[time-nuts] Re: Leviton VTP24 Is this Time Accurate enough?
On Fri, Aug 27, 2021 at 9:29 AM Lux, Jim wrote: > > When your requirement is "turn the lights on and off with the sun" 5 > min/year is pretty good. > > When I bought my current house, I forgot to call the electric company before closing, and they turned off the power right at 5am of the day I moved in. I called them that very day, but since it was the Friday of a holiday weekend, they said they couldn't send someone out to get it turned back on until Tuesday, so we had a nice time in the house without power. On Tuesday, right exactly at 5:00, the power came back on. And the old mechanical timer that turned the driveway light on around sunset and back off in the morning didn't need to be adjusted at all — it had missed exactly 96 hours, and came back to life without noticing the difference. Andrew ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Comparison/evaluation of u-blox timing receivers
Very interesting. When I built my Arduino Due-based Rb clock (currently disassembled) around a NEO-M8T (more specifically, an EVK-M8T), I used the EXTINT to measure the difference between my onboard PPS and the GPS top-of-second. I ran it pretty long term without seeing any lost or duplicated TIM-TP messages. Is it possible that you had some mundane issues with drive levels or coupling, there? Andrew KC2G On Mon, Aug 23, 2021, 9:52 PM John Ackermann N8UR wrote: > In 2020 I did an extensive evaluation of the timing ability of the > u-blox LEA-M8F, NEO-M8N, NEO-M8T, NEO-M9N, ZED-F9P, and ZED-F9T. The > work was made possible by support from the HamSci consortium > (https://hamsci.org) under NSF grants supporting HamSci activities. > > I was sure I'd posted about the paper on time-nuts, but I can't find any > record that I did, so this is a belated announcement. It's available > for download from > > > https://hamsci.org/sites/default/files/publications/2020_TAPR_DCC/N8UR_GPS_Evaluation_August2020.pdf > > As BobC says, "Lots of fun!" > > John > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: GPS antenna question
On Thursday, July 22, 2021 9:05:47 PM EDT Robert DiRosario wrote: > If I want to use GPS for time and frequency standards, just how solidly > does the antenna need to be mounted? > The easiest and least expensive way to mount a GPS antenna would be up > on two 10' TV mast sections, but that > would move around a bit in the wind. Maybe two or three inches. Or do > I need to do better? All of the "easy" or > "good" spots in my yard already have amateur radio antennas. Well, applying the rule of thumb, 1 foot = 1 nanosecond at the speed of light, which would make you think that two or three inches of wiggle (250ps) would be down below most of your other noise sources. Andrew KC2G ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
[time-nuts] Re: Adding PTP or NTP to my GPSDO
On Sunday, May 30, 2021 3:09:16 PM EDT Pluess, Tobias wrote: > Besides that, I also thought about adding a NTP. That would not require a > MAC with PTP capability. Any thoughts on that? has anyone ever written > their own NTP server on a microcontroller? I have, twice — once for the Arduino Uno (ATmega328) with W5100 Ethernet (not great; the W5100's own processor adds quite a lot of jitter, but it was still good to better than 100us), and once for an Arduino Due clone (ATSAM3X8E) using the internal Ethernet MAC. Both of them are up on GitHub: https://github.com/arodland?tab=repositories&q=ntp Probably most of it is not much use to you, but the NTP protocol implementation at lines 27 - 216 of https://github.com/arodland/Due-GPS-NTP-Server/blob/master/ethernet.cpp might be educational. One trick to keep in mind when doing NTP on a micro is: you don't need to bother with an ARP implementation, just swap the src and dst MAC addresses along with the src and dst IP addresses when you send your reply. Cheers, Andrew KC2G ___ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
Re: [time-nuts] Voyager space probe question
RTGs, much like solar cells, have a terminal voltage that drops pretty much linearly with the current you draw from them, and a "maximum power point" where V*I reaches a maximum (see for example page 37 and several later pages from https://apps.dtic.mil/dtic/tr/fulltext/u2/a057483.pdf ). As they age, the open-circuit voltage goes down, and so does the maximum-power current. So the goal with load shedding is to keep the current to a level where the RTG develops a sufficient voltage to make everyone happy. Exact details depend on what kind of regulators you have downstream (I have no clue, in Voyager's case). Andrew On Sunday, November 29, 2020 3:39:37 PM EST Jeremy Nichols wrote: > As the RTGs aged, the Voyagers were commanded to shed parts of their load. > Did the RTG voltage drop, was it the current-supplying capability (or both) > and how did that affect the oscillators, if at all? > > Jeremy > N6WFO > > On Sun, Nov 29, 2020 at 10:11 AM jimlux wrote: > > For those interested in a "typical" (hah!) TCXO spec for a space radio, > > generically similar to the Electra UHF radios on and orbiting Mars, it's > > attached. > > > > The excessively precise frequency (49.244. MHz) is because it > > matched a particular channel assignment for S-band, and the idea was to > > have the PN code (which is about 3 MHz, proportional to the carrier) be > > exactly 16 samples long. > > > > This is in pre "we can trust an NCO/DDS" days. When it takes years to > > build your spacecraft, ordering a crystal with a 24 month lead time to > > get the frequency "just right" isn't considered a problem. Historically, > > the SDST used a VCXO with a crystal at the frequency at 8*f0, where f0 > > is about 9.xx MHz, and multiplies up by 880 to the transmit frequency > > between 8.4-8.45 GHz. > > > > Today, we use 50 or 100 MHz oscillators (Electra uses 24 MHz, but it's > > an older design) and synthesize the carrier with a DDS feeding a PLL. > > For instance, the Iris cube-sat transponder uses a 50 MHz oscillator, > > and that drives a DDS running at 20 MHz, which is multiplied up in an > > integer N PLL to the carrier frequency. > > > > This is because the missions are shorter development time, and we don't > > want to have to know the frequency until after the radios are built (or > > at least, the oscillators are ordered). For Iris, there were 7 of them > > built for the Artemis-1 mission, and the frequencies are all over the > > space science X-band allocation. > > > > The SDST and older used a DRO as the microwave oscillator, and they just > > don't have the tuning range needed to cover 50-100 MHz tuning range (and > > lordy, we tried a bunch of techniques) - not do mention that DROs have > > noticeable microphonics because the physical cavity is part of the > > resonator. > > ___ > > 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] SMPS or conventional?
On Monday, November 23, 2020 7:33:49 AM EST 李 wrote: > When the Rb clock is working, it needs a high temperature, isn't heat > dissipation breaking the heat balance?Increased power consumption？ It needs a *stable* temperature. It has a heater to provide regulation. The thing about a heater for stabilizing temperature is... it can only heat, it can't cool. A modest amount of cooling ensures that the system can respond to ambient temperature variations in both directions. A super-insulated device that gets too hot is helpless. Andrew ___ 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] Need help in test board pinout for SA22.c oscillator - thanks in advance
I remember when I started experimenting with Rb and I thought "why would I want to give it more cooling? That's just more contact with the outside world, and more chance for the room temperature variation to throw things off. I'll just put it on the desk, it'll be more stable that way." And then someone finally got through to me: the Rb has a heater to regulate the temperature, but the heater can only regulate temperature *up*, not *down*. If you have enough cooling to remove the operating heat output plus some fraction of the heater's output, at the specified case temperature and your range of room temperatures, then the heater will operate some fraction of the time and the physics package temperature will be well-regulated. With less cooling than that, the temperature becomes effectively unregulated, because if the unit is too hot, the heater can't help. Of course, lots of thermal mass in the heatsink helps too if you want to damp out the effects of air-conditioner cycling and the like. On Thu, Nov 7, 2019 at 8:18 PM Bob kb8tq wrote: > > Hi > > You probably need more heat sinking than that assembly provides. It’s a case > of “better to much > than to little”. The life of the device will extended with more heat sinking. > > Bob > > > On Nov 7, 2019, at 2:47 PM, Fio Cattaneo (.US) wrote: > > > > Hello folks, I just got a Symmetricom SA22.C oscillator on Ebay. The > > oscillator comes mounted on a test board which seems to drastically reduce > > the number of pins (I’m guessing it consolidates all the GND and VDD pins > > in one) and potentially obviating the need of providing both +15V and +5V > > (looks like there is a voltage regulator). > > > > > > > > However, I do not recognize the board (it’s definitely not the one shown in > > the SA22.C user manual), so I’m asking here…… Thanks much in advance ! > > > > > > > > > > > > > > > > > > > > > > > > --- Fio Cattaneo > > > > > > > > Universal AC, can Entropy be reversed? -- "THERE IS AS YET INSUFFICIENT > > DATA FOR A MEANINGFUL ANSWER." > > ___ > > 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.
