Re: [time-nuts] Low Phase Noise Amplifiers
Lifespeed, The cryogenic amplifiers were used in very broadband situations (often hundreds of MHz BW) with "signals" that were basically noise. Most radio astronomy lies in the art of measuring very small *changes *in noise level, such as between pointing at an object of interest or pointing away from it at a known quiet spot in the nearby sky. So we are talking about radiometry, where the "Radiometer Equation" rules. In this game, the best results are had by using the widest possible RF/IF BW, then running the noise into a square law detector, then passing the output of the detector through a very low BW filter. I mention the above because I suspect it means that phase noise in the predetection part of the path has little of no effect (unless, of course, there is a strong signal lurking not far outside the IF passband). To my knowledge, we've never tried to measure phase noise of any of the cryogenic amplifiers. Our LNAs mostly have noise temperatures in the range of 2K to 3K, which is roughly 0.03 to 0.04 dB NF. Dana On Sun, Jan 12, 2020 at 3:33 PM wrote: > -Original Message- > From: time-nuts On Behalf Of Dana > Whitlow > Sent: Saturday, January 11, 2020 8:28 AM > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] Low Phase Noise Amplifiers > > FWIW, at the Arecibo Observatory all our cryogenic LNAs had bias stabilized > with active stabilizers based on opamps. Since the opamps do not work at > ~15K, bias connections to the drain and gate of the RF FETs were brought > out > separately from the RF connections, and the opamp circuitry was at room > ambient temp. > This approach would nicely stabilize both drain DC voltage and drain > current > over the whole temperature range from room ambient to 15K, which was handy > for testing and monitoring LNA behavior during cool-down, which takes > several hours (or more). > > Dana > ** > Opamp stabilization is nice. Do you have any idea of the residual phase > noise or broadband noise floor you were getting with this bias, or was that > not a figure of merit for the cryo LNAs? Even though an opamp circuit can > be designed for low noise, probably large passive filtering components > would > be required to tamp down the broadband noise. > > Lifespeed > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] 5065A phase-noise
> Now, while these measures is performed not on the oscillator itself but > oscillator and output buffers, unless something is wrong with output > buffers on either box, the output buffer noise seems to support good > enough flicker and white noise to support the output of both > oscillators. Then running with that assumption it seems like the > 00105-6013 has excess flicker noise issue while the 05065-6097 has > excess white noise. HP's signal conditioning approach was OK for 5061As and 5065As with the original 00105-series oscillators, but it doesn't do the 10811-based versions any favors. I've found it handy to add a 'native' front-panel 10 MHz output to all of my units, repurposing the 100 kHz or 1 MHz jack. It is possible to improve the white noise floor substantially at the same time. There are numerous possible strategies, but they all come down to tapping into the 10811's output signal before it enters the divider used to emulate the old 5 MHz oscillator. A reasonably-quiet amplifier with good isolation and moderate-to-high input impedance is called for. E.g., http://www.ke5fx.com/norton.htm , which yields PN plots like the (somewhat hard to read) 5065A trace at the bottom of the page at http://www.ke5fx.com/rb.htm . These days, I'd probably just use an LMH6702. It's somewhat noisier than the discrete 2N5109 amp, but still good enough to preserve the 10811's performance while providing isolation in the 100 dB vicinity at 10 MHz. Isolation with the common-emitter amp is adequate at ~40 dB but not great. Either way, a highly recommended mod for all 5061As and 5065As with the newer OCXOs. Re: your trace with the conspicuous flat area between 10 Hz and 1 kHz, my guess is that you have some excess intermittent noise or jumpiness in one of your dual references. Try hitting ctrl-r to see if the cross-spectrum average is higher than either of the two raw FFT output traces, maybe? That's something that won't normally happen in a good run. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Low Phase Noise Amplifiers
-Original Message- From: time-nuts On Behalf Of Dana Whitlow Sent: Saturday, January 11, 2020 8:28 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Low Phase Noise Amplifiers FWIW, at the Arecibo Observatory all our cryogenic LNAs had bias stabilized with active stabilizers based on opamps. Since the opamps do not work at ~15K, bias connections to the drain and gate of the RF FETs were brought out separately from the RF connections, and the opamp circuitry was at room ambient temp. This approach would nicely stabilize both drain DC voltage and drain current over the whole temperature range from room ambient to 15K, which was handy for testing and monitoring LNA behavior during cool-down, which takes several hours (or more). Dana ** Opamp stabilization is nice. Do you have any idea of the residual phase noise or broadband noise floor you were getting with this bias, or was that not a figure of merit for the cryo LNAs? Even though an opamp circuit can be designed for low noise, probably large passive filtering components would be required to tamp down the broadband noise. Lifespeed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Low Phase Noise Amplifiers
-Original Message- From: time-nuts On Behalf Of Richard (Rick) Karlquist Sent: Saturday, January 11, 2020 7:39 AM To: Discussion of precise time and frequency measurement ; Charles Clark Subject: Re: [time-nuts] Low Phase Noise Amplifiers A VERY long time ago, it was discovered that simply degenerating a transistor with an emitter resistor makes a worthwhile improvement in 1/f noise. I want to say this was published in 1970 by Dick Baugh of HP but don't hold me to it. Note that the resistor was NOT bypassed: it's purpose was RF feedback, and any stabilization of bias current was incidental. The resistor value was a few dozens of ohms. That is not enough to do anything special in terms of stabilizing collector current. In oscillators, a designer might want to use a high performance bias stabilization scheme to minimize frequency drift (as opposed to noise). Various publications out of NIST (Fred Walls, et al) recommend using a transistor with high Ft vs the operating frequency to get low 1/f noise. This becomes more important when working at 100 MHz vs 10 MHz. As far as bias is concerned, the main emphasis seems to be on using a bias scheme that doesn't ADD noise to the amplifier. Rick N6RK ** Yes, while I am familiar with active bias and generally like the stabilization I think you're correct that low noise bias will be key. Transistor ft, emitter degeneration (inductive, I'm thinking), minimizing thermal noise from resistors and impedance matching for low noise figure will all be important. Lifespeed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there?
Current Trimble Timing product is the Accutime 360 multi-GNSS Smart Antenna https://www.trimble.com/Timing/index.aspx Trimble Inc (Embedded Products, In-Vehicle Navigation, Timing) Sales Manager: Brad Lynch Charlotte, NC, 28269 United States Phone: 704-875-0875 Fax: 408-273-6992 URL: www.trimble.com greg == Date: Sat, 11 Jan 2020 20:54:16 -0700 From: Skip Withrow To: time-nuts@lists.febo.com Subject: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there? I have an NTP server that uses a Trimble GPS receiver (Accutime 2000, p/n - 39091-00, ROM 3.06) that has fallen prey to WNRO. Just wondering if there are any Trimble (or other brand) receivers that have TSIP serial comms that are available for a reasonable price? Any help appreciated. Skip Withrow ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there?
Trimble replacement for EOL and WNRO was discussed here on Time-Nuts, five years ago (2015). Heol Designs is the solution. I have the Heol Design N024 GPS receiver in my Datum/Symmetricom/Microsemi TymServe 2100. == Cheap? TSIP drop-in? Relative term ... unless you desire a 19” door stop. Heol Design N0xx series https://www.heoldesign.com/-Trimble-GPS-replacement-boards- Heol Designs manufactures replacement GPS receivers (upgrade & update using Copernicus II chipset). Used for replacing Trimble iQ, SQ, SK2, LP, ACE II/III GPS receivers (due to EOL and WNRO). Contact Heol about your specific requirements/replacement. https://www.heoldesign.com/IMG/pdf/heol_design_like__series_en.pdf Datum / Symmetricom TS2100 replacement of Trimble Ace III using Heol N024 GPS receiver. Solves more than WNRO. https://www.heoldesign.com/IMG/pdf/heol-tech_note_119_en_r02.pdf greg w9gb == Date: Sat, 11 Jan 2020 20:54:16 -0700 From: Skip Withrow To: time-nuts@lists.febo.com Subject: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there? I have an NTP server that uses a Trimble GPS receiver (Accutime 2000, p/n - 39091-00, ROM 3.06) that has fallen prey to WNRO. Just wondering if there are any Trimble (or other brand) receivers that have TSIP serial comms that are available for a reasonable price? Any help appreciated. Skip Withrow ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] OCXO Advice
Bob Q, Both of your UCT 108663 oscillators look ok, although the blue plot seems 2x to 3x worse than the red plot. Neither is strongly correlated with temperature. It appears that you're using a GPSDO as a testbed so some of the noise and strange wiggles seen in your plot may be coming from the GPSDO board and not the oscillator itself. In that case a better OCXO might not help. Each vertical grid line of your plot is 0.5 mHz / 10 MHz = 5e-11. Your red plot matches mine pretty well: http://leapsecond.com/pages/uct108663/uct-01.png BTW, a California eBay seller for UCT 108663 is: https://www.ebay.com/itm/202863421344 Suggestions: 1) Swap the OCXO's to see if the noise follows the OCXO or follows the GPSDO board. I mention this because the 2nd hour of the blue plot looks like GPSDO wander, not typical OCXO noise. 2) Maybe try each OCXO in an isolated test for a day. That is, remove the GPSDO from the equation -- place the OCXO in an open but undisturbed no air flow location, power it from a clean stable power supply, and float or ground the EFC. Measure with your Rb (LPRO) as the reference. The results of these baseline tests will suggest if the instability that you see is due to the OCXO or due to the GPSDO boards you're playing with. 3) Consider using both your phase comparators on one OCXO at the same time to verify the consistency of your measurement system. For example, the unusual red glitch at T+6 hours looks more like a measurement issue than something a OCXO would do. In general, when you have two GPSDO boards, two OCXO, and two counters, it's not likely they are all equal. So these multiple tests allow you to gain confidence in your parts and to pinpoint the weak element(s) in your setup. /tvb ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] The difficulty of low noise measurements
Hi, On 2020-01-12 17:08, Poul-Henning Kamp wrote: > > In message <95f82880-6cec-1885-c59e-046ab7a79...@rubidium.se>, Magnus > Danielson writes: > I have a ham friend that is fairly well into batteries as he needs to for his telecom installations. >>> LVDC people are much better at this than UPS people, the latter often >>> think that batteries only need to last "until the diesel kicks in" >>> and that is a very different application. >> If you have a diesel, then the UPS is just a bridge. If you don't it is >> the bridge until the power grid is back. > Indeed, but the batteries still matter. > > UPS people tend to fail to explain to their customers that batteries > dimensioned for only 10 or 20 minutes will not last many such cycles. > > If you do not test your UPS on a regular basis, that may be a valid > tradeoff, but if you test it, as you should, once per month, you > will kill such underdimensioned batteries in three years. Sure. I have not cared myself so far, because I have so far not really considered my lab being "in production" enough to care about such details. I will get there. > > I tell my customers to dimension UPS batteries for at least one hour. Which covers most issues on power-grid anyway. > > It is be cheaper in batteries in the long run, at it gives their > staff a fighting chance if the diesel does not auto-start. > The folks I know actually test their diesels auto-start regularly. They also check condition of batteries and how much diesel is left. Yes, some people do test their diesel engines regularly, but fail to check how much diesel remains. Now, I think the UPS things is starting to be a little too off topic, so let's not continue this part of the thread much longer. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] The difficulty of low noise measurements
In message <95f82880-6cec-1885-c59e-046ab7a79...@rubidium.se>, Magnus Danielson writes: >>> I have a ham friend that is fairly well into batteries as he needs to >>> for his telecom installations. >> LVDC people are much better at this than UPS people, the latter often >> think that batteries only need to last "until the diesel kicks in" >> and that is a very different application. > >If you have a diesel, then the UPS is just a bridge. If you don't it is >the bridge until the power grid is back. Indeed, but the batteries still matter. UPS people tend to fail to explain to their customers that batteries dimensioned for only 10 or 20 minutes will not last many such cycles. If you do not test your UPS on a regular basis, that may be a valid tradeoff, but if you test it, as you should, once per month, you will kill such underdimensioned batteries in three years. I tell my customers to dimension UPS batteries for at least one hour. It is be cheaper in batteries in the long run, at it gives their staff a fighting chance if the diesel does not auto-start. -- 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@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there?
ntpsec, a fork of the classic NTP distribution, supports an option to compensate for the 1024 week rollover: https://docs.ntpsec.org/latest/ntp_conf.html time1 sec Specifies a constant to be added to the time offset produced by the driver, a fixed-point decimal number in seconds. Each "g" on the end of the constant adds the number of seconds in a 10-bit GPS era; each "G" adds the number of seconds in a 13-bit GPS era. On Sun, Jan 12, 2020 at 3:10 AM Björn wrote: > Hi Skip, > > Are your NTP-server using the Palisade ref clock driver? > > http://doc.ntp.org/current-stable/drivers/driver29.html > > If it’s using the event-poll mode you might need a receiver supporting > that. I have not seen that outside the Palisade/Accutime family. > > Can you fudge the time1 all the way up to 1024wk (translated into seconds) > to compensate for the wnro with your current receiver? > > # Set packet delay > fudge 127.127.29.0 time1 0.020 > > - > > Björn > > Sent from my iPhone > > > On 12 Jan 2020, at 04:55, Skip Withrow wrote: > > > > I have an NTP server that uses a Trimble GPS receiver (Accutime 2000, > > p/n - 39091-00, ROM 3.06) that has fallen prey to WNRO. Just > > wondering if there are any Trimble (or other brand) receivers that > > have TSIP serial comms that are available for a reasonable price? Any > > help appreciated. > > > > Skip Withrow > > > > ___ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] The difficulty of low noise measurements
Hi, On 2020-01-11 21:53, Poul-Henning Kamp wrote: > > In message <643136da-9599-18ca-be85-ffa62ab04...@rubidium.se>, Magnus > Danielson writes: > >>> I have on my ever-growing TODO list to test if serial-BLE adapters >>> are any good. Has anybody tried that yet ? >> My recommendation is to build on the ESP32, then you can get serial port >> to WiFi directly and the entry level price is small enough and there >> exist a community of things. It is competent enough that you may let it >> do some of the processing for you. > The reason I noted "BLE" and not "WIFI" is the lower power: Less RF > can never be a bad thing in these circumstances. With ESP32 you can do both Bluetooth and BLE besides WiFi and Ethernet. Cost is low, so it is worth considering. > >> The EFOS10 maser has UPS and batteries, sure they are not prime but I >> can for shorter measurements just go and unplugg power if needed. > Have you tried it ? Yes. > > How is the electrical grid configured on your rocks with respect to PEN ? > > Do you have a ground electrode at each house or does the utility > provide the PEN potential via their cable ? PEN provided with the three-phase as per standard delivery here. Then from the central PE and N is separated. > In the former case: How old are the one at your house ? If more > than few decades old, it may not provide good contact any more. I have not had reason to consider such problems. > > In the latter case, your PEN will be very noisy, and if you think > you can hammer a 2.5m hard copper "electrode" into some kind of wet > underground, a galvanic trafo on the mains might be relevant. Actually, it's not my absolute noise which would eat into my measurements, it's the relative differences between different parts of the installation. In practice the lab is a relatively dense connection on a separate branch of the rest of the house, with only a weak link to the other part. My main problem is in 50 Hz and overtones from what I so far have been able to derive from noise. I did sniff one of the common mode surpressions and it was very quiet in that range, so I saw some noise that is more due to switcher supplies but not that strong. One needs to think about isolation between sources, but actual isolation may be the wrong method to go about it. The correct method can be to tie things tighter together at low frequency. Mesh-bonding networks is easier to maintain and has EMI benefits. > >> I have a ham friend that is fairly well into batteries as he needs to >> for his telecom installations. > LVDC people are much better at this than UPS people, the latter often > think that batteries only need to last "until the diesel kicks in" > and that is a very different application. If you have a diesel, then the UPS is just a bridge. If you don't it is the bridge until the power grid is back. Yet again, I have analyzed spurious 8,5 kHz noise from a large UPS (it was running a load of 400 kW) and let me tell you, they did care about this spurious even if it took them 18 months to replicate. With an older type of the filter, the switching transistors could miss-fire out of phase such that cancellation was not as intended. There is UPS folks that *DO* care, because with their massive power the spurious can start to have unpleasent consequences such as florescent lights singing and making people go nuts. Having a background with high dynamic audio systems, sniffing noise and low signals is natural, I will follow the many threads there is. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] The difficulty of low noise measurements
Keep in mind that BLE and "classic" Bluetooth are completely different animals. There is no "serial emulation" with BLE. If you want to use Bluetooth modules to isolate serial traffic, I recommend the JDY-30/31 modules. They are a much improved (and cheaper) version of the HC-05 that you can get anywhere. I have a brief review of them (and an English spec) on my web site. I have used them fairly extensively for remote control between Android tablets and microcontrollers. Didier KO4BB On Sat, Jan 11, 2020, 11:58 AM Poul-Henning Kamp wrote: > I have on my ever-growing TODO list to test if serial-BLE adapters > are any good. Has anybody tried that yet ? > > > ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there?
On Sun, Jan 12, 2020 at 3:55 AM Skip Withrow wrote: > > I have an NTP server that uses a Trimble GPS receiver (Accutime 2000, > p/n - 39091-00, ROM 3.06) that has fallen prey to WNRO. Just > wondering if there are any Trimble (or other brand) receivers that > have TSIP serial comms that are available for a reasonable price? Any > help appreciated. > > Skip Withrow > As TSIP is a Trimble proprietary protocol, to the best of my knowledge it is only found on Trimble devices. Does your NTP server only work with TSIP or might it be able to use "standard" NMEA ? possible with PPS ? Cheers Arne ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Any (relatively) cheap TSIP GPS receivers without WNRO out there?
Hi Skip, Are your NTP-server using the Palisade ref clock driver? http://doc.ntp.org/current-stable/drivers/driver29.html If it’s using the event-poll mode you might need a receiver supporting that. I have not seen that outside the Palisade/Accutime family. Can you fudge the time1 all the way up to 1024wk (translated into seconds) to compensate for the wnro with your current receiver? # Set packet delay fudge 127.127.29.0 time1 0.020 - Björn Sent from my iPhone > On 12 Jan 2020, at 04:55, Skip Withrow wrote: > > I have an NTP server that uses a Trimble GPS receiver (Accutime 2000, > p/n - 39091-00, ROM 3.06) that has fallen prey to WNRO. Just > wondering if there are any Trimble (or other brand) receivers that > have TSIP serial comms that are available for a reasonable price? Any > help appreciated. > > Skip Withrow > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
