Re: [time-nuts] Heathkit clock available
I have a couple of Nixie clock kits I got from pvelectronics.co.uk. They have a plug in GPS module. No doubt it does not meet time-nuts standards but to my eye and ear, the tick is spot-on with WWV, which makes it suitable for setting my watch and knowing when to walk the dogs. With the Pound Sterling doing so poorly against the dollar, these actually seem like a pretty reasonable deal. http://pvelectronics.co.uk Besides, Nixies are cool. -- Brian Lloyd 706 Flightline Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Modern HW replacement for ATOM based NTP server?
On Mon, Apr 6, 2015 at 5:29 PM, Frank Hughes via time-nuts < time-nuts@febo.com> wrote: > Looking for a platform not needing a fan. While the ATOM and SSD seem to > be OK w/o direct airflow, the Mini ITX Power Supply fan is needed. > After three years, the stupid sleeve bearings are beginning to > rattlewhich led me to this design review. > Recently built a Caching DNS for the home LAN using a "Technologic Systems > TS-7250-V2, general purpose PC/104 embedded system " Runs Debian, 3.14 > kernel. > Beagle Bone Black. -- Brian Lloyd 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Trimble Thunderbolt question, splitting its output.
On Fri, Mar 27, 2015 at 12:22 PM, Chris Wilson wrote: > > > 27/03/2015 17:14 > > My T/Thunderbolt has operated flawlessly for some years feeding a > David Partridge frequency divider board. The board gives 10Mhz and > lower divisions of 10MHz down to the KHz level out, as square waves. > What I need to know is, can I T off the T/Thunderbolt 10MHz feed to > this board and take a second sine wave output direct from the > Thunderbolt, to drive a transceiver GPS disciplined 10 MHz frequency > standard input as well as having it feed the divider baord, which has > a square wave output? Thanks. > You might want to use something like a TAPR TADD-1 board to provide multiple, buffered, isolated 10MHz outputs. See: http://tapr.org/kits_tadd-1.html This is what I am doing with my T-bolt. I'm also using the TADD-3 1pps pulse distribution amp to distribute the 1pps from my T-bolt and my JL LTE-lite. -- Brian Lloyd 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Trimble Thunderbolt NMEA ?
On Mon, Mar 2, 2015 at 5:06 PM, Tim wrote: > On 3/03/2015 4:33 AM, Didier Juges wrote: > >> Tim, >> >> NMEA is normally used for navigation. It would seem unlikely that anyone >> would want to use a Thunderbolt for navigation. Can you elaborate on what >> you are trying yo do? >> >> >> Hi Didier, > > I' building a multi frequency beacon based on QRP-labs U3 beacon kit. It > has the ability to discipline its oscillator with a PPS input and, using > NMEA input, set and maintain time and location for exact control of WSPR > and OPERA modes of operation. > > As it currently only accepts NMEA input I was wondering there was a way to > get NMEA out of a thunderbolt. I've lodged an RFE with the developer to add > TSIP support to the U3, but I don't think that's going to happen anytime > soon. > > I'd rather use the Thunderbolt as the time and PPS source since its way > more accurate than the LEA-M8FGPS module that optionally comes with the kit. > This may be a case where duplication of hardware might be the simplest solution. Navigation receivers that output 1pps and NMEA data are a dime-a-dozen now, under $50. Go look at what is available from the likes of SparkFun or Adafruit. For disciplining the clock in in the computers running your WSPR and OPERA software even the cheapest receivers greatly exceed the required timing accuracy. (NTP across the net is sufficient for these applications.) What I am doing is using a BeagleBone Black and a Jackson Labs LTE-lite receiver as my household stratum-1 NTP server and backup 10MHz and 1pps reference. In the same enclosure I am mounting my Trimble Thunderbolt to use as my primary 10MHz and 1pps reference. Fan-out of these signals is accomplished using the TAPR TADD-1 and TADD-3 distribution modules. All of this is easy to accomplish with a minimum of hardware and software hacking. I am mounting everything in a 2U rack case into which I plan to incorporate a battery backup. By time-nuts standards this is pretty mundane, but still represents a very credible level of performance from a ham-radio and general timing point-of-view. -- Brian Lloyd 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Sources for Mission Time Clock
On Sun, Jan 11, 2015 at 10:10 PM, Wayne Holder wrote: > > But, 7 segment just doesn't quite capture that retro feel, IMO. > I know precisely what you are saying and I get the feel. Nixie clocks seem so much cooler than seven-segment LED clocks. (And vacuum fluorescent just seems cheesy. Go figure.) So early '60s is retro but late '60s is not. From my view 50 years down the road that seems just ... humorous. Seems like a BBB driving a good-sized 1080P display (both are cheap) would be a good platform to do something like this. You can make it count or display anything you want. Since the linux distro in the BBB has NTP installed already, it should be able to keep reasonably accurate time from a human PoV. Hmm, I am going to want a display like that for my video wall. -- Brian Lloyd 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
On Thu, Dec 11, 2014 at 1:22 PM, Bob Bownes wrote: > > If there is always a system running, why go with the bbb? I use the file > server in the basement fed with 1pps to the non USB serial port from a > TBolt in my office. > > You do have a file server in the basement don't you? :) > Yes, I do. Two in fact. They are two of the machines running 7x24 on the network. Unfortunately I have found that NTP on them does not perform well. So being able to throw a $55 board at the problem of optimizing NTP performance and decoupling it from the up/down status of anything else on the network makes sense to me. I consider routing, DNS, and NTP to be services of the network infrastructure and should be independent of anything else. > I suppose it would be an interesting experiment to feed an NTP server with > several PPS signals (either simultaneous or offset) to see how it handles > it. Or to set up an NTP chorus fed from multiple PPS sources or even a > single PPS source to see how they average out. Maybe over the holidays. I > really should finish up running the coax for a shared GPS antenna to the > basement. > That does make sense to me. > > Bob > > PS: As to the buy a second BBB/RPi question, I've taken to buying what I > think will be key spare parts for projects and stocking them. Each project > gets a shoebox sized storage bin on the shelves in the basement. One part > of the shelves is completed projects, the other is in process. It has the > added side benefit of telling me when I have too many unfinished projects. > :) > That makes sense to me too. As for the 1U time and frequency server, there is a LOT of extra space in the 1U box for an extra BBB and, potentially, for another LTE-lite. Of course, the NTP function will work with just a generic GPS module with 1pps out. Said: are you going to be doing another run of LTE-lite eval boards? I think I would like to get one as a spare. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
On Thu, Dec 11, 2014 at 10:46 AM, Jim Lux wrote: > Actually, I think my point was that the problems I face at JPL are > essentially identical to the problems we face at home. I'm not in the time > and frequency group (and I don't know that they actually are better off.. > although they do have rooms full of good clocks), so in our areas, we tend > to have little point solutions to problems. > > It's not like there's a big time/frequency infrastructure with *free* > spigots from the maser in every lab. You have to pay for this stuff on > your project funds, and a lot of times, it seems easier to find a one time > expense (summer hire intern!) than sign up for a perpetual monthly charge > plus the infrastructure change cost to pull the fiber/coax. > > We do have NTP, of course. But network drops are about $30-40/month, so in > a lab, you might decide, hey, I can buy a widget for a few hundred dollars, > and I'll have a better than NTP time source forever. And if you've got a > student hire, buying that $200 unit off eBay or Amazon and taping a GPS > antenna to the window starts to look pretty attractive. > > There's probably more than a 100 (certainly dozens) of little GPS antennas > all over the lab connected to a bewildering variety of time/frequency > sources in labs. Sure, there's a goodly number of > TrueTime/Fluke/Pendulum/Symmetricom > boxes of various vintages and models, but there's also all manner of > home-grown stuff. > Has anyone there noticed the amount of time and money spent recreating the same thing over and over? Sure, individually it is cheap but when you do the same thing hundreds of times, it is no longer a tiny amount. Clearly it is a common needed service/device that your IT (or whatever) dept could provide for nearly nothing. Sheesh. > > Which is exactly what we do at work.. Lots of old PCs doing something, but > there's that "what do we do when the PC fails" question. Just like at > home, you've got a limited budget and time available. Do you stock a > couple extra BBBs or RPis? That costs money, and you need to have a place > to store them where you'll be able to find them. > Why not? The freakin' things are down to about $35 for an RPi and $55 for a BBB. And the price for this is going to go down again. (Well, eventually fabbing the board and soldering the nearly-free components is going to define the lower bound in price but the performance can't help but increase.) > > Or do you hope that when it fails 5 years hence, you'll have time and > budget to rebuild? > And in 5 years there will be equivalent or better hardware at the same price point. Stay in and eat beans for dinner one night to pay for your new NTP server. > > >> So, I am still looking for a straight-forward, "here is a really good way >> to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if >> someone is using their LTE-lite to do it. It seems like a nice little >> package for the amateur time-nut for everyday time and frequency keeping. >> > > Essentially, you want the equivalent of a Microsemi (Symmetricom/TrueTime) > XL-GPS with the right options for, say, $500 or less. > Well, it is looking like I can do this very nicely for about $250 including the BBB or RPi, LTE-Lite, and a 1U rack-box. Yes I have to build a buffer for the 1pps and 10MHz output but that has been covered here very nicely. > > I do too. > > But I'm also not under any illusion that when my homegrown unit fails that > I'll be able to fix it, or rebuild it for the same price. It will depend > on someone having done the redesign using whatever is available then, and > published the cookbook. > I'm still thinking that the spare RPi or two tucked into the box with the OS already loaded and configured will go a long way toward making sure I can recover and keep going for many years. I have a BBB with Debian running NTP that has been running for about 5 months now without a reboot as just a local NTP stratum-3 server for my local machines. Works pretty well so I am satisfied that it is stable to do the job. Once it is started I don't expect to be doing a lot of OS upgrades. If it only runs NTP and all the other services/daemons are turned off, it is going to be pretty difficult to exploit. If it ain't broke, don't fix it. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
On Thu, Dec 11, 2014 at 10:03 AM, Paul wrote: > On Thu, Dec 11, 2014 at 10:27 AM, Dan Drown > wrote: > > > Is this better or worse than other NTP server platforms? I haven't > tested > > them, so I have no idea. > > > Tharp says his appliance > > "can sustain thousands of queries per second. Even under high throughput > timekeeping operations are never disrupted or perturbed." > > But enough of that. > > From the time-nut perspective what's the interest in high resolution NTP? > I mean beyond the "can I do this?" appeal. > We are all time nuts to one degree or another or we wouldn't be here. I personally want all the clocks in my house, including all the computers (I have about 10 running at any given moment here), to have time resolution better than my ability to perceive errors. (To my eye that is about 100ms for clocks with a sweep second hand.) and in the 1ms-or-better range for the computers. I want to know that, when two things get time-stamped on different machines, I can tell which happened first from the point of view of a DBMS dealing with concurrency issues. So a stratum 1 server in my house that is independent of my external internet connectivity seems desirable. Look, I used to leave WWV running all the time on a receiver. That background D D D was very reassuring as I moved through the house watching the sweep second hands ticking in time with WWV. Time to move forward in true time-nut fashion. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
Discussing the lifetime of NTP server hardware is all well and good but given the thrust of this list, i.e. individual time-nuttery, I don't see it as being too germane. Few of us have the same problems that Jim Lux has at JPL. I want to have a good time and frequency source in my little network that I run. I can put an extra BBB or two aside to run NTP. Eventually I will want to replace it but I bet that there will be an adequate SBC and free OS to do that when need arises. So, I am still looking for a straight-forward, "here is a really good way to use a BBB coupled to a GPS 1pps to do NTP," treatise. Better still if someone is using their LTE-lite to do it. It seems like a nice little package for the amateur time-nut for everyday time and frequency keeping. Oh, and if it has nixie tubes to display current time, umso besser! After all, I still need to set my old-style watch and a few mechanical chronographs I have kicking around. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
On Thursday, December 11, 2014, Jim Lux wrote: > > Ah, but will the exact same single board computer be available for > replacement in 5 years? Most likely not. These days I can't imagine a manufacturer making the same SBC or mobo board for more than a year. If you consider BBB to be the logical continuance of the original beagle board then it is going on two years but is at rev C. > Or will it be Rev F instead of Rev B, with "just a few tweaks to improve > performance", but also enough that it's not "drop the image on it and run" > > What about 10 years? > 15? If that is an issue, buy a spare and keep it in the same box with each running one. Heck, buy two spares. > Philosophically it might be a straightforward thing, but it might not be > as easy as one might hope. > > Legacy support with processor boards is a real challenge. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
On Wed, Dec 10, 2014 at 10:15 PM, Chris Albertson wrote: > Those sub 1 u-second numbers are very good. They argue for using the BBB > as an NTP server but I wonder if it really is the best. I think the > numbers that matter are measures of the close on the computers who use your > BBB as a server. In other words the goal is to synchronize a set of > computers. Can The little BBB push accurate time out to a set of user > computers and keep then in sync better then some other NTP server platform? > When I think of what we have been using to run NTP down through the years, this is almost funny. The BBB is little in physical package size only. Its processing power is not inconsequential. Fuzzballs anyone? -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
On Wed, Dec 10, 2014 at 10:21 PM, Michael Tatarinov wrote: > Hello > > Try to run ntpd with realtime priority (options '-N' or '-P priority'). > Your an hourly jobs can be executed several slower but it may improve > the time synchronization. > And given the price, why try to run multiple, time-critical applications on one BBB or RPi? Just get lots of them. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Beaglebone NTP server
Well, I am hoping to get to the point where the path to using the BBB as an NTP server using the PRU for more precise timing, and using the LTE-lite to provide the 1pps and time data. Of course, the LTE-lite can also provide 1pps and 10MHz to my workbench. (It's all going to go in a 1U box in the rack next to my workbench.) Yes, I know that all the information is out there and much if it can be gleaned from this list by following several threads back through several months. But that brings to mind playing Adventure. Has anyone compiled a how-to for turning a BBB into an NTP server using the PRU for timing? Seems like a straight-forward and useful turn-key kind of thing. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] 1968 Scientific American Magazine: Cesium ClockStandards
On Wed, Dec 10, 2014 at 8:31 AM, Alan Melia wrote: > Hi Dave, as a long time reader (since 1955) and subscriber I remember the > Amateur scientist pages ending in the 1980s. I think the contributer > retired. At around that time I think the many adherents formed the Society > of Amateur Scientists. Though I have not visited fot several years the web > site was www.sas.org and I believe had pdfs of old SciAm Amateur > Scientist articles. > > I particularly remember one scary article about an X-ray generator that > consisted of a 6J5G tube ( I think a triode valve in the UK :-)) ) with a > piece of aluminium foil secured round the smaller diameter part of the top > with a twist of copper wire, and conected between the cathode pin and the > foil, a 2kV psu !! The end of the tube cathode (and heater wire) was > clearly visible through the top and formed a spot source of electrons. I > believe an X-ray plate of a hand was included in the article !! > Yes, good times! Some of the projects had great potential to do harm if not treated with substantial respect. Just the thing to attract the elementary school student I was at the time. I mean, it showed me how to make rockets, x-rays, a linear accelerator, a vacuum, a precise clock, and measure the electrostatic potential of the atmosphere! (At some point in time in my life I think I have built a version of nearly everything in there but it provided the spark.) > There were many inovative ways of building quite sophisticated > experiments. Another I rememer was a Proton precession magnetometer using a > radar magnetron magnet. > Actually, it was a nuclear magnetic resonance spectrometer. I built it. It worked -- after a fashion. I won at the California State Science Fair with it in 1968 at the ripe old age of 13. It was a fantastic learning tool because I screwed it up 13 ways to Sunday due to my misunderstanding of the basic way that a pentode vacuum tube works and the physics behind NMR. I had to climb up a long learning curve for a kid with no formal electronics or physics training. And I pestered the hell out of a bunch of people who could each give me a piece of the understanding I could put together to eventually understand the whole thing. I was sad to see SciAm change and move away from, "reader as active participant in scientific endeavor," to, "reader as passive spectator to scientific endeavor." Hmmm, that probably says something about humanity in general. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] LTE-Lite
Mount the LTE-lite to the front panel with a cutout and a green bezel so you can see the LEDs directly. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Lucent KS-24361 24V DC power requirements
On Fri, Nov 21, 2014 at 8:17 PM, Bob Camp wrote: > Hi > > We’ve been around this one before. The KS boxes are powered by a switcher > brick inside the box. There’s not a lot of reason go super crazy on the DC > input. It’s fully isolated from the case ground. Even leakage / stray > grounds should not be an issue in this situation. I would not run it off of > raw un-filtered rectifier output. Anything that’s at least got a filter > capacitor in it should do fine. > Or batteries. Two 12v batteries in series on float charge not only powers it nicely, it keeps everything going should the mains fail. You won't have to wait for it to reacquire and stabilize after a mains power failure. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Fluke 7260a manual
On Wednesday, November 19, 2014, Szeker K. wrote: > Hi Brian, > Tucker has it, but for $75,- > http://www.etestmanuals.com/Search.aspx?Mfg=FLU&Page=4 > K. Thank you. I have been able to find the manual but, as you indicated, only at a price exceeding what I paid for the unit. Still hoping to find a scanned copy. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Fluke 7260a manual
Does anyone have a Fluke 7260a manual? I am able to use mine pretty well but would like to better understand the interval measuring functions. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Lord Vetinari wall clock
On Sunday, November 2, 2014, Mike Baker wrote: > Time-Nutters-- > > I have been tempted to build a (hacked) wall clock > (after Lord Vetinari) that has an erratic second hand > that sometimes skips ticks and sometimes ticks > several times very rapidly but still keeps "correct" > time. > Clock action, stepper-motor drive, and an arduino. Have fun! -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] float chargers for oscillator backup power
On Sun, Oct 26, 2014 at 10:29 AM, Jim Lux wrote: > There are a variety of inexpensive wall-wart packaged float chargers for > lead acid batteries around. Might be easier to just get something off the > shelf. > > http://www.power-sonic.com/images/powersonic/chargers/AC- > Series_12_Aug_15.pdf > > > http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=172260151 Some of these things are *extremely* noisy. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] LTE-Lite module
On Mon, Oct 20, 2014 at 6:48 AM, Bob Camp wrote: > Hi > > We tend to focus on this or that enhanced feature in a piece of code. It’s > fun to talk about. That’s not what keeps most designs from doing what they > should. By focusing on this rather than the testing required, we set people > up to fail. If you start off the project believing you mostly need fancy > code when you mostly need long term testing instead, you hit a wall pretty > fast. Setting up for one is not at all the same as setting up for the other. > Sounds to me like the hardware and code are pretty straight-forward. The difference comes from the terms and coefficients in the PLL loop filter and those need to be optimized for each OCXO. There appear to be here a handful of people who have a pretty good idea of what those coefficients should be for various well-known OCXOs out there. So why not do the GPSD hardware, software, and then provide the coefficients that will get a handful of the more popular OCXOs available out there to within a decade of optimum, certainly closer than what one would be talking about by just bolting x-random OCXO onto an LTE-lite? I suspect there would be a market in the time-nut world for such a critter. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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 once a day issues" ?
On Mon, Oct 20, 2014 at 2:43 AM, Magnus Danielson < mag...@rubidium.dyndns.org> wrote: > Bob, > > Since the satellite orbit the earth with a period of 11 hours and 58 > minutes, it is actually twice a day. > But then your house has only completed half an orbit. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Wine cooler as temperature chamber
On Mon, Oct 13, 2014 at 6:17 PM, ed breya wrote: > I have experimented with R-12 type mini-friges for this purpose - they can > typically reach minus 40 deg running continuously, but will be oil-starved > at the high vacuum, low flow conditions there, so may not last long > compared to normal service. They're kind of awkward and ugly too - the best > would be a nice small, glass-doored wine chiller, with a normal > refrigeration system built in, but maybe a TEC type would be OK for some > uses. > Stirling cooler. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Homemade GPS Receiver
On Fri, Sep 26, 2014 at 4:07 AM, Dr. David Kirkby (Kirkby Microwave Ltd) < drkir...@kirkbymicrowave.co.uk> wrote: > On 17 Sep 2014 23:38, "Peter Putnam" wrote: > > > > Greetings, > > > > The link below describes a homemade GPS receiver. > > > > It is presented in a detailed and elegant manner that is certain to > appeal to this reflector's subscribers. > > > > Peter > > > > > > http://www.aholme.co.uk/GPS/Main.htm > > I don't understand the units of signal strength > > "The L1 carrier is spread over a 2 MHz bandwidth and its strength at the > Earth's surface is -130 dBm. Thermal noise power in the same bandwidth is > -111 dBm" > > Then goes on to talk about the signal being 20 dB below the noise. > > Unless the -130 dBm is over the whole surface area of the earth, which I > doubt, the units make no sense to me. The units of signal strength should > be V/m, A/m or W/square metre. > > The noise power should be in Watts or dBm. So taking the difference (19 dB, > which is approximately 20 dB) between these figures seems odd to me. > I think you may be confusing field strength with signal strength. What comes out of the feed-line and reaches the antenna connector at the receiver, i.e. signal strength, is indeed measured in watts and can therefore be compared directly with thermal noise power to produce an effective S/N. The antenna itself subtends an "effective" area (aperture) on the surface of a theoretical sphere where the emitter is at the center. So the units of area found in the field strength, i.e. the m^2 in W/m^2, are canceled by the units of the effective area of the antenna, leaving only units of power to appear at the feedline connection. Every unit tells a story. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] SMTP with Trimble Thunderbolt-E
On Fri, Sep 26, 2014 at 8:17 AM, Luc Gaudin wrote: > Hello, > > I need to have remotely access to Trimble Thunderbolt-E to manage it. > I first sort out the physical (network) parts to get the Serial port out > on the network (unit CSE-H53N from Sollae Systems). > For management I am looking to use SNMP. > Is there any system capable to convert the serial information from the > Trimble Thunderbolt to SNMP ? > Some people are talking about proxy agent. > That is probably the only way. > Is any can help ? > The world seems to have split the problem into two parts: using SNMP for monitoring and HTTP for configuration/management of a device. This happened because of the problem of how to manage disparate devices from different manufacturers in a common management platform. So, what do you need to accomplish? -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Eureka, no more Cs, active or passive H-masers or GPSDOs needed
On Wed, Sep 10, 2014 at 9:42 AM, Azelio Boriani wrote: > Really? Not noticed but then it makes sense, anyway a rather expensive > April fools' as the patent was issued and I presume it was done at a > cost. > What you say is true. I was making a joke by suggesting that the patent itself is a joke. I skimmed through the patent but did not read it in detail. There may be some nugget in there that represents something new but nothing jumped out at me. The Patent system is now used aggressively and offensively. Patents are granted for things that actually represent common knowledge and/or prior art. The holders of these patents then use them to attack legitimate companies with successful products, hence the term "patent trolls". So, mostly I was just making a joke. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] Eureka, no more Cs, active or passive H-masers or GPSDOs needed
On Tue, Sep 9, 2014 at 4:26 AM, Azelio Boriani wrote: > Take a look at this patent > <http://www.google.com/patents/US20130342278> and you will learn how > to build the ultimate time and frequency reference. > Yes, but there was an error in he patent. The actual filing date was April 1, not March 16. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) ___ time-nuts mailing 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] time.windows.com statistics
On Mon, Jul 14, 2014 at 11:10 AM, Kenton A. Hoover < ken...@nemersonhoover.org> wrote: > But a perfectly reasonable source of time for SNTP where you just slam the > clock, rather than NTP where you're figuring out drift... > And if you use pool.ntp.org it doesn't matter and this entire discussion becomes moot. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Setting Windows XP clock.
On Sun, Jul 13, 2014 at 3:18 PM, Don Latham wrote: > Whee! Chris: the text box in the xp clock set window is ONE CHARACTER too > short to contain the suggested url. It just gets better and better. > pool.ntp.org. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Antenna
On Tue, Jul 8, 2014 at 5:17 PM, Poul-Henning Kamp wrote: > In difference from the loop which needs none, this antenna needs a > really good earthing. > Loops are a joy. No counterpoise and no worrying about ground/earth conductivity. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Magnetic Resonance Spectrometer - redux
On Sat, Jul 5, 2014 at 10:47 PM, Bob Stewart wrote: > First, an apology. When I changed the topic on my original post, I > thought that would be OK. Apparently that's still a thread-jacking. Sorry. > > I'm still interested in this Magnetic Resonance Spectrometer thing, > though. On page 335 of the pdf linked below by Dave, there's an experiment > with an MRS using water and the magnet from a magnetron available back > then. Apparently the resonant frequency of hydrogen nuclei in water is > 6.131325 MHz in that magnetic field. Did anyone ever pursue this with the > idea of creating a frequency standard, or was the technology just too > primitive at the time? Perhaps it's a repeatability problem from the > magnetic flux standpoint? I can guess that temperature changes would cause > enough of a flux strength change to cause a problem, but that's just a > guess. > The substance recommended was Ferric Chloride as I recall. The characteristic was that the peak occurred quickly even with the rapid change in the B-field. The B-field was modulated at a 60Hz rate, enough to sweep the resonance across the oscillator's frequency. When the nuclei precessed at the frequency of the oscillator, the nuclei would absorb power from the oscillator, changing the plate-current of the oscillator. It was really just a fast grid-dip oscillator. (Well, plate dip oscillator.) Pretty simple. I keep threatening to build a new one that works much better and has a wider range, just to prove that I can. :-) And I can't think of any way of tying this to time-nuttery. If there are others still interested in this topic perhaps we can just communicate off-channel. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Interesting frequency standard project
On Fri, Jul 4, 2014 at 5:27 PM, Hal Murray wrote: > > paulsw...@gmail.com said: > > The key to these systems is that the transmitters have very good > references. > > In the US at least we have no requirement for that level of stability on > the > > MW broadcasts. Though evidently some stations are quite good. I think I > have > > a list some place have to re-look. > > How stable are they? Could they provide a good regional reference if > somebody with a good setup would measure several stations and publish the > results? How often would you have to measure? > > How do you measure the frequency of an AM or FM station? Wait for silence > and process it like CW? > > Any suggestions for a receiver (or whatever) that would be appropriate for > that sort of project? I assume the main requirements are an external freq > in > and a serial/USB port to adjust the knobs. > You might want to go talk to the FMT guys as they do testing against some of the MW stations and know which ones have high-accuracy references. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Loran, GPS, Lightning, Timing
On Sat, Jun 28, 2014 at 10:13 PM, Hal Murray wrote: > > namic...@gmail.com said: > > Fibre optic would seem to be the answer for protection. > > Assuming I use fibers for the data, how do I safely get power to the other > end? > I recommend a kite, wet string, and a Leyden jar. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Magnetic Resonance Spectromater; was Re: Loran, GPS, Lightning, Timing
On Sat, Jun 28, 2014 at 6:55 PM, DaveH wrote: > I built the Van de Graaff generator / electron accelerator with a buddy for > a high-school science project. My Dad was a physicist so was able to > borrow > a vacuum system and not have to make that part. > > Lost to a guy who had done a ruby laser - this was back in 1966. > I built the MRS and won the LA County Science fair and placed in the California State Science fair with it in 1968. I was 13. I also build one of the seismograph designs just for fun. I did not build the quartz reference clock design in the book but used the idea to motivate me to add a quartz reference to the 60Hz inverter I built from the ARRL handbook, using a bunch of DTL flip-flop dividers, to drive a mechanical clock with a synchronous motor. This was in 1969. So I guess that delimits the beginning of my time-nuttery. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Loran, GPS, Lightning, Timing
On Fri, Jun 27, 2014 at 11:34 PM, DaveH wrote: > > I also searched for "Lightning" and found nothing about detecting nearby > strikes, only about protection. Searched from around 1980 back through > 1940. > There are a number of products on the market that make use of lightning detection and ranging. The BF Goodrich "Stormscope" is based on that. There have to be some documents around on its design. It is, in essence, a LF ADF and somehow qualifies the envelope to deduce range to the strike which it then displays to the pilot. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] DIY FE-5680A lobotomy (disable temp compensation)
On Sat, Jun 28, 2014 at 4:32 AM, wb6bnq wrote: > wicking surface. The final question is how much, if any, external oil > cooling would be necessary. That would have to be experimentally > determined. The mineral oil, by the way, has a higher flash point then the > container and is electrically NON-conductive. > But it does have a dielectric constant different from air. How much effect would it have at microwave frequencies? Also, what would its effect be on the optical path from the Rb lamp and through the Rb cell? -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Loran, GPS, Lightning, Timing
On Thu, Jun 26, 2014 at 9:08 PM, DaveH wrote: > The tube was probably the FP-54 > > http://frank.pocnet.net/sheets/141/f/FP54.pdf > > No luck on finding the article - it is not in the Handbook of Projects for > the Amateur Scientist by C.L. Stong > > > http://www.sciencemadness.org/library/books/projects_for_the_amateur_scienti > st.pdf > > I thought it might be as I remember there was a project to detect sferics > but this one used plain 12AU7s and 6AU6s > When I was a kid this may have been my favorite book. I did build the MRS when I was 12. Sucker actually worked too! I was amazed. I have built several things from this and used many of the projects with modern electronics as projects for my students in middle school. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Loran, GPS, Lightning, Timing
On Wed, Jun 25, 2014 at 4:42 PM, paul swed wrote: > I am currently using a 12AX7 as a ELF preamp and have for years. > A note in the coldest part of winter preheat the tube low filament voltage. > They tend to fracture. > It sits 200 ft from the house as far away in the woods as possible. > That said and back to the thread. At these frequencies tubes do work. The > 12AX7 can be found on vlf.it and numbers of tubes will work. They run 12 V > on the plate. They also stand up to nearby lightning very well. > So Diddier now you have no excuse. I can't wait to implement your design on > one of my stm boards. Not sure how to get this back on time-nuts topics > Regards > Try a 6DJ8 instead of the 12AX7. It has a higher GM and a LOT more bandwidth. What kind of risetime are we talking about for a lightning strike? And why not a loop antenna? That should provide plenty of signal but not destructive voltages. I know you are talking about measuring lightning strikes but if you get the impedance high enough, you can actually measure the earth's electric field. (It is about 200V/m if I recall properly.) Interestingly it is affected by the solar flux and solar wind. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Boeing 787 GPS reception trouble
On Mon, Jun 2, 2014 at 10:36 PM, Jim Lux wrote: > On 6/2/14, 7:16 AM, Brian Lloyd wrote: > >> On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux wrote: >> >> O, and since navigation using the ADF and tuning to a AM >>> broadcast station wasn't unusual. >>> >> >> >> Well, it is quite unusual for IFR (instrument flight rules) operation. But >> VFR pilots would sometimes use an AM broadcast station for navigation >> assistance. >> >> > Back in 1980, the examiner asked me how to do it, but didn't make me do it. > He wasn't allowed to. It is not part of the practical test standard for the private pilot certificate. Still, it is useful. I have been flying long enough to experience nearly every form of electronic navigation available in aircraft. I have actually flown an Adcock "A/N" range. I have landed an aircraft in instrument conditions using precision approach radar (PAR or GCA). I have used ADF, VOR, DME, RNAV, LORAN-C, INS, and now GPS. Airplanes haven't changed much but boy the radios sure have! >> I had to learn how to do it when taking flying lessons: it was widely >>> acknowledged ( in 1980) to be nearly useless, >>> >> >> >> Not entirely. I still make sure my planes are equipped with ADF (LF/MF >> direction finding) due to my experience with GPS outages over the >> Caribbean >> and Atlantic. I have experienced outages of over an hour where both my >> panel-mount and hand-held GPS receivers stopped working. ADF was all I >> had. >> I suspect that since I was flying a plane popular with drug-smugglers (a >> Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in >> the Virgin Islands, traveling to Florida on a regular basis. I would stop >> in the Turks and Caicos or Bahamas to refuel.) >> > > I was referring to the "AM station as beacon", and to be fair, they were > all talking about compared to conventional VOR/DME, and maybe if you had > one of them new fangled RNAV units that mathematically transformed VOR/DME > into lat/lon, etc. > ADF is less accurate than VOR/DME. It is much less accurate than DME/DME. It is archaic. But it works. If the beacon is at the airport itself ADF is amazingly accurate for making an approach. It has a unique characteristic that it is difficult to jam. (LORAN-C was better and I *REALLY* miss LORAN-C as a backup to GPS.) There are large stretches of the Atlantic and Caribbean where the only two navaids that are available are GPS and LF/MF NDBs. Sure I can use pilotage/ded-reconing and hop from island to island. But I have now experienced multiple total GPS outages. It makes me nervous the dependence we are developing on a system that is surprisingly vulnerable to a denial-of-service attack. I do hope that LORAN-C comes back. The original idea of the European Galileo system to use LORAN-C to distribute DGPS data was brilliant. The DGPS datalink was itself a source of high-quality time and position information that is nearly impossible to jam. What a concept! Has anyone considered how a large-area GPS outage would effect us? I *really* don't like having all my eggs in one basket. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Boeing 787 GPS reception trouble
On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux wrote: > On 6/2/14, 2:27 AM, Poul-Henning Kamp wrote: > > >> It would be trivial to add a passive GPS repeater to the plane, but >> the airtraffic industry has never been happy about people being >> able to receive navigation signals inside planes, worrying that >> somebody might try to blow up the plane at some specific place >> (or non-place), so that ain't gonna happen. >> >> >> > I don't know that it's that reasoning. It's more about the innate > conservatism of people who make things that fly. > > The reason for "radio receiver ban" originally was fear that Local > Oscillator leakage would adversely affect cockpit instrumentation: > particularly things like low frequency beacon receivers, which were none > too selective, and since navigation using the ADF and tuning to a AM > broadcast station wasn't unusual. Well, it is quite unusual for IFR (instrument flight rules) operation. But VFR pilots would sometimes use an AM broadcast station for navigation assistance. > I had to learn how to do it when taking flying lessons: it was widely > acknowledged ( in 1980) to be nearly useless, Not entirely. I still make sure my planes are equipped with ADF (LF/MF direction finding) due to my experience with GPS outages over the Caribbean and Atlantic. I have experienced outages of over an hour where both my panel-mount and hand-held GPS receivers stopped working. ADF was all I had. I suspect that since I was flying a plane popular with drug-smugglers (a Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in the Virgin Islands, traveling to Florida on a regular basis. I would stop in the Turks and Caicos or Bahamas to refuel.) > but, hey, if all the other radios fail, any port in a storm, etc. About > the only older radio nav technology is A-N ranges (if you believe > Wikipedia, they were gone by 1980 "mostly disappearing by the 1970s") > > Birdies in a consumer radio in your living room or car aren't a big > problem. Birdies in a navigation instrument are a potentially big problem. > They could be and they are. Interestingly enough, the only radios that ever interfered with my VHF nav receivers were my own VHF comm and nav receivers. LO leakage from one radio would show up on one of the others. I have never experienced that problem with any consumer device. Even in the 1980s, there were a lot of planes flying with fairly archaic > radios, although I suspect no commercial jet was using a VFO tuned radio: > they'd be using "banks of crystals" or PLL tuning. In general aviation, > the first non VFO radios were from King in the 60s, and I think > synthesizers came in around 1970 (King KX 170 and 175). I was astounded at > the number of crystals in one of my Narco radios when I took it out of the > plane to fix it (a 1973-74 vintage radio). Half that box was basically a > big rotary switch and dozens of crystals. > A "crystalplexer" radio that was dual-conversion with both LOs using switched crystals. CB radios used the same thing back in the late 1960s and early 1970s. PLL LOs came later. Typical spurious responses in a COM or NAV receiver would be something like > -60dB down, but a few milliwatts leaking from some guy's FM radio on board > would easily be bigger than than that, since the receiver threshold is > about 1 microvolt into 50 ohms (-110 dBm). > That may be true but I have never experienced it, even when I tried. The only time I have ever experienced interference with my comm or nav radios it was from another comm or nav radio in the plane. Most use a 10.7MHz IF which means, for the spectrum from 108MHz-138MHz, you are very likely to have a lot of overlap between LO and desired receive frequency. Once the rule is in place, it's very, very hard to get it removed, because > of the "if we allow X, and a plane has a problem, everyone is going to say > "it was because of X" even if it wasn't, so let's just keep things the > same." Amen. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Toy radiolocation and LORAN envelope
On Tuesday, May 27, 2014, Mark Sims wrote: > I should mention that the circuit that I attached in the previous post > does not output at 49.152 MHz The output is the third (or fifth?) > harmonic of the crystal frequency... > I have had very good luck with these 433 MHz TX modules. Easily received with a ham 70cm SSB RX. http://www.dx.com/p/433mhz-wireless-transmitter-module-superregeneration-for-arduino-green-149254?tc=USD&gclid=CM3Opqf4zL4CFVQFMgodPHEAlw#.U4T1YNq9KK1 Great because there is no need to tweak to make them operate and you can easily do OOK to tx telemetry using a PIC or other uP. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Weather/units question for European members
On Saturday, May 24, 2014, David J Taylor wrote: > > Now the question... I would like it to be able to output data in imperial > or metric units. In what units is the typical wind speed reported > (meters/sec, km/hour, ?). Also air pressure (millibars/hectopascals/ > pascals/?). In the US wind speed is in MPH (civil) or knots (aviation or marine). Atmospheric pressure is in inches of mercury (US) or millibars. I have seen wind speed in m/s in Europe. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] BeagleBone Black NTP server
On Fri, May 9, 2014 at 8:49 PM, Chris Albertson wrote: > On Fri, May 9, 2014 at 1:55 PM, Brian Lloyd wrote: > > > Has anyone here made NTP run on BBB? My plan is to run NTP disciplined by > > my Trimble Thunderbolt on BBB. > > > NTP is likely already installed on the BBB. It ships with the BBB. That may be the case for the Angstrom distro but it is not the case for the Debian distro, which seems to be the future direction of BBB. > Some > configuration is needed to enable the service. Do this first and verify > you can run using Internet pool servers. Then after this is running you > physically connect your GPS then add lines in NTP's config file telling NTP > you have added another ref. clock. > This link: http://the8thlayerof.net/2013/12/08/adafruit-ultimate-gps-cape-creating-custom-beaglebone-black-device-tree-overlay-file/ Seems to have the bulk of the requisite information including building a GPS cape using the Adafruit GPS module. See: https://www.adafruit.com/product/746 This isn't a timing receiver but would probably be adequate for NTP. But since I already have a T-bolt I figured I would use that as my timing source. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] BeagleBone Black NTP server
On Fri, May 9, 2014 at 7:26 PM, Graham wrote: > I too have ntp running on the BeagleBone Black, also without GPS > interfaced. > > However, I stumbled across this website; > > http://the8thlayerof.net/2013/12/08/adafruit-ultimate-gps- > cape-creating-custom-beaglebone-black-device-tree-overlay-file/ > > with details on interfacing GPS but I haven't dug into the details yet but > it looks like a good start. > Wow! Yes. The Debian packages are all out there. I am making a custom "cape" that just brings the 5V 1pps in and converts it to 3.3V for compatibility with the BBB. First step is to configure ntp to run and then add in the hardware support for 1pps and taking to the T-bolt. I will keep all apprised of my progress. Thank you much! > > cheers, Graham ve3gtc > > > On 2014-05-10 00:16, nuts wrote: > >> On Fri, 9 May 2014 15:55:08 -0500 >> Brian Lloyd wrote: >> >> Has anyone here made NTP run on BBB? My plan is to run NTP >>> disciplined by my Trimble Thunderbolt on BBB. If someone has gotten >>> there ahead of me I would like to follow in your footsteps rather >>> than finding the mines in the minefield all by myself. :-) >>> >>> >>> I'm running NTP on it now, but not with GPS timing. >> ___ >> time-nuts mailing 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. > -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] BeagleBone Black NTP server
On Friday, May 9, 2014, nuts wrote: > On Fri, 9 May 2014 15:55:08 -0500 > Brian Lloyd > wrote: > > > Has anyone here made NTP run on BBB? My plan is to run NTP > > disciplined by my Trimble Thunderbolt on BBB. If someone has gotten > > there ahead of me I would like to follow in your footsteps rather > > than finding the mines in the minefield all by myself. :-) > > > > > > I'm running NTP on it now, but not with GPS timing. Ok. Did you build from source or did you have binaries? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] BeagleBone Black NTP server
Has anyone here made NTP run on BBB? My plan is to run NTP disciplined by my Trimble Thunderbolt on BBB. If someone has gotten there ahead of me I would like to follow in your footsteps rather than finding the mines in the minefield all by myself. :-) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] The Problem with Time & Timezones - Computerphile
On Thu, May 8, 2014 at 3:34 PM, Chris Albertson wrote: > I wonder how many people have tried to do what this guy describes, not > knowing that as he says at the end, you don't have to. > Well, I did but it was back in the '70s. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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 length correction
I want to thank everyone for their answers. I was sure I had the geometry right and that the additional latency would make the position "fuzzier" because I kept thinking that the clock was absolutely correct. Of course, the clock in the GPS receiver converges on a time that is offset from absolute time by the delay in the cable. This time offset is equal and opposite to the extra path length for each satellite's range, thus ensuring that the position calculation is independent of connecting cable length. So this corrects for the (apparent) path length error but still leaves a clock offset error which is then corrected by the cable length input value. I get it now. Thank you all very much. This is something that has bothered me for some time and finally seeing the solution makes me feel a lot better about GPS installations in aircraft. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS antenna length correction
I am taking this out of the "New timing receivers" thread as it is only peripherally related. As I think about the geometry of satellite position and path length, it seems to me that, since the geometry is determined by the antenna position and not the receiver position, additional antenna cable introduces a fixed delay value and hence a fixed constant that gets added to each path regardless of direction. It seems to me that this would produce a much "fuzzier" solution to position and/or variation in timing. Knowing cable length and propagation velocity, would allow the software to subtract that constant from all ranges and thus provide a more correct position and time solution. Is this not the case? Does it do something simpler but "good enough"? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] First success with very simple, very low cost GPSDO, under $8
On Wed, Apr 9, 2014 at 11:43 PM, Tom Van Baak wrote: > > You are right in the I don't even need data cycles. All I want is the > > error which is 5,000,000 minus the count. this is hopefully zero. > > Correct. Keep the counter running. No need to zero it, ever. Use > differential measurements. Essentially you are using binary modulus > arithmetic. > Chinese remainder theorem. Use that and stop worrying about how big your word is. Since we have these really great integer divisors we can use between 1e7 and 1e0, it becomes trivial. Your counter word only needs to be large enough to handle the maximum possible accumulated error in an interval. In fact, you probably can get by comfortably with an 8-bit counter. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] First success with very simple, very low cost GPSDO, under $8
On Wed, Apr 9, 2014 at 1:34 PM, Hal Murray wrote: > > > But I think you over looked one point that makes this project easier: We > > KNOW 100% for certain that the interrupts happen only once per second. > So > > the foreground code knows for certain it has exclusive access to shared > > variables for a given period of time. There is zero chance of a problem > in > > the next .999 seconds after an interrupt. > > Actually, you don't know that. You know that's the way it's supposed to > work, but there are all sorts of ways that things can (and do) screw up and > making that sort of assumption can lead to problems that are very hard to > debug. > So create a semaphore that says who owns the variable. Or, better still, us a message-passing executive. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WWV 12 Hz doppler shift
On Mon, Mar 31, 2014 at 4:32 PM, nuts wrote: > On Mon, 31 Mar 2014 13:54:04 +0200 (CEST) > "iov...@inwind.it" wrote: > > > Seehttp://www.spaceweather.com/ Antonio I8IOV > > ___ > > I had considered modifying one of my fully synthesized radios to use a > GPSDO. Now I regret not getting around to doing this since I could use > it to see this shift. > Just get a Hermes board. Used to be available from TAPR but now you get it from Apache Labs. See: https://apache-labs.com/ If you want just the board, get that. It is the complete receiver and sufficient drive for an external PA (or transverter). If you want a 10W PA to go with it, get the ANAN-10. If you want it with a 100W PA get the ANAN-100. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Beaglebone NTP server
You know, we have two threads going on here for both GPSDOs and NTP servers. Frankly, the device I want in my shack is a box that does both. I would love to have a BBB be an NTP server but also discipline an OCXO. I would like it to have a nice distribution amp as well for the 10MHz reference signal. Lastly, it should probably have a really cool Nixie tube display of UTC. (OK, LCD is cheaper but not nearly as cool. Maybe big, bright, 7-segment LED displays?) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Beaglebone NTP server
On Wed, Mar 26, 2014 at 7:17 PM, Bob Camp > wrote: > Hi > > With a GPIO pulse width should not be an issue. With RS-232 you might have > needed a pulse stretcher. > That is what I was thinking as well. Any suggestions on software issues in getting this running? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Beaglebone NTP server
On Wed, Mar 26, 2014 at 5:05 PM, Bob Camp wrote: > Hi > > The quick / dirty / easy way for any of the NTP stuff with a GPSDO is to > simply run the PPS in. PPS into serial is one way, pps into a GPIO is > another way. > Well, yeah. I figured that I would run the 1pps from my T-bolt to a GPIO line with appropriate clamping to 3.3V. But if anyone has done this before and run into anything of note, that would be nice to know ahead of time. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Beaglebone NTP server
On Wed, Mar 26, 2014 at 4:51 PM, Henry Hallam wrote: > Hi Gabs, > > I have a Z3805A and a Beaglebone, and would like to set up an NTP > server for the lab. Any kernel drivers and/or setup hints would be > appreciated :) > Actually, I was thinking of doing exactly the same thing. I am interested in any answers for this too. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Equinox and sidereal time
On Sunday, March 23, 2014, Neville Michie wrote: > Hi, > can anyone out there point me to a source > for the exact time of the equinoxes and solstices > so that I can synchronise a sidereal clock? Check the USNO's website. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Aircraft ping timing
On Sun, Mar 23, 2014 at 3:37 AM, nuts wrote: > > Note that the ADS-B mentioned is just a fancy version of the > transponder that was turned off. > I guess it depends on your concept of what a transponder does. Yes, ADS-B does transmit in the same band as the standard transponder (1090MHz) but the function and content of the transmissions are very different. With the standard mode-A, mode-C, and mode-S system, the transponder only replies to interrogation, and then only replies with the 12-bit ID code (mode-A) or 12-bit ID code plus 12-bit altitude code (mode-C). Mode-S turns it into a two-way data link and adds a bit more more data (aircraft ID) to the reply. The key here is that, if nothing is sending an interrogation, the transponder is silent. The interrogating station must do the position determination based on distance and azimuth of the reply. In the case of ADS-B, the transponder is no longer just a transponder. It is a full transceiver with an application, ADS-B, sending unsolicited data. In this case the aircraft actively transmits its position and velocity data along with its ID. No interrogation is required. Anyone within range and with a receiver can pick up the signal and determine the location of the transmitting aircraft. This means it is possible for a receiver to collect this data passively. The major problem with ADS-B is that they came up with two systems and, rather than fight it out to determine which would win, they just adopted both systems. So we have ADS-B on 978MHz using a bit more sensible modulation and framing, and on 1090MHz using the older OOK pulse-code modulation (1090ES). And to add insult to injury, they have mandated that anything that flies at FL180 (18,000') or above (meaning all airliners) must use 1090ES. The transmission mode for 1090ES (extended squitter) is very inefficient. The signal is broad as a barn door due to the use of pulse code modulation using on-off keying. Each transmission requires 5 frames. The end result is that it isn't going to take a lot of airplanes transmitting in the same airspace before you saturate the channel. So you have two separate-and-incompatible ADS-B systems flying around. The FAA "solved" this problem by deploying a series of ground stations that will repeat ADS-B data from one channel onto the other. If a ground station detects transmissions on 978MHz, it will repeat them on 1090MHz and repeat transmissions from 1090MHz onto 978MHz, otherwise it is silent. This means that a receiver-only system is not guaranteed to see all traffic unless one has receivers for both bands. If an aircraft is to be completely autonomous for traffic detection, the aircraft must transmit and receive on both bands. Alternatively it can transmit and receive on 978 and rely on the ground stations to repeat the 1090ES traffic. Also, because of the capacity limitations of 1090ES, the FAA does not data link weather data on 1090ES. That is only available on 978MHz. So any aircraft wishing to avail itself of the ground-based weather radar data and ground weather reporting must have a receiver for 978MHz. Bottom line, ultimately every aircraft is essentially going to need both systems. (I'm sorry but the level of stupidity that led to the ADS-B design as it now stands just boggles my mind. You have to work at it in order to take something so conceptually simple and make it this brain-damaged.) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] NIST time services
On Sat, Mar 22, 2014 at 3:53 PM, Chris Albertson wrote: > Thanks, Yes of course "ARM" refers only to "ARM" > > Would you know which other systems include the PRUs? Is it only in > the TI products? It seems like an ideal solution to the problem of > non-deterministic latency. > > This may not even be required. There is no point to extreme levels of > accuracy because the weak link with any NTP server is the Internet. > NTP's purpose is to transfer time over unreliable data links and these > links will always be the limiting factor. > NTP running in broadcast mode over a local Gig-E network shouldn't be too bad. I suspect timing jitter is pretty low. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] NIST time services
On Sat, Mar 22, 2014 at 2:24 PM, Chuck Forsberg WA7KGX wrote: > I can see a use for an inexpensive GPSDO with a built-in > gigabit ethernet or USB3 port powering an NTP server. > Why not a BeagleBoneBlack with a GPS module that has 1pps out connected to an I/O pin. For that matter, add your OCXO and let the BBB discipline that at the same time. I bet you can come up with an NTP server and a GPSDO for not more than $200. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Aircraft ping timing
On Fri, Mar 21, 2014 at 11:22 PM, Joe Leikhim wrote: > In retrospect it is kind of crazy that fleet owners will put tracking > devices on $100K semi trucks and cranes yet $100 million aircraft have to > rely upon 60 year old technology (Transponders) and ACARS to keep track of > them. I don't question the utility of TCAS and Transponders, it is just the > issue of not tracking such a valuable asset that is kind of crazy. Can you > imagine how much an aircraft like that is worth in spare parts alone? -on > the world market. If I were an insurer I would be asking questions of the > industry. First, just because you imagine there is a problem does not mean that there is a problem. It is possible to determine the position of every airplane but they just don't go missing all that often, as this recent event illustrates. If this were a common problem, we wouldn't be talking about it. ;-) But the solution already exists and is being deployed - ADS-B. By 2020 each aircraft will be beaconing its ID, position, and velocity vector on 978MHz and/or 1090MHz. The solution for long over-water tracking is either to receive and relay such information, or put up some LEO birds to wiretap and forward the broadcasts. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Frequency Counter using OCXO and MCU
On Wed, Mar 12, 2014 at 10:48 AM, d0ct0r wrote: > > LCD connected to the same MCU. And it has relation to the core clock too. > So, nothing on LCD before I reset entire MCU. I think initial incorrect > core clock reading cause a lot of issues. Probably my only option will be > to implement some external relay and timer to turn on MCU few seconds after > OCXO. Or may be to put 10Mhz oscillator to PCB and connect OCXO output in > parallel to it (not sure if its good idea or it will works). > Why not debounce reset from power-up using an RC network and a Schmitt trigger? Set the time constant so that it will hold the mpu in reset until power has been asserted long enough to ensure that the OCXO is producing output. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Why using HP5370 ext-ref is (maybe) a bad idea
Instead of using the external reference input, any thoughts on actually disciplining the internal OCXO to bypass the problem? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] 5370 processor boards available
On Fri, Feb 28, 2014 at 8:20 AM, Didier Juges wrote: > If you use a flash-based embedded ARM board, how much is it worth to you > that it works everyday? How much is it worth to you that you do not have to > rebuild it once a year or once a month? > > I have several of them and I corrupted one a couple of years ago. It was > not something that was on 24/7 and it was not a power outage. I turned it > off myself and it did not come back. OK, you turned it off and it did not come back. Sounds like a different failure from what we are talking about. You did a normal shut down and it failed. Of course we are going to have some number of random failures in normal operation. S--- happens. And I agree that, if the system has a R/W filesystem and there is no power-fail processing provided, odds are good the filesystem will become corrupted during power-fail at some point in time. But has anyone determined whether or not that happens with the BBB in question? Does it have PF processing? Is there PF detection? Does the PSU hold power up long enough for PF processing to complete? > Fortunately, it had a pretty much stock distribution on it and it was easy > to rebuild. I am more careful now. Yet, my Raspberry Pi is on 24/7 and it > survived the many storms we have had in the last 2 months (Florida is the > lightning capital of the world, as they say) > And the other side is that a group of negatives does not prove the problem does NOT exist, it only suggests that it does not exist, it only suggests that the probability is lower than originally thought. It is perfectly OK to not care, but most of us are used to equipment that > powers up each time you need it and that only requires to flip the power > switch to off when you are done. Ah, that is not the point. I agree and I *DO* care. I want my test equipment to power up and work EVERY time. I am still waiting for someone to show that this is a real problem and not just an imagined problem. > It is bad enough to have to properly close Windows (replace with your > favorite OS, they all have similar requirements) and most open apps when > you are done before turning the switch off on your desktop system. > Most of them let the processor turn off the power after completing shutdown. That does seem like a useful approach. Allow the "power" switch to initiate the system shutdown and then let the system remove power. Of course, this is a hardware change and in this case the replacement CPU board is supposed to be a drop-in replacement. The fact that it may do it 100 times in a row and not fail is not great > consolation if it fails at 101. It is a documented failure mode, not pie in > the sky. > N, it is STILL pie-in-the-sky because, as far as I can remember back up this thread, no one has experienced an actual failure, only imagined that it is possible, which gets back to my original question: is this a real problem? It is only an issue with regard to your own expectations. Do not disparage > people who expect more of the hardware than you do. > I am not disparaging anyone. I am approaching this from an engineering standpoint. When presented with a problem from a client/customer, the first thing to do is to qualify the report. And I am not saying that it is NOT a problem, only that it MAY be an IMAGINED problem where none exists. I have no ego involved in all of this. I actually don't care if I am right or wrong. I am presenting a counter thought process in an attempt to balance the discussion. I would happily pay the $5 and then buy the beer for a good laugh after the fact. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] 5370 processor boards available
On Thu, Feb 27, 2014 at 9:03 PM, paul swed wrote: > Looks like I win the fiver. > Really? You power-failed it and corrupted the file system? > Johns created a great board for the 5370. > However you can't just turn the 5370 off as this lazy person is used to. > Really? You tried it and screwed up the file system? > Plus I really have to say after a full day of time-nuttery I won't remember > to shut the linux down. > So thats the need good old shutdown controlled by the power off button. > But as Tom says please send the thoughts to John. > Regards > Paul > WB8TSL > > -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] 5370 processor boards available
And after all that, *STILL* no one has been able to answer the question, "Is there a problem that must be solved?" Oh, lots of supposition, rules of thumb, boatloads of experience, etc., but still no determination that something really needs to be solved. One of the interesting things that came from building the internet protocol suite was a whole bunch of, "well, let's just try it and see," that resulted in a whole LOT of, "Oh, wow, it turns out it's just not a problem because it just doesn't happen." I would be willing to lay a fiver that this is one of those situations. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] 5370 processor boards available
It is interesting to watch this thread. The most interesting thing is the fact that no one has asked or answered the basic question: is there a problem? There are a lot of solutions for what may be a complete non-issue. Given that Linux and BSD are reliable and stable on standard PC platforms connected to mains power without a UPS, that suggests to me that there is likely no issue. Sure, back in the bad ol' days you had to sync;sync;sync the filesystem prior to shutdown and then, if there had been a power fail, fsck it on power up. But those days have been gone for a LONG time. The modern filesystems reduce the exposure to the possibility of file system corruption to a tiny probability, and then the system further reduces that by providing a power-fail detection system that allows the critical pending writes to be flushed prior to final power-fail, thus leaving the FS in a completely deterministic state. I suppose that on the night of a full moon when the lightning flashes and the dog barks, conditions might be right to corrupt the file system, but then, that could happen when the battery goes dead or catches fire too. ;-) It seems to me that the bard put it pretty well, "... much ado about nothing." -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] 5370 processor boards available
The only time there is any exposure is during a write operation. When the processor board is used to run the 5370, how often is data written and what is the exposure interval? I would be willing to bet that Linux already has a power-fail NMI input. I would bet that you can find out what the worst-case PF NMI latency is and then ensure that the PS output stays up at least that long without having to worry about a battery or "super cap". (I bet PF latency is under 1ms.) In that case, all you need to do is assert the PF interrupt line. Hmm, check to see if it is already there and based on nothing more than sagging Vcc/Vdd. I bet it is and therefore this whole discussion may be moot. But the idea of making the boot partition RO and the /var partition R/W makes a whole lot of sense to me. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Serial port splitter s/w
On Wed, Feb 26, 2014 at 2:05 PM, Chris Albertson wrote: > > Chris, even with Wi-Fi connected computers, mostly running Windows, there > > is a huge difference between talking to a stratum-1 server on my LAN > > compared to running just Internet servers. Our experiences differ, as I > am > > on a cable modem connection from the UK's Virgin Media. Folks need to > > measure what performance they are getting and choose their own best path, > > otherwise it's guesswork. > > > > Yes, exactly. It depends entirely on your internet connection. As soon as > you get even "slow" 10Mb/s fiber the distinction between LAN and Internet > starts to melt away. The problem with Cable TV is that it is a shared > connection with who knows how many others. Shared media have collisions > with back off and retries and are not deterministic. > Not generally with broadband. (True broadband that is, such as Internet-over-cable. I do find it annoying that all higher-speed, i.e. non-dial-up, access is referred to as "broadband".) There are no collisions coming downstream because there is only one source -- the head end. There you just have variable queueing delays if a burst of traffic exceeding downstream capacity arrives at once. Collisions are possible on the upstream but less likely. I do have a local NTP server. I had one back in the days of dial-up phone > modems and still have one with my current fiber connection. I was just > pointing out that the local NTP server is less useful as the Internet > connections get better. > True, but far more deterministic. As you suggest, a local NTP server is independent of upstream traffic, queueing, and backoff/retry delays. Personally I would like to have a local stratum-1 source for that reason. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Different breed of time nuttery
On Sun, Feb 23, 2014 at 10:11 PM, Daniel Mendes wrote: > > This is a different breed of time nuttery than usual in this list but i > think that at least some of you will enjoy it: > > http://www.behance.net/gallery/FLUX-1440/2420150 > > Found it at hack a day > That is just ... cool. But I thought of a way to do the same thing without the rope and mechanical parts. I figured I can replace the ropes with rows of LEDs. Then I can turn on the LEDs to simulate the white rope and turn them off to simulate the black marks. Now you don't need the bearings and stepper motor. Pretty neat idea, huh! -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WWVB antennas
On Sat, Feb 22, 2014 at 11:56 AM, J. Forster wrote: > You are about 1/4 the distance away. Inverse square law. > If we were in free space I might concur on the inverse square law. We aren't and propagation certainly has an effect on path loss. I posted signal levels coming from my Pixelsat loop for WWVB at my location right now (-82dBm at 1800Z) which might be a useful datum for someone contemplating building or fielding a WWVB receiver and considering this particular antenna. (More data, the S:N is 36dB based on an 11Hz bin-width for the FFT I am running right now.) BTW, the distance from WWV in Ft. Collins, Colorado, to my antenna is 1,346.75km, great circle ground route. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WWVB antennas
On 2/21/14, 2:21 PM, Robert Roehrig wrote: > John Forster said: > > "WWVB is hard to detect w/ a 3-foot diameter HP shielded loop w/ integral > preamp & 2 stages of mechanical filters. (HP 117A). The other half of the > time it was undetectable. Paul S uses a loop that is much larger." > > I am near Chicago and I have 2 60 kHz antennas. One is a ferrite > rod type and the other a 5 foot diameter loop. Both are tuned > and feed identical 2 transistor preamp. The loop does work better. I am in San Antonio, TX, and I use a Pixelsat untuned loop. It receives WWVB just fine. It also receives pretty much everything from DC-20MHz just fine. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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 WWVB modulation format receivers (NOT)
On 2/20/14, 11:35 PM, Hal Murray wrote: > Can somebody give me a lesson in the tradeoffs between number of bits and > sampling rate? Sure, the Shannon-Hartley Theorem. See: http://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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 WWVB modulation format receivers (NOT)
On 2/20/14, 11:08 PM, John Marvin wrote: > I have an OpenHPSDR Hermes and it has no problem receiving WWVB; > however, since I live in Fort Collins - Colorado, part of the success > might just be the strong signal. I wonder if I could just stick a piece > of wire into one of the channel inputs of a 192Khz sample rate audio > interface (especially if it had a good low noise mic preamp) and decode > WWVB from baseband audio! Yes, presuming that the mic preamp doesn't cut off near 20kHz. Some do. 192kHz sampling ADCs are not all equal in their performance up there. Just because they sample that fast doesn't mean they are flat out to the Nyquist frequency. Just remember it is a spec game with the audio ADC people. Sure they may sample at 192kHz but many (most?) really are no better than those that sample at 48kHz or even those that sample at 44.1kHz. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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 WWVB modulation format receivers (NOT)
On 2/20/14, 10:35 PM, Graeme Zimmer wrote: >> I have a Kenwood TS-940S transceiver that can receive 60 kHz but I >> have never heard anything > > Where are you? It must be deaf as a post. Most ham receivers that purport to have coverage down there really don't. I thought my Flex 5000 should hear that handily but all it ever heard were images of the AM-BCB. The HPSDR Hermes board in my ANAN-10 hears WWVB a treat. Direct Down Conversion (DDC) is your friend and anyone considering playing with this stuff really needs to be thinking about a DDC receiver. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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 WWVB modulation format receivers (NOT)
On 2/20/14, 8:51 PM, Bob Camp wrote: > Hi > > You can get parts in the 18 bit and up range for not a whole lot of money > with rational sample rates for a WWVB receiver. Analog Devices and Linear > Tech both make some interesting looking parts. They get you into the >=100 db > dynamic range area. Yes. 192ksps is considered audio and is now available as a common part for consumer devices. Or go with a 1-bit part and then decimate the hell out of the result. > Even with a lower bit count part, you pick up some bits in the downsampling > process. As long as you have enough noise to keep things moving, you can > track pretty far down into the crud. GPS receivers do that sort of thing all > the time. > > Since this is slow audio after the CIC decimator, things like ARM chips > probably have enough DSP horsepower to do what you need to do. The decimator > it’s self is not terribly taxing if you don’t go too crazy with the rate > change. This all makes more sense to me than hacking a bunch of op amps and filter hardware. Use a low bit-depth but fast part then decimate. If it is fast enough you can get by with very simple anti-alias filtering. Like you said, if you have enough noise to randomize the LSB you are good to go. I bet that the AMBCB provides more than enough randomization power. And if it doesn't, just inject enough broadband noise to randomize the LSB. The rest is just SMOP. Just for giggles I took a look at the output of the ADC on my Hermes board. The input is my Pixelsat loop which is broadband from 50kHz to 30MHz. (It has significant output down to below 20kHz.) The ADC of my Hermes HPSDR board is being fed with the raw output of the antenna with no filtering so the ADC is seeing everything from DC to 60MHz that comes out of the antenna. Peak ADC level at my location is -40dBFS. I live about 35km N of San Antonio so my location is neither particularly RF quiet nor noisy. Seems like the 16-bit ADC has plenty of headroom. I hear WWVB very handily on this setup and I am seeing -83dBm out of my antenna for WWVB on peaks. (Actually the S:N is pretty good at over 16dB in a 300Hz bandwidth.) This is near noon local time. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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 WWVB modulation format receivers (NOT)
On Thursday, February 20, 2014, J. Forster wrote: > The large amplitude swings happen on a very short time scale too. > Certainly <1 second at times. 8-bits is 48 dB. 16-bit parts at 60kHz should be cheap now. Why bother with AGC? Just make sure the ADC doesn't clip. <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Good use for an HP 10811
On Mon, Feb 17, 2014 at 8:31 AM, David J Taylor < david-tay...@blueyonder.co.uk> wrote: > @uhf_satcom just tweeted: > > "Finally, a signal from ESA Rosetta @ 755Million Km distance! Best DX so > far @uhf_satcom FFT; http://pjm.uhf-satcom.com/ > twtr/rosetta_8422496_170214.jpg ... - antenna 1.8M diameter" > > https://twitter.com/uhf_satcom/statuses/435339066024808448 > > Hope the link works! > > His receiver chain is synced to an HP 10811, allowing him to use sub-Hz > bandwidths to get that singal with just a 1.8 m dish. Very well done! > > (and apologies for it being frequency and not time!) > But it is! Time is just 1/f. Or is frequency 1/t? I can never remember which is which. ;-) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] TIC model
On Sat, Feb 15, 2014 at 7:10 PM, Tom Van Baak wrote: > For Arduino and other less fortunate uC you can always use external chips > to obtain optimal and jitter-free charge/discharge timing. I'm not that > familiar with Atmel chips; could capture/compare be used instead of > interrupts somehow? > One should investigate the Propeller. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Now For Something Completely Different...GPS Security
On Fri, Feb 14, 2014 at 7:45 AM, J. Forster wrote: > You should not denigrate PhotoMultiplier tubes. > > They are virtually perfect, almost noiseless, detectors. With the right > photocathode, they are capable of QEs >50%, spectral response from the VUV > to near IR, and dark counts <1 PPS, with maximum count rates >10 MPPS. > Thay can easily have current gains of >10E+6 > Really? I used to work on photon-counting systems for photometric astronomy. As I recall, the best quantum efficiency I had ever seen was around 21%. Which cathode material are you talking about? Conversely I remember working on current amps for photodiodes. The photodiodes I was playing with had QEs of 90% but, of course, they had no current gain. Detecting individual photoelectrons is a challenge. Yeah, PM tubes are very cool devices, especially if you cool them to reduce the emission of thermal electrons. ;-) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Now For Something Completely Different...GPS Security
On Fri, Feb 14, 2014 at 8:14 AM, Paul wrote: > Perhaps my browser is too conservative but it looks like you have to be a > subscriber to read the Financial Times article. > > Here's one about eLoran vs. GPS jammers which has some security > implications. > > http://nakedsecurity.sophos.com/2014/02/13/revamping-an-old-technology-to-jam-the-gps-jammers/ Yes. I thought it criminally stupid when the US shut down its LORAN service. I thought that Galileo, with its eLORAN backup and distribution of WAAS data, was brilliant. For aviation the US kept its antiquated network of VORs and discarded LORAN, even though the annual maintenance and operation costs were about the same for both. And LORAN provides more accurate positioning than VOR (but not DME-DME and no one bothers to use DME-DME, go figure). -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Arduino GPSDO with 1ns res TIC
On Thu, Feb 13, 2014 at 8:36 AM, paul swed wrote: > Lars has done a very good job here and good to see the comments and > excitement. > Have to agree with HAL that holdover is far more than a second and I am in > a good location with the GPS antenna at 90'. I see my 3801 go into holdover > occasionally and its not seconds. > > Cheapest tinker 10 Mhz is a Xtal with a varicap diode in circuit to adjust > frequency. > Sub $ 5 I would guess. > One can find 10MHz VCTCXOs on eBay for under $10. That makes life a lot simpler and makes the construction simpler too. And if you don't mind SMD there are new sub 1ppm VCTCXOs available for under $10. On the latter watch out because some of these oscillators use digital temperature correction and while they meet spec, the correction is quantized. Make sure the temperature correction is analog. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] clock and cannon at noon story
On Tue, Feb 4, 2014 at 6:22 PM, Michael Blazer wrote: > Wouldn't the watchmaker notice that his clock is always a few seconds > fast? If the cannon is a mile away, the watchmaker would be adjusting the > clock so that 'noon' would sound around tea time after about 10 years. > Now THAT is serious time-geek humor! -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] housing multiple GPS timing receivers in the same box.
Get a signal splitter from minicircuits specifically designed with a passband tailored for GPS that has DC pass-through to power the antenna and LNA. If you can't find one that has DC pass-through then you will need to add a power injector to power the antenna/LNA. Here: http://www.minicircuits.com/pages/npa/ZAPD-2DC+.pdf On Tue, Feb 4, 2014 at 7:08 AM, mike cook wrote: > Hi, > Till now I have been putting receivers in individual boxes. So to limit > the growing number of boxes, I want to put two Resolution-T SMT receivers > in one box, sharing power and antenna inputs. My question is " How best can > I share the antenna input, minimizing any interference between the > receivers?" . Will any interference matter? For example, I can easily > connect three bits of shielded coax in a "Y" , but will probably get > reflections from each receiver. As the cables will only be about 15cm long, > would it matter? How about the DC antenna supply? The antenna DC will NOT > be powering an antenna as it passes through a DC blocked splitter used to > share an antenna between most of my receivers. I might be able squeeze a > Mini-Circuits splitter in the box and DC-block both outputs but that may be > overkill. What discrete circuitry might be a replacement? Will the "Y" do > it? > > Someone must have already succeeded with this type of config. > > Thanks in advance for your input. > > Regards, > Mike > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] PICPET- was Affordable (cheap) COTS (etc)
On Thu, Jan 23, 2014 at 2:00 PM, Tom Van Baak wrote: > > Has anyone else looked at the Parallax Propeller processor for timing > > functions? > > Hi Brian, > > Oh yes. Really nice chip. But for precise timing applications I had huge > problems with phase and temperature stability of its internal PLL. I tried > half a dozen different boards purchased over several years. Tech support > was not interested in someone who worried about nanoseconds. > Well, my disciplining code is going to run as an FLL rather than a PLL to generate the correction for the OCXO or the Rb reference. I didn't think that noise on the PLL multiplier to take the clock from 10MHz (using the OCXO or Rb as the processor clock) to 80MHz would hurt when I am accumulating clock cycles over many 10's of seconds. OTOH, one can clock the processor directly from the reference without the processor clock PLL and run the CPU at 10MHz. The Propeller is static CMOS and will run at any clock speed down to DC. They spec the clock input up to 8MHz but say that it will clock just fine at 10MHz. The PLL will operate at powers of 2 up to 2^4 (16). Most people use a 5MHz crystal and the x16 PLL to clock the processors at 80MHz. I have been told that the Propeller will run at 100MHz just fine. > The architecture is really interesting, but it is such an odd chip, with > almost zero market visibility these days, that I set aside the goal of > using it as the basis of a general purpose 8-channel 6 ns precision > counter. You can find various timer and counter examples at > obex.parallax.com. If you make progress on the project, please let me > know, ok? > Wilco. There are some nice things out there using the propeller. By contrast, the PIC chips I use are fully synchronous so when you use 10 > MHz atomic references the clock/output jitter and phase stability is almost > below what I can measure here. Same with the Propeller. You can clock it directly from the 10MHz reference without using the PLL and then all 8 cores are running synchronously. (They do anyway but usually they are running at 80MHz. I need to try to see just how fast I can run the main clock input.) I just thought that, while the PLL would have a bit more jitter, having the extra 3 bits of resolution would be useful in accumulating the error. > Maybe under 2 ps. So that's why I use PIC's as the basis of all my picDIV > and picPET projects. But I'm open to using something different in the > future. > It does seem to be a very interesting processor and seems to me ideal for performing timing functions. One can easily use it to generate pulses at integer divisors of the system clock. At that point one would definitely not want the jitter from the PLL. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] PICPET- was Affordable (cheap) COTS (etc)
Has anyone else looked at the Parallax Propeller processor for timing functions? It has 8 cooperative cores and has a number of intrinsic timing functions for measuring intervals accurately, or for generating tightly-timed repetitive pulse trains, within the frequency accuracy range of the processor's clock. (Up to 80MHz by spec but the chip runs at 100MHz just fine.) One can dedicate one or more cores to performing the low-level timing functions while using another core to handle housekeeping functions asynchronously. The only real limitation I have encountered is no built-in A:D or D:A. (Low-pass filtered PWM is how I handle D:A usually.) The processor is 32-bit throughout so one can do reasonable timing operations using integer arithmetic. Using the Propeller to discipline an oscillator using 1pps would be trivial. Use the oscillator to be disciplined as the processor's clock and use the 1pps to gate an accumulator. (Use the internal PLL to multiply the reference oscillator up to 40 or 80 MHz to increase resolution in the accumulator.) This operation is performed with a single machine instruction. You just let one core sit there and process the error accumulation from the reference and the 1pps while another core processes the error and sets a third core generating the PWM error signal to correct the reference. Using multiple cores means that one really doesn't have to worry much about interrupt latency (just poll) or race conditions. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Local Solar Time Clock
On Sat, Jan 18, 2014 at 10:09 PM, David J Taylor < david-tay...@blueyonder.co.uk> wrote: > I am looking for a physical clock (not software) that will indicate local > solar time. IOW when the sun is at its highest point, the clock would > reliably read 12:00 throughout the year. > > Is there a commercial product or kit available for this? > For a mechanical clock, probably not. The problem is demonstrated by what I suggested that you do with a stick and pebbles. By marking the position of the sun to locate the point where the sun is highest in the sky you identify local solar noon. By marking the position of the sundial's shadow at a fixed time every day relative to GMT you will find that, over the course of a year, your shadow will inscribe an analemma, whose lateral displacement represents the correction factor between sidereal (GMT) noon and local solar noon. This is all caused by the tilt of the rotational axis of the earth which causes the poles to be displaced either advanced or retarded relative to the centroid at the equinoxes. (Equinoxae?) So your mechanical clock would need to speed up and slow down in a smooth fashion twice over the course of a year. Pretty hard to do with a mechanical clock. Definitely a job for a uP. BUT a really cool thing would be to interface a camera to find the point in time where YOUR local noon actually occurs and corrects the clock. Automatic meridian circle anyone? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Local Solar Time Clock
On Sat, Jan 18, 2014 at 2:25 PM, P Nielsen wrote: > I am looking for a physical clock (not software) that will indicate local > solar time. IOW when the sun is at its highest point, the clock would > reliably read 12:00 throughout the year. > Put a stick vertically in the ground. Once a week place pebbles along the tip of the shadow of the stick from about 11AM until about 1PM *standard* time (not daylight savings time). Find which pebble is closest to the stick and leave it there, removing all other pebbles. Repeat for a year. At that point in time you will have a collection of pebbles that describes a figure '8' (an Analemma). Label the each pebble with the date. Now you can find local solar noon very accurately. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WAAS.....
On 1/9/14 7:53 PM, J. L. Trantham wrote: > I have had loss of GPS position on a 'hand-held' unit (Garmin GPSMAP 396) > when flying into PNS. When I switch to tower frequency (119.9 MHz) the unit > loses its position. I think it is related to some 'spur' related to the #1 > Nav/Com (King KY197) being tuned to that frequency. If I replace the unit's > GPS antenna with the 'remote' antenna, secured to the windshield, all the > problems go away. > > I think it is a 'spur' of the appropriate magnitude when the 'portable' > antenna is still installed. Before a panel-mount GPS in an airplane may be used for IFR (instrument) flight it must be tested with the comm radios set to a number of harmonically-related frequencies to ensure there is no interference with the GPS signal and then signed off. So, yes, it is very likely a harmonic of one of your comm radios was jamming the GPS. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WAAS.....
On Thu, Jan 9, 2014 at 12:21 PM, Hal Murray wrote: > > br...@lloyd.com said: > > navigation system that is going up. For that matter, is anyone running > one > > of the new multi-system receivers? I notice that Garmin is selling them > as a > > matter of course now. The prevalence of jamming might be the reason why. > > Aren't the alternatives using frequencies that are very close? Close > enough > so one the same receiver can pick up all the satellites. How much wider is > the total bandwidth? Does the filter on a typical L1 antenna reject, or > maybe just weaken, any of the other systems? > GLONASS works on 1602.0 MHz (+/- ~4MHz). GPS works on 1575.42 MHz. There is only about 20 MHz difference at 1.6GHz so it is entirely possible that a wideband (noise-based) jammer would take out both, but be quite limited in range. A narrow-band jammer would probably take out GPS but GLONASS uses FDMA and separates each satellite in frequency by 0.5625 MHz. That means that a narrow-band jammer might get one, two, or three birds but probably not all of them. It does seem to me that a combined GPS/GLONASS receiver is going to be more resistant to jamming than a GPS-only receiver. And I make no claims to being an expert. I am just mostly thinking aloud here. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WAAS.....
On 1/9/14 12:20 AM, Joe Leikhim wrote: > > GPS jamming, intentional or not is pretty serious, and the FCC takes > this seriously, but unless you have some pretty hard evidence they may > not find it. In my case my most interesting outage was when I lost all GPS while over the Atlantic ocean between Haiti and the island of Great Inagua in the Bahamas. It is a bit difficult to stop and look around while flying at 8,500'. I took it for a general GPS outage but now I suspect jamming. When I was living on my boat in the Virgin Islands (I built a WiFi-based WISP for marinas and anchorages in the USVI) the US Customs interdiction boat was only about 4 slips away from me. I often talked with the agents either going out or coming back from "a run". (You do NOT want to screw with these guys! They are armed to the teeth!) I now realize that they would jam GPS so that the druggies couldn't get their drops right. (They also admitted that, most of the time, they couldn't find the drug runners' boats anyway and figured they got less than 5% of what they were after. So much for the "War on Drugs.") The US Coast Guard had (has?) a base on Great Inagua. They run a fleet of helicopters out of there for __ (redacted - read between the lines). I got a kick how, when they were coming and going, they would announce their movements to other aircraft using a civil ID rather than their military flight ID. At this point I suspect I may have been shadowed and my GPS jammed. Thank god my airplane still had an LF/MF automatic direction finder (ADF) aboard. I was able to fall back to navigating using the non-directional LF beacon on Great Inagua. After refueling at Great Inagua I continued on sans GPS for nearly 100mi when >POOF< GPS suddenly came back on. I wonder what the FCC does if it discovers it is another governmental agency that is doing the jamming? ;-) I must admit, I like the idea of multi-system sensors that will track GPS, GLONASS, and (hopefully) Galileo and the Chinese satellite-based navigation system that is going up. For that matter, is anyone running one of the new multi-system receivers? I notice that Garmin is selling them as a matter of course now. The prevalence of jamming might be the reason why. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 USA br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WAAS.....
On Wed, Jan 8, 2014 at 12:02 PM, Brian, WA1ZMS wrote: As far as I have seen first-hand, the jamming is short in nature and events > that I saw were from trucks on highways trying to defeat any tracking > systems in the trucks. An FCC enforcement issue here in the US resulted in > one such user being made an example of by heavy fines since his truck was > near a major airport where the FAA was trying to test GPS landing aids. > I have experienced loss of GPS while using it as my primary nav-aid while flying. Twice it occurred over the ocean while out of sight of land. I suspected at that time that it was a general outage (it took down my panel-mount GPS as well as my hand-held back-up), but now suspect that it was close-in jamming. I remember the general availability of Russian-made GPS jammers about 15 years ago. I didn't realize that the use of GPS jamming was prevalent. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Trimble Studio, what is it?
On Sun, Jan 5, 2014 at 4:58 AM, Chris Wilson wrote: > > > 05/01/2014 10:57 > > I see occasional references to "Trimble Studio" here. What is it > please? An alternative to Lady Heather for Thunderbolts, or have I > missed the plot entirely? Thanks. > I just picked up a copy based on a posting here a few days ago. It appears to be an updated replacement for Tboltmon but works for all of their products. Grab a copy from Trimble and run it to see if you like it. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Trimble Thunderbolt 1pps
On Sat, Jan 4, 2014 at 3:51 PM, Tom Van Baak wrote: > > Pulse quality of single-ended RS232 over unbalanced twisted pair is going > > to be pretty bad beyond a few feet. If you want to transport the 1pps > over > > twisted pair there are a couple of options: > > Hi Brian, > > I suspect this is true at one level, but what would be helpful to to > *quantify* it. What is "pretty bad"? What is "few" feet? You are implying > that 1PPS timing is dependent in cable quality and cable length. I would > agree. But please provide some numbers, even rough numbers, because what is > important for modern T&F applications (picoseconds and nanoseconds) can be > irrelevant for NTP, which still lives in the millisecond and microsecond > world. > Oh, called on the carpet I am! ;-) Very good point. More to the point would probably be protection, isolation, noise pick-up, ground noise, etc., for a long run. RS-232 is pretty susceptible to noise, hence my recommendations. And what might work for one person might not for another. But here is the point -- there is the concept of Best Engineering Practice. There are lots of things you can get away with most of the time but they are a bad idea to do as a general thing. Using an RS-232 signal over any distance at all is one of those bad things. It has poor noise immunity and when you are trying to catch the leading edge of a pulse it just isn't going to do very well. Or maybe it will be just fine ... until you are counting on it. Or maybe you have a transmitter around. What I'd like to see, and what would be educational for the group, is if > you could take some 'scope traces at a few inches, at a "few feet", and at > a few meters or tens of feet to graphically demonstrate your point. > I suppose I could. And what would be the advantage of that? Just because it can be made to appear relatively good in controlled environment still doesn't make its use valid. My situation is not yours. I am not operating in the same EM field you are. I have no idea what kind of ground-loop you are going to create and I am not (or vice versa). So, the key point is, and remains valid: RS-232 is a poor means to transmit signals over more than a relatively few feet. Sometimes it works great. Other times it won't work at all. If you want to transport a pulse over any distance the right answer is coax or a differential signal, e.g. RS-422. > > My gut tells me 1 ns or 10 ns or 100 ns or 1 us or 10 us makes no > measureable difference to the quality of NTP/PC timekeeping. > And my gut, based on designing data communications equipment, is that it is poor engineering practice. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Trimble Thunderbolt 1pps
On Sat, Jan 4, 2014 at 12:05 PM, Hal Murray wrote: > > albertson.ch...@gmail.com said: > > Where those using the cat-5 wire as a twisted pair? If sothat's > "cheating" > > Yes. I was thinking that 4 pairs would be Rx, Tx, PPS, and power. If I > need > Ethernet, I'll pull another Cat-5. > Pulse quality of single-ended RS232 over unbalanced twisted pair is going to be pretty bad beyond a few feet. If you want to transport the 1pps over twisted pair there are a couple of options: 1. A BALUN. There are lots of 75ohm-to-CAT5 BALUNs out there specifically for transporting NTSC video over CAT-5. At the far end use another BALUN before running into a TTL-to-RS232 line driver. There should be sufficient drive without too much extra hardware. (Terminate into 75 ohms tho'.) 2. Use an RS-422 driver. This will accept the TTL-level 1pps in and produce a nice differential output to drive the twisted pair. You can find serial cards that have RS-422 line receivers that will plug directly into the PC. 3. Simply use coax that is properly terminated at the far end to drive a TTL-to-RS232 line driver right at the computer's RS-232 input. All three of these should result in an acceptable 1pps with jitter levels lower than the timing resolution of the NTP server you are running on the target machine. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Trimble Thunderbolt 1pps
On Fri, Jan 3, 2014 at 8:32 PM, Graeme Zimmer wrote: > > Can you tell me which (Windows) time synch programs can use the 1PPS on > DCD of the RS232 interface please? > > To answer my own question: > > Here's one... > http://www.visualgps.net/NMEATime/default.htm > > There are a few others listed at > http://www.gpskit.nl/links-en.htm > > > Zim > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > Unless you bring the 1pps in and synchronize with that, you are probably better off just running NTP. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] WWV/WWVH audio simulator?
On Fri, Jan 3, 2014 at 12:09 PM, Bob Albert wrote: > Jayson, > > I chuckle because WWV is my favorite radio station also. > > > Why not tune it in on a good day and record the audio? Then you can > digitize it on the computer and have a .WAV file which you can play any > time. > > Trouble is, if you have recorded the announcements, you won't have the > correct time. But it might be fun to write a program that generates the > correct figures. After all, NIST must have that software - perhaps you can > ask them to share it. > I just checked and WWV does not stream audio over the internet. You can get it through the phone. But why not just set up a receiver and listen to that? I can't remember a time when WWV wasn't audible on at least one of its frequencies. Shortwave receivers that will tune 2.5MHz, 5MHz, 10MHz, 15MHz, and 20MHz are not expensive, especially if you look for something on eBay. That will also allow you to tune in CHU for a change. (One can often hear WWV or CHU in my house.) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Trimble Thunderbolt 1pps
On Fri, Jan 3, 2014 at 11:35 AM, Chris Albertson wrote: > No. The serial port is just three wires, the PPS signal is TTL level on > one of the BNC connectors.You will have to level sift it to re-232 > voltage levels and then make a costom cable > Thank you. No problem. Just seemed like a logical thing they might have done for less-critical timing. -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Trimble Thunderbolt 1pps
Does the Trimble Thunderbolt provide 1pps on DCD of the RS232 interface? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing 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] Measuring TV delays
On Thu, Jan 2, 2014 at 11:10 AM, Gregory Muir wrote: > Reading all of this brings back memories of a project I was involved in > back in the early 70's in the Denver area. NBS-Boulder was experimenting > with injecting their time standard into the video of the analog signal > before it hit the transmitter. I bet they encoded it into a single line of the vertical interval. I worked on a similar project at PBS but there it was used that to implement a message broadcast service to send textual messages to selected affiliate stations. It was an outgrowth of the closed-captioning system. PBS didn't want to pay telephone charges to send the same message to all 200 stations in the US when they already had a "pipe" into every station. And I do remember being intrigued with the creation of the network master clock to ensure that all the video sources were synchronized. I also remember the early digital frame buffers that were there to deal with different frame clock phase from non-PBS-network sources. As I recall, WWVB was the preferred frequency reference but I also remember that they had either a couple of Rb or Cs local references. (It was 1980 and my mind is going. So much to remember.) -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
