Re: [time-nuts] Why are 1PPS signals so skinny?
On May 14, 2012, at 09:33 , b...@lysator.liu.se wrote: More modern 3-5.5V into 50ohm, 20us. http://contracting.tacom.army.mil/majorsys/jab/DAGR%20Interface%20Specification.pdf Is a similar standard available for the older PLGR devices? -- Mark J. Blair, NF6X n...@nf6x.net http://www.nf6x.net/ ___ 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 unit of time measurement
On Jan 14, 2012, at 23:12 , Poul-Henning Kamp wrote: You are not the first researcher of this interesting phenomena: http://www.washingtonpost.com/opinions/cellphone-ban-would-be-a-distraction/2011/12/16/gIQAdv2GyO_story.html Article states: Upon arriving at a red light, drivers apply the brakes, pick up their mobile devices, and begin reading and sending e-mails. The signal to resume driving comes not from the green light but from some motorist in the back tapping politely on the horn. This is why I begin honking immediately after stopping. It removes the latency, which can otherwise be annoying at a light with a short green cycle. :-) -- Mark J. Blair, NF6X n...@nf6x.net http://www.nf6x.net/ ___ 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] Thunderbolt Supply
On Feb 10, 2011, at 3:16 PM, Larry McDavid wrote: I'm seeking a recommendation for a power supply for this Thunderbolt receiver. I use an HP 6236B that I bought inexpensively on eBay, after reading about others having good results with that combination. I had to repair it (it had one or two bad caps), but it was still inexpensive after the cost of the components. The TBolt draws more than the supply's rated current on the +12V output during cold start, but neither the TBolt nor the power supply seem to mind, and the operating current settles down into the supply's normal operating range after a few minutes of warm-up. I have the TBolt bolted right on top of the supply (over the coolest corner). This is far from ideal, but the supply's ventilation holes are conveniently spaced to line up with the T-Bolt's mounting holes. I'll improve my setup eventually, when I feel a surge of time-nuttiness coming on. :) Even in its current configuration, it far exceeds my needs for a frequency reference. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Thunderbolt Supply
On Feb 12, 2011, at 11:03 PM, Kevin Rosenberg wrote: Exceeding your needs? Doesn't seen like that surge of time-nuttiness has hit yet ;) Don't worry, I'm just pacing myself. :) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] worth salvaging ?
On Jan 29, 2011, at 6:43 AM, paul swed wrote: It seems to interpret the almanacs wrong because amazingly enough its actually does know the correct GPS week which was a shock to me. Unless thats a simple calculation from the date I might guess. It's the other way around: The GPS week is directly decoded from the GPS signal. If I'm not mistaken, the GPS week roll-over causes a problem of being able to correctly calculate the calendar date from the GPS week. I could be mistaken, but I think that a receiver that doesn't handle the rollover properly but is otherwise in good shape should be able to track satellites and provide a correct position, but the calendar/clock time calculation would be wrong. In a receiver that doesn't have a recent almanac, and particularly in an older receiver that takes a very simple approach to downloading ephemeris and almanac information, initial acquisition could take a long time. It'll need to do a slow full-sky search for its first satellite, and older receivers couldn't do that nearly as quickly as newer ones can. Once it gets that first bird, it may sit there downloading ephemeris and almanac data for at least 12.5 minutes before it does anything else. With an old receiver from that era, give it at least a half hour of good open-sky conditions before you begin to suspect that it's dead. Back to the original topic now: That OCXO may seem mundane by time-nutty standards, but I'd certainly consider it to be worth salvaging. It could have all sorts of applications for radio stuff, portable test equipment, and even time-nutty stuff in an application that wants to be smaller and more portable than a Rb standard or full GPSDO. I also agree that there's likely to be a lot more salvageable stuff on those boards. I see lots of socketed parts. UV-erasable EPROMs are worth saving. Are those Altera parts reprogrammable? If so, then they're worth keeping. Keep any microcontrollers or CPUs that are reprogrammable, or rely on external program memory, or can still be used in spite of fixed internal programming (e.g., an old mask-programmed 8051 can be used as an 8031 by strapping a pin to tell it to ignore its mask ROM and use external program memory). I'd say that any units which track satellites at all after a half hour should be considered for repair, and the rest of the units are goldmines of parts. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] worth salvaging ?
On Jan 29, 2011, at 4:03 PM, David Martindale wrote: It all depends on the receiver firmware. [...] In a little while, Garmin released a small utility that you ran on a PC connected to the GPS via its serial port, and it reset something that allowed the GPS to do a successful cold start. I remember an rumour that it simply reset the saved date and time far enough away that the receiver dumped all its old almanac entries, forcing it to do a cold start that worked. Ah, yes. If the receiver is too stubborn to give up and do a very cold start, then it may single-mindedly continue searching exactly where the satellites aren't! -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 based on mobile services
On Jan 25, 2011, at 7:25 AM, Raj wrote: A thought occurred to me that there should be a way to lock our OCXO/TCXOs to cell phone services signals that that is present almost everywhere. I am not conversant with cellular technology so I am curious! Any ideas and/or thoughts? There's a software tool called Kalibrate for use with the GNU Radio software and USRP radio hardware, which uses GSM base station signals as a standard to measure the frequency offset of the USRP's oscillator. It's not really a time-nutty application, but it serves as an example of using cellular base stations as a frequency reference. http://thre.at/kalibrate/ GNU Radio is a free open-source development environment for implementing software-defined radios. The USRP is one of the more popular RF hardware options for use with GNU Radio. http://gnuradio.org/redmine/wiki/gnuradio -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 -Receiver Mutual Interference...
On Dec 30, 2010, at 6:53 PM, Burt I. Weiner wrote: Has anyone run into a situation where two GPS Navigation type Antenna/Receivers interfere with each other? It's possible that LO leakage from one is jamming the other. When doing mobile GPS receiver testing at work with a single antenna feeding multiple receivers through a splitter, we sometimes had to insert attenuators in each receiver's antenna feed to keep them from jamming each other. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 -Receiver Mutual Interference...
On Jan 3, 2011, at 1:00 PM, Burt I. Weiner wrote: I'm not sure of the nature of the two receivers, but using conventional receiver design thinking, the only thing that comes to mind that might be radiating would be the oscillators or possibly the I.F. section taling to each other. My company's earlier GPS receivers used a frequency plan with the IF at around 2 MHz, so the LO was well within the passband of the SAW filter and common patch antennas (both typically have passbands around 5 MHz wide, IIRC). Thus, we had quite a bit of LO leakage then. While our own receivers generally didn't mind sharing an antenna through a simple splitter, we tended to have trouble when doing this with a mixture of our own receivers and some of our competitors' receivers. Some combinations apparently resulted in LO leakage from our receivers causing problems for our competitors' receivers. While there's something to be said for jamming one's competitors, this prevented us from gathering the comparative data that we needed. :) We fixed this with the simple expedient of putting an attenuator on each splitter output to reduce cross-coupling. I haven't been directly involved in receiver testing for a while, but I think that we now use a higher IF, and thus I'd expect that we get a lot less LO energy leaking out through the front end. In any given setup involving multiple GPS receivers sharing an antenna and/or located close to each other, you may or may not have problems. It'll depend on the particular combination of receivers, the LO frequencies, how much LO leaks out of each one, whether that LO leakage lands in a bad spot for any of the other receivers, how much isolation is between the receivers, etc. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] beats was Re: If there a FAQ
On Nov 30, 2010, at 8:42 AM, William H. Fite wrote: I expect you can do the same thing with an electric fan. Or by chewing something crunchy (like ice) while watching a raster-scanned (CRT) television. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] A real-world precision timing need....
On Oct 31, 2010, at 8:06 AM, Bob Camp wrote: Adequate protection starts at about 1 of steel plate if it's angled to the incoming projectiles. Using hardened armor plate (as used for steel gong targets) can get that down under a half inch, resulting in a lot less mass to drag downrange and back. It won't hurt to locate the sensor behind a berm, either. The sky screen and/or its supports will still get shot eventually, but that will be a lot cheaper to replace than the sensor. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] A real-world precision timing need....
On Oct 31, 2010, at 7:21 PM, Bob Camp wrote: The gotcha is that the gong can move / twist when hit. The plate buried in front of the electronics has to just sit there and take it. More energy transfer to the anchored plate. I'm sure there are alloys that will get you under 1, the issue will be making sure you have the right one... Ah, good point. Also, it won't matter if the steel stops the bullet from penetrating if the shock turns the enclosed electronics and optics into powder. As an aside, when I bought my high power rifle rated steel gong target (which, sadly, I haven't taken for a test drive yet), I looked at pre-shot samples from about four different vendors who had displays at the gun show, and there was a noticeable difference in the steels that they used. The vendor I chose had little more than faint dimples surrounded by lead spatters where .308 rounds allegedly hit their target, while other vendors had substantial craters. Back to the topic at hand: If muzzle velocity and time of flight alone would provide enough data (*), then one possibility would be a downrange target with an attached transducer (piezo?) to register the bullet impact, with a wire pair going back to the shooting bench. In this case, the downrange sensor would be cheap to replace when it eventually fails, and all of the expensive/delicate stuff would be back at the shooting bench. (*) I haven't studied ballistic equations carefully enough yet to know whether this would provide enough information to estimate fun details like ballistic coefficient. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Determining Time-Nut infection severity.
On Oct 24, 2010, at 1:44 PM, Richard H McCorkle wrote: The disease will continue to progress until ultimately all of the patients personal time and money are exhausted or they die. One can only hope that the local coroner is also a Time-Nut, so that time of death can be determined with suitable accuracy and precision. Does anybody know how many bits of precision are used on tombstones these days? -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Determining Time-Nut infection severity.
On Oct 24, 2010, at 1:58 PM, Poul-Henning Kamp wrote: In message 53601812-fc62-4098-9266-55edf50af...@nf6x.net, Mark J. Blair wri tes: Does anybody know how many bits of precision are used on tombstones these days? Most tombstones are engraved with CNC machines and while I have yet to see a company advertise it as a competitive parameter, your vital lack of stats will be engraved with better than 1/50mm precision. Oh, I was mostly concerned with the bits of precision used for the birth and death timestamps. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Determining Time-Nut infection severity.
On Oct 24, 2010, at 2:03 PM, Magnus Danielson wrote: The real mourning of the deceased from fellow time-nuts comes when they realize just how much of precious gear has been lost forever. Of course, we would like to know precisely when the precious gear was lost. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Determining Time-Nut infection severity.
On Oct 24, 2010, at 3:36 PM, mike cook wrote: A nut in the final stages of the disorder would request to be buried with their clocks . The lab would be sealed for eternity. In that case, I'd better rush out and patent tombstones with integrated GPS antennas for entombed GPSDOs. I'll make millions on the licensing fees, thus funding the H-maser that I'll be buried with. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] I have a new toy
That sounds (and looks) thoroughly delightful! With a proper external reference, you'll be able to synthesize another reference at *precisely* the wrong frequency. :) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 backup for the stationary time and frequencyuser
On Oct 9, 2010, at 12:47 PM, jimlux wrote: Simple GPS jammers are pretty easy, since consumer GPS is very vulnerable to repeater jammers. Hmm I wonder if that would adversely affect a GPSDO? Probably not, since the repeated signal is just as stable as the original one. I would think that with a little bit more effort, one could make a fairly simple repeater jammer that broadcasts a substantially less stable signal. With a suitable slack buffer between the receiver and transmitter, the retransmission delay doesn't need to be constant or even predictable, thus messing with apparent time and frequency. With still more effort, one could detect individual satellite signals and retransmit them separately with different and varying delays, thus messing with the apparent position relationships of the birds at any point in time. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 backup for the stationary time and frequencyuser
On Oct 8, 2010, at 10:27 AM, J. Forster wrote: GPS needs several birds to lock up, To get a position fix, this is true; 3 birds minimum for a 2D fix, 4 birds minimum for a 3D fix. and if you look at a single bird, Dopplar will make the signal useless as a frequency reference. Only if you don't already know your position. Once your position has been determined accurately and you have the current ephemeris data for the bird you're listening to, you can factor out the predictable doppler and use a single bird for timing and frequency. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 backup for the stationary time and frequencyuser
On Oct 8, 2010, at 10:44 AM, J. Forster wrote: KISS. This seems like a lot of work for not particularily good results. Among other things, you have no closure so no measure of how good your measuremwent is. Single-satellite timing mode is already commonly implemented in timing receivers; there's no work to be done other than turning it on. Closure is only lacking if all of the USAF ground stations are taken out such that the ephemeris and health information can no longer be updated on any intact birds; otherwise you know where every existing bird is at any instant in time, and each bird indicates whether it should be trusted. Bottom line: If there's still one intact bird and one intact ground station to control it, you can get accurate time and frequency whenever it's visible (assuming no local jamming/spoofing) if you've already surveyed your position, using off-the-shelf hardware like a TBolt. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] 60 KHz Receiver
On Oct 5, 2010, at 1:15 PM, shali...@gmail.com wrote: That is basically the sauce behind GPS. What is the power of the transmitters on the satellites? It can't be much, and the signal on the ground is quite a bit below the noise floor before correlation. If I recall correctly, the transmit power is around 15W. A received signal of -130dbm is considered strong, and tracking (but not acquisition or data decoding) can still be done at signals approaching -160dbm. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] antennas
What is the purpose of the temperature sensor chip on the PCB, anyway? Isn't the temperature inside the OCXO much more important? -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] [qs1r] Looking for good, cheap, external reference
On Sep 22, 2010, at 5:57 PM, Bob Camp wrote: The temp sensor is the one that moves in real small steps. The bad one moves in (1/2 degree???) big steps. All of that (and much more) is visible if you bring up Lady Heather and see what's going on. My TBolt has the 3.0 firmware and the silver Trimble-marked OCXO. As I recall, Lady Heather plots the temperature with the scale set as small as 5 millidegrees C per division when the temperature isn't moving around too much. Does that mean that I got lucky and got one with the good temperature sensor, new firmware and good OCXO? BTW, I fixed the crashing issue I had previously mentioned. It turned out that my HP 6236B supply from eBay had a bad filter cap in the 5V supply, causing it to have poor load regulation and a lot of ripple, and in turn causing the TBolt's power supervisor to randomly trip. Now that I've replaced the cap I managed to complete a 48-hour survey, which I wasn't able to do before. Hooray! -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] [qs1r] Looking for good, cheap, external reference
On Sep 22, 2010, at 7:50 PM, Ed Palmer wrote: Does the temperature move around a little or is it a flat, straight line? If it never moves, it's probably the bad one. As Bob mentions below, the temperature only changes in large steps with the bad sensor. The good one has steps in the millidegree range. I got my chips from the auction place. Make sure that they are C or D revision, the E revision is the bad one. Check the list archive for lots of info on this topic. It does move around, so I think I have the good one. I should be powering it off soon to do some more work on the power supply, so I can open it back up to check the temperature sensor revision. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Thunderbolt initial check out?
On Sep 19, 2010, at 4:38 PM, Bob Camp wrote: Lady Heather is a good program to dig into a TBolt with. It's free... It also plots oscillator and PPS error (the oscillator error plot may be off by default). If the error plots look good and both signals can be seen at the BNC outputs with an oscilloscope (and everything else reads green, of course), then I'd say that your Tbolt is likely to be in good shape. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timing Distribution in Mountainous Terrain
I presume that there's a good reason for the selection of antenna sites which don't have LOS to each other. However, would it be possible to select additional sites at which to install repeaters to allow timing calibrations to be made between pairs of primary receiving sites? These repeaters could also provide backup communications so that a primary receiving site isn't necessarily taken out of action if its communication channel (wireline?) gets cut by a wandering backhoe. Each repeater site would be selected to have LOS to two or more primary receiving sites, or when that's not possible, to one primary receiving site and another repeater that can see a different site. While multiplying the number of sites wouldn't be cheap (even considering that the repeater sites may host much less expensive equipment than the primary receiving sites, and may be able to operate without wireline communications or power lines to the sites), it might be cheaper than installing hydrogen masers and radio telescopes, designing custom aircraft and flying them overhead every 20 minutes, etc. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timing Distribution in Mountainous Terrain
On Sep 10, 2010, at 10:47 AM, Pete Rawson wrote: Can you use tethered balloons at each site to obtain adequate S/N in their position to permit time calculations to 30ns uncertainty? Tether a single balloon to three sites to reduce the balloon's displacement due to wind, and then measure its position relative to the three sites by laser or radar ranging! :-D -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timing Distribution in Mountainous Terrain
On Sep 9, 2010, at 10:42, Ralph Smith ra...@ralphsmith.org wrote: Paranoia. People making the requirements are concerned with GPS going away due to solar flare or some other reason. Hmm... So the decision makers think that after a solar flare or some other reason (hostile destruction of the birds, perhaps?) takes out the GPS system, it'll be back up and running within six days? That sounds optimistic to me. It sounds to me more like you would need to function indefinitely without GPS, and just use GPS for initial position survey and as a convenient way to synchronize to external time reference (with ground-based backup methods in place and periodically tested). ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timing Distribution in Mountainous Terrain
On Sep 9, 2010, at 12:03 PM, Ralph Smith wrote: 1e-11 only buys you 3000 seconds of drift before blowing the 30 ns budget. Without going to cesium we will most likely need some form of mutually visible synchronization. How about a rubidium or cesium standard at each site for holdover, with an extra cesium standard that is physically carried from site to site (say, by helicopter) during an extended holdover period to distribute a common time reference around? Or, a specially-equipped aircraft which is periodically flown along paths visible to multiple antenna sites during an extended holdover in order to adjust out drift based on measured round-trip times between the sites and aircraft? In effect, flying your own low-altitude satellite over the sites when the GPS system is down. These may be silly ideas, but brainstorming is fun. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] What position is measured?
On Sep 7, 2010, at 6:30 AM, jimlux wrote: Another analogy is that if you had a machine that recorded all the signals, mounted right at the antenna, and then carried the recording half way around the world, and then ran the recording into a receiver, it would give you the position of the antenna, not the receiver. The cable is just a time delay. Does this mean that while the antenna feedline cable length does not influence the measured position (at the phase center of the antenna), and it does not influence the accuracy of a disciplined frequency reference output, it does introduce an error into the absolute time output (i.e., adding a delay to the PPS output)? In other words, do I correctly assume that I may safely ignore the length of my TBolt's antenna feedline if I am only interested in its 10 MHz OCXO output, but I may want to compensate for it if I ever find a need to use its PPS output as an absolute time marker? -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] What position is measured?
On Sep 7, 2010, at 5:16 PM, jimlux wrote: Yes.. except that the cable's physical and electrical length *do* vary with temperature, so if you're looking at the gnat's eyelash sort of thing, you need to take that into account. Maybe 10 ppm/degree, so a 20 meter run will change a bit less than a millimeter. That's down in the fractional picoseconds time-wise. It's an issue if you're doing things like interferometry at higher frequencies.. I see a bright future selling oven-controlled speaker cables to audiophiles... ;-) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Maser info (vacuum levels)
On Sep 2, 2010, at 10:28 AM, Corby Dawson wrote: This EFOS maser typically runs with the two vacuum pressures below 1.5 X 10-6 Torr. (as measured via the ion pump current) Maximum should not exceed about 3.6 X 10-6 Torr for either pump. The internal vacuum will drop to about 1 X10-7 Torr if the Hydrogen to the disassociator is turned off. Back in college, I took a semiconductor device physics course which included a lab where we made simple ICs (the most complex devices were SR latches). We had a vapor deposition system for plating on gold or aluminum, which pumped the chamber down below 10E-12 Torr as I recall, within ten minutes or so after a clueless freshman opened the beast up and tossed in a bit of aluminum or gold wire and a few chunks of silicon with their grubby hands (ok, we used tweezers, but still...). The whole unit was about as big as a refrigerator or two. It used a rotary-vane roughing pump and an oil diffusion pump with a liquid nitrogen trap. This was about 25 years ago. Reading here about the troubles of pulling a very good vacuum, I'm now wondering what sorts of painful engineering went into making the machine turn-key and freshman-proof? It's entirely possible that I've mis-remembered the pressure level, but that's the exponent that stuck in my mind for whatever reason. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] WeirdStuff tbolt $75 [eBay Link]
On Sep 2, 2010, at 10:06 AM, Oz-in-DFW wrote: http://cgi.ebay.com/300457580821 And still more than 10 available. That listing appears to have ended. If I had gotten there in time, I'd have been tempted to buy a couple of them. My Thunderbolt is flaky (stops outputting serial data or responding to serial commands after a period of minutes to hours), so I could have tried out a couple others in hopes of finding a reliable one, followed by harvesting OCXOs from the ones that didn't make the cut. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Maser info (vacuum levels)
On Sep 2, 2010, at 12:00 PM, Scott Newell wrote: I think I took that same class (sub-basement of Steele, right?) just a few years after you. That would be the one! See, I knew that most anybody who attended that particular institution would recognize my description of that piece of equipment. I took the classes in '86-'87. I would have been class of '90 if I hadn't flunked three quarters of math and two quarters of physics... but the lure of the device physics lab was enough incentive for me to bludgeon my brain into passing that pair of device physics courses. I also thoroughly kicked butt in the freshman-level digital electronics courses, which oddly enough were easily as advanced as the junior-level digital electronics courses that I eventually took at UC Irvine. A big portion of my career naturally has involved digital ASIC design, since that and software development appear to be the things that I can idiot-savant my way through while only understanding enough math to be able to count to 1! :-) What house were you in? I was in the red one, with a guest membership in the black one due to my disrespect of security devices and interest in telephone switching networks. Have you ever followed the yellow brick road to cold under Arms? -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Have Quick Tools
On Aug 23, 2010, at 7:52 AM, Brooke Clarke wrote: Has anyone made a PIC based Have Quick device to either compare two have quick outputs, generate a HQ data stream or read a HQ stream? I've been interested in playing with the HQ outputs of my HQ-compatible GPS receivers for a long time. It's on my list of things to do before the heat death of the universe, but there are a lot of projects ahead of that one. Not that it matters since there are so many projects ahead of it, but if I was going to do this today I'd probably use a TI MSP430 family processor, since those are what I'm presently set up to develop for. Hmm, maybe one could set up one of those Chronos wristwatch development kits to automatically set the watch time from a HQ source over its wireless link? You know what they say: Measure it with a micrometer, mark it with a chalkline, and cut it with a chainsaw! :-D -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Have Quick Tools
On Aug 23, 2010, at 11:29 AM, Pieter ten Pierick wrote: I would just use an axe for that, much less precise };-P And of course for the measuring I would use a laser interferometer based system, with nm precision! I suggest replacing the chalkline with one of those inverted spray cans for painting markings on the ground, then. Because the chalkline string would block the laser beam. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 11:17 AM, Rick Karlquist wrote: The AMC-123 can also be homebrewed by reading the patent, which is listed on the data sheet. I found it here: http://www.freepatentsonline.com/3624536.pdf Having read the patent, I find I'm still weak enough in the area of discrete amplifier design that I'd have low confidence of creating an amplifier with the required phase noise, gain, isolation and compression specifications. Assuming the simple amplifier in Figure 1, I think I'm make or break the design (more likely the latter) by selecting a suitable in-production replacement for the 2N5109, figuring out the required turns ratio of autotransformer L1, biasing the transistor amplifier correctly, etc. I'd have no problem building it; if I identified off-the-shelf magnetics then I could even build a whole bunch of them, as I design PCBs for a living (mostly GPS stuff; I can lay out the microwave stuff as long as a smart RF guy comes up with the necessary LNA circuit topology), and I even have a bit of experience designing mechanical stuff (i.e., in case it wanted to be in a nice machined aluminum shield/heat-sink box, though my CNC mill is presently in pieces so I'd need to farm out mechanical fabrication). I'm just weak in the analog/RF design area so far. Since the Q: Which amplifier? A: AMC-123! thing appears to be a FAQ, and that patent may be old enough to have expired, I wonder if the world wants a nice plug-and-play TIME-NUTS-123 amplifier based on the Norton patent, designed with currently-available off-the-shelf components (aside from the custom PCB and possibly enclosure), which could be made in smallish batches, characterized by somebody with the right equipment, and sold at a reasonable price to help folks cobble together their home-brewed phase noise measurement and frequency reference distribution systems. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 3:41 PM, Rick Karlquist wrote: It might still be available through Tyco/MAcom. They have continued to make selected Anzac components. There was also an AM-123, which was a TO-something can version. My first quick scan didn't turn up any offered for sale, though I did dig up the datasheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/184840/MACOM/AM-123/+074853VKvwOxcER.tvC+/datasheet.pdf -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 5:11 PM, John Miles wrote: Also, it looks like you (Mark) are only about an hour from Cerritos, where the MUD ( http://www.microwaveupdate.org ) conference will be held at the end of October. This could be one option for you. As part of the $35 registration cost, you get access to a test lab set up to help attendees measure noise figure, PN, etc. on any homebrew or commercial gear they wish to bring. Interesting. I still think I'd like to be able to measure low phase noise signal sources at home if practical. In particular, I've been toying with the idea of starting my own little company on the side, making and selling ham-radio-related/test-equipment-related stuff that seems to be missing from the market, as a (probably small but hopefully positive) secondary source of income and an excuse to design, build, accumulate (and deduct!) fun electronic equipment. My desire to learn to characterize phase noise stems from the idea that some of my products would be things whose phase noise should be specified, and it wouldn't be right for me to leech off other people's test equipment and effort if I plan to make a buck at it. Thus, I feel the need to learn how to do it myself, and then use that ability to add some value to the world in some manner. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 21, 2010, at 12:04 PM, Bob Camp wrote: There are a number of articles on the web detailing the art of getting one of these to work. Since it's broad band feedback you need to be a little careful with the layout and the transformer. Thanks, I'll continue digging. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 21, 2010, at 12:10 PM, Adrian wrote: It's still being made by Tyco / MaCOM: http://www.macomtech.com/datasheets/AM-123_AMC-123.pdf Thanks! According to Avnet (the only one of their US distributors where I found a price posted online), the price is around $600 each at quantity 5 for the SMA connector version. !! I think I'll continue investigating a homebrew implementation for now! -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 problems
On Aug 21, 2010, at 7:15 PM, Peter Krengel wrote: Warren found out that the signals TB gets out of my small ceramic typ antenna are too weak. They are too noisy. So I had a look for a good antenna and found some commercial typs called choke-ring antenna. As they are really expensive is there any DIY solution avaliable? I think that the TBolt wants a fair amount of gain up at the antenna, based on the signal levels it reported from the roof antenna feed at work (we're in the GPS industry) compared to what I normally see from our normal GPS receivers. Mine is installed at home with a Lucent/Alcatel +26dB antenna which I believe was primarily intended for use at cellular base stations, and my TBolt sees nice, strong signals from it with about 9m of feedline. These antennas are all over eBay, both used and unused, and with or without the pole mount. The TBolt will power them with its +5V bias. An eBay search for lucent gps antenna should turn up a few antennas and several mounts at the moment. There are probably many other antennas that will work fine. I'd suggest looking around for active GPS antennas meant for outdoor fixed installations (they'll generally have a somewhat pointy radome to keep snow, birds, etc. from accumulating on them), powered by +5VDC, and with at least 20dB of gain. Used ones can be cheap. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] (no subject)
On Aug 20, 2010, at 5:07 AM, Bob Camp wrote: The TBolt OCXO does have good noise characteristics. Unfortunately you have to pull it out of the unit to figure that out. Is its phase noise substantially worse when it's in the unit? I.e., is the rest of the TBolt adding a lot of phase noise to its output via its power and/or tuning voltages? I'm powering my TBolt with an HP 6236B bench supply rather than the cheap open-frame switcher that came with it. Based on what I read, powering the TBolt with a switcher adds a lot of noise/spurs to the OCXO spectrum. My unit has the Trimble-marked OCXO, which I gather is supposed to be a lot better than the Piezo-marked one. My TBolt is presently just screwed onto the top cover of the 6236B, which is probably far from optimal. I have the whole setup installed in a closet, so at least it doesn't get nailed with a blast of cold air every time the air conditioner turns on. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 4:56 AM, Grant Hodgson wrote: You've come to the right place - well, that is if you want to devote a significant amount of your life in the pursuit of ever-more accurate time and frequency measurements :) If you've only got one source then you need to use the frequency discriminator method (aka delay line method) of phase noise measurement. Basically you take the output of the source, split it in two, delay one of the signals, re-combine the two and then measure the resultant signal on a base-band spectrum analyser. [...] The limitation of the frequency discriminator method is that the noise floor of the measurement system is often worse than the DUT, especially if your DUT is very good, and it's even worse if you're trying to measure close-in noise. The Sherer article gives a good graph illustrating this. If you're trying to measure the phase noise of the oscillator inside a Tbolt then I don't think that a frequency discriminator will be sensitive enough, although I might be wrong. I got the impression that for good OCXOs like the HP 10811 or (supposedly) the OCXO in my TBolt, the delay line method wouldn't provide enough sensitivity for measuring close-in phase noise. Despite what you said, you might want to consider buying an HP 10811 oscillator or similar which you could use in a phase detector measurement system which is likely to give superior results. I might need 2 or 3 of them so I can weed out the under-performers! :) I had originally considered getting one of the surplus HP/Agilent GPSDOs with HP 10811 OCXOs, but I settled on the TBolt since it appeared to be almost as good (in terms of phase noise), a bit cheaper, and a bit easier to power than one of the HPs that need 48VDC. Well, I bought another power supply for the TBolt, anyway, but at least it would be easier to build a power supply that operates from +12VDC, a voltage that's always available in a ham shack. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 7:40 AM, Adrian wrote: - you may build your own HP 3048A alike system, but be prepared to invest serious money and time, and much more time than you thought in the beginning... (if that is what you're after, you'll have the most fun you can). I did a quick survey of surplus phase noise measurement system prices on eBay, and was shocked by how cheap they apparently aren't. I'll set up some searches to warn me when any of the instruments you mentioned appear, since it may be a while before the right one shows up at the right price. - Compare 3 similar DUT's with a HP 3048A and calculate the individual PN using the three cornerd hat method. That sounds like a method I'll want to learn about, since I'll necessarily be building up my testbench with surplus equipment of unknown condition, and the things I'd want to characterize initially would likely be the best oscillators I can get my hands on (except for the ones that no longer perform to spec, which I'd want to weed out). Once I have the bugs worked out of my test system, I could then use it to characterize other oscillators (probably far inferior to the Trimble/HP OCXOs) in practical applications. Btw. do not assume that the phase noise of a disciplined VCXO is the same as the VCXO alone. Also keep the power supply contribution into account that can be surprisingly high. In the case of my TBolt OCXO, I'll be interested in characterizing it while it's in the TBolt, with its regular power supply, and under discipline, since that's the way I'd be using it as a frequency reference on my bench. And, the PN of most frequency standards is significantly lower than what you can measure with any spectrum analyzer with PN measurement software (except for the RS FSUP of course). Yup, the phase noise plots I've seen of the HP and TBolt OCXOs show close-in phase noise very far beyond the dynamic range of any spectrum analyzers I'm familiar with. I wandered through the labs at work in hope of finding something I could use to look at the phase noise of my new toys (I'm in the GPS industry, and have access to some nice spectrum and network analyzers), but it looks like I'm on my own. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 8:30 AM, Bob Camp wrote: You can make a pretty good front end (mixer / amp / lock) for under $100. That will let you measure phase noise with an audio spectrum analyzer. I am intrigued by your ideas, and I would like to subscribe to your newsletter. Oh, wait, I've already subscribed to your newsletter. :-) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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 counters
On Aug 20, 2010, at 10:35 AM, Stephen Farthing wrote: I want to find a frequency counter that will read to 1 hz precision up to a minimum of 30 Mhz that I can clock using the output from my Efratom 101 Rb frequency standard. I am quite happy to make one if there is a suitable design out there. Any suggestions? I'm also beginning to look for a counter with very similar requirements. Studying eBay the other day, I came to the conclusion that an HP 5384A would be a good option, combining small size (compared to older rackmount counters), adequate resolution, an external reference input, and availability at fairly low prices. I decided that I probably don't need to hold out for one with the TCXO or OCXO options, since I'd generally only use it on my bench with my TBolt's OCXO as a reference, and it simply switches between its built-in reference and the external one rather than phase-locking its own reference (so I wouldn't be using its internal reference, and thus its performance wouldn't matter). -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 11:17 AM, Rick Karlquist wrote: On the 10811 production line, they would use Anzac AMC-123 amplifiers to drive a +17 dBm mixer, and then amplify the IF output with a low noise current amplifier like the Linear LT1028. You can easily homebrew this setup. You will need to have a DC coupled connection to the IF output to make a narrow PLL that drives the EFC of one of the oscillators. You can use a PC based audio spectrum analyzer program to look at the phase noise output. You can break the PLL to get a beat note to calibrate the system. The AMC-123 can also be homebrewed by reading the patent, which is listed on the data sheet. No need at all to get a 3048, etc. Interesting. I'm also the proud new owner of an Ettus Research USRP with a nice selection of RF front end boards, so maybe I could press that into service for spectrum analysis as long as I'm looking at things that will fall within its dynamic range and noise floor. I have a lot of learning to do... ;) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 11:17 AM, Rick Karlquist wrote: On the 10811 production line, they would use Anzac AMC-123 amplifiers How does this amplifier look for this application? http://minicircuits.com/pdfs/ZFL-500LN.pdf If I understand the specifications properly, the noise figure is better and it has higher reverse isolation and higher gain, but a lower output intercept point. -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] Phase noise measurement (was - no subject)
On Aug 20, 2010, at 2:19 PM, Rick Karlquist wrote: It is good that you asked this FAQ. Basically, what is magic about the AMC-123 is that it has certifiably low phase noise, guaranteed by design and characterization, although not specified by Anzac. [...] Having a low noise figure is necessary but not sufficient to have good phase noise. Ah, I see. Is the AMC-123 or an equivalent still in production, or was homebrewing brought up as an option because it's not? -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] (no subject)
On Aug 19, 2010, at 4:54 PM, Bob Camp wrote: Yup, the original question was why a TBolt? I just joined time-nuts today, so please forgive me if I'm beating a dead horse. For me, the answer to why a TBolt was it automatically calibrates itself against somebody else's well-maintained cesium beam oscillator that I didn't have to pay for, along with (presumably) low phase-noise OCXO output, which interests me for radio-related applications. I might have chosen a different kind of reference for a different application. I haven't fabricated a good excuse to want my own rubidium standard yet, but I'll keep working on that. :) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] (no subject)
On Aug 19, 2010, at 6:42 PM, Didier Juges wrote: Well, you need another reference that does not use the same principles to check your first reference against. That one worked for me. Ooooh, good one! Now I am working on the next one, because a man with two clocks... ...needs a third one to cancel out systematic errors? Or how about Chicks dig guys with stable frequency and time references. :-) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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] (no subject)
On Aug 19, 2010, at 7:13 PM, Bob Camp wrote: Hopefully they will keep GPS running long enough for me to find something to compare it to. My new GPSDO leaves me with the question of how do I measure the phase noise of what is by far the best oscillator I own... without buying a better one to compare it to. That question is what brought me to time-nuts. I'm starting to read some papers on oscillator characterization that are collected together in a technical note from NIST that a co-worker pointed me towards, but some of them are giving me a math-induced headache. :) -- Mark J. Blair, NF6X n...@nf6x.net Web page: http://www.nf6x.net/ GnuPG public key available from my web page. ___ 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.