[time-nuts] Smart Phone time display accuracy...?
Hello, Time-nutters-- Any thoughts on what the likely accuracy of smart phone time displays might be? I am thinking that the stacking of delays along the path to its receive antenna plus any internal processing delays would accumulate to some unknown degree. Any thoughts on this? Mike Baker * ___ 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] Need 10 MHz for DSN space-probe hunting
Hello, Time-Nutters-- Full disclosure-- I am a complete newbie at understanding the intricacies of generating a really stable, low phase noise, accurate frequency reference for microwave reception up around the 8 GHz DSN (Deep Space Network) band. I have been following the back and forth comments on the Time-Nuts list about improving the Trimble T-bolt's 10 MHz output but confess that most of it is pretty much deeper technical voo-doo than I am comfortable with. I have been following the exploits of a group of folks around the world who receive the incredibly weak signals from space probes such as Juno. The idea is to detect the signals and then deduce and confirm what probe is being detected by analyzing its doppler and orbital characteristics. This is being done at around 8.4 GHz with relatively small dishes of under 8-ft diameter. Part of the magic that permits identifying signals so far below the noise floor is the ability to use very narrow bandwidth; as little as couple of Hz or even more narrow than that. In order to do this a really accurate/stable/low phase-noise frequency reference is needed. I have been running a Trimble T-bolt 24/7/365 on Lady Heather for around 5 years but have just started to take note of comments on this list that the T-bolt is not really very good as a source to phase-lock to for producing super narrow bandwidths of only one or two Hz at 8 GHz. The comments I hear on the DSN space-probe hunters chat-list is that obtaining a really high quality freq reference is one of the big obstacles to success at this game. My workbench test gear is limited to a pair of spectrum analyzers (Tek 495AP and a Tek 494AP) and an HP 8714ES Vector Network Analyzer. John Miles was the source for the Tek 495 spec-analyzer a few years ago. John-- you might recall the check I sent you for the Tek495AP that got lost...? Did it ever turn up? Accordingly, what possible options might I have open to obtaining a decent 10 MHz frequency reference for working up at the 8 GHz DSN band? Any feedback on this will be much appreciated! Mike Baker Gainesville FL (Micanopy, actually, about 12 miles south of Gainesville) As a side note, I built a tracking downlink to receive and display the digital imagery from the environmental low-earth polar orbit satellites several years ago. This HRPT data comes down at around 1.7 GHz. The USA, Russia, Japan and China each have 2 to 4 of these low-earth orbit birds (100 minute orbits) and one of them passes overhead every other hour or so. I have a lot of trees around my house and these limit my open-sky area but I can still start to get solid reception when the birds pass over Cuba and drop-off when they are over Tennessee. Photos of my home-brew tracking station can be seen here in the back yard behind my workshop building: *http://tinyurl.com/j676ap2* And some low-res screen-grabs of false-color infrared earth surface images here: http://tinyurl.com/jsv323l *http://tinyurl.com/jvxkc9g **http://tinyurl.com/hbo886y* ___ 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] Wenzel Timekeeper Oscillator
Hello, Time-Nutters-- I have been sorting through items accumulated in my workshop over the past 10 or 15 years which I will likely never have any more use for. I came across an oscillator made by Wenzel Associates, Austin Texas. Model 500-01301. I bought it to replace the the original defective oscillator in a Motorola communications signal analyzer / service monitor. The service monitor worked fine for a decade or so after that but at some point suffered a short on the freq synthesizer PC board which damaged it beyond repair and the cost for a replacement board was more than I wanted to invest in it. I saved some particular components from the unit including the Wenzel precision low-aging 1 MHz crystal oven oscillator. I suppose I could put it on eBAY but have no idea how much to ask for it. I thought I would pass it by the Time-Nuts family first in case there is any interest in it. What is a reasonable price to ask for this? $50 plus shipping? Trade it for a racoon hunting beagle puppy plus shipping? (Just kidding!) Please-- any responses from fellow Time-Nutters should be sent to me OFF-LIST so as not to load the List with unnecessary traffic! I still have the documentation info sheet that came with it which says: Very Low Aging 1 MHz Timekeeping Oscillator Frequency 1 MHz Output TTL Compatible Stability / Aging +/- 2 X 10 -10/Day after 30 days Temperature Stability +/- 8 X 10 -9, (+10 to +50 deg C) Dimensions 2 X 2 X 4" Connections 7-(solder) pin header Pin-5 +10 V Reference Output Pin-6 Electrical Tuning Input Solder Sealed Steel Can Supply +15 VDC Coarse Frequency 2 X 10 -6 Fine Frequency +/- 2 X 10 -7 (+/-5 V) Crystal 5 MHz SC-cut Third Overtone with divide by 5 output The output waveform was not symmetrical and the Motorola service monitor did not like that so I cobbled up a simple PLL chip to to deal to cure that issue. I just powered it up and you can see the output waveform in the Dropbox link below. The output was not properly loaded so it looks a bit rough. Photos can be seen at these Dropbox URLs: https://dl.dropboxusercontent.com/u/60102282/Wenzel-%20Oscillator/Wenzel-1-WS.jpg https://dl.dropboxusercontent.com/u/60102282/Wenzel-%20Oscillator/Wenzel-2-WS.jpg https://dl.dropboxusercontent.com/u/60102282/Wenzel-%20Oscillator/Wenzel-3-WS.jpg https://dl.dropboxusercontent.com/u/60102282/Wenzel-%20Oscillator/Wenzel-4-WS.jpg Mike Baker Micanopy, FL ___ 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] HP Z3801A GPSDO excess to my needs
Hello, Time-nutters-- I have an HP Z3801A GPS receiver that I used the 10 MHz output from to phase-lock my Tek-494 spec-analyzer and HP 8714 VNA to. It worked well, but then I discovered how neat the Lady Heather program showed off the functions of a Trimble T-bolt and switched over to one of those. The Z3801A has been sitting unused on a shelf in my workshop for at least 2 years and I am trying to free up some shelf space. Is anyone on the Time-Nuts list interested in this unit for $100 plus $10 USPS shipping costs?If not, I will list it on eBay for $150 plus $10 shipping. I have forgotten what software program I used to display & control the Z3801A functions with. I believe it was "GPSCon Pro" found at this URL: http://www.realhamradio.com/GPS_Frequency_Standard.htm * Instead of connecting the Z3801A to an external 28 VDC supply I installed a 28 VDC power supply internally. Photos of the unit can be seen here in my DropBox folder: https://www.dropbox.com/s/8heuqaamusugd68/IMG_0443.JPG?dl=0 https://www.dropbox.com/s/6e27erk5zw671v3/IMG_0447.JPG?dl=0 https://www.dropbox.com/s/1a9k080qt8skxeo/IMG_0449.JPG?dl=0 https://www.dropbox.com/s/5f764smp1jkrira/IMG_0451.JPG?dl=0 https://www.dropbox.com/s/ezzis5w4hfjw0l7/IMG_0452.JPG?dl=0 https://www.dropbox.com/s/qcqt2fcbgn6j867/IMG_0453.JPG?dl=0 Thanks for any feedback on this!! Mike Baker Micanopy, FL USA ___ 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] Explanation of how a GPS RX generates time/freq precision?
Hello, Time-Nutters-- I have a couple of friends who have asked how GPS based time & frequency units arrive at their level of precision. One sent me some questions and comments (see below) which indicate his lack of understanding of how GPS disciplined oscillators can deliver the precision they do. My question is-- Can anyone on the Time-Nuts list point me to a source I can give them that will explain how the process works? Seems to me that I have seen some papers describing the process but my search for this info has not turned up anything suitable that goes into some detail on this. Any feedback or suggestions on this is much appreciated!! Mike Baker Micanopy, FL Here is what one of the guys sent me: A 2GHz Intel processor can't measure 10^-12, let alone getting a P4 to do it. RS232 delay times are measured in mSec, not 10^-9. Yes it can time-stamp PPS at 10^-9 if it had a time source that accurate but that has nothing to do with when the pulse gets to the receiver or the original time source of the system. Given that my phone has a 2+ GHz processor / clock and a GPS receiver, what is the advantage of a 6 GHz (or 10 MHz) oscillator? I could well believe that system is accurate to 100 nSec (10^-7) or that a Stratum 0 GPS system good down close to 10^-8 (40 nSec). I don't see any way of getting down to 10^-12 with that technology or transmitting a time more accurate than 10^-7. If the original GPS time source is 10^-7 or a little better, how can it ever be more accurate than that? What are we missing? ** ___ 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] Lord Vetinari wall clock
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. I would love to put one of these up on a doctor's patient waiting room wall just to see what people's reactions are. http://www.youtube.com/watch?v=YpqFU4SGe1Y I suppose this would not generate the same reaction if it were done to a digital (numerical) clock. H--- maybe if a "tick" sound were added...? Nah... Whoever heard of a digital clock that ticked... See: http://www.youtube.com/watch?v=YpqFU4SGe1Y Mike Baker ___ 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] 1903 Self-setting / self-winding clock
Time-Nutters-- This particular 1903 Railroad self-setting/winding pendulum regulated clock needed only an hourly signal from a Western Union telegraph line to provide momentary closure of a relay contact. This supplied +3 VDC to rewind the spring and also reset the sweep seconds hand on the hour, every hour. From what I have learned about this, the resetting of the sweep seconds hand is mechanically coordinated to occur when the pendulum is at either end of its swing. It appears that is no way (that I know of) to guarantee that the "telegraphed" reset pulse would coincide with either end of the pendulum's travel. Apparently, the resetting of the sweep seconds hand will only occur within the time frame of any single pendulum swing. I suppose this means that the clock might be in error by as much as nearly one swing of the pendulum because it has to reach the end of its swing before the second hand is reset. Just guessing here, but I am thinking that all this clock needs is a 1-second long closure of a relay contact on the hour, every hour. I don't think that leap-seconds are an issue here as the clock can be manually adjusted for that whenever a leap second occurs. So-- it comes back to counting 3600 one-second pulses from a GPS clock...? Or am I missing something here...? Mike Baker ___ 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] 1903 Railroad self-Winding / Self-setting Clock
Hello, Time-Nutters-- A friend has a vintage oak-cabinet pendulum movement clock made by The Self Winding Clock Company some time around 1903. The company was formed in 1886. By the early 1900's era, this clock was known for its relative accuracy. These clocks were pendulum controlled and powered by a rather small and frequently reset mainspring that was wound hourly by a set of 1.5 VDC dry-cell batteries. In 1890 (?) the Naval Observatory agreed to telegraph standard railway time.Western Union, which also owned the Self-Winding Clock Company, sold these clocks to the railroads and sent the hourly time coordinating signals around the country by telegraph. My friend has one of the railroad clocks that has the Western Union Telegraph hourly resetting option. My friend thought it would be an interesting juxtaposition of technology from two different eras by creating the momentary 3-volt resetting pulse every hour from a GPS disciplined oscillator / clock pulse. I am wondering what the easiest approach to this might be?I suppose I could take the 1-sec pulses from a GPSDO (Trimble Thunderbolt ?) and count 3600 of them to generate a momentary reset 3VDC signal. In any event, I thought I would pass this by the Time-Nuts gang to see if any feedback is available as to what the least complicated (simplest) way might be to accomplish this. Mike Baker *** ___ 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.
