[time-nuts] HP5065A manual and advice
G'Day All, I have acquired a HP5065A standard. Sn 1840A000838 with option J19 fitted (whatever that is). I am seeking a copy of the service manual and any advice on what to look for or repair before I try to power the unit on. It has been running on 24VDC I guess as it came with the DC plug and cable. It looks like it was first calibrated in 1979 and last in 1990. It has the following measurements on the front. The first figure is for 1979 and the last for 1990. supply 30-41 lamp oven 28-26 cell oven 28-28 osc oven 36-35 Photo 1 49-38 Thanks regards Scott ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY While the website is not explicitly about frequency measurement, there is an interesting bit on improving the stability of crystal oscillators with external heater controllers. While it may not be suitable for long term high stability control it might be suitable for many other purposes. http://www.qrss.thersgb.net/Crystal-Ovens.html The main page is also a good read: http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction Need a vacation? Get great deals to amazing places on Yahoo! Travel. http://travel.yahoo.com/ ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Tom: That's a cleaver improvement to a non ovenized crystal. Usually crystals are ground to have a temp vs freq turnover point occur at a specified temperature. The common one is to be on frequency at room temperature. So if a room temperature crystal is heated it's no longer operating at the turnover temperature and so there is a steep delta frequency vs. temperature slope. Did you get a crystal cut for your heater temperature or somehow match the heaters temperature to a turnover point on your crystal? I spent many many hours adjusting the oven temperature of a Gibbs frequency standard to get it right on the turnover point. Since the improvement in frequency stability depends on minimizing the temperature excursions it's good to have as much gain as possible in the heater feedback circuitry. This was done for the HP E1938 10 MHz oscillator, see: http://www.prc68.com/I/HPE1938.shtml and the paper: The Theory Of Zero Gradient Crystal Ovens, R.K. Karlquist, L.S. Cutler, E.M. Ingman, J.L. Johnson, T. Parisek Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Tom Clifton wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY While the website is not explicitly about frequency measurement, there is an interesting bit on improving the stability of crystal oscillators with external heater controllers. While it may not be suitable for long term high stability control it might be suitable for many other purposes. http://www.qrss.thersgb.net/Crystal-Ovens.html The main page is also a good read: http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction Need a vacation? Get great deals to amazing places on Yahoo! Travel. http://travel.yahoo.com/ ___ 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] Crystal Ageing
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I support what Rick has said about crystal ageing. I also work for an OCXO manufacturer, and will add my 2c worth.. Here are some points - * Manufacturers do indeed have their own special techniques for minimizing ageing and numerous other quality related parameters. Cleanliness, quality and attention to process are very important. Many techniques will be specific to their own manufacturing process, and of course they are trade secrets. * Because many different ageing processes are involved, prediction of future ageing from past history is not in general reliable. A very good analogy is prediction of weather - to say that tomorrow's weather will be similar to today's is a fairly safe bet, but is no help in predicting the weather for next weekend! The same applies to good crystal oscillators - you can reasonably expect the rate of ageing next month to be closely similar to last month's, but the slight differences build up in extrapolation, and prevent long term prediction. Make your measurements, predict the trend, then do the same next month and note the differences. * It is very important to recognise the difference between INITIAL ageing (when a newly made crystal is first used) and long term ageing. Most users will never see initial ageing, as it takes place in the factory. Initial ageing is much more predictable, and the factory will monitor this and from this behaviour, within a week or so can predict when (if ever!) the device will be within specification and so ready for final calibration and delivery. I recommend reading the various papers on ageing published by the UFFC and others. Start with this fairly comprehensive and authoritative one: http://www.ieee-uffc.org/freqcontrol/vigaging91/aging.htm#CONTENTS 73, Murray ZL1BPU ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY This is getting off topic (because it's far to practical!) but hanging heaters on crystals is a time-honored activity for hams. Many of the surplus FM rigs for VHF and UHF that we obtained from the likes of Motorola, GE, RCA, etc. that were made B.S. (before synthesizers) had ovens, or later channel elements that were actually TCXOs. This was particularly necessary for UHF systems that operated in rugged environments. But most ham-grade gear didn't have anything like this. I spent quite a bit of time 15 years ago building a packet radio network that linked Columbus, Dayton, and Cincinnati Ohio using UHF (440 MHz) 19.2 kbps data radios made by Kantronics, a company with limited RF experience. The data transmission scheme we used required a frequency tolerance of about +/- 2 kHz at 440 MHz (i.e., about 5x10e-6). The standard crystals could almost maintain that tolerance in a nicely regulated room, but we had these radios out in transmitter shacks in the middle of corn fields, and with wide temperature swings the radio links would die completely. We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. The original crystals (designed for room temperature) worked OK and we could warp them onto frequency even with the heaters installed, but we noticed what seemed to be accelerated aging; after a couple of years, the crystals could no longer be brought onto frequency. Later, we ordered some crystals designed for higher temperature (I think it was something like 50 degrees C) and those were both easier to trim, and didn't seem to suffer the rapid aging. That network is now dead and gone, victim of single-source components (Kantronics stopped making or supporting the radios, and some of the transistors became Unobtanium) as well as the death of traditional packet radio in the face of the internet. Sigh... John Brooke Clarke said the following on 10/10/2007 01:52 PM: Hi Tom: That's a cleaver improvement to a non ovenized crystal. Usually crystals are ground to have a temp vs freq turnover point occur at a specified temperature. The common one is to be on frequency at room temperature. So if a room temperature crystal is heated it's no longer operating at the turnover temperature and so there is a steep delta frequency vs. temperature slope. Did you get a crystal cut for your heater temperature or somehow match the heaters temperature to a turnover point on your crystal? I spent many many hours adjusting the oven temperature of a Gibbs frequency standard to get it right on the turnover point. Since the improvement in frequency stability depends on minimizing the temperature excursions it's good to have as much gain as possible in the heater feedback circuitry. This was done for the HP E1938 10 MHz oscillator, see: http://www.prc68.com/I/HPE1938.shtml and the paper: The Theory Of Zero Gradient Crystal Ovens, R.K. Karlquist, L.S. Cutler, E.M. Ingman, J.L. Johnson, T. Parisek Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Tom Clifton wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY While the website is not explicitly about frequency measurement, there is an interesting bit on improving the stability of crystal oscillators with external heater controllers. While it may not be suitable for long term high stability control it might be suitable for many other purposes. http://www.qrss.thersgb.net/Crystal-Ovens.html The main page is also a good read: http://www.qrss.thersgb.net/Receiving-QRSS.html#Introduction ___ 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] Improving the stability of crystal oscillators
In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? Thanks Said ** See what's new at http://www.aol.com ___ 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] Crystal Ageing
); SAEximRunCond expanded to false
Errors-To: [EMAIL PROTECTED] RETRY
On Wed, 10 Oct 2007 07:34:30 +0200, Bernd Neubig wrote
There is much more to say, but I will stop here, hoping that this
contribution gave some time nuts a better understanding - and may kill
their firm believe into aging predictions ;-)
I have been working hard on adaptative algorithms to predict OCXO ageing, and
I completely agree with Bernd.
Besides the fact that ageing is actually random (althoug it can be linearly
modeled for time intervals of days, may be a week), there is an effect that
should be added to ageing: temperature variations. Depending on many factors,
temperature effect can be orders of magniture more significant than ageing.
Moreover, temperature change (altough small in a good oscillator) produce non
linear effects: change temperature and go back to original one: frequency
will not be the original. It is beautiful to perform an experiment: measure
temperature and oscillator frequency and change temperature smoothly (e.g.
normal room day/night variations). Revove ageing from frequency measurements
and make a temperature/frequency X-Y plot. Do not expect a line, but
something simmilar to a cloud. It slongly depends on oscillator and the
amount of temperature variation.
My experience is that nice prediction ('nice' definition: time drift lower
than, say 1 us) is difficult to maintain for more than few days, but this
*strongly* depends on temperature variations and oscillator characteristics.
Please notice that 1 us in one day is a really good figure: these all
discussions depend on how good matching you want to obtain.
I have run all my work with free running OCXOs. I have no direct experience on
disciplined oscillators, but I suspect that non linear effects may be even
worst.
Best regards
Luis Miguel
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Re: [time-nuts] Improving the stability of crystal oscillators
[EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM: In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part Name Yaesu Part Number Murata Part Number PosistorG9090019PTH507A01BG330N020 They used to be about $7.00 each. Yaesu's parts-order phone number at the time was (800) 255-9237. I'm not sure if there's another source for the Murata part; back then, we couldn't find one. Amazingly, I still have a web page documenting all that we learned about those cursed radios, including the schematic of our original homebrew heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY [EMAIL PROTECTED] said the following on 10/10/2007 02:39 PM: BTW: I wonder how much effect thermistor and resistor-bridge aging as well as opamp offset drift has on the long term aging of typical OCXO's since it will shift the temperature setpoint of the crystal. I think this is an issue that's not receiving a lot of attention in the literature.. More anecdotes. I have a bunch of old Sulzer 2.5 and 5 oscillators. As Tom will happily tell you, one of these guys that still works well can be one of the best pieces of quartz you'll ever find (and a great toilet flush detector!). But most of mine are a bit flaky, and the thermistors seem to be the main problem. Each unit has at least two -- one is inside the inner oven and is part of a bridge that drives the TEMP meter position; it's supposed to read 0 when the oven is at temperature. Another is part of the bridge that sets the oven temperature; there are hand-chosen components designed to work with the thermistor to drive the heater to the right temperature. I've seen units where one or both was so far off, you couldn't really tell what the oven was doing. In at least one case, there was an open that drove the oven full blast continuously. Someday I'd like to build a test fixture that would allow measuring the crystal turning point and setting the ovens back to optimal temperature... So, aging of these parts can certainly be an issue. 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In a message dated 10/10/2007 11:34:43 Pacific Daylight Time, [EMAIL PROTECTED] writes: heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. John Thanks John! BTW: I wonder how much effect thermistor and resistor-bridge aging as well as opamp offset drift has on the long term aging of typical OCXO's since it will shift the temperature setpoint of the crystal. I think this is an issue that's not receiving a lot of attention in the literature.. Said ** See what's new at http://www.aol.com ___ 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Try DigiKey pn: 235-1123-ND for a simple PTC Thermistor that can be soldered to the xtal case if one were so inclined. Do so at your own risk to the xtal! -Brian -- Original message -- From: John Ackermann N8UR [EMAIL PROTECTED] [EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM: In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part Name Yaesu Part Number Murata Part Number Posistor G9090019PTH507A01BG330N020 They used to be about $7.00 each. Yaesu's parts-order phone number at the time was (800) 255-9237. I'm not sure if there's another source for the Murata part; back then, we couldn't find one. Amazingly, I still have a web page documenting all that we learned about those cursed radios, including the schematic of our original homebrew heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. 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.
Re: [time-nuts] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY In a message dated 10/10/2007 19:34:55 GMT Daylight Time, [EMAIL PROTECTED] writes: We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part NameYaesu Part NumberMurata Part Number Posistor G9090019PTH507A01BG330N020 - I don't know if this is the same part, Ebay Ref...110177471348, but this seller has been selling these two at a time for quite a while. Might be ok if you just want a couple to play with, probably not ideal for planning a production run:-) 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.
Re: [time-nuts] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Brian: I used to use Balco (as far as I can remember) positive coefficient resistors that had specs similar to the Digikey units you linked to. These were only available in values under 200 Ohms and have a positive linear coefficient. The more common negative coefficient type like: http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1storeId=10001catalogId=10001productId=207036 have a much larger change with temperature and so are a very common way to sense a set point. When a resistor with the same value is used to make a half bridge the voltage change around the balance point is nearly linear. There's a way to fit a third order polynomial to the data and once you have the coefficients it's only a linear equation to solve for converting resistance back to temperature. 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 [EMAIL PROTECTED] wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Try DigiKey pn: 235-1123-ND for a simple PTC Thermistor that can be soldered to the xtal case if one were so inclined. Do so at your own risk to the xtal! -Brian -- Original message -- From: John Ackermann N8UR [EMAIL PROTECTED] [EMAIL PROTECTED] said the following on 10/10/2007 02:17 PM: In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? We bought them as a replacement part from Yaesu USA. This data is 10 years or more old, but here you go: Part Name Yaesu Part Number Murata Part Number Posistor G9090019PTH507A01BG330N020 They used to be about $7.00 each. Yaesu's parts-order phone number at the time was (800) 255-9237. I'm not sure if there's another source for the Murata part; back then, we couldn't find one. Amazingly, I still have a web page documenting all that we learned about those cursed radios, including the schematic of our original homebrew heater design: http://www.febo.com/hamdocs/d4art.html. The quality of the heater schematic isn't very good, but it's all I have. 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. ___ 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] Improving the stability of crystal oscillators
From: [EMAIL PROTECTED] Subject: Re: [time-nuts] Improving the stability of crystal oscillators Date: Wed, 10 Oct 2007 14:17:24 EDT Message-ID: [EMAIL PROTECTED] John, In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Agree! Thanks! 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] Improving the stability of crystal oscillators
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I bought 10kohm nominal NTC thermistors from Digikey, P/N 490-4653-ND. They are very small, 1/10th of an inch long or so. I have used those (or similar parts) in projects both at home and at work (in military equipment...) for about 15 years. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, October 10, 2007 1:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Improving the stability of crystal oscillators In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? Thanks Said ** See what's new at http://www.aol.com ___ 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] Improving the stability of crystal oscillators
I have made several ovens for oscillators over the years. The recipe is: get a piece of aluminium big enough to contain the oscillator, voltage regulator and first stage amplifier. With a mill remove the shapes of each component. Bolt a large power transistor, large power fets are best, to the outside of the block as a heater, and it is run off the unregulated input power. Judicious selection of a component decides the start-up current. Make a plate to cover the excavation for the components, and bolt it down. The circuit can be made with discrete transistors in the most unstable looking amplifier ever seen, alternating NPN and PNP transistors, connected directly to each other with load resistors. The main temperature sensor is a resistor bridge with a high value glass encapsulated thermistor. These are available a several trade houses. The amplifier is also temperature sensitive, but is within the thermal loop. The thermistor bridge gives a very large signal ~ 50mV per degree. Gain may have to be backed off if thermal oscillations do not die down, but the metal block acts as an integrator and the circuits are very easy to get high gain and sensitivity. The whole block is packed in two inches of foam insulation, my 1MHz oscillator only draws about 80 mA at 12 volts. The temperature is set to 40 C. The stability of the oscillator is very good, but as I have not yet got a disciplined oscillator going I dont know which is drifting, the HP 10811 in my frequency counter or the 1MHz oscillator. After a year, the difference is currently 0.3 ppm. cheers Neville Michie On 11/10/2007, at 9:24 AM, Didier Juges wrote: I bought 10kohm nominal NTC thermistors from Digikey, P/N 490-4653- ND. They are very small, 1/10th of an inch long or so. I have used those (or similar parts) in projects both at home and at work (in military equipment...) for about 15 years. Didier KO4BB -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, October 10, 2007 1:17 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Improving the stability of crystal oscillators In a message dated 10/10/2007 11:13:21 Pacific Daylight Time, [EMAIL PROTECTED] writes: We first built a small proportional heater circuit that we could shove in next to the crystal, and that worked OK. We finally found a source for thermistors spot welded to a spring clip that would mount snugly directly to the crystal case. With 12 volts applied, these heated the crystals very nicely. With the heaters, we were able to keep the systems running year round with about 1/10 the service calls. Hi John, interesting anecdote! Would you know if the thermistors are still available? Who made them? Thanks Said ** See what's new at http://www.aol.com ___ 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] Phase locked local oscillator results
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi all, I have been playing with a phase and frequency locked local oscillator in my 3816A GPS receiver. The simple setup uses the OCXO output as an external reference input to a HP 3325A and with a trivial mod to the VP GPS receiver the 3325A becomes its local oscillator. The setup improves the short term stability of the OCXO. Which I guess in hindsight is not very surprising. Logging data every 5 seconds using GPSCon the AD drops to under 0.5. I tested two different approaches. One setup used a fixed LO frequency of 19095750.191 Hz. To my surprise the prime number fraction chosen to give the time interval interpolator a workout results in an auto correlation peak at 1000 seconds when the EFC is viewed with the plotter program. The second approach used dithering. The LO center frequency was set to 19095750.2 Hz and continuously ramped up and down every 10 seconds +-0.035 Hz. This causes the pps pulse to dither slightly more than one sawtooth period over a 5 second interval (the GPS pps pulse edge is just a LO clock edge). Dithering however is a pain to adjust because timing the start of the ramp with respect to the pps output is trial and error and not at all repeatable with my setup. Both approaches result in a pps standard deviation of about 6.4ns. Further small improvements might be possible but would require adjusting the phase of the 3325A over the gpib interface to lock the sawtooth residual to some constant value. For the truly adventurous the next level requires some artificial intelligence like http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/19/30540/01408297.pdf?arnumber=1408297http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/19/30540/01408297.pdf?arnumber=1408297 unfortunately only the abstract is on the web. As I recall the authors report 2.5ns of uncertainty over a day when compared to a cesium reference and over 10 times improvement in the MDEV plot of the OCXO. A second rather simple modification to reduce temperature induced tuning I tried is to power the oven with a separate isolated 12V supply. The only common connections are the EFC pin the reference output voltage pin and whatever point you decide to attach in the oven as a signal ground (if you are worried about power supply sequencing you can always add a diode). I connected the signal ground to the inner oven ground pin which does not have any voltage drops caused by the outer oven heater current. The ideal signal ground point would be somewhere inside the inner oven where no current induced voltage drops would modulate the EFC tuning voltage. To get an idea of the magnitude of the improvement you can measure the voltage drop from the oven ground pin to the ground pin of the DAC voltage reference. I haven't combined the isolated oven supply and the phase locked LO in a single test yet. For the curious I have a 6 day GPSCon log file of the two LO setups compressed down to a half Meg let me know if interested and I will email it to you. Enjoy, Peter [EMAIL PROTECTED] ___ 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] Improving the stability of crystal oscillators
Neville Michie wrote: I have made several ovens for oscillators over the years. The recipe is: get a piece of aluminium big enough to contain the oscillator, voltage regulator and first stage amplifier. With a mill remove the shapes of each component. Bolt a large power transistor, large power fets are best, to the outside of the block as a heater, and it is run off the unregulated input power. Judicious selection of a component decides the start-up current. Make a plate to cover the excavation for the components, and bolt it down. The circuit can be made with discrete transistors in the most unstable looking amplifier ever seen, alternating NPN and PNP transistors, connected directly to each other with load resistors. The main temperature sensor is a resistor bridge with a high value glass encapsulated thermistor. These are available a several trade houses. The amplifier is also temperature sensitive, but is within the thermal loop. The thermistor bridge gives a very large signal ~ 50mV per degree. Gain may have to be backed off if thermal oscillations do not die down, but the metal block acts as an integrator and the circuits are very easy to get high gain and sensitivity. The whole block is packed in two inches of foam insulation, my 1MHz oscillator only draws about 80 mA at 12 volts. The temperature is set to 40 C. The stability of the oscillator is very good, but as I have not yet got a disciplined oscillator going I dont know which is drifting, the HP 10811 in my frequency counter or the 1MHz oscillator. After a year, the difference is currently 0.3 ppm. cheers Neville Michie Neville A correctly tuned PID control loop should allow even tighter temperature control. A boostrapped oven like that used by Wenzel should be even better. (http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf). Despite Wenzel's claims this type of oven isn't new it was used for portable standard cell enclosures decades ago. 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.
