Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Hi Rex, Here is a plot of my sound card. Maybe I'm just lucky with this particular sound card/computer, but the drift was only about 250 micro Hertz over a four hour period. Also for critical measurements I try to run at 200 Hz center frequency rather than 1000 Hz. Cuts the error by five. Maybe that's not practical for you modulation schema. I did not bother to calibrate the sound card before I started the test so there is about 550 micro Hertz of static error when the test starts. www.k5cm.com/soundcard.htm 73, Connie K5CM ___ 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] Sound Cards for locking to GPSDO 10 MHz references
> -Original Message- > From: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] On Behalf Of Rex Moncur > Sent: Tuesday, June 02, 2009 3:06 PM > To: 'Discussion of precise time and frequency measurement' > Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 > MHz references > > Hi all > > Thank you all for you advice and suggestions re my request. > At this stage it does not look like there is a simple > solution of a readily available USB sound card that can be > locked to a 10 MHz GPSDO reference. > > The constraints of portable operation with a Laptop rule out > a number of solutions. I have tried the software solution > using Spectrum Lab but ran into problems and perhaps this > just needs more work. One of the main problems is that in > working at milli-Hz binwidths the FTT word length needs to be > very long to cover even a few tens of Hz range and we run > into memory problems. So there is little room to have a > reference frequency spaced well away from the frequency range > being used. The reference frequency can be right on top of your signal, as long as it's within the dynamic range. You can subtract it out before doing the FFT, after having determined where it is and how big it is. > Some people asked for more details of the cloud scatter > experiments which area at http://reast.asn.au/optical.php > There is also a series of articles on our work in the last 3 > and next issue of DUBUS. > > ___ 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] Sound Cards for locking to GPSDO 10 MHz references
Hi all Thank you all for you advice and suggestions re my request. At this stage it does not look like there is a simple solution of a readily available USB sound card that can be locked to a 10 MHz GPSDO reference. The constraints of portable operation with a Laptop rule out a number of solutions. I have tried the software solution using Spectrum Lab but ran into problems and perhaps this just needs more work. One of the main problems is that in working at milli-Hz binwidths the FTT word length needs to be very long to cover even a few tens of Hz range and we run into memory problems. So there is little room to have a reference frequency spaced well away from the frequency range being used. The SP DIF solution seems promising if I can generate the required input. This could perhaps be done with a product that already provides the SP DIF word output and locking that. But that could be just as hard as locking the sound-card in the first place. So at this time I think I will put some more effort into locking the sound card and let you know how I go, hi. Injection locking as suggested by some of you may be the answer. Some people asked for more details of the cloud scatter experiments which area at http://reast.asn.au/optical.php There is also a series of articles on our work in the last 3 and next issue of DUBUS. On the question of Doppler shift from clouds - this is much less than a mHz and not an issue due to the fact that we are using base band and the Doppler only applies to the audio frequency. In addition the very narrow beamwidths (around 2 degrees) mean that the possible paths are all very similar in length. Thanks again to everyone for their input. 73 Rex VK7MO ___ 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] Sound Cards for locking to GPSDO 10 MHz references
Magnus Danielson wrote: Hmm, do you get a feeling that I am actually object very much to just toss it into the processor. I think you are right. :) I suppose you are familiar with the old American adage that says that to a man with a hammer every problem looks like a nail :-) Each of us is more familiar with one or another technology (broadly speaking), and tend to see it as the best way to solve problems. I am not immune from this... Nothing wrong with software, but use it wisely. Build the test-benches as if you where doing a ASIC or full-custom design and thus also think about each compile costing you milions of dollars and a pipe-line depth of many months (6-9). Given the rate of compiles that sometimes I do especially when near to find the solution of a problem that bugged me for a long time, I would be bankrupted since long, should each compile cycle cost me thousands or millions of dollars, even if bogus dollars... :-) :-) I guess I am becomming more conservative by the day. From my own and others mistakes and succsesses. This is a privilege of becoming older and wiser :-) Cheers, Alberto I2PHD ___ 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] Sound Cards for locking to GPSDO 10 MHz references
Alberto di Bene skrev: Magnus Danielson wrote: No need to switch on the soldering iron... Never do in hardware what can be done in software :-) Respectfully I disagree. There are tasks which is better managed by software and tasks which is better managed by hardware. In the world of FPGAs, it is also worth mentioning that some tasks is best done there. The big trick is to find a balance between various methods, available resources, partitioning of the problem, doing it on time and achieving the needed performance. Of course you are right, the best solution must be decided case by case. But the biggest plus of the software is that it can be changed on the fly, without an expensive reworking station, and the manual ability to correctly use it. And a side effect is speed : you can test many variants of a solution in a time frame of a few minutes. Not so easily doable with hardware changes. This is why we do alot of things in FPGAs today, and in the FPGAs we often put dedicated DSPs of various complexity, often adapted to their task. Keeping quick turn-around is on our mind, but in general, the shorter turn-around, the poorer testing usually happends, and the sloopier design is often found, and the longer it takes to get the job done. In general, a CPU is suitable for doing non-common tasks. More dedicated designs like firmware and hardware is suitable to do things which is essentially the same but happends over and over and over and often at a high speed. Such monotonic tasks just waste energy, space and complexity when done in CPUs. The problem with a generic CPU is that it is generic, so it can do all kinds of tasks, which makes timing-critical bulk-processing tasks problematic to combine with sporadic and possibly high-dynamic processing. Splice the bulk off to some dedicated processing, which can be done in another CPU, and better performance is yielded. There are loads of designs where a few well thought 8-bit processors work together and shine over a more modern fancy design. One such example is found in the SR-620 which has a Zilog Z-8000 processor as main CPU and a Z-80 co-processor which only does the X-Y vector display. The Z-80 has so small program that it is loaded into SRAM from the Z-8000 as it boots. The HP 5334A has actually 3 different 3870 processor, one for overall control, one for measurements and one for GPIB. Hmm, do you get a feeling that I am actually object very much to just toss it into the processor. I think you are right. :) Nothing wrong with software, but use it wisely. Build the test-benches as if you where doing a ASIC or full-custom design and thus also think about each compile costing you milions of dollars and a pipe-line depth of many months (6-9). I guess I am becomming more conservative by the day. From my own and others mistakes and succsesses. 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] Sound Cards for locking to GPSDO 10 MHz references
Magnus Danielson wrote: No need to switch on the soldering iron... Never do in hardware what can be done in software :-) Respectfully I disagree. There are tasks which is better managed by software and tasks which is better managed by hardware. In the world of FPGAs, it is also worth mentioning that some tasks is best done there. The big trick is to find a balance between various methods, available resources, partitioning of the problem, doing it on time and achieving the needed performance. Of course you are right, the best solution must be decided case by case. But the biggest plus of the software is that it can be changed on the fly, without an expensive reworking station, and the manual ability to correctly use it. And a side effect is speed : you can test many variants of a solution in a time frame of a few minutes. Not so easily doable with hardware changes. 73 Alberto i2PHD ___ 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] Sound Cards for locking to GPSDO 10 MHz references
Alberto di Bene skrev: J.D. Bakker wrote: You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. I am in complete agreement with this kind of solution. Sampling on the second channel a reference signal of known value allows the software to make a simple adjustment. Such a double-frequency conversion cancels fairly well the transfer oscillators frequency and jitter, as long as it is sufficienly low. No need to switch on the soldering iron... Never do in hardware what can be done in software :-) Respectfully I disagree. There are tasks which is better managed by software and tasks which is better managed by hardware. In the world of FPGAs, it is also worth mentioning that some tasks is best done there. The big trick is to find a balance between various methods, available resources, partitioning of the problem, doing it on time and achieving the needed performance. There is an overbeleif in what software is suitable for IMHO. 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] Sound Cards for locking to GPSDO 10 MHz references
Lux, James P skrev: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Tuesday, June 02, 2009 10:08 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Some of the "pro" sound interfaces have a "word clock" input. There are a variety of things that take a external input and generate a S/PDIF that's properly timed, as well. Lots of boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 which was used by lots of Flex-Radio folk), so maybe that's something you could easily generate from your 10MHz. A chart at Cakewalk shows that MOTU has a USB interface (828MkII) which has a word clock sync. It's going to be a pricey beast though, with 8in/8out ($800?) Even if you have a word clock input, you're going to have to synthesize that from the 10 MHz. Maybe it's easier to just make a S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is something like 3 MHz) S/P-DIF [iec60958-3] has a baudrate which is 128 x sample rate and a bit rate which is 64 x sample rate, which is inherited properties from AES/EBU [aes3] [tech3250] [iec60958-4]. Locking up a S/P-DIF (128 x sample rate) is about the same job as locking up a superclock (256 x sample rate) or wordclock (1 x sample rate). However, if you're buying an off the shelf audio interface, you're stuck with whatever the mfr is providing for a sync input, and a (very) casual inspection of what's available these days (particularly at low cost) shows that S/PDIF seems to be the most common. Do they really lock up to the S/P-DIF input? I doubt it for the cheap boards. Rather, they decode the S/P-DIF signal and ship the samples into the DSP. The DSP tends to make very rought sample-rate conversions like dropping samples etc. A lockable board isn't that expensive. You can get them off ebay for instance. 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] Sound Cards for locking to GPSDO 10 MHz references
Hello The Net: For portable operations with a laptop, usually only one input channel is available and it is at mike (not line) level. The alternative to sum the analog reference and the analog signal of interest may be possible if the reference noise can be kept out of the signal of interest bandwidth. Maybe a external USB soundcard with at least 2 input channels is more appropriate. Stan, W1LEFN41sr Cape Cod Alberto di Bene wrote: J.D. Bakker wrote: You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. I am in complete agreement with this kind of solution. Sampling on the second channel a reference signal of known value allows the software to make a simple adjustment. No need to switch on the soldering iron... Never do in hardware what can be done in software :-) 73 Alberto I2PHD ___ 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] Sound Cards for locking to GPSDO 10 MHz references
J.D. Bakker wrote: You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. I am in complete agreement with this kind of solution. Sampling on the second channel a reference signal of known value allows the software to make a simple adjustment. No need to switch on the soldering iron... Never do in hardware what can be done in software :-) 73 Alberto I2PHD ___ 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] Sound Cards for locking to GPSDO 10 MHz references
> -Original Message- > From: time-nuts-boun...@febo.com > [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson > Sent: Tuesday, June 02, 2009 10:08 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Sound Cards for locking to GPSDO 10 > MHz references > > > > > > > Some of the "pro" sound interfaces have a "word clock" input. > > > > There are a variety of things that take a external input > and generate a S/PDIF that's properly timed, as well. Lots of > boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 > which was used by lots of Flex-Radio folk), so maybe that's > something you could easily generate from your 10MHz. > > > > A chart at Cakewalk shows that MOTU has a USB interface (828MkII) > > which has a word clock sync. It's going to be a pricey > beast though, > > with 8in/8out ($800?) > > > > Even if you have a word clock input, you're going to have to > > synthesize that from the 10 MHz. Maybe it's easier to just make a > > S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is > > something like 3 MHz) > > S/P-DIF [iec60958-3] has a baudrate which is 128 x sample > rate and a bit rate which is 64 x sample rate, which is > inherited properties from AES/EBU [aes3] [tech3250] [iec60958-4]. > > Locking up a S/P-DIF (128 x sample rate) is about the same > job as locking up a superclock (256 x sample rate) or > wordclock (1 x sample rate). However, if you're buying an off the shelf audio interface, you're stuck with whatever the mfr is providing for a sync input, and a (very) casual inspection of what's available these days (particularly at low cost) shows that S/PDIF seems to be the most common. ___ 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] Sound Cards for locking to GPSDO 10 MHz references
Lux, James P skrev: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rex Moncur Sent: Monday, June 01, 2009 3:00 PM To: 'Discussion of precise time and frequency measurement' Subject: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references Hi all Does anyone have any experience of locking a USB external soundcard to a GPSDO 10 MHz reference. I am interested in advice on any good quality soundcards that can be readily locked to either 10 MHz or if necessary to some other frequency that we can derive from a GPSDO source. I have done some tests with the SignalLink soundcard that uses a Texas Instruments PCM2904 chip and requires a 12 MHz lock frequency. This requires some cutting of tracks to remove the internal oscillator feedback and insert the locking frequency. 12 MHz is readily derived from 10 MHz but I have not been able to get it to lock. The Texas instruments data sheet suggests that it is possible to use an external refernce but also says this is not recommended. With this expereicne I would rather find a sound card that is designed for external locking that does not require the cutting of tracks. For info the purpose of this request is that we are looking at using very narrow bandwidth modes at less than 1 mHz for light wave communcation. To date using LEDs and cloud reflection we have worked over 200 km with WSJT but we should be able to do 20 dB better if we can get down to milli-Hz bandwidths (at the expense of spending all night to complete a QSO). Our expereince to date is that standard sound cards are just not stable to better than 5 milli-Hz at 1000 Hz which should be readily solved by GPS locking let us get down to sub milli-Hz levels. Rex VK7MO Some of the "pro" sound interfaces have a "word clock" input. There are a variety of things that take a external input and generate a S/PDIF that's properly timed, as well. Lots of boxes will take a S/PDIF sync input (e.g. the Edirol FA-66 which was used by lots of Flex-Radio folk), so maybe that's something you could easily generate from your 10MHz. A chart at Cakewalk shows that MOTU has a USB interface (828MkII) which has a word clock sync. It's going to be a pricey beast though, with 8in/8out ($800?) Even if you have a word clock input, you're going to have to synthesize that from the 10 MHz. Maybe it's easier to just make a S/PDIF which is a MUCH more common sync signal. ( I think S/PDIF is something like 3 MHz) S/P-DIF [iec60958-3] has a baudrate which is 128 x sample rate and a bit rate which is 64 x sample rate, which is inherited properties from AES/EBU [aes3] [tech3250] [iec60958-4]. Locking up a S/P-DIF (128 x sample rate) is about the same job as locking up a superclock (256 x sample rate) or wordclock (1 x sample rate). As long as the signal is samples with low jitter and A/D converted in a good fashion, delivery over S/P-DIF should not be too hard. An ADC is slammed onto a AES/EBU/S/P-DIF chip which is fairly trivial extra work. 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] Sound Cards for locking to GPSDO 10 MHz references
You could always transform this from a hardware problem to a software problem. Take the output of your GPSDO, divide it down to somewhere inside the audio band, feed it to a spare input on your USB sound card and have software track this reference and correct the received signal. JDB. -- LART. 250 MIPS under one Watt. Free hardware design files. http://www.lartmaker.nl/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Thunderbolt - any negatives ?
Didier Your comments regarding SMPS are very valid, but there are SMPS designs and then some ! I bought a Wavetek 395 Function Generator with a totally blown up SMPS for approx $100. I attempted to repair this unit but the PCB was badly damaged/burned and one 8-pin Dil device was blown to bits - plus burnt out resistors. I tried to obtain a replacement from the manufacturers without success. After hooking up external supplies and proving that it was otherwise OK, I contemplated building a linear supply within the box - it would have been heavy and difficult to fit. This latter point reinforces your comment about size and power dissipation. The original unit was identical to the average small PC PSU, but with very different outputs. After about 10 months of looking for a solution - I thought I recognized a Wavetek 395 Function Generator in Bob Mokia's Lab. photo, and ask him if he could find me a spare PSU, after a short while he came back with a replacement for around $50 - presto I now have a fully working 395 for $100, which I notice sells for $1500 in the US. Footnote: No axe to grind, but like others in the Group,I have found Bob Mokia to be a "straight" and helpful dealer. Roy - Original Message - From: "Didier Juges" To: "'Discussion of precise time and frequency measurement'" Sent: Tuesday, June 02, 2009 3:24 AM Subject: Re: [time-nuts] Thunderbolt - any negatives ? Most likely failures on power supplies are with the power components. Failure of the pass transistor in a linear supply is likely to result in overvoltage at the output, while failure of the switch on a switchmode supply will blow the fuse instantly. It is been my experience (after 30 years in the field) that a properly designed switchmode supply is at least as reliable as a linear supply of the same output power, if for no other reason than the lower dissipation and resulting reduced failure rate. By using integrated controllers with lots of protection features built-in, switchmode supplies tend to be smarter than linear ones, and their failures tend to cause fewer damage to other circuits. Of course, your mileage may vary... Didier KO4BB -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Robert Atkinson Sent: Monday, June 01, 2009 2:46 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt - any negatives ? Most switch mode power supplies actually run a voltage doubler on the input when running on 110V. This puts over 300V across the transformer and switch. Also the regulation loop crosses the isolation barrier introducing more failure points that can result in overvoltage. Robert G8RPI. --- On Mon, 1/6/09, saidj...@aol.com wrote: > From: saidj...@aol.com > Subject: Re: [time-nuts] Thunderbolt - any negatives ? > To: time-nuts@febo.com > Date: Monday, 1 June, 2009, 6:17 PM > Hi there, > > A switcher has much more stresses on the components, since it usually > switches the primary side rectified 110/220V high-voltage across a > transformer. > Thus the switching FET has to be very high voltage capable (about > ~170V DC in the US), and the second component under stress is the > primary high voltage capacitor, because it sees a very fast AC > switching current on it (current draw is on when the FET is on, and > off when the Fet is off). Also there has to be a fast snubber network > to prevent the back-emf from destroying the primary Fet with > over-voltage. > > A linear supply has none of these fast current/voltage transients on > it, only a couple of diodes switching the 60Hz secondary onto a > capacitor at low voltage. > > A secondary concern is thermally induced stress, switchers will > usually be packed into a very small enclosure with very high power > capability/density. > This is not possible for linear supplies, since the transformer size > will usually determine overall sizing. Compare a Laptop power supply > size (usually these have between 40W and 90W rating!) to a similar > rated linear supply. > > bye, > Said > > > In a message dated 6/1/2009 09:48:29 Pacific Daylight Time, > hmur...@megapathdsl.net > writes: > > Is there something I don't understand in this area? What makes a > linear supply more reliable than a switcher? > > My first guess would be a switcher would be more reliable because it > would run cooler. > > That's probably assuming the same amount of design effort which is > probably not a valid assumption if I'm comparing a brand-X linear > with a brand-Z switcher. A quick glance at the general construction > might give a better answer. > > > ___ > 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 h
Re: [time-nuts] Sound Cards for locking to GPSDO 10 MHz references
Brian Kirby skrev: I use a Lynx One sound card, it has analog and digital I/O and MIDI I/O and clock I/O. Their manuals are available on line at www.lynxstudio.com. These are profession 24 bit cards, the analog I/O uses balanced interfaces. They handle AES/EBU and SP DIF digital audio formats. The sound card can take an internal clock, an external clock input on the MIDI port, there is a parallel clock header on the PC board, and a digital clock input on the digital audio lines. It can accept a 13.5 Mhz video dot clock, a 27 Mhz video dot clock, and a word clock and word clock/256. 13,5 MHz is ITU-R BT.601/BT.656 luminance sampling rate. 27 MHz is BT.601/BT.656 luminance/chroma-difference combined sampling rate (4:2:2). 27 MHz is the video reference rate of them all. Sad that they broke it when they did the North American HD stuff. Breaking numerology like that isn't very nice... it always cost extra now. I think you mean word-clock * 256 as this is Digidesign/ProTools clock distribution strategy, giving 12,288 MHz for 48 kHz sampling rate. 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] What type of Crystal?
For an OCXO you can determine whether it is an AT, BT or SC cut crystal by looking at the frequency difference between warm-up and after. Jim wrote earlier, that his "10544 osc is sitting about 1.5KHz LOW at room temp and then increases in freq at warmup (OVEN temp rising)". 1.5 kHz = 150 ppm @ 10 MHz. 1. A BT cut crystal has a second order tempco of approx. -4*10^-8 per K^2 with reference to the turn-over temperature. Assuming an oven temperature of around 85°C, makes a temp difference to room temp of abt. 60K: (60K)^2*(0.04ppm/K^2) = 144 ppm = 1.44 kHz. This matches closely to Jims measurement. 2. An AT cut crystal has a frequency vs. temperature response described by a 3rd order parabola with its symmetry point around 25°C~35°C. Without going into the math in detail: A cut angle with a UTP of 85°C has an offset at 85°C compared to 25°C of about -45 ppm. This is much less than Jim's observation, and the direction of the frequeency change is opposite to the observed one. 3. An SC-cut crystal also has a frequency vs. temperature response described by a 3rd order parabola with an inflection (symmetry) temperature of around 95°C. But the SC-cut f(T) response has a much flatter curvature than an AT-cut (see the HP magazine article cited earlier). An OCXO with an SC-cut crytal operating at 85°C shows about -18ppm offset at room temperature compared to the frequency at assumed TOP of 85°C. This is a much smaller amount than Jim's measurement. Therefore it is easy to conclude, that Jim's 10544 uses a BT-cut crystal. Best regards Bernd Neubig DK1AG __ AXTAL GmbH & Co. KG www.axtal.com Ed Palmer schrieb: The recent discussion regarding the type of crystal in the HP 10544A brought this question to mind. We're always coming across unknown oscillators. Usually we can figure out the pinouts and voltages. Then we can measure stability, aging, etc. But are there any tricks to figure out what type of crystal is in the oscillator? How can you detect the differences between AT, BT, SC, etc? I think that AT crystals have a broader tuning range than SC and that when warming up AT crystals tend to overshoot the final frequency and fall back. Are these generalizations correct? Are there other tricks to help differentiate the crystal types? Ed ___ 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.
