Re: [time-nuts] Can a quartz crystal go off by 2% ?
Hi My guess, is it's a mechanical failure, as unless you've had a series of long power cuts, the battery/quartz backup won't kick in. AFIK, the Quartz clock only is in effect, if the 50Hz supply fails. The utility 50Hz is maintaind to a close tolerance and tweaked to maintain a very good 24 hour clock, though it may wander one way or t'other during the day. A good friend a while back, had the imersion heater fail, in such a way that it welded the E7/Normal relay in the E7 position. It was some weeks (in the summer, so heating not in use) before he noticed that the Normal meter clock was not incrementing! Much hand wringing later, he phoned the electric co, who without question replaced the E7 clock/changeover unit and DIDN'T sting him for the cheap electricity he had used, instead of the full price stuff. Two choices, and I didn't say this(!) 1) ignore it, and reap the benefit of a wandering 7 hour cheap electric period :-) (But that could be seen as Fraud by some) 2) call the electric co, and they will probably change the clock/changeover unit for free, as after all, it is to their benefit, not yours! If they do change it, I doubt they will let you keep the old one (your might re-fit it, in their eyes) and I doubt the tech who does the job will know the details of it's internal workings. As you use little of the E7 facility, it may pay to have the clock etc removed and go onto a standard tarrif. But, as you say, have to do the math first. I did sit down one time, and worked out that taking into account inverter and battery charge/discharge efficiency (or lack of) it is not worth putting together a large UPS for the PC's I run 24/7 (4 of the blighters at present) that would charge up overnight, and run them on battery during the day. At least, not with the level of technology currently available to the likes of us. It is close, but excluding the cost of buying/building the thing, the resulting running costs would not be worth having. It would not even pay for itself in my lifetime! Best Regards. Dave B. PS: Does anyone else miss the odd digest mail at times? -- Message: 4 Date: Mon, 28 Dec 2009 19:47:41 -0500 From: Bob Camp li...@cq.nu Subject: Re: [time-nuts] Can a quartz crystal go off by 2% ? To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: a0c20146-6482-45ab-b219-bb76ba5fa...@cq.nu Content-Type: text/plain; charset=us-ascii Hi Even with a tuning fork crystal, anything past about 0.2% is a very large changel. That's true for tuning and also true for normal aging. I suspect that something mechanical has happened. 1) A cracked crystal - unlikely 2).An electro magnet in the driving circuit no longer firing fully. a) Due to a bad magnet b) Due to low power c) Due to a dying chip 3) A worn escarpment. Time to get it replaced Bob On Dec 28, 2009, at 6:22 PM, Dr. David Kirkby wrote: I'm on the so-called 'Economy 7' electric in the UK, where I'm supposed to get cheap electric from 0030 to 0730 - i.e. a 7 hour period when electricity demand is low. I'm no longer heating by electric, but do run some computers 24/7. It's not totally clear whether this saves me money or costs me money, as I pay a higher price per unit during the expensive period, to compensate for the fact I get it cheap for 7 hours. But I run some computers 24/7. I guess I should do the maths and work it out. Apart from some heaters in the garage, which are very rarely used, I no longer heat with it. The time when the electric is cheap is set by a clock, which rotates once/day. It says on it quartz somewhere, so it must be regulated by a crystal and not from the 50 Hz supply, which would be pretty useless, as the clock would go wrong if there was ever a power failure. The clock has not been changed in the 17 years I've lived at my house, though the meter has on a couple of occasions. The clock used to keep accurate, but now it looses time about 30 minutes/day. I wrote a computer program to predict when the electric is cheap, so we can schedule when things like the washing machine, dishwasher, Hoover etc are used. Even cooking to a certain extent, if it's convenient, though our life does not revolve around the cheap electric. I'm wondering if this is a mechanical fault in the clock, or whether the crystal has developed a fault. It's clearly well outside any tolerance or aging process of any crystal - even the cheapest ones. I've not done any very extensive tests, but the error does not appear to be constant. Hence every month or so I need to produce a new table, as my predictions get less accurate with time. Since one can only read the clock to an accuracy of about 15 minutes, it's not easy to know how far it is out. Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters,
Re: [time-nuts] Can a quartz crystal go off by 2% ?
AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn, Cumbria). You would need to have some sort of automated system to accommodate daylight savings switchovers in Spring and Autumn. That said, I would have thought once synchronised, they would tick off the 50 Hz supply. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David Kirkby Sent: 28 December 2009 23:22 To: Discussion of precise time and frequency measurement Subject: [time-nuts] Can a quartz crystal go off by 2% ? I'm on the so-called 'Economy 7' electric in the UK, where I'm supposed to get cheap electric from 0030 to 0730 - i.e. a 7 hour period when electricity demand is low. I'm no longer heating by electric, but do run some computers 24/7. It's not totally clear whether this saves me money or costs me money, as I pay a higher price per unit during the expensive period, to compensate for the fact I get it cheap for 7 hours. But I run some computers 24/7. I guess I should do the maths and work it out. Apart from some heaters in the garage, which are very rarely used, I no longer heat with it. The time when the electric is cheap is set by a clock, which rotates once/day. It says on it quartz somewhere, so it must be regulated by a crystal and not from the 50 Hz supply, which would be pretty useless, as the clock would go wrong if there was ever a power failure. The clock has not been changed in the 17 years I've lived at my house, though the meter has on a couple of occasions. The clock used to keep accurate, but now it looses time about 30 minutes/day. I wrote a computer program to predict when the electric is cheap, so we can schedule when things like the washing machine, dishwasher, Hoover etc are used. Even cooking to a certain extent, if it's convenient, though our life does not revolve around the cheap electric. I'm wondering if this is a mechanical fault in the clock, or whether the crystal has developed a fault. It's clearly well outside any tolerance or aging process of any crystal - even the cheapest ones. I've not done any very extensive tests, but the error does not appear to be constant. Hence every month or so I need to produce a new table, as my predictions get less accurate with time. Since one can only read the clock to an accuracy of about 15 minutes, it's not easy to know how far it is out. Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters, which we no long use. Dave ___ 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] Can a quartz crystal go off by 2% ?
Over here they use a tone system that is modulated onto the mains to operate a relay to switch over to night rate and turn on the immersion heater in the hot water cylinder. Steve Rooke 2009/12/29 Rob Kimberley r...@timing-consultants.com: AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn, Cumbria). You would need to have some sort of automated system to accommodate daylight savings switchovers in Spring and Autumn. That said, I would have thought once synchronised, they would tick off the 50 Hz supply. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David Kirkby Sent: 28 December 2009 23:22 To: Discussion of precise time and frequency measurement Subject: [time-nuts] Can a quartz crystal go off by 2% ? I'm on the so-called 'Economy 7' electric in the UK, where I'm supposed to get cheap electric from 0030 to 0730 - i.e. a 7 hour period when electricity demand is low. I'm no longer heating by electric, but do run some computers 24/7. It's not totally clear whether this saves me money or costs me money, as I pay a higher price per unit during the expensive period, to compensate for the fact I get it cheap for 7 hours. But I run some computers 24/7. I guess I should do the maths and work it out. Apart from some heaters in the garage, which are very rarely used, I no longer heat with it. The time when the electric is cheap is set by a clock, which rotates once/day. It says on it quartz somewhere, so it must be regulated by a crystal and not from the 50 Hz supply, which would be pretty useless, as the clock would go wrong if there was ever a power failure. The clock has not been changed in the 17 years I've lived at my house, though the meter has on a couple of occasions. The clock used to keep accurate, but now it looses time about 30 minutes/day. I wrote a computer program to predict when the electric is cheap, so we can schedule when things like the washing machine, dishwasher, Hoover etc are used. Even cooking to a certain extent, if it's convenient, though our life does not revolve around the cheap electric. I'm wondering if this is a mechanical fault in the clock, or whether the crystal has developed a fault. It's clearly well outside any tolerance or aging process of any crystal - even the cheapest ones. I've not done any very extensive tests, but the error does not appear to be constant. Hence every month or so I need to produce a new table, as my predictions get less accurate with time. Since one can only read the clock to an accuracy of about 15 minutes, it's not easy to know how far it is out. Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters, which we no long use. Dave ___ 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. -- Steve Rooke - ZL3TUV G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. ___ 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] Can a quartz crystal go off by 2% ?
Rob Kimberley wrote: AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn, Cumbria). You would need to have some sort of automated system to accommodate daylight savings switchovers in Spring and Autumn. That said, I would have thought once synchronised, they would tick off the 50 Hz supply. Rob Kimberley The electricity bill always states the times are approximately 0030 to 0730 GMT. Therefore, there is no change for daylight saving. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David Kirkby Sent: 28 December 2009 23:22 To: Discussion of precise time and frequency measurement Subject: [time-nuts] Can a quartz crystal go off by 2% ? I'm on the so-called 'Economy 7' electric in the UK, where I'm supposed to get cheap electric from 0030 to 0730 - i.e. a 7 hour period when electricity demand is low. I'm no longer heating by electric, but do run some computers 24/7. It's not totally clear whether this saves me money or costs me money, as I pay a higher price per unit during the expensive period, to compensate for the fact I get it cheap for 7 hours. But I run some computers 24/7. I guess I should do the maths and work it out. Apart from some heaters in the garage, which are very rarely used, I no longer heat with it. The time when the electric is cheap is set by a clock, which rotates once/day. It says on it quartz somewhere, so it must be regulated by a crystal and not from the 50 Hz supply, which would be pretty useless, as the clock would go wrong if there was ever a power failure. The clock has not been changed in the 17 years I've lived at my house, though the meter has on a couple of occasions. The clock used to keep accurate, but now it looses time about 30 minutes/day. I wrote a computer program to predict when the electric is cheap, so we can schedule when things like the washing machine, dishwasher, Hoover etc are used. Even cooking to a certain extent, if it's convenient, though our life does not revolve around the cheap electric. I'm wondering if this is a mechanical fault in the clock, or whether the crystal has developed a fault. It's clearly well outside any tolerance or aging process of any crystal - even the cheapest ones. I've not done any very extensive tests, but the error does not appear to be constant. Hence every month or so I need to produce a new table, as my predictions get less accurate with time. Since one can only read the clock to an accuracy of about 15 minutes, it's not easy to know how far it is out. Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters, which we no long use. Dave ___ 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. ___ 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] Can a quartz crystal go off by 2% ?
Do you have a photo of your meter? Rob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David Kirkby Sent: 29 December 2009 13:59 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Can a quartz crystal go off by 2% ? Rob Kimberley wrote: AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn, Cumbria). You would need to have some sort of automated system to accommodate daylight savings switchovers in Spring and Autumn. That said, I would have thought once synchronised, they would tick off the 50 Hz supply. Rob Kimberley The electricity bill always states the times are approximately 0030 to 0730 GMT. Therefore, there is no change for daylight saving. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David Kirkby Sent: 28 December 2009 23:22 To: Discussion of precise time and frequency measurement Subject: [time-nuts] Can a quartz crystal go off by 2% ? I'm on the so-called 'Economy 7' electric in the UK, where I'm supposed to get cheap electric from 0030 to 0730 - i.e. a 7 hour period when electricity demand is low. I'm no longer heating by electric, but do run some computers 24/7. It's not totally clear whether this saves me money or costs me money, as I pay a higher price per unit during the expensive period, to compensate for the fact I get it cheap for 7 hours. But I run some computers 24/7. I guess I should do the maths and work it out. Apart from some heaters in the garage, which are very rarely used, I no longer heat with it. The time when the electric is cheap is set by a clock, which rotates once/day. It says on it quartz somewhere, so it must be regulated by a crystal and not from the 50 Hz supply, which would be pretty useless, as the clock would go wrong if there was ever a power failure. The clock has not been changed in the 17 years I've lived at my house, though the meter has on a couple of occasions. The clock used to keep accurate, but now it looses time about 30 minutes/day. I wrote a computer program to predict when the electric is cheap, so we can schedule when things like the washing machine, dishwasher, Hoover etc are used. Even cooking to a certain extent, if it's convenient, though our life does not revolve around the cheap electric. I'm wondering if this is a mechanical fault in the clock, or whether the crystal has developed a fault. It's clearly well outside any tolerance or aging process of any crystal - even the cheapest ones. I've not done any very extensive tests, but the error does not appear to be constant. Hence every month or so I need to produce a new table, as my predictions get less accurate with time. Since one can only read the clock to an accuracy of about 15 minutes, it's not easy to know how far it is out. Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters, which we no long use. Dave ___ 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. ___ 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] Timenoob - Cheap and simple 10MHz reference
Semiconductorstore.com also have the CW25-TIM at a cheaper price ($64 vs $89) and it is more sensitive, so can possibly work indoors. They both, apparently, use the same NavSync chips, so does the '25 have disadvantages I haven't spotted? Peter 2009/12/28 Hal Murray hmur...@megapathdsl.net: Does the factory sell direct in small quantities ? From here (California), googling for Navsync CW12-TIM finds: http://www.semiconductorstore.com/pages/asp/supplier.asp?pl=0138gclid=CL_G5ar W-Z4CFU1M5Qod1XNWLA (Sorry for the line wrap.) ___ 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] Can a quartz crystal go off by 2% ?
I wonder how the power company changes the meter rate, based on the local timer. Are there two different meters, with a separate circuit for cheap loads? Perhaps not, because you continue to run your computers without interruption. OTOH, you said in the first posting, Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters, which we no long use. If you don't power anything with the storage heater circuit, are you really getting any cheap electric? Do your power bills show a difference as the faulty clock loses time? Does the bill just show total power, or is there a separate line item for cheap power? Could the power company be ignoring clock maintenance because they know that you no longer have storage heaters? Can the person reading the meter see the time on the clock, or is reading automated? Just another way of looking at the problem . . . Bill Hawkins -Original Message- From: Dr. David Kirkby Sent: Monday, December 28, 2009 7:19 PM No, I'm quite happy to get cheap electric during the day some times! It's more useful than having it in the middle of the night. So I'm not concerned over this, but just interested what might be the problem with it. ___ 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] Can a quartz crystal go off by 2% ?
Hi Rob, Actually they are controlled from a low bit-rate signal phase-modulated onto Radio-4 long-wave (198KHz). If you have an SSB or CW receiver that tunes down to that frequency, switch on the BFO and look at the output on something like Spectrum Lab, and the phase modulation is readily seen! TTFN, Peter 2009/12/29 Rob Kimberley r...@timing-consultants.com: AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn, Cumbria). You would need to have some sort of automated system to accommodate daylight savings switchovers in Spring and Autumn. That said, I would have thought once synchronised, they would tick off the 50 Hz supply. Rob Kimberley ___ 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] Can a quartz crystal go off by 2% ?
They just switch the meter over to count night units. Strictly of course both day and night units are counted as kWh, and the supply company apply different charge rates to the night units. Effectively there are two meters in the same case that are switched over by the time clock output signal. There may also be a contactor connected to the line from the time clock to the meter. That will switch on some circuits that are intended to be night only. The guy who reads the meter just reads off day units and night units, and unless they suspect there's a problem with it they won't look at the time clock. D. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bill Hawkins Sent: 29 December 2009 17:17 To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Can a quartz crystal go off by 2% ? I wonder how the power company changes the meter rate, based on the local timer. Are there two different meters, with a separate circuit for cheap loads? Perhaps not, because you continue to run your computers without interruption. OTOH, you said in the first posting, Sometimes we hear the contactor go over, as this is supposed to then power the storage heaters, which we no long use. If you don't power anything with the storage heater circuit, are you really getting any cheap electric? Do your power bills show a difference as the faulty clock loses time? Does the bill just show total power, or is there a separate line item for cheap power? Could the power company be ignoring clock maintenance because they know that you no longer have storage heaters? Can the person reading the meter see the time on the clock, or is reading automated? Just another way of looking at the problem . . . Bill Hawkins ___ 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] chip scale atomic clock
2009/12/26 Robert Lutwak lut...@alum.mit.edu: ... CSAC is intended for portable battery-powered operation. Surely your basement has the space and wallplug power to support an LPRO. (p.s. don't cool the damn thing, heat it). ... Hi Robert, Do I understand you are suggesting heating an LPRO, not cooling it? That seems to go against what I understood, that greater cooling leads to increased life. As an aside, a newbie question if I may: being so used to Caesium standards being THE reference, I was surprised to hear that the CSAC has an aging mechanism - can you say a few words to explain that please? Peter ___ 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] Timenoob - Cheap and simple 10MHz reference
Thanks Ed, yes, I hadn't looked closely enough at the pictures. The higher sensitivity I mentioned came from the second line of the Features section near the bottom of: http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=41599 Enables indoor use -173 dBW acquisition and -185 dBW tracking although admittedly right underneath that in the Specifications section is does say: Track Sensitivity: -155 dBm A cased of specmanship? Peter 2009/12/29 Ed Palmer ed_pal...@sasktel.net: The CW-12 consists of the CW-25 mounted on a circuit board with some glue logic, connectors, etc. The CW-25 itself is the surface-mount module in the middle of the CW-12. Compare the pictures - you'll see what I mean. Both units are listed as having a tracking sensitivity of -155 dbm. I don't know what you mean when you say that the CW-25 is more sensitive. By the way, the CW-12 works great indoors. Through a typical wood-frame construction I usually get 7 or 8 satellites with a cheap active patch antenna. With a VIC-100 timing antenna, I usually have 10 or more satellites. 1 PPS performance is also very good. Multiple measurements of 1000 periods shows a standard deviation of 5 ns with a min-max range of 30 ns. This is without sawtooth correction because this unit doesn't support it - even with the Motorola software. Ed - Original Message - From: Peter Vince pvi...@theiet.org Date: Tuesday, December 29, 2009 10:21 am Subject: Re: [time-nuts] Timenoob - Cheap and simple 10MHz reference Semiconductorstore.com also have the CW25-TIM at a cheaper price ($64 vs $89) and it is more sensitive, so can possibly work indoors. They both, apparently, use the same NavSync chips, so does the '25 have disadvantages I haven't spotted? Peter 2009/12/28 Hal Murray hmur...@megapathdsl.net: Does the factory sell direct in small quantities ? From here (California), googling for Navsync CW12-TIM finds: http://www.semiconductorstore.com/pages/asp/supplier.asp?pl=0138gclid=CL_G5ar W-Z4CFU1M5Qod1XNWLA (Sorry for the line wrap.) ___ 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. __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __ ___ 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] Notes on the Driscoll VHF Overtone Crystal Oscillator
I've had several discussions with Chris Bartram about this and similar VHF oscillators. My understanding is that Chris' variant of this particular Driscoll osc. has been designed specifically for low close-in phase noise, and that is why the phase-shift network has a low-pass response (to try and reduce flicker noise) rather than the more common high-pass network. The NE688xx was chosen for the active devices due to it's claimed low flicker noise; the flicker noise parameters are actually specified on the datasheet for the NE68833 - which is quite unusual. The high Ft may not be desirable, but it seems that is the price to pay for low flicker noise. I've built a couple of oscillators similar to Chris Bartram's design at around 116MHz, albeit with the more conventional 'high-pass' phase shift network, and they seem to perform quite well - certainly no sign of spurious high frequency oscillation, but that may be a function of PCB layout. I'm not aware of anyone yet measuring the close-in phase noise of the Bartram variant of this oscillator, and that's really the only way to verify or otherwise that the new topology gives any advantage in terms of close-in phase noise, compared to a similar, low cost design using similar crystals. BTW I've tried simulating the phase noise of this oscillator using ADS, but wasn't able to get meaningful results from the simulator, and on this occasion Agilent technical support were not able to resole the issues either. Maybe Microwave Office or Ansoft Designer would yield better results, but I haven't tried them. (LT Spice is unable to simulate phase noise of oscillators). regards Grant An inductor in series with the 220 ohm emitter resistor will improve the phase noise floor. In theory, yes. But already with only 220 Ohms, Q3 will oscillate wildly at a few hundred MHz. The mechanism is this: Somewhat hot RF transistor NE688, collector at RF ground, emitter at high-ish impedance --- When you measure into the base, you see a negative resistance in series with a few pF. Using a transistor with a higher ft than necessary in an oscillator circuit isnt usually a good idea. ___ 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] Timenoob - Cheap and simple 10MHz reference
-185dBW = -155dBm so both sensitivity measures are equivalent. Bruce Peter Vince wrote: Thanks Ed, yes, I hadn't looked closely enough at the pictures. The higher sensitivity I mentioned came from the second line of the Features section near the bottom of: http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=41599 Enables indoor use -173 dBW acquisition and -185 dBW tracking although admittedly right underneath that in the Specifications section is does say: Track Sensitivity: -155 dBm A cased of specmanship? Peter 2009/12/29 Ed Palmered_pal...@sasktel.net: The CW-12 consists of the CW-25 mounted on a circuit board with some glue logic, connectors, etc. The CW-25 itself is the surface-mount module in the middle of the CW-12. Compare the pictures - you'll see what I mean. Both units are listed as having a tracking sensitivity of -155 dbm. I don't know what you mean when you say that the CW-25 is more sensitive. By the way, the CW-12 works great indoors. Through a typical wood-frame construction I usually get 7 or 8 satellites with a cheap active patch antenna. With a VIC-100 timing antenna, I usually have 10 or more satellites. 1 PPS performance is also very good. Multiple measurements of 1000 periods shows a standard deviation of5 ns with a min-max range of 30 ns. This is without sawtooth correction because this unit doesn't support it - even with the Motorola software. Ed - Original Message - From: Peter Vincepvi...@theiet.org Date: Tuesday, December 29, 2009 10:21 am Subject: Re: [time-nuts] Timenoob - Cheap and simple 10MHz reference Semiconductorstore.com also have the CW25-TIM at a cheaper price ($64 vs $89) and it is more sensitive, so can possibly work indoors. They both, apparently, use the same NavSync chips, so does the '25 have disadvantages I haven't spotted? Peter 2009/12/28 Hal Murrayhmur...@megapathdsl.net: Does the factory sell direct in small quantities ? From here (California), googling forNavsync CW12-TIM finds: http://www.semiconductorstore.com/pages/asp/supplier.asp?pl=0138gclid=CL_G5ar W-Z4CFU1M5Qod1XNWLA (Sorry for the line wrap.) ___ 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. __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __ ___ 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] Timenoob - Cheap and simple 10MHz reference
Oh Good Lord - not paying attention to the units! Sorry guys! Peter. 2009/12/29 Bruce Griffiths bruce.griffi...@xtra.co.nz: -185dBW = -155dBm so both sensitivity measures are equivalent. Bruce Peter Vince wrote: Thanks Ed, yes, I hadn't looked closely enough at the pictures. The higher sensitivity I mentioned came from the second line of the Features section near the bottom of: http://www.semiconductorstore.com/cart/pc/viewPrd.asp?idproduct=41599 Enables indoor use -173 dBW acquisition and -185 dBW tracking although admittedly right underneath that in the Specifications section is does say: Track Sensitivity: -155 dBm A cased of specmanship? Peter 2009/12/29 Ed Palmered_pal...@sasktel.net: The CW-12 consists of the CW-25 mounted on a circuit board with some glue logic, connectors, etc. The CW-25 itself is the surface-mount module in the middle of the CW-12. Compare the pictures - you'll see what I mean. Both units are listed as having a tracking sensitivity of -155 dbm. I don't know what you mean when you say that the CW-25 is more sensitive. By the way, the CW-12 works great indoors. Through a typical wood-frame construction I usually get 7 or 8 satellites with a cheap active patch antenna. With a VIC-100 timing antenna, I usually have 10 or more satellites. 1 PPS performance is also very good. Multiple measurements of 1000 periods shows a standard deviation of5 ns with a min-max range of 30 ns. This is without sawtooth correction because this unit doesn't support it - even with the Motorola software. Ed - Original Message - From: Peter Vincepvi...@theiet.org Date: Tuesday, December 29, 2009 10:21 am Subject: Re: [time-nuts] Timenoob - Cheap and simple 10MHz reference Semiconductorstore.com also have the CW25-TIM at a cheaper price ($64 vs $89) and it is more sensitive, so can possibly work indoors. They both, apparently, use the same NavSync chips, so does the '25 have disadvantages I haven't spotted? Peter 2009/12/28 Hal Murrayhmur...@megapathdsl.net: Does the factory sell direct in small quantities ? From here (California), googling forNavsync CW12-TIM finds: http://www.semiconductorstore.com/pages/asp/supplier.asp?pl=0138gclid=CL_G5ar W-Z4CFU1M5Qod1XNWLA (Sorry for the line wrap.) ___ 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. __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __ ___ 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. __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __ ___ 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] Notes on the Driscoll VHF Overtone Crystal Oscillator
Grant Hodgson wrote: I've had several discussions with Chris Bartram about this and similar VHF oscillators. My understanding is that Chris' variant of this particular Driscoll osc. has been designed specifically for low close-in phase noise, and that is why the phase-shift network has a low-pass response (to try and reduce flicker noise) rather than the more common high-pass network. Since an overtone crystal is usually used a bandpass feedback network response is usually required to ensure that oscillation occurs on the desired overtone. The dc biasing network has more effect on the flicker noise than the RF feedback network. The NE688xx was chosen for the active devices due to it's claimed low flicker noise; the flicker noise parameters are actually specified on the datasheet for the NE68833 - which is quite unusual. The high Ft may not be desirable, but it seems that is the price to pay for low flicker noise. Actually close in flicker noise is usually better for lower ft transistors with larger junction areas. According to the datasheet the device is obsolete or about to be phased out. I see no mention of flicker noise specs in the datasheet except perhaps in the models which are not guaranteed. I've built a couple of oscillators similar to Chris Bartram's design at around 116MHz, albeit with the more conventional 'high-pass' phase shift network, and they seem to perform quite well - certainly no sign of spurious high frequency oscillation, but that may be a function of PCB layout. I'm not aware of anyone yet measuring the close-in phase noise of the Bartram variant of this oscillator, and that's really the only way to verify or otherwise that the new topology gives any advantage in terms of close-in phase noise, compared to a similar, low cost design using similar crystals. BTW I've tried simulating the phase noise of this oscillator using ADS, but wasn't able to get meaningful results from the simulator, and on this occasion Agilent technical support were not able to resole the issues either. Maybe Microwave Office or Ansoft Designer would yield better results, but I haven't tried them. (LT Spice is unable to simulate phase noise of oscillators). regards Grant 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] Best test setup?
I have severa crystal, rubidium, and GPSDO oscillators that I would like to characterize. I have a 5370B and cesium that has 1, 5, and 10 MHz output. The question is what is the best configuration of internal/external oscillator, start input, and stop input of the 5370B (and do I use an external 1pps trigger)? I use my 5370 in +TI mode, with 1-pps at the START channel and 10 MHz at the STOP channel. This yields one reading per second between 0-100 ns. (Or, rather, about 6-106 ns on my particular counter, since the START pulse has to come before the STOP pulse from the counter's point of view. The distinction isn't important.) If you want to watch the oscillator during warmup, when it may be drifting too rapidly for meaningful observation at 100ns/sec intervals, you can feed 1-pps inputs to both START and STOP. This requires two 1-pps dividers. If you have a HP 5061 cesium, be _very_ careful using its 1-pps output. The amplitude is something like 10V pk-pk and can easily fry a counter input. :( Then there is the issue of whether to use the cesium as the reference in all cases. Seems the GPSDO would have better long term stability for very long tau. Any insight appreciated. It comes down to the question of what's worse, your cesium beam tube's SNR or your GPS receiver's SNR? You can think of your GPS receiver as a cesium standard with a really awesome beam tube but a noisy radio link in the control loop. My 5061A/B is a bit more stable than my (modified/optimized) Thunderbolt beyond a few hundred seconds but it's a close contest, and a GPS clock would most likely be a better reference at timescales beyond a few hours. OTOH if you have a modern cesium standard it may well outperform the best local GPS clocks at all timescales. It seems that the best overall medium-term reference, on a cost/performance basis, is a high-performance rubidium like the 5065A. A telecom-grade LPRO-101 Rb module was tested in the attached plot against both my 5061 and Thunderbolt, without any temperature stabilization. The tests ran concurrently using two different counters, one 5370B and one homebrew. The 5370's residual jitter (red) dominated the Cs-based measurement (purple) below about 20 seconds. There's good agreement beyond that point, until the Thunderbolt's loop characteristic becomes worse than either the Cs or Rb standard beyond 400 seconds (blue). At 1000 seconds the Rb becomes less stable than the Cs, and by 4000 seconds the Rb is unstable enough, once again, to be characterized by both the TBolt and Cs references. Moral of the story is that unless you have a really good reference at all timescales of interest (which I don't), you need to be prepared to use multiple references at different timescales. Even so, you may not get all the information you're after. This graph looks nifty, but it conveys little or no information about the LPRO-101's true performance between t=20s and t=1000s! -- john, KE5FX attachment: cs_vs_tbolt.gif___ 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] Best test setup?
Skip Withrow wrote: Hello time-nuts, I'm looking for the group expertise to tell me what would be the best test setup for looking at ADEV of several oscillators. I have severa crystal, rubidium, and GPSDO oscillators that I would like to characterize. I have a 5370B and cesium that has 1, 5, and 10 MHz output. The question is what is the best configuration of internal/external oscillator, start input, and stop input of the 5370B (and do I use an external 1pps trigger)? Then there is the issue of whether to use the cesium as the reference in all cases. Seems the GPSDO would have better long term stability for very long tau. Any insight appreciated. Regards, Skip Withrow One setup that works well is to divide down one of the oscillators being compared to 1Hz (or 10Hz, 100Hz) and use this to arm the 5370B. Use the input signal for the divider to Start the 5370B and use the other source to stop the 5370B. This setup minimises the effect of divider jitter so that the technology employed in the divider isnt critical. Then one has to unwrap the phase of the measured time intervals, a fairly straightforward task. This method also ensures that the 5370B time base accuracy isn't critical as the 5370B only measures time intervals of around 1 period of the STOP input frequency. For quiet sources the measurement noise of the 5370B will dominate for tau less than 100sec or so (depends on the source ADEV vs tau). 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] Best test setup?
Bruce Griffiths wrote: Skip Withrow wrote: Hello time-nuts, I'm looking for the group expertise to tell me what would be the best test setup for looking at ADEV of several oscillators. I have severa crystal, rubidium, and GPSDO oscillators that I would like to characterize. I have a 5370B and cesium that has 1, 5, and 10 MHz output. The question is what is the best configuration of internal/external oscillator, start input, and stop input of the 5370B (and do I use an external 1pps trigger)? Then there is the issue of whether to use the cesium as the reference in all cases. Seems the GPSDO would have better long term stability for very long tau. Any insight appreciated. Regards, Skip Withrow One setup that works well is to divide down one of the oscillators being compared to 1Hz (or 10Hz, 100Hz) and use this to arm the 5370B. Use the input signal for the divider to Start the 5370B and use the other source to stop the 5370B. This setup minimises the effect of divider jitter so that the technology employed in the divider isnt critical. Then one has to unwrap the phase of the measured time intervals, a fairly straightforward task. This method also ensures that the 5370B time base accuracy isn't critical as the 5370B only measures time intervals of around 1 period of the STOP input frequency. For quiet sources the measurement noise of the 5370B will dominate for tau less than 100sec or so (depends on the source ADEV vs tau). Bruce For most caesium standards and for some GPSDOs the jitter of the PPS output exceeds the jitter of the 5370B so using the PPS output to arm the 5370B reduces the measurement noise over the setup where the PPS output is used to start (or stop) the 5370B. 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] Sending me Lady Heather screen-captures....
Mike Assuming you have learned to tame some of LH behavior issues, and that is not what is causing the problems then: MB) the temperature graph exhibits a sharp, which recovers over a period of a few minutes. ws)Likley a basic 'bug' in the LH Hardware. Best to ignore it. MB) blue PPS ADEV and the red OSC ADEV ws)The best thing I have found so far for most to do with the Blue and Red ADEV curves is to turn them off using GA They can provide some useful advanced information BUT they are not too comparable to 'standard' ADEV. MB) Periodically, the violet PPS graph and the green DAC graph will go off scale for 10-15 minutes. ws)The really LARGE jumps can and most likely are caused when the Tbolt goes into and returns from holdover. To verify if that is your cause, Look at the Sat Counts LH plot, if it goes to zero, then that is what is happing. Also check the 'holdover sec, That counts how many seconds has been spent in holdover. IF Holdover is the cause then setting the AMU down to around 1.0 from the default 4.0 can help IF you can not get a better signal and view from your antenna. If you set the Elevation up to around 25 to 30 and set the TC to 250 + from the default 100 both of these will help reduce the smaller jumps, even when your antenna has a good signal. And to reduce the Phase error that the Higher TC will cause with changing temperature and ageing reduce the Damping setting from the 1.2 default to 0.7. And before doing that set the 'Dac gain' correct. It's all a compromise, but with some effort and experience you can make things much better over the default settings. If you send me a LH screen dump or better yet a 24 hr log plot, I'd better be able to point out the causes of you problems without all the guessing. have fun ws From: Mark Sims Those spikes/decays in the temperature plot are due to false readings the Tbolt firmware gets from the temperature sensor chip. They are an artifact of how the temperature sensor works in its high resolution mode. They are actually single sample spikes of 1C (I think) in the output of the sensor chip. The reported amplitude/decay is due to the filtering the Tbolt firmware does on the temperature readings. Also, remember that the ADEV values calculated by Lady Heather are from its internal measurements of the oscillator and PPS signal against the rather-noisy-in-the-short-term GPS signal. They tend to depart from the true ADEV values measured against a real external reference particularly at shorter values of tau (like 100 secs). Turn on the satellite count display (G C from the keyboard in ver 3.0). The Tbolt reacts rather poorly to changes in the group of satellites that it is tracking. When the tracked satellite constellation changes, you can get big jumps in the osc/pps/dac signals. To minimize constellation changes, set the signal level mask to a low value (like AMU=1.0) and the satellite elevation mask to a high value (like 25 degrees). - Original Message - From: John Miles jmi...@pop.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, December 28, 2009 10:26 PM Subject: Re: [time-nuts] Sending me Lady Heather screen-captures One mystery is that once or twice daily, the temperature graph exhibits a sharp, almost perfectly vertical spike which recovers over a period of a few minutes. The temperature cannot possibly change that rapidly so there is something else going on. Note that the existing (non-beta) version of LH has some pretty debatable serial-port code in it. You may just be seeing data corruption. If it happens with the 3.0 beta version, it's may be worth investigating. LH often indicates that the blue PPS ADEV and the red OSC ADEV are both in the high E-13 zone for several hours and then invariably, both will drop back to the mid E-12 zone and sometimes stay there for many hours. Nature of the beast, really. A single outlier can affect your whole ADEV plot. Periodically, the violet PPS graph and the green DAC graph will go off scale for 10-15 minutes and I cannot find a reason for this-- it does not seem to be either temperature related or have anything to do with how strong the signals from the birds are or where the birds are relative to any tall tree foliage blocking the antenna sky view. The auto-scaling has undergone some improvements, too... if you're not running the beta, give that a try. -- john, KE5FX *** From: Michael Baker Hello, Time-Nuts-- Many thanks to Warren S for sending me over 20 Lady Heather screen-captures showing different configurations!! I really appreciate seeing these and welcome anyone else on the list sending me their screen captures. John Miles commented that individual screenshots may not be very useful without specifying the timescale, filters, and graphs you're looking for. This is true, but I am not even sure what I am
Re: [time-nuts] Notes on the Driscoll VHF Overtone Crystal Oscillator
My understanding is that Chris' variant of this particular Driscoll osc. has been designed specifically for low close-in phase noise, and that is why the phase-shift network has a low-pass response (to try and reduce flicker noise) rather than the more common high-pass network. The NE688xx was chosen for the active devices due to it's claimed low flicker noise; the flicker noise parameters are actually specified on the datasheet for the NE68833 - which is quite unusual. The high Ft may not be desirable, but it seems that is the price to pay for low flicker noise. I've built a couple of oscillators similar to Chris Bartram's design at around 116MHz, albeit with the more conventional 'high-pass' phase shift network, and they seem to perform quite well - certainly no sign of spurious high frequency oscillation, but that may be a function of PCB layout. I'm not aware of anyone yet measuring the close-in phase noise of the Bartram variant of this oscillator, and that's really the only way to verify or otherwise that the new topology gives any advantage in terms of close-in phase noise, compared to a similar, low cost design using similar crystals. When I get a sample in known working condition, I'll stress the friendliness of my customer to get it tested on their signal source analyzer. What we already have seen is that crystals from the same production run may yield up to 15 or 20 dB worse phase noise at 100 Hz than the best. (in the same oscillator) That confirms: Close-in to the carrier, the phase noise is dictated by the resonator. [1] 73, Gerhard DK4XP [1] Grant Moulton: Analysis And Prediction Of Phase Noise In Resonators and Oscillators, HP signal analysis division 1985 http://www.hparchive.com/seminar_notes.htm ___ 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] Phase noise vs warmup or time
dk...@arcor.de said: What we already have seen is that crystals from the same production run may yield up to 15 or 20 dB worse phase noise at 100 Hz than the best. (in the same oscillator) If I have several crystals and I want to find the ones with good phase noise, do I have to let them run in their ovens for a week/month, or can I just turn them on and measure the phase noise? -- 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.
Re: [time-nuts] Best test setup?
If both sources drift less than 100ns max (pk to pk) at 10MHz, then their 10MHz outputs can be used directly to start/stop the 5370B. Choose a cable length, and a rise/fall trigger so as to measure as close to 50ns as possible, so the signals can drift up or down from that 50ns average. The advantage is getting many (up to 20 samples per second or more) rather than just 1 sample per second. bye, Said In a message dated 12/29/2009 11:04:49 Pacific Standard Time, bruce.griffi...@xtra.co.nz writes: For most caesium standards and for some GPSDOs the jitter of the PPS output exceeds the jitter of the 5370B so using the PPS output to arm the 5370B reduces the measurement noise over the setup where the PPS output is used to start (or stop) the 5370B. 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] Phase noise vs warmup or time
If I have several crystals and I want to find the ones with good phase noise, do I have to let them run in their ovens for a week/month, or can I just turn them on and measure the phase noise? I'll make a distinction between time domain and frequency domain measurements. A long warm-up is helpful if you want to measure frequency stability (e.g., sigma of tau, or ADEV). But, depending on the equipment you use, a phase noise measurement (e.g., script L of f) doesn't require the source to be long-term stable; you get pretty much the same phase noise results in the first minute as you would a day or week later. /tvb ___ 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 vs warmup or time
Tom Van Baak said the following on 12/29/2009 04:24 PM: But, depending on the equipment you use, a phase noise measurement (e.g., script L of f) doesn't require the source to be long-term stable; you get pretty much the same phase noise results in the first minute as you would a day or week later. As a practical matter, you need to allow an OCXO time to stabilize or else the warm-up frequency drift may cause difficulties in the phase noise measurement. You need to keep the DUT and reference in the proper phase relationship, and if the drift is too fast the PLL may not be able to keep up. From what I've seen using the TSC test set, you'll get glitches in the flicker-noise region (say, around 1 Hz offset); the floor isn't much affected. I fully agree with Tom on the main point -- I'm not talking days or weeks, but an hour or so is probably a good idea. John ___ 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 65, Issue 121
Lady Heather version 3.0 flags holdover events in the plot with a red line at the top of the plot. You can toggle the display from the G)raph menu. If the holdover display is enabled, you can go to the start of the plot (HOME key), place the mouse cursor in the plot area, and press %. The plot will scroll to the next holdover (and/or time sequence skip) event each time you press '%'. If you have the active temperature control enabled, those temperature spikes are also flagged as holdover events. The temperature control PID has code to filter out the spikes (but they are left in the plot data where they can generally wreak havoc on the temperature plot autoscaling) - The really LARGE jumps can and most likely are caused when the Tbolt goes into and returns from holdover. To verify if that is your cause, Look at the Sat Counts LH plot, if it goes to zero, then that is what is happing. _ Hotmail: Powerful Free email with security by Microsoft. http://clk.atdmt.com/GBL/go/171222986/direct/01/ ___ 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] Best test setup?
That relies on the internal arming of the 5370B which isnt all that stable in that the time interval between successive measurements doesnt have great stability and one actually has to measure this by other means. Using an external arm signal with known repetition rate that is synchronised to the zero crossing of the start input avoids this problem. The actual requirement is that the phase difference doesnt change by more than the period of the stop input signal between successive measurements. Unwrapping of the phase measurements (adding or subtracting one period of the stop frequency when required) can then be done unambiguously. The sample rate depends on the arm frequency (set the divider appropriately) ie one can set the arm frequency to any value for which the 5370B doesn't lose measurements. Bruce saidj...@aol.com wrote: If both sources drift less than 100ns max (pk to pk) at 10MHz, then their 10MHz outputs can be used directly to start/stop the 5370B. Choose a cable length, and a rise/fall trigger so as to measure as close to 50ns as possible, so the signals can drift up or down from that 50ns average. The advantage is getting many (up to 20 samples per second or more) rather than just 1 sample per second. bye, Said In a message dated 12/29/2009 11:04:49 Pacific Standard Time, bruce.griffi...@xtra.co.nz writes: For most caesium standards and for some GPSDOs the jitter of the PPS output exceeds the jitter of the 5370B so using the PPS output to arm the 5370B reduces the measurement noise over the setup where the PPS output is used to start (or stop) the 5370B. 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] Phase noise vs warmup or time
Tom Van Baak wrote: If I have several crystals and I want to find the ones with good phase noise, do I have to let them run in their ovens for a week/month, or can I just turn them on and measure the phase noise? I'll make a distinction between time domain and frequency domain measurements. A long warm-up is helpful if you want to measure frequency stability (e.g., sigma of tau, or ADEV). But, depending on the equipment you use, a phase noise measurement (e.g., script L of f) doesn't require the source to be long-term stable; you get pretty much the same phase noise results in the first minute as you would a day or week later. I agree fully, but the first minute of operation can for some designs have significantly higher phase-noise. Discovered that for one oscillator of lesser quality. Viewed it with a spec with a fairly wide sweep (to get fairly quick update rates) which is sufficient to see the noise level decrease as it runs. I suspect it takes time for the signal level in the oscillator to stabilize, but that is to be expected. 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] Best test setup?
If both sources drift less than 100ns max (pk to pk) at 10MHz, then their 10MHz outputs can be used directly to start/stop the 5370B. Choose a cable length, and a rise/fall trigger so as to measure as close to 50ns as possible, so the signals can drift up or down from that 50ns average. The advantage is getting many (up to 20 samples per second or more) rather than just 1 sample per second. bye, Said I tend to see GPIB errors pretty frequently when I do that, for some reason. For long-term tests it may be less frustrating to limit the rate to 1 PPS. Also, you need to measure the actual tau interval when the counter free-runs like that, which is an extra complication. It won't be something nice and round like 100ms or 1s. -- john, KE5FX ___ 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 vs warmup or time
Hi It depends a lot on who made the crystals, how long they have been on the shelf, and how accurate your sort needs to be. If the crystals are from an unknown source or have been sitting for years, some burn in (days) may be helpful. I would suggest sorting out the dogs pretty quickly and then run the best of the bunch for a coupe of hours to see what happens. Bob On Dec 29, 2009, at 3:43 PM, Hal Murray wrote: dk...@arcor.de said: What we already have seen is that crystals from the same production run may yield up to 15 or 20 dB worse phase noise at 100 Hz than the best. (in the same oscillator) If I have several crystals and I want to find the ones with good phase noise, do I have to let them run in their ovens for a week/month, or can I just turn them on and measure the phase noise? -- 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. ___ 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] Can a quartz crystal go off by 2% ?
Rob Kimberley wrote: AFIK a lot of the clocks were radio controlled from MSF Rugby (now Anthorn, Cumbria). You would need to have some sort of automated system to accommodate daylight savings switchovers in Spring and Autumn. That said, I would have thought once synchronised, they would tick off the 50 Hz supply. Radio 4, actually. There's a low-speed phase-modulated signal riding on the 198kHz carrier, which encodes the clock time and a few bits of data for radio teleswitching, i.e. Economy 7. If you meddle about a bit with a PLL, you can even use it as a frequency reference (it's apparently driven off a rubidium oscillator and the NPL monitor its frequency in relation to the UK standard frequency, same as they do with GPS and the Rugby/Anthorn/MSF time signal). The fact that the meter isn't resetting itself implies that there's more wrong with it than just the crystal. I'd go with a failure in the RF section that's caused it to lose the teleswitching signal and date/time... There's no RF (as far as it's concerned), thus it's fallen back to the quartz in the dim hope that maybe, just maybe, it'll start hearing the distant voice of R4 in the not too distant future... It's another possibility, anyway. -- Phil. li...@philpem.me.uk http://www.philpem.me.uk/ ___ 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] chip scale atomic clock
Peter Vince wrote: 2009/12/26 Robert Lutwak lut...@alum.mit.edu: ... CSAC is intended for portable battery-powered operation. Surely your basement has the space and wallplug power to support an LPRO. (p.s. don't cool the damn thing, heat it). ... Hi Robert, Do I understand you are suggesting heating an LPRO, not cooling it? That seems to go against what I understood, that greater cooling leads to increased life. While not directed to me, these are my understandings: Besides the power applied to heat the Rb lamp, the physical package needs to be at the sweet-spot in temperature, so heating is performed. By lowering the cooling of the physical package, the powerconsumption goes down. So better isolation has to cool of less effect. This stands in contradiction to the lifetime of the electronics, but the physical package and electronics have two different requirements. As an aside, a newbie question if I may: being so used to Caesium standards being THE reference, I was surprised to hear that the CSAC has an aging mechanism - can you say a few words to explain that please? Don't confuse the stability and repeatability of elaborate beam clocks with that of (cheaper) gas cell clocks. Rubidium and Thallium beams has existed but Cesium was a better match for that purpose, Rubidium was found more suitable for the simpler and cheaper gas cell standard. Rubidium excells over Cesium in laser cooled fointains, since it reacts better to the laser cooling. Thus, each technology finds different technological balances with different atoms. May one suspect that the gas cells buffert gas mixture and resulting wall-shift/gas-shift balance is one of the long-term age effects, just as with ordinary rubidium gas cells. Another aspect to consider is that this clock does not have the C-field servo loop which modern cesium beams have. Then again, I think Robert can lecture a mere student (lazy such) to the field like me. 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] Timenoob - Cheap and simple 10MHz reference
Bruce Griffiths wrote: -185dBW = -155dBm so both sensitivity measures are equivalent. But -185 dB(something) looks more impressive than -155 dB(something). Specsmanship... indeed. I also spoted this detail. 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] Timenoob - Cheap and simple 10MHz reference
Peter Vince wrote: Oh Good Lord - not paying attention to the units! Sorry guys! This is exactly what they wanted to achieve, but the good thing is that more people got to become aware of it, so something good came out of that misstake. At least something good came out of it. When something looks 30 dB better than the competition, it may be good to check the nitty gritty. 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] Phase noise vs warmup or time
If you have a spectrum analyzer, depending on its resolution, you can also measure the phase noise directly. When I worked in the Satellite Communications industry, we needed up and down converters faster than our vendor could make them. They use to go thru a long QA process and they were very reliable. We waved the long QA test and tested the local oscillators in the field. If they were bad, we sent them back and they replaced them. If you analyzer does not have the resolution, you can notch the carrier and get more dynamic range or use the classic setup , which is the loose phase lock loop. Brian KD4FM John Ackermann N8UR wrote: Tom Van Baak said the following on 12/29/2009 04:24 PM: But, depending on the equipment you use, a phase noise measurement (e.g., script L of f) doesn't require the source to be long-term stable; you get pretty much the same phase noise results in the first minute as you would a day or week later. As a practical matter, you need to allow an OCXO time to stabilize or else the warm-up frequency drift may cause difficulties in the phase noise measurement. You need to keep the DUT and reference in the proper phase relationship, and if the drift is too fast the PLL may not be able to keep up. From what I've seen using the TSC test set, you'll get glitches in the flicker-noise region (say, around 1 Hz offset); the floor isn't much affected. I fully agree with Tom on the main point -- I'm not talking days or weeks, but an hour or so is probably a good idea. John ___ 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.
