a GPSDO for time nuts purposes: Do not settle for a low-quality crystal oscillator (and especially not a TCXO). You will never achieve best performance at tau about 100 seconds that way. Insist on a 10811-quality OCXO (one of the many nice things about the Thunderbolt is that it has a very good OCXO). 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] New timing receivers?
And quite a few companies use them. In a message dated 4/26/2014 8:27:57 P.M. Eastern Daylight Time, li...@rtty.us writes: Hi There are a number of timing receivers on the market. They still are a very small percentage of the total units sold. A lot of people play with the uBlox parts. Bob On Apr 26, 2014, at 7:59 PM, Jim Miller j...@jtmiller.com wrote: I'm reading though the manual for my recently acquired M12+T which I'm looking forward to using. I notice that the manual is dated 09FEB05. So the M12+T has been around for about a decade. Are there more recent timing receivers available now or has the ubiquity of the consumer GPS market distracted all investment from timing receivers except at the high end? Thanks Jim AB3CV ___ 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] Rb vs.Crystal OCXO
The thunderbolt is one of the best timing devices but not for frequency, if you want high resolution. Over time it is ok but high resolution short gate times and you see the frequency changes. They use the OCXO to correct for timing error and if you have a Tracor 527E you can see it. Also how else do you think they control the 1 pps. Bert Kehren Hi Bert, Put your TBolt (or any other GPSDO) in holdover (freeze the DAC) and then take a close look again. Tell me what you see. The difference (if any) is due to steering. What's common (if any) is due to the OCXO itself. Have a look at http://leapsecond.com/pages/gpsdo/ to see the results for 4 common GPSDO. Focus on the left edge of the plots only. Note also that tuning parameters can make a big difference in the results (I used only defaults for those plots). /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] New timing receivers?
On Sat, Apr 26, 2014 at 7:59 PM, Jim Miller j...@jtmiller.com wrote: Are there more recent timing receivers available now Yes. Google gps timing receiver for a start. Sawtooth (quantization) correction is probably the defining characteristic. So even though u-Blox makes 'T' versions (e.g. LEA-6T) they have non-T versions (e.g. NEO-6M) that provide quant. correction. Position hold / Survey In/ etc. is also a timing receiver characteristic. ___ 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] New timing receivers?
How does the u-bloc's performance compare to the M12+T?One of these is on my list of things to buy someday. I thought the M12+T had a 1-sigma error in the single digit nanoseconds.The u-bloc is newer it is even better? On Sat, Apr 26, 2014 at 6:02 PM, Paul tic-...@bodosom.net wrote: On Sat, Apr 26, 2014 at 7:59 PM, Jim Miller j...@jtmiller.com wrote: Are there more recent timing receivers available now Yes. Google gps timing receiver for a start. Sawtooth (quantization) correction is probably the defining characteristic. So even though u-Blox makes 'T' versions (e.g. LEA-6T) they have non-T versions (e.g. NEO-6M) that provide quant. correction. Position hold / Survey In/ etc. is also a timing receiver characteristic. ___ 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. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
