[time-nuts] quartz / liquid nitrogen
And you want your semiconductors to be in ceramic/lided packages with the bond wires flapping in free air. Bond wires embedded in epoxy like to break... don't ask how I found this out ;-) ... it brings back bad memories... and makes bad memories... Quantum chips have very elaborate/specialized bonding to survive liquid helium... even with that, thermal cycling still breaks them. ___ time-nuts mailing 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] TV Signals as a frequency reference
Here's a local guy's take on monitoring time and DST errors on the stations in the Dallas area: http://home.earthlink.net/~schultdw/atsc/ ___ time-nuts mailing 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] Harrison's birthday
Google reminds us that 3 April is Harrison's birthday.. https://en.wikipedia.org/wiki/John_Harrison Interesting he (depending on your calendar) was born and died on the same day. And, interesting he died in 1776, which is of some significance in the US. ___ time-nuts mailing 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] TV Signals as a frequency reference
I wrote a program that would scan the PSIP data from my local stations and the STT was always quite poor. Usually several stations had the GPS-UTC offset that was stale, even a year after a leap second. It would be trivial to make an automatic correct STT generator some online data (NTP, etc.), why this was not part of the software that generated the PSIP data is a mystery to me. DST was a mess. I think this bit from A/65 was confusing: When the transition into daylight saving time is between one day less than one month away and the actual transition the DS_day_of_month field takes the value day_in, and the DS_hour field takes the value hour_in. The DS_status bit is 0 indicating it is not yet daylight saving time. What exactly does "less than one month away" mean? Does it mean less than 31*24 hours away? Does it mean in the current calendar month? What happens is you get a STT that says "DST begins on the 11th at 2:00 AM". They couldn't figure out how to pack the month in 16 bits so you just get "the 11th", no month. It's now Feb 12th. Has DST started? Some devices would decide the answer is yes and others no. On Mon, Apr 2, 2018 at 10:08 AM, Mark Sims wrote: > I read that there is a requirement that the time data in the PSIP data stream > has to be within one second. > > I have an over-the-air DVR that would mess up the time and recordings because > it was originally not filtering the times the stations broadcast. They > finally modified the DVR firmware to do something like a median filter to > throw out the outliers. A local TV guru beat up on all the local stations > with a copy of the FCC rules to get the stations to broadcast the correct > time. And don't me started on the ways the stations still mess up the > daylight savings time transitions. Many are a month, week, or day off. > > --- > >> There is no requirement for us to inject time of any prescribed accuracy > into the digital stream. > ___ > time-nuts mailing 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] quartz / liquid nitrogen
On 4/2/18 1:39 PM, Hal Murray wrote: If not Nitrogen, how about dry ice (-109F -78C)? Dry ice is relatively easy to get. It wouldn't be hard to try a quick experiment. CTE mismatch in packages will be a significant problem - you might find that your ICs don't work because bond wires have been ripped off the die. Parts might have popped off the board too. But if you have one, and it's sacrificable, give it a try - a cooler with some dry ice, and put the circuit above the dry ice, and it will cool slowly ___ time-nuts mailing 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: quartz / liquid nitrogen
at low temperatures bipolar devices will have reduced gain 73 KJ6UHN Alex Forwarded Message Subject:[time-nuts] quartz / liquid nitrogen Date: Mon, 2 Apr 2018 12:46:26 -0700 From: Tom Van Baak Reply-To: Tom Van Baak , Discussion of precise time and frequency measurement Organization: LeapSecond.com To: Discussion of precise time and frequency measurement Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, but maybe something of value to a time nut. Would that dramatically lower temperature improve phase noise & short-term performance? Is there a crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? If not Nitrogen, how about dry ice (-109F -78C)? /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. --- This email has been checked for viruses by AVG. http://www.avg.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] quartz / liquid nitrogen
Hi > On Apr 2, 2018, at 5:38 PM, Attila Kinali wrote: > > On Mon, 2 Apr 2018 12:46:26 -0700 > "Tom Van Baak" wrote: > >> Has anyone tried running a quartz oscillator at liquid nitrogen >> temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, >> but maybe something of value to a time nut. Would that dramatically lower >> temperature improve phase noise & short-term performance? Is there a crystal >> cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? >> >> If not Nitrogen, how about dry ice (-109F -78C)? > > Yes, it has been done. Down to liquid helium tempratures even. > The main benefit is that the Q of the crystal increses with > decreasing temperatures, but the effect is not as large as with > dielectric resonators (aka whispering galery mode CSO). > > Of course thermal noise decreases as well, but usually quartz > oscillators are limited by their amplifiers and the 50 Ohm system > for termal noise. I do not remember reading anything about flicker > noise, but my guess would be that it decreases as well. The gotcha there is that the 1/F noise of the resonator is already below the oscillator “result” at room temperature. Reducing it further is great, but it doesn’t translate directly to an improved signal source. Unless you have a “flat” crystal temperature wise *and* good temperature controll (like micro degree level) improving ADEV …. not so much. Bob > > I am sure I have some paper on this somewhere in my collection, > if you want I can dig it out. > > Attila Kinali > > > -- > The bad part of Zurich is where the degenerates >throw DARK chocolate at you. > ___ > time-nuts mailing 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] quartz / liquid nitrogen
On Mon, 2 Apr 2018 12:46:26 -0700 "Tom Van Baak" wrote: > Has anyone tried running a quartz oscillator at liquid nitrogen > temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, > but maybe something of value to a time nut. Would that dramatically lower > temperature improve phase noise & short-term performance? Is there a crystal > cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? > > If not Nitrogen, how about dry ice (-109F -78C)? Yes, it has been done. Down to liquid helium tempratures even. The main benefit is that the Q of the crystal increses with decreasing temperatures, but the effect is not as large as with dielectric resonators (aka whispering galery mode CSO). Of course thermal noise decreases as well, but usually quartz oscillators are limited by their amplifiers and the 50 Ohm system for termal noise. I do not remember reading anything about flicker noise, but my guess would be that it decreases as well. I am sure I have some paper on this somewhere in my collection, if you want I can dig it out. Attila Kinali -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ time-nuts mailing 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] quartz / liquid nitrogen
Hi If you dig back in the FCS archives, you will find papers on “cold” OCXO’s. You also will find papers on cryo cooled quartz. The bottom line appears to be that if you are going to all the trouble of cooling things, sapphire (or other exotic materials) are a better bet. Quick simple answer: not enough improvement in ADEV, aging, or phase noise to make it wroth it. As PHK mentioned, coming up with a “ideal” cut for your arbitrary temperature cryo setup is non-trivially difficult ( = plan on spending a few million dollars and a lot of years). Bob > On Apr 2, 2018, at 3:46 PM, Tom Van Baak wrote: > > Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: > -196 C (-321F, 77K)? It's probably impractical commercially, but maybe > something of value to a time nut. Would that dramatically lower temperature > improve phase noise & short-term performance? Is there a crystal cut that > could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? > > If not Nitrogen, how about dry ice (-109F -78C)? > > /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. ___ time-nuts mailing 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] quartz / liquid nitrogen
Tom: I sense a nice experiment! Dry ice temps can be attained with modest Dewars and thermoelectric fridge devices. PID controller and bob's your uncle. Type K thermocouple modules on epay. With that apparat, a nice set of adev vs temperature possible? Dry ice/acetone or ethyl alcohol (everclear) slurry is often used as a calibration point BTW. Liquid N2 may be too cold, or is it He I'm thinking of??? Don On 2018-04-02 13:46, Tom Van Baak wrote: Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, but maybe something of value to a time nut. Would that dramatically lower temperature improve phase noise & short-term performance? Is there a crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? If not Nitrogen, how about dry ice (-109F -78C)? /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. -- Dr. Don Latham PO Box 404, Frenchtown, MT, 59834 VOX: 406-626-4304 ___ time-nuts mailing 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] quartz / liquid nitrogen
Hi Tom: Put the dry ice in acetone to the lowest temp. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html Original Message Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, but maybe something of value to a time nut. Would that dramatically lower temperature improve phase noise & short-term performance? Is there a crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? If not Nitrogen, how about dry ice (-109F -78C)? /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. ___ time-nuts mailing 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] quartz / liquid nitrogen
You also run in to mechanical vibration issues from the cooling system. At the temperatures involved you are looking at something like a Stirling cycle cooler. Here is a good article; https://arxiv.org/pdf/1309.5445.pdf Maintaining a very stable temperature probably has a much greater impact. Tisha Hayes, AA4HA *Ms. Tisha Hayes* On Mon, Apr 2, 2018 at 2:58 PM, Poul-Henning Kamp wrote: > > In message <299B45118C9248498D7B4F3AFE72231E@pc52>, "Tom Van Baak" writes: > > >Has anyone tried running a quartz oscillator at liquid nitrogen > >temperatures: -196 C (-321F, 77K)? It's probably impractical > >commercially, but maybe something of value to a time nut. > > Whispering gallery sapphire resonators at cryogenic temperatures > is a thing for phase-noise, but those are dielectric (microwave) > resonators, not piezoelectric resonators. > > > Would that dramatically lower temperature improve phase noise & > > short-term performance? > > Yes it will reduce your thermal noise as a source of PN, and > dramatically so. > > But I doubt short and long term performance will improve. > > Even if you can find a zero-turnover cut at a convenient temperature, > I don't think anybody know how to produce mK temperature *stability* > at cryogenic temperatures ? > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing 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] quartz / liquid nitrogen
> If not Nitrogen, how about dry ice (-109F -78C)? Dry ice is relatively easy to get. It wouldn't be hard to try a quick experiment. -- 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] quartz / liquid nitrogen
Is the thermal noise generated in the loss in a quartz resonator a significant part of the overall phase noise picture? I would have not thought so. I'd think that a greater benefit ought to be derived from chilling the other parts in the oscillator, such as the active devices. Unless, of course, chilling the quartz actually improves the Q significantly, which I don't know about. If cooling (whatever) by just a modest amount helps much, then one could consider using Peltier cooling. It doesn't really get things very cold, but is a lot more convenient than either dry ice or LN2. But then you don't get the fun that you do when playing with LN2, either. Dana On Mon, Apr 2, 2018 at 2:46 PM, Tom Van Baak wrote: > Has anyone tried running a quartz oscillator at liquid nitrogen > temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, > but maybe something of value to a time nut. Would that dramatically lower > temperature improve phase noise & short-term performance? Is there a > crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60 > C (oven)? > > If not Nitrogen, how about dry ice (-109F -78C)? > > /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. > ___ time-nuts mailing 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] quartz / liquid nitrogen
In message <299B45118C9248498D7B4F3AFE72231E@pc52>, "Tom Van Baak" writes: >Has anyone tried running a quartz oscillator at liquid nitrogen >temperatures: -196 C (-321F, 77K)? It's probably impractical >commercially, but maybe something of value to a time nut. Whispering gallery sapphire resonators at cryogenic temperatures is a thing for phase-noise, but those are dielectric (microwave) resonators, not piezoelectric resonators. > Would that dramatically lower temperature improve phase noise & > short-term performance? Yes it will reduce your thermal noise as a source of PN, and dramatically so. But I doubt short and long term performance will improve. Even if you can find a zero-turnover cut at a convenient temperature, I don't think anybody know how to produce mK temperature *stability* at cryogenic temperatures ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] quartz / liquid nitrogen
Has anyone tried running a quartz oscillator at liquid nitrogen temperatures: -196 C (-321F, 77K)? It's probably impractical commercially, but maybe something of value to a time nut. Would that dramatically lower temperature improve phase noise & short-term performance? Is there a crystal cut that could be optimized for 77 K instead of ~25 C (room) or 60 C (oven)? If not Nitrogen, how about dry ice (-109F -78C)? /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] timing an ITR master clock
Jerry, Most people I know who time mechanical clocks use Bryan Mumford's Microset timer: https://www.bmumford.com/microset.html https://www.bmumford.com/mset/model3.html Bryan has a wide variety of sensors: optical, acoustic, magnetic, laser, etc. Of course it is possible to home-brew a solution. Many of us have done that. But it's not quite as easy as it sounds to get a system that gives you reliable data. Several people use PC's as the timer, but be aware that pendulum clocks can easily achieve ppm levels of stability in which case the data you get might actually be your PC being timed by a pendulum, not a pendulum being timed by a PC. You might also get good advice from one of the watch & clock forums on the 'net. We tend to stay away from generic mechanical clock topics here on time-nuts. /tvb - Original Message - From: "Jerry Hancock" To: "Discussion of precise time and frequency measurement" Sent: Monday, April 02, 2018 8:42 AM Subject: [time-nuts] timing an ITR master clock >I have a new to me International Time Recorder (pre-IBM) master clock. I has >second, minute and hour closures and was thinking of using the second closure >to check the beat and time. If others have done this kind of thing, let me >know. I have a mix of timing equipment, of course, and have to be careful >with DC always, so I was thinking of just using an oscillator looped through >the second switch to get a rough idea of the timing. > > Thoughts? Beautiful clock, a friend of mine is the current expert having > over 300 such clocks and affiliated secondary clocks, etc. > > Regards, > > Jerry > > > Jerry Hancock > je...@hanler.com > (415) 215-3779 > > ___ > time-nuts mailing 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] TV Signals as a frequency reference
I read that there is a requirement that the time data in the PSIP data stream has to be within one second. I have an over-the-air DVR that would mess up the time and recordings because it was originally not filtering the times the stations broadcast. They finally modified the DVR firmware to do something like a median filter to throw out the outliers. A local TV guru beat up on all the local stations with a copy of the FCC rules to get the stations to broadcast the correct time. And don't me started on the ways the stations still mess up the daylight savings time transitions. Many are a month, week, or day off. --- > There is no requirement for us to inject time of any prescribed accuracy into the digital stream. ___ time-nuts mailing 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] timing an ITR master clock
I have a new to me International Time Recorder (pre-IBM) master clock. I has second, minute and hour closures and was thinking of using the second closure to check the beat and time. If others have done this kind of thing, let me know. I have a mix of timing equipment, of course, and have to be careful with DC always, so I was thinking of just using an oscillator looped through the second switch to get a rough idea of the timing. Thoughts? Beautiful clock, a friend of mine is the current expert having over 300 such clocks and affiliated secondary clocks, etc. Regards, Jerry Jerry Hancock je...@hanler.com (415) 215-3779 ___ time-nuts mailing 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 GNSS chipsets
I was measuring the jitter and adevs of the PPS signal from a GT-8736. GPS only seems to be slightly better (1-3 ns more span) than GPS+GLONASS. GLONASS only seems have around 50% more jitter than GPS only. Glonaas only adevs are 3 times as large as GPS only (at tau=1 seconds). - > It is indeed a benefit to use the different constellations. ___ time-nuts mailing 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 ANTENNA
Hi The problem with “to much gain” is that it is very hard to tell when you have to much gain. The system quite happily chugs along reporting fine S/N ratios. Cut the gain by 20 db and you get the same C/N ratios. The reason is pretty simple - the noise figure is set by the front end of the preamp. As long as you have “enough” gain it will dominate. Is “enough” 10 db or 100 db? Either way it’s enough to make that equation work. The issue comes in mainly because these modules have a limited AGC range (or dynamic range). For whatever reason, the AGC situation is not reported upstream. If the module has run out of AGC and is about to loose it …. you simply have no way to tell. It’s not just TimeNuts that have trouble with this stuff. Very large / smart / big budget / outfits run into this stuff as well. The same issues of poorly documented system requirements / non-standard system requirements are a major hassle for them. I’ve seen them spend major effort because of this stuff. So how to work it out? Stuff a (dc blocked) variable attenuator in the line. Pick a sat that is reporting something like 35 db S/N. Flip between two attenuator settings every 30 seconds or so. Note any change. Do it multiple times with multiple sats. Then move on to your next settings pair. I’d start big, maybe a 10 db step and go smaller if you can stand the boredom. As long as 35 db stays roughly 35 db, you have “enough” gain. Since sat’s move and that impacts S/N, there is no exact 0.05 db sort of number. Even looking at numbers over a day can be tricky. Things are never quite the same today as they were yesterday. It does seem strange that you want the minimum gain. It’s not so strange if you dig into things like land mobile radio design. Your best overload performance is always going to be the design with barely enough gain in the front end. Lots of fun. Bob > On Apr 2, 2018, at 6:07 AM, ew via time-nuts wrote: > > Question > Using L/H what is too much signal > Bert Kehren > > In a message dated 4/1/2018 10:54:23 PM Eastern Standard Time, > david.partri...@perdrix.co.uk writes: > > > just use a bias tee to feed in the antenna volts :) > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio > Boriani > Sent: 01 April 2018 23:29 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS ANTENNA > > An unusual attenuator with a DC pass. > > On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge > wrote: >> Or use a choke ring survey antenna and an attenuator :) >> >> Dave >> >> -Original Message- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob >> kb8tq >> Sent: 01 April 2018 14:43 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] GPS ANTENNA >> >> Hi >> >> Indeed, it is *very* easy to put to much gain in front of a timing GNSS >> receiver. These beasts are trying to dig out a signal that you can’t even >> see with a spectrum analyzer. >> It’s way to far below the noise floor to detect that way. They optimize >> things pretty tightly to get that done (and to hit a price target ….). Put >> to much gain in front of them and they get unhappy. >> >> Making this even more crazy, the survey industry standard antenna *does* >> have a lot of gain. Survey receivers need way more gain in front of them >> than timing receivers. Put a survey antenna directly on a timing device and >> trouble will likely be the outcome. Equally, a survey instrument probably >> will not be happy with a timing receiver. >> >> Why all this nonsense? As far as I can tell, it goes back to how the very >> early L1 / L2 survey boxes were designed back in the 1980’s and early >> 1990’s. They made a basic decision to put a lot of gain at the antenna. >> Motorola came along with their GPS modules later on. They made a *very* >> different decision about how to distribute the gain. There are very good >> arguments on both sides for why they did it this way. >> The bottom line is still - you need to match things up … >> >> Bob >> >>> On Apr 1, 2018, at 2:36 AM, cfo wrote: >>> >>> On Sat, 31 Mar 2018 10:58:19 -0500, >>> donandarline-Re5JQEeQqe8AvxtiuMwx3w >>> wrote: >>> I found a supplier for high quality GPS antennas at a very reasonable price. PCTEL GPSL1-TMG-SPI-40NCB. >>> >>> *** SNIP *** >>> >>> I had one of those on 25m cable, and it worked fine on a Tbolt , >>> until i got an active antenna splitter that also had some gain. >>> Then i had to replace it w. a 26dB version of same type, else the >>> "Jackson Lite" was loosing sync. >>> >>> What i mean here, is that you can get too much gain too. >>> >>> Btw: Good price. >>> >>> CFO >>> Denmark >>> >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>
Re: [time-nuts] GPS ANTENNA
Hi As you rummage around your junk box, do be a bit careful Most of what I have here are tee’s that include DC blocks. There are blocks that don’t do that. Trying to run your bias supply into 50 or 25 ohms is not a real good idea. Bob > On Apr 1, 2018, at 9:43 PM, David C. Partridge > wrote: > > just use a bias tee to feed in the antenna volts :) > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio > Boriani > Sent: 01 April 2018 23:29 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS ANTENNA > > An unusual attenuator with a DC pass. > > On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge > wrote: >> Or use a choke ring survey antenna and an attenuator :) >> >> Dave >> >> -Original Message- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob >> kb8tq >> Sent: 01 April 2018 14:43 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] GPS ANTENNA >> >> Hi >> >> Indeed, it is *very* easy to put to much gain in front of a timing GNSS >> receiver. These beasts are trying to dig out a signal that you can’t even >> see with a spectrum analyzer. >> It’s way to far below the noise floor to detect that way. They optimize >> things pretty tightly to get that done (and to hit a price target ….). Put >> to much gain in front of them and they get unhappy. >> >> Making this even more crazy, the survey industry standard antenna *does* >> have a lot of gain. Survey receivers need way more gain in front of them >> than timing receivers. Put a survey antenna directly on a timing device and >> trouble will likely be the outcome. Equally, a survey instrument probably >> will not be happy with a timing receiver. >> >> Why all this nonsense? As far as I can tell, it goes back to how the very >> early L1 / L2 survey boxes were designed back in the 1980’s and early >> 1990’s. They made a basic decision to put a lot of gain at the antenna. >> Motorola came along with their GPS modules later on. They made a *very* >> different decision about how to distribute the gain. There are very good >> arguments on both sides for why they did it this way. >> The bottom line is still - you need to match things up … >> >> Bob >> >>> On Apr 1, 2018, at 2:36 AM, cfo wrote: >>> >>> On Sat, 31 Mar 2018 10:58:19 -0500, >>> donandarline-Re5JQEeQqe8AvxtiuMwx3w >>> wrote: >>> I found a supplier for high quality GPS antennas at a very reasonable price. PCTEL GPSL1-TMG-SPI-40NCB. >>> >>> *** SNIP *** >>> >>> I had one of those on 25m cable, and it worked fine on a Tbolt , >>> until i got an active antenna splitter that also had some gain. >>> Then i had to replace it w. a 26dB version of same type, else the >>> "Jackson Lite" was loosing sync. >>> >>> What i mean here, is that you can get too much gain too. >>> >>> Btw: Good price. >>> >>> CFO >>> 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. >> >> ___ >> time-nuts mailing 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] New GNSS chipsets
Hi > On Apr 1, 2018, at 9:47 PM, Hal Murray wrote: > > > mag...@rubidium.dyndns.org said: >> I have advocated for receivers able to handle multiple frequencies and >> multiple GNSS for some time, sneaking it into documents, so there should be >> some preparations for this now. > > How well do various GNSS track UTC and/or eachother? These days Glonass puts out an offset number that should be good to the single digit nanoseconds (unless it’s broke). The Europeans have set up to effectively stay “as close as you can get” to sync. Right now those are the only three that are likely candidates for time sources. > > >> The benefit is naturally redundancy, but also higher precision. > > I've been assuming the cheap GPS jammers will kill the others too. Maybe not. Glonass is not on quite the same frequencies. The signal formats of each system are very different. A jammer that nukes one may not have any impact on the rest. Indeed a megawatt level broadband DC to light jammer would take out a lot of things. It’s also a pretty easy item to track down. Straight broadband jamming *should* simply shut a receiver down. That’s why GPSDO’s go into holdover (and why you have GPSDO’s). Are all receivers ever made perfect in the face of any and all crud … maybe not. The bigger issue is a “spoof” signal that deliberately tricks the receiver into thinking it is locked to legitimate satellites. There are ways to do that. Receivers are not going to reject that solution and away you go. Doing a working spoof for multiple systems …. much harder than a single system. Bob > Are there > any signals far enough away from L1 that they might get through? > > > -- > 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] New GNSS chipsets
Hi A….. but ….. The uBlox parts are available with the existing chip sets pretty easily today. That has not always been the case with uBlox. Back when the chips were new / unique / hard to support it was significantly more difficult to get anything out of them (at least at a rational price). Broadcom …. yikes … I’ve sat in around in meetings where giant telecom companies can’t get adequate information on chips they are using from those guys. Even simple stuff like “what does this register do”. Three years later back comes “the XXX register must be set this way for the chip not to lock up intermittently” …. gee … maybe it wasn’t Bob’s fault :) It *is* a big bet so I can’t say any of this with certainty. It’s simply my guess that on something this complex, we are back to the way things worked a decade or two ago. Bob > On Apr 1, 2018, at 8:06 PM, Joseph Gray wrote: > > Bob, > > If it was a glass of good bourbon, I'd take you up on that offer :-) > > The Broadcom chipsets are touted as being specifically for phones. Whether > we'll be able to buy stand alone modules, I don't know. The uBlox chipsets > have in that past been widely available at rational prices. Hopefully the > new "9" series will be, also. As for the ST Micro, I haven't a clue, but > considering how their microcontrollers are so widely available from China, > who knows what will happen. > > Joe Gray > W5JG > > > On Sun, Apr 1, 2018 at 9:37 PM, Bob kb8tq wrote: > >> Hi >> >> I’d bet a warm glass of beer ( pick up only, no free delivery ) that you >> will not see them in user level >> modules ( = something you can fire up) at a rational price ( < $500) for >> quite a while ( = years …). >> The target market is integration in self driving / autonomous vehicles. If >> you are GM or Toyota, >> they will gladly support you. For the rest of us …. go to the back of the >> line ….. That’s been the pattern >> on this stuff like this for quite a while. >> >> Bob >> >>> On Apr 1, 2018, at 1:04 PM, Joseph Gray wrote: >>> >>> Magnus, >>> >>> When I can buy one of these new, multi-frequency receivers, I'll remember >>> to thank you :-) I wonder if any of the three will be available this >> year. >>> The Broadcom chipset in phones will be nice, but I'd also like a >> standalone >>> module from anyone. More fun stuff to play with. >>> >>> Joe Gray >>> W5JG >>> >>> >>> On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson < >> mag...@rubidium.dyndns.org wrote: >>> Hi Joe, On 03/31/2018 01:16 PM, Joseph Gray wrote: > I've been reading announcements by Broadcom, uBlox and ST Micro for new > chipsets that will use L1, L2, L5 to provide significantly more precise > positioning for every day applications like cell phone, autonomous > vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says "centimeter > level". The next few years ought to be very interesting, as these chipsets > become available in consumer products. I have advocated for receivers able to handle multiple frequencies and multiple GNSS for some time, sneaking it into documents, so there should be some preparations for this now. The benefit is naturally redundancy, but also higher precision. Natural I would enjoy cheap multi-frequency receivers myself, but I would never admit that this would be a reason for advocating it. ;-) 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. >> >> > ___ > time-nuts mailing 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 ANTENNA
Question Using L/H what is too much signal Bert Kehren In a message dated 4/1/2018 10:54:23 PM Eastern Standard Time, david.partri...@perdrix.co.uk writes: just use a bias tee to feed in the antenna volts :) -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani Sent: 01 April 2018 23:29 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] GPS ANTENNA An unusual attenuator with a DC pass. On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge wrote: > Or use a choke ring survey antenna and an attenuator :) > > Dave > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob > kb8tq > Sent: 01 April 2018 14:43 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS ANTENNA > > Hi > > Indeed, it is *very* easy to put to much gain in front of a timing GNSS > receiver. These beasts are trying to dig out a signal that you can’t even see > with a spectrum analyzer. > It’s way to far below the noise floor to detect that way. They optimize > things pretty tightly to get that done (and to hit a price target ….). Put to > much gain in front of them and they get unhappy. > > Making this even more crazy, the survey industry standard antenna *does* have > a lot of gain. Survey receivers need way more gain in front of them than > timing receivers. Put a survey antenna directly on a timing device and > trouble will likely be the outcome. Equally, a survey instrument probably > will not be happy with a timing receiver. > > Why all this nonsense? As far as I can tell, it goes back to how the very > early L1 / L2 survey boxes were designed back in the 1980’s and early 1990’s. > They made a basic decision to put a lot of gain at the antenna. Motorola came > along with their GPS modules later on. They made a *very* different decision > about how to distribute the gain. There are very good arguments on both sides > for why they did it this way. > The bottom line is still - you need to match things up … > > Bob > >> On Apr 1, 2018, at 2:36 AM, cfo wrote: >> >> On Sat, 31 Mar 2018 10:58:19 -0500, >> donandarline-Re5JQEeQqe8AvxtiuMwx3w >> wrote: >> >>> I found a supplier for high quality GPS antennas at a very >>> reasonable price. PCTEL GPSL1-TMG-SPI-40NCB. >> >> *** SNIP *** >> >> I had one of those on 25m cable, and it worked fine on a Tbolt , >> until i got an active antenna splitter that also had some gain. >> Then i had to replace it w. a 26dB version of same type, else the >> "Jackson Lite" was loosing sync. >> >> What i mean here, is that you can get too much gain too. >> >> Btw: Good price. >> >> CFO >> 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. > > ___ > time-nuts mailing 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] New GNSS chipsets
Hi Hal, On 04/02/2018 03:47 AM, Hal Murray wrote: > > mag...@rubidium.dyndns.org said: >> I have advocated for receivers able to handle multiple frequencies and >> multiple GNSS for some time, sneaking it into documents, so there should be >> some preparations for this now. > > How well do various GNSS track UTC and/or eachother? Within a handful of ns from UTC, which is quite good. GPS masterclock is to be held with +/- 1 us of UTC USNO, but in practice it is held much tighter, as within 3-5 ns or so. I expect the other constellations to be in that neighborhood even if not with that low value. It should be easy to check, but I'm a bit lazy to do so right now. >> The benefit is naturally redundancy, but also higher precision. > > I've been assuming the cheap GPS jammers will kill the others too. Are there > any signals far enough away from L1 that they might get through? The cheap jammers hit L1 C/A. It takes more jammer-cores to cover more frequencies, and the more frequencies you track, the harder to pinpoint them all, and well, until full constellation full frequency receivers is common, jammers will not adapt fully to it. How well antennas and receivers handle sideband jamming depends on the receiver design, just as in normal radio setups. 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] New GNSS chipsets
I think Bob is right and knows what he is talking about. Example Furuno GT-87, how many years have I known about it and tried to buy some, just recently became available. Bert Kehren In a message dated 4/1/2018 10:52:50 PM Eastern Standard Time, jg...@zianet.com writes: Bob, If it was a glass of good bourbon, I'd take you up on that offer :-) The Broadcom chipsets are touted as being specifically for phones. Whether we'll be able to buy stand alone modules, I don't know. The uBlox chipsets have in that past been widely available at rational prices. Hopefully the new "9" series will be, also. As for the ST Micro, I haven't a clue, but considering how their microcontrollers are so widely available from China, who knows what will happen. Joe Gray W5JG On Sun, Apr 1, 2018 at 9:37 PM, Bob kb8tq wrote: > Hi > > I’d bet a warm glass of beer ( pick up only, no free delivery ) that you > will not see them in user level > modules ( = something you can fire up) at a rational price ( < $500) for > quite a while ( = years …). > The target market is integration in self driving / autonomous vehicles. If > you are GM or Toyota, > they will gladly support you. For the rest of us …. go to the back of the > line ….. That’s been the pattern > on this stuff like this for quite a while. > > Bob > > > On Apr 1, 2018, at 1:04 PM, Joseph Gray wrote: > > > > Magnus, > > > > When I can buy one of these new, multi-frequency receivers, I'll remember > > to thank you :-) I wonder if any of the three will be available this > year. > > The Broadcom chipset in phones will be nice, but I'd also like a > standalone > > module from anyone. More fun stuff to play with. > > > > Joe Gray > > W5JG > > > > > > On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson < > mag...@rubidium.dyndns.org > >> wrote: > > > >> Hi Joe, > >> > >> On 03/31/2018 01:16 PM, Joseph Gray wrote: > >>> I've been reading announcements by Broadcom, uBlox and ST Micro for new > >>> chipsets that will use L1, L2, L5 to provide significantly more precise > >>> positioning for every day applications like cell phone, autonomous > >>> vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says > >> "centimeter > >>> level". The next few years ought to be very interesting, as these > >> chipsets > >>> become available in consumer products. > >> > >> I have advocated for receivers able to handle multiple frequencies and > >> multiple GNSS for some time, sneaking it into documents, so there should > >> be some preparations for this now. > >> > >> The benefit is naturally redundancy, but also higher precision. > >> > >> Natural I would enjoy cheap multi-frequency receivers myself, but I > >> would never admit that this would be a reason for advocating it. ;-) > >> > >> 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. > > ___ time-nuts mailing 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 GNSS chipsets
Hi Tom, It is indeed a benefit to use the different constellations. However, I want to make one point regarding propagation delay. As you observe one satellite in 2 frequencies, you can use the fact that the ionospheric shift at one frequency depends on the frequency and the TEC of that path. As you now observe on two frequencies, you can now on the difference between the measures estimate how much the difference of frequency picked up at TEC, thus one can separate out the TEC effect. By estimating TEX from those observations, the ionspheric effect can be removed from both observations. If you try to do this with another constellation, you add a number of complicating factors and loose precision as you do so. Can you observe the same satellite in three frequencies, you can build a more accurate estimation and compensation. Also, you an loose one of the signals and still be able to perform the processing. One should be prepared to do L1 only, L2C only, L5 only, L1 & L2C, L1 & L5, L2C & L5 and finally L1 & L2C & L5. Cheers, Magnus On 04/01/2018 11:53 PM, Tom Knox wrote: > Hi All; > > I think the real break through is using these different constellations and > their different frequencies and looking at carrier phase verses timing > elements. This should allow the removal of propagation delay. > > Cheers; > > Thomas Knox > act...@hotmail.com > > > > From: time-nuts on behalf of Magnus Danielson > > Sent: Sunday, April 1, 2018 2:40 PM > To: time-nuts@febo.com > Cc: mag...@rubidium.se > Subject: Re: [time-nuts] New GNSS chipsets > > Joe, > > I'm not sure I had much influence, but I at least try to advocate for it > to become a good market, so hopefully it will be affordable. It has > actually been affordable for quite some time, so going multifrequency > should be the next step and with that the benefits. > > Cheers, > Magnus > > On 04/01/2018 07:04 PM, Joseph Gray wrote: >> Magnus, >> >> When I can buy one of these new, multi-frequency receivers, I'll remember >> to thank you :-) I wonder if any of the three will be available this year. >> The Broadcom chipset in phones will be nice, but I'd also like a standalone >> module from anyone. More fun stuff to play with. >> >> Joe Gray >> W5JG >> >> >> On Sun, Apr 1, 2018 at 3:15 AM, Magnus Danielson >> wrote: >> >>> Hi Joe, >>> >>> On 03/31/2018 01:16 PM, Joseph Gray wrote: I've been reading announcements by Broadcom, uBlox and ST Micro for new chipsets that will use L1, L2, L5 to provide significantly more precise positioning for every day applications like cell phone, autonomous vehicles, UAV, etc. Broadcom is claiming 30 cm, uBlox just says >>> "centimeter level". The next few years ought to be very interesting, as these >>> chipsets become available in consumer products. >>> >>> I have advocated for receivers able to handle multiple frequencies and >>> multiple GNSS for some time, sneaking it into documents, so there should >>> be some preparations for this now. >>> >>> The benefit is naturally redundancy, but also higher precision. >>> >>> Natural I would enjoy cheap multi-frequency receivers myself, but I >>> would never admit that this would be a reason for advocating it. ;-) >>> >>> 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. > ___ > time-nuts mailing 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 ANTENNA
Or find an Arra “level set” variable attenuator. 3844 and 3854 models can often be found cheaply, have dc-pass and attenuate at both L1 and L2. /Björn Sent from my iPhone > On 2 Apr 2018, at 03:43, David C. Partridge > wrote: > > just use a bias tee to feed in the antenna volts :) > > -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio > Boriani > Sent: 01 April 2018 23:29 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS ANTENNA > > An unusual attenuator with a DC pass. > >> On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge >> wrote: >> Or use a choke ring survey antenna and an attenuator :) >> >> Dave >> >> -Original Message- >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob >> kb8tq >> Sent: 01 April 2018 14:43 >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] GPS ANTENNA >> >> Hi >> >> Indeed, it is *very* easy to put to much gain in front of a timing GNSS >> receiver. These beasts are trying to dig out a signal that you can’t even >> see with a spectrum analyzer. >> It’s way to far below the noise floor to detect that way. They optimize >> things pretty tightly to get that done (and to hit a price target ….). Put >> to much gain in front of them and they get unhappy. >> >> Making this even more crazy, the survey industry standard antenna *does* >> have a lot of gain. Survey receivers need way more gain in front of them >> than timing receivers. Put a survey antenna directly on a timing device and >> trouble will likely be the outcome. Equally, a survey instrument probably >> will not be happy with a timing receiver. >> >> Why all this nonsense? As far as I can tell, it goes back to how the very >> early L1 / L2 survey boxes were designed back in the 1980’s and early >> 1990’s. They made a basic decision to put a lot of gain at the antenna. >> Motorola came along with their GPS modules later on. They made a *very* >> different decision about how to distribute the gain. There are very good >> arguments on both sides for why they did it this way. >> The bottom line is still - you need to match things up … >> >> Bob >> >>> On Apr 1, 2018, at 2:36 AM, cfo wrote: >>> >>> On Sat, 31 Mar 2018 10:58:19 -0500, >>> donandarline-Re5JQEeQqe8AvxtiuMwx3w >>> wrote: >>> I found a supplier for high quality GPS antennas at a very reasonable price. PCTEL GPSL1-TMG-SPI-40NCB. >>> >>> *** SNIP *** >>> >>> I had one of those on 25m cable, and it worked fine on a Tbolt , >>> until i got an active antenna splitter that also had some gain. >>> Then i had to replace it w. a 26dB version of same type, else the >>> "Jackson Lite" was loosing sync. >>> >>> What i mean here, is that you can get too much gain too. >>> >>> Btw: Good price. >>> >>> CFO >>> 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. >> >> ___ >> time-nuts mailing 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.
