Re: [time-nuts] re low noise regulators
Gentlemen, over the last years I have been confronted with numerous nonsense and rubbish technical ideas as part of my job. Over the years I came to the conclusion that just for the sake of clarity it MUST be allowed to call them nonsense and rubbish without applying any political or other correctness. I stand for that claim even if it caused some Kiss my back reactions from my boss form time to time. Best regards Ulrich Bangert -Ursprungliche Nachricht- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im Auftrag von Bruce Griffiths Gesendet: Freitag, 14. Dezember 2007 22:11 An: Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] re low noise regulators Rob Kimberley wrote: Nonsense, rubbish?? Not the words I want to hear from a fellow Time Nut. Bruce, next time how about giving constructive criticism without belittling other peoples efforts? Remember that this group contains everyone from professionals to complete newcomers. We want to encourage and grow the group by collective help and encouragement, not by insulting them. Season of goodwill to all men? Cheers Rob Kimberley No insults or belittling intended, they were merely robust comments about the statements made. If you ever think that anything I say is nonsense (or rubbish) please don't hesitate to say so, I will not be offended in any way. Bruce ___ 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.
Re: [time-nuts] Time Transfer
Didier Juges [EMAIL PROTECTED] wrote: I would have thought the GPS receiver averages the readings when it locks on multiple satellites. Are you saying it only uses one at a time? Average is perhaps too simple of a word. The good GPS receivers (here I'm assuming we aren't talking about Trimble SV6!) look at all the satellites in view and in mask, throw out obvious outliers, and average among the remaining. If so, what's the point of a self survey? ??? If you're wrong by 1000 feet about where you are, then that could be hundreds of nanoseconds in time error. And that hundreds of nanoseconds would jump around like the dickens as you chose different satllites or the chosen satellite pans across the sky. I talk about WWV because most ham operators have a receiver that receives WWV, so it is an inexpensive and convenient way to get an absolute reference, even though it is not as good as GPS. WWV is great. But again, you gotta know where you are to have the right time. Fluctuations in propogation will change path length and if you don't know the path length, it is NOT an absolute reference in the nanosecond or even microsecond range. For typical conditions the propogation delay for WWV cannot be estimated much better than the tens of microseconds; combining WWV with a better absolute clock in fact lets you study propogation by studying the shifting of the various ionospheric layers. (There have been ham operators who do this, including me!) Tim. (N3QE) ___ 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 Transfer
Tim, -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tim Shoppa Sent: Sunday, December 16, 2007 7:29 AM To: time-nuts@febo.com Subject: Re: [time-nuts] Time Transfer Didier Juges [EMAIL PROTECTED] wrote: I would have thought the GPS receiver averages the readings when it locks on multiple satellites. Are you saying it only uses one at a time? Average is perhaps too simple of a word. The good GPS receivers (here I'm assuming we aren't talking about Trimble SV6!) look at all the satellites in view and in mask, throw out obvious outliers, and average among the remaining. That's what I meant I suppose. The interesting part is that the timing GPS receivers don't continualy try to select the best satellites from all those it can see, so other than eliminating outliers, there may still be some that are not far out enough to be eliminated, but will negatively affect the average. What is the criterion to determine an SV is an outlier? How far off should it be? An algorithm could select the best 3 at all times for instance, even if 5 are visible and unmasked. I am not sure that would be better, but it's a possibility. On the other hand, I suppose that's what the mask if for. Maybe we need a dynamic mask so that we could force the receiver to never look at more than the best 3 or 4? If so, what's the point of a self survey? ??? If you're wrong by 1000 feet about where you are, then that could be hundreds of nanoseconds in time error. And that hundreds of nanoseconds would jump around like the dickens as you chose different satllites or the chosen satellite pans across the sky. I agree, but to do a self-survey, you need to look at more than one satelite, which was my point. I talk about WWV because most ham operators have a receiver that receives WWV, so it is an inexpensive and convenient way to get an absolute reference, even though it is not as good as GPS. WWV is great. But again, you gotta know where you are to have the right time. Fluctuations in propogation will change path length and if you don't know the path length, it is NOT an absolute reference in the nanosecond or even microsecond range. For typical conditions the propogation delay for WWV cannot be estimated much better than the tens of microseconds; combining WWV with a better absolute clock in fact lets you study propogation by studying the shifting of the various ionospheric layers. (There have been ham operators who do this, including me!) Tim. (N3QE) OK, once again I confused frequency standard and time standard. I promise that's the last time :-) Yes, it's interesting to look at the WWV signal wander on the HP 3586, compared to it's OCXO, and while listening to it on the speaker or on a receiver. I need to plot it over a 24 hour period or so. Didier KO4BB ___ 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-nuts Digest, Vol 41, Issue 57
i thought of tha balcony option. The balcony as an overhang which effectively blots out the other half of ths sky not covered by the building. I cannot hang any antenna over the railing or on it(in my lease and enofrce;I asked), plus there are birds and squirrels which would get into it. Any other suggestions? Date: Sat, 15 Dec 2007 21:25:14 -0600 From: Jack Hudler [EMAIL PROTECTED] Subject: Re: [time-nuts] Upgrading possibilities for more accurate, precise stable mark ii To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii If you have a porch or balcony, just drilled a 1/4 inch hole through the edge of the sliding door frame to handle an external antenna. Hide the wire in the carpet edge or behind the baseboard. When you leave just caulk up the holes and no one's the wiser. Most of the time (well the ones I lived in) apartments have touch up paint kits (or the paint codes at the local big box) so you can fill nail holes and such for move out. I did this at four different apartments and no one ever found it, or if they did, didn't care. Most of the time I drilled three holes for coaxial cables to DirecTV and 58532A GPS antenna mounted on the back of the DirecTV antenna (Note: I never used the thin flat strip to run coax through the door there was too much static build up. That being said; it is still a viable option for GPS or DirecTV). ___ 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] newbie questions
Hi, My name's Jason, and I must admit to being drawn in by the fascinating article on Wired. ( if that makes me a dork, so be it!) As a kid I thought it was neat to try and set my watches and clocks to WWV from the cheap, crummy 1960's JC-penny all-band receiver , but was always annoyed that the net result was The time on the clock in the front of the classroom IS the correct time, and the only clock that matters, PERIOD. ;) In terms of Knowing thy enemy, I find this study of time very intriguing. I've also built the AVR oscilloscope clock kit, (board which drives a regular scope) which has the option of being driven by an external source. I've also scrounged some battered gear with Nixie displays, a Nixie clock is definitely on my list of things to do. So I've read through the links on http://www.leapsecond.com/time-nuts.htm... some of this stuff I understand, some I clearly don't! Any other links to newbie-type documentation would be greatly appreciated. I guess my interest at this point would be as such: Obtaining an accurate time signal, from GPS, etc, possibly accurising it further, and then using it to likely BOTH drive a homebrew clock, AND setting the time on one of my computers that would become my master time server. My first two targeted questions are: 1) I have a Handar 541 WWV receiver. I've searched high and low for a manual for the the thing (so I can power it up without frying it) with no luck, even the company that acquired Handar couldn't put their hands on a copy. Would anybody on this list have this info? 2) What exactly IS, and what is contained within the Lucent RFG XO? I did a bit of googling, and didn't come up with any documentation for this device. Is the manual out there? Being a Ham who enjoys older tube-based gear, I gather that at its simplest, its not unlike a xtal calibrator reference oscillator. Thanks, Jason kf6pqt -- --... ...-- -.. . -.- ..-. - .--. --.- - AMI #1625 SKCC #3768 http://kf6pqt.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] time-nuts Digest, Vol 41, Issue 57
In a message dated 16/12/2007 18:17:18 GMT Standard Time, [EMAIL PROTECTED] writes: i thought of tha balcony option. The balcony as an overhang which effectively blots out the other half of ths sky not covered by the building. I cannot hang any antenna over the railing or on it(in my lease and enofrce;I asked), plus there are birds and squirrels which would get into it. Any other suggestions? --- I can't quite picture the overhang arrangement, but when you consider that a variety of manufacturers supply GPS antennas that are approx 1 1/2 inches square by 1/2 inch deep I'd be very surprised if you couldn't attach one of these somewhere outside without it noticing. They may not have the filtering etc of a proper timing antenna but they'd do the job and certainly be a lot less obtrusive. Alternatively, I've used one of these quite succesfully on an internal window sill and am running an Odetics timing antenna just propped up on the same window sill right now. That's feeding an Oncore UT+ timing module in a test jig and tracking 6 of the 8 satellites it can see. Oncore modules, sometimes complete with a small antenna, are regulalrly on Ebay quite cheaply so why not invest a small amount and run some tests? You might find the results are better than expected but even if not you'd at least have some definite answers. regards Nigel GM8PZR ___ 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] Unit of Fame
How about calling the unit the Borat? Doug Millar ___ 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] Unit of Fame
In message [EMAIL PROTECTED] , Doug Millar writes: How about calling the unit the Borat? Doug Millar That would be a hard unit to use, because you would have to calibrate out any talent, of which your chosen reference has a non-zero amount. A much better unit would be the Hilton. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@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 Transfer
Didier Juges [EMAIL PROTECTED] wrote: That's what I meant I suppose. The interesting part is that the timing GPS receivers don't continualy try to select the best satellites from all those it can see, so other than eliminating outliers, there may still be some that are not far out enough to be eliminated, but will negatively affect the average. What is the criterion to determine an SV is an outlier? How far off should it be? An algorithm could select the best 3 at all times for instance, even if 5 are visible and unmasked. I am not sure that would be better, but it's a possibility. On the other hand, I suppose that's what the mask if for. Maybe we need a dynamic mask so that we could force the receiver to never look at more than the best 3 or 4? Didier - I think this is what many are doing when they set their timing receiver to only use satellites above a given elevation. If so, what's the point of a self survey? ??? If you're wrong by 1000 feet about where you are, then that could be hundreds of nanoseconds in time error. And that hundreds of nanoseconds would jump around like the dickens as you chose different satllites or the chosen satellite pans across the sky. I agree, but to do a self-survey, you need to look at more than one satelite, which was my point. Oh, all the timing receivers I know of refuse to self-survey without at least 6 satellites in view. By definition it's impossible to do without at least 4. Presumably those who advocate very picky elevation angles dial the angle up only after getting a decent survey. I think the Motorola timing receivers specifically disable any custom elevation angle mask before doing a self-survey; at least that's the way the one in my Z3801A works (although to be honest it might be the firmware in the Z3801A and not on the GPS board). I talk about WWV because most ham operators have a receiver that receives WWV, so it is an inexpensive and convenient way to get an absolute reference, even though it is not as good as GPS. WWV is great. But again, you gotta know where you are to have the right time. Fluctuations in propogation will change path length and if you don't know the path length, it is NOT an absolute reference in the nanosecond or even microsecond range. For typical conditions the propogation delay for WWV cannot be estimated much better than the tens of microseconds; combining WWV with a better absolute clock in fact lets you study propogation by studying the shifting of the various ionospheric layers. (There have been ham operators who do this, including me!) Tim. (N3QE) OK, once again I confused frequency standard and time standard. I promise that's the last time :-) Yes, it's interesting to look at the WWV signal wander on the HP 3586, compared to it's OCXO, and while listening to it on the speaker or on a receiver. I need to plot it over a 24 hour period or so. It depends on where you are and how long you average over, but by eye I see WWV on 10 and 15 MHz going up and down by tenths of a Hz in the several minute timespan from here on the East Coast. Dave Mills has done a lot of DSP-type work on extracting the leading edge of the second and minute pulse tones from WWV in autocorrelator fashion. I think that overall, you and I need to better quantify needs before deciding on a solution as suitable :-). It's easy to overkill in time and frequency, and I think the point of this list is to do even more overkill! Personally I am so delighted with the abilities of any but the cruddiest GPS timing receivers that I see no need to tweak elevation angles. (I think I already said that I think that several consumer non-timing GPS receivers common out there are not worth crap for timing applications. Remember the SV6, it's PPS will go in and out by six milliseconds as satellites go in and out of view!! Most new stuff is better...) Tim. ___ 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-nuts Digest, Vol 41, Issue 57
On Sun Dec 16 17:43 , 'Poul-Henning Kamp' sent: Find a bird-feed where the top-lid is plastic. Mount the GPS-antenna inside the bird-feeder lid. But take some precautions to prevent those pesky squirrels chewing on the cable! Peter Vince ___ 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] re low noise regulators
On Dec 16, 2007 6:09 AM, Ulrich Bangert [EMAIL PROTECTED] wrote: Gentlemen, over the last years I have been confronted with numerous nonsense and rubbish technical ideas as part of my job. Over the years I came to the conclusion that just for the sake of clarity it MUST be allowed to call them nonsense and rubbish without applying any political or other I certainly agree, as long as such criticisms are clearly directed to the mistaken or false claims, and not an attack on the person who made the claim. -Michael ___ 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 Transfer
- Original Message - From: Tim Shoppa [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Monday, December 17, 2007 8:37 AM Subject: Re: [time-nuts] Time Transfer snip-- Yes, it's interesting to look at the WWV signal wander on the HP 3586, compared to it's OCXO, and while listening to it on the speaker or on a receiver. I need to plot it over a 24 hour period or so. It depends on where you are and how long you average over, but by eye I see WWV on 10 and 15 MHz going up and down by tenths of a Hz in the several minute timespan from here on the East Coast. Its also instructive to use a scope triggered off a local PPS and watch the timing of the 1 second pips on WWV bounce around. DaveB, NZ ___ 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-nuts Digest, Vol 41, Issue 57
On Dec 16, 2007 1:16 PM, Ronald Held [EMAIL PROTECTED] wrote: i thought of tha balcony option. The balcony as an overhang which effectively blots out the other half of ths sky not covered by the building. I cannot hang any antenna over the railing or on it(in my The tiny mag mount antennas with small diameter coax commonly sold for as an accessory for automotive GPS units should work fine with a modern GPS module (perhaps a cheap SiRF III based unit if it includes PPS out), and I believe you can find the mag mount antennas for about $20-30 online. It would be small enough that if you secured the cable (tie wraps or tape) that it would be undetectable. http://www.wi-sys.com/products/antennas/WS3915-HR.php -Michael ___ 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-nuts Digest, Vol 41, Issue 57
Sounds like you need to move! Daun -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ronald Held Sent: Sunday, December 16, 2007 1:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] time-nuts Digest, Vol 41, Issue 57 i thought of tha balcony option. The balcony as an overhang which effectively blots out the other half of ths sky not covered by the building. I cannot hang any antenna over the railing or on it(in my lease and enofrce;I asked), plus there are birds and squirrels which would get into it. Any other suggestions? Date: Sat, 15 Dec 2007 21:25:14 -0600 From: Jack Hudler [EMAIL PROTECTED] Subject: Re: [time-nuts] Upgrading possibilities for more accurate, precise stable mark ii To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii If you have a porch or balcony, just drilled a 1/4 inch hole through the edge of the sliding door frame to handle an external antenna. Hide the wire in the carpet edge or behind the baseboard. When you leave just caulk up the holes and no one's the wiser. Most of the time (well the ones I lived in) apartments have touch up paint kits (or the paint codes at the local big box) so you can fill nail holes and such for move out. I did this at four different apartments and no one ever found it, or if they did, didn't care. Most of the time I drilled three holes for coaxial cables to DirecTV and 58532A GPS antenna mounted on the back of the DirecTV antenna (Note: I never used the thin flat strip to run coax through the door there was too much static build up. That being said; it is still a viable option for GPS or DirecTV). ___ 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.
Re: [time-nuts] re low noise regulators
In a message dated 12/14/2007 15:00:00 Pacific Standard Time, [EMAIL PROTECTED] writes: A simple RC filter of say 2 Ohms into 4700uF has a -3dB cut-off at around 17Hz (4700uF caps are getting quite small these days). That would take care of most of the 100Hz to 10KHz noise. It still helps to have as low a noise as possible before using such brute force filtering to get that extra few dB of noise reduction. Using a typical current of 0.16A at 12V for a Euro-can OCXO we would only have 0.32V voltage drop across the resistor. However the resultant drop will depend on the ambient temperature. In principle the regulator output could be given a suitable temperature drift characteristic to compensate. However doing this without degrading the noise at the filter output may be challenging. Hi Bruce, the tempco effect of the series resistor may not be a factor at all for typical OCXO's. If we take a standard 1% resistor such as the Panasonic ERO-S2PHF2R00 (available on Digikey) with 100ppm/C tempco (that's a fairly bad tempco), then we get: 0.32V * 100ppm = 32 microvolts per Degree C change (actually it's +/-50ppm, so this example is worse than what we would see in real life). If we now take the Supply-Voltage-versus-Frequency characteristic of a typical standard single oven OCXO of 1E-08, at +/-5% variation for a 12V part we get: 1E-08 for 1.2V change, then we get: 8.33E-09/V * 32E-06V = 2.66E-013 change per degree C. For this particular OCXO with a stability of 1E-09 per degree C, the change in frequency due to the change in the 2 Ohm resistor value is about 3700x less than the temperature stability of the OCXO itself. In other words the effect of the resistor is inconsequential. For a good double-oven OCXO this is even less of a factor, for exampe the MTI double oven we use only has 8.3E-11 per volt change - two orders of magnitude less sensitivity than the example above. The capacitors' microphonic sensitivity may actuallyy be more of a factor here. It still helps to have as low a noise as possible before using such brute force filtering to get that extra few dB of noise reduction. It's not just a few dB, it's -3dB at 17Hz already, and that drops at ~-20dB per decade. At 170Hz it could theoretically give -23dB already, or in other words if the noise floor was entirely due to the supply voltage noise, then the difference would be between say -140dBc/Hz and about -160dBc/Hz at 170Hz - this could be a very significant improvement. You are absolutely right, it is very difficult to get low noise 10Hz. bye, Said **See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop000304) ___ 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 Transfer
Hi Dave: The HP 114 is a 1 PPS trigger generator with offset and was made for use with WWV, see: http://www.prc68.com/I/TF_rack.html The audio from an HF receiver is fed to the V input on the scope and you can adjust the sweep speed as fast as propagation will allow. The 114 time offset moves the trace left or right. Then watching how long it takes to drift a division you can see what your house standard is doing. An interesting way to use HF for time transfer would be to use a chirp based system. Most chirp transmitters now use GPS control of their timing. Chirp is used to determine what the propagation is between a given transmitter and receiver. Since the chirp receiver knows exactly what the propagation is it should make for a more acccurate HF timing receiver. http://www.prc68.com/I/RCS-5A.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Dave Brown wrote: - Original Message - From: Tim Shoppa [EMAIL PROTECTED] To: time-nuts@febo.com Sent: Monday, December 17, 2007 8:37 AM Subject: Re: [time-nuts] Time Transfer snip-- Yes, it's interesting to look at the WWV signal wander on the HP 3586, compared to it's OCXO, and while listening to it on the speaker or on a receiver. I need to plot it over a 24 hour period or so. It depends on where you are and how long you average over, but by eye I see WWV on 10 and 15 MHz going up and down by tenths of a Hz in the several minute timespan from here on the East Coast. Its also instructive to use a scope triggered off a local PPS and watch the timing of the 1 second pips on WWV bounce around. DaveB, NZ ___ 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.
Re: [time-nuts] Upgrading possibilities for more accurate, precise stable time system
Hi Ronald: Have a look at the different time transfer methods at: http://www.prc68.com/I/timefreq.shtml#TT Since these involve receiving a signal from a transmitter you need to have a way to know which signals you can get in your building. For example LORAN-C and WWVB are low frequency signals. CDMA cell phone is microwave. VLF military stations are used to send subs encrypted messages and have well controlled carriers. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Ronald Held wrote: i thought of tha balcony option. The balcony as an overhang which effectively blots out the other half of ths sky not covered by the building. I cannot hang any antenna over the railing or on it(in my lease and enofrce;I asked), plus there are birds and squirrels which would get into it. Any other suggestions? Date: Sat, 15 Dec 2007 21:25:14 -0600 From: Jack Hudler [EMAIL PROTECTED] Subject: Re: [time-nuts] Upgrading possibilities for more accurate, precise stable mark ii To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii If you have a porch or balcony, just drilled a 1/4 inch hole through the edge of the sliding door frame to handle an external antenna. Hide the wire in the carpet edge or behind the baseboard. When you leave just caulk up the holes and no one's the wiser. Most of the time (well the ones I lived in) apartments have touch up paint kits (or the paint codes at the local big box) so you can fill nail holes and such for move out. I did this at four different apartments and no one ever found it, or if they did, didn't care. Most of the time I drilled three holes for coaxial cables to DirecTV and 58532A GPS antenna mounted on the back of the DirecTV antenna (Note: I never used the thin flat strip to run coax through the door there was too much static build up. That being said; it is still a viable option for GPS or DirecTV). ___ 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.
Re: [time-nuts] re low noise regulators
I think the issue with the series resistor is that the oven current is temperature dependant, so the drop through the 2 ohm resistor is temperature dependant too, regardless of the tolerance or stability of the resistor itself. As long as the current/temperature curve of the oven is predictable, that could be compensated, assuming the loop response of the oven has no overshoot. I think it requires making too many assumptions for that scheme to work though. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Sunday, December 16, 2007 2:27 PM To: time-nuts@febo.com Subject: Re: [time-nuts] re low noise regulators In a message dated 12/14/2007 15:00:00 Pacific Standard Time, [EMAIL PROTECTED] writes: A simple RC filter of say 2 Ohms into 4700uF has a -3dB cut-off at around 17Hz (4700uF caps are getting quite small these days). That would take care of most of the 100Hz to 10KHz noise. It still helps to have as low a noise as possible before using such brute force filtering to get that extra few dB of noise reduction. Using a typical current of 0.16A at 12V for a Euro-can OCXO we would only have 0.32V voltage drop across the resistor. However the resultant drop will depend on the ambient temperature. In principle the regulator output could be given a suitable temperature drift characteristic to compensate. However doing this without degrading the noise at the filter output may be challenging. Hi Bruce, the tempco effect of the series resistor may not be a factor at all for typical OCXO's. If we take a standard 1% resistor such as the Panasonic ERO-S2PHF2R00 (available on Digikey) with 100ppm/C tempco (that's a fairly bad tempco), then we get: 0.32V * 100ppm = 32 microvolts per Degree C change (actually it's +/-50ppm, so this example is worse than what we would see in real life). If we now take the Supply-Voltage-versus-Frequency characteristic of a typical standard single oven OCXO of 1E-08, at +/-5% variation for a 12V part we get: 1E-08 for 1.2V change, then we get: 8.33E-09/V * 32E-06V = 2.66E-013 change per degree C. For this particular OCXO with a stability of 1E-09 per degree C, the change in frequency due to the change in the 2 Ohm resistor value is about 3700x less than the temperature stability of the OCXO itself. In other words the effect of the resistor is inconsequential. For a good double-oven OCXO this is even less of a factor, for exampe the MTI double oven we use only has 8.3E-11 per volt change - two orders of magnitude less sensitivity than the example above. The capacitors' microphonic sensitivity may actuallyy be more of a factor here. It still helps to have as low a noise as possible before using such brute force filtering to get that extra few dB of noise reduction. It's not just a few dB, it's -3dB at 17Hz already, and that drops at ~-20dB per decade. At 170Hz it could theoretically give -23dB already, or in other words if the noise floor was entirely due to the supply voltage noise, then the difference would be between say -140dBc/Hz and about -160dBc/Hz at 170Hz - this could be a very significant improvement. You are absolutely right, it is very difficult to get low noise 10Hz. bye, Said **See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop000304) ___ 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.
Re: [time-nuts] re low noise regulators
[EMAIL PROTECTED] wrote: Hi Bruce, The capacitors' microphonic sensitivity may actuallyy be more of a factor here. Are electrolytics microphonic? Ferroelectric (X7R, Z5U,Y5V, X5R, etc but not NP0/C0G) ceramic caps are microphonic It still helps to have as low a noise as possible before using such brute force filtering to get that extra few dB of noise reduction. It's not just a few dB, it's -3dB at 17Hz already, and that drops at ~-20dB per decade. At 170Hz it could theoretically give -23dB already, or in other words if the noise floor was entirely due to the supply voltage noise, then the difference would be between say -140dBc/Hz and about -160dBc/Hz at 170Hz - this could be a very significant improvement. You are absolutely right, it is very difficult to get low noise 10Hz. bye, Said Bruce ___ 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] re low noise regulators
From: Bruce Griffiths [EMAIL PROTECTED] Subject: Re: [time-nuts] re low noise regulators Date: Mon, 17 Dec 2007 11:19:05 +1300 Message-ID: [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Hi Bruce, The capacitors' microphonic sensitivity may actuallyy be more of a factor here. Are electrolytics microphonic? Ferroelectric (X7R, Z5U,Y5V, X5R, etc but not NP0/C0G) ceramic caps are microphonic All caps is more or less microphonic. Even a pair of plates with vacuum between them are microphonic. However, the higher capacitivity of the dielectrum, the higher microphonic sensitivity can you expect. You can as always reduce the microphonic aspect through mechanical design, including wise use of symmetry, but the effect will always be there. The point being, the effect is always there, but the coupling degree may be stronger or weaker. Traditionally electrolytics have not been the main concern thought. But they are not always the best choice for many other reasons, as you are fully aware. Cheers, Magnus ___ 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-nuts Digest, Vol 41, Issue 56
-- Original Message -- Received: Sat, 15 Dec 2007 05:53:00 PM PST From: Ronald Held [EMAIL PROTECTED] To: time-nuts@febo.com Subject: Re: [time-nuts] time-nuts Digest, Vol 41, Issue 56 My apartment is in a reinforced concrete building, not near the roof. Many years ago I tried a Garmin handheld and could not get a lock. Recently, I tried a GPS watch near the window, and could not get e lock, even though it did lock up outside(cold) after a few minutes. that is why i do not think I can use a GPS disciplining option. Since my unit already gets no worse than 1 millisecond when locked up, i would want no worse than 1 microsecond in phase over long periods of time. What non GPS options are there with the electronic building skills I do not have? Does a cell phone work in your apartment? If so, you might consider an oscillator that gets its frequency discipline indirectly: GPS receiver disciplines oscillator at cell phone tower, then CDMA cell phone network disciplines oscillator in your apartment. See http://www.endruntechnologies.com/frequency-standard-lowcost.htm for an example. James Maynard, K7KK Salem, Oregon, 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.
Re: [time-nuts] Antennas in apartments
i thought of tha balcony option. The balcony as an overhang which effectively blots out the other half of ths sky not covered by the building. I cannot hang any antenna over the railing or on it(in my lease and enofrce;I asked), plus there are birds and squirrels which would get into it. Any other suggestions? You said I cannot hang any antenna over the railing or on it. Does that mean you can put things out there as long as they are not visible from the outside? Try it just inside/below the railing. Talk to your building superintendent. Offer to provide NTP service to the whole complex if he will help you setup a GPS antenna. What do people who want satellite TV do? I like the hide-it-in-a-bird-feeder suggestion. Are plants and bird feeders prohibited? -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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.
