Message	Date	From	Subject
3339	2009-07-26 10:17:29	Phil Sittner	Measuring Crystal Parameters
I've been using the G3UUR method for establishing the Lm and Cm parameters of crystals as documented by Wes's work. The only downfall of this method is that it doesn't (at least it's not obvious to me) establish Rs that's needed for establishing the Q factor. There is also the K6OLG's method, using a test set designed by the late W1FB, as shown in the Jan. 1990 QST using a substitution method to establish Rs and a similar method shown by Wes in his May 1982 QST article. I built the W1FB jig and obtained an approximate +/- 10% difference in calculated values. Finally, I came across an article presented by Kortage, K8IQY, at Atlantacon and built his test fixture as well but used SMD components in an attempt to minimize all stray values. And finally, after reading the dialog of this group, I adapted an SMD version of Wes's 17Jan2002 test oscillator, a modified version of the classic G3UUR test oscillator. The correlation between the two SMD versions is quite close-most results are within 3%. But the question still remains, is there a method using the G3UUR fixture to establish Rs, and consequently the Q? regards, Phil KD6RM [Non-text portions of this message have been removed]
3340	2009-07-26 11:40:03	Chris Trask	Re: Measuring Crystal Parameters
> > I've been using the G3UUR method for establishing the Lm and Cm parameters > of crystals as documented by Wes's work. The only downfall of this method > is that it doesn't (at least it's not obvious to me) establish Rs that's > needed for establishing the Q factor. > <> > > But the question still remains, is there a method using the G3UUR fixture > to establish Rs, and consequently the Q? > No. To measure Rs properly you need to make the measurements where the crystal is operating in the series mode. The G3UUR test set is actually making measurements in the parallel mode with a Colpitts oscillator, however the two voltage divider capacitors are so large that the series and parallel mode frequencies are only a 100Hz or so apart. A Pierce oscillator operates between the series and parallel modes. One of the very few oscillator topologies that uses the crystal in a series mode is the circuits devised by Butler, a variation of which which I used in my crystal parameter test set: http://www.home.earthlink.net/~christrask/Paper008.html Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3341	2009-07-26 16:13:10	Phil Sittner	Re: Measuring Crystal Parameters
Chris- I'm intrigued by your paper and wish to thank you for forwarding it. In fact, I'm going to build your design in smd and have a couple of questions regarding the calibration. On page 7, calibration, you mention to disconnect the circuitry to the test socket and switch. If I understand, that would mean I would take my measurements prior to installing C4, Q6, R14, R15 and Q5. In my prior test sets I used a 2-pin .100" male header with a shorting jumper as the test switch to minimize stray capacitance and plan to do the same here. My other question regards T1 as I plan on using a T37-43 core with a trifilar 10 turn winding, 2 turns in series to form the secondary. Do you see any problem with that? Thanks again for the paper and I'll await your comments. 73's Phil KD6RM ----- Original Message -----
3342	2009-07-26 16:56:45	Chris Trask	Re: Measuring Crystal Parameters
> > I'm intrigued by your paper and wish to thank you for forwarding it. In fact, > I'm going to build your design in smd and have a couple of questions regarding > the calibration. > Let us know how it works out. Others have built it and it sees regular use. It is a bit intensive, but I wanted to be able to make good, quantitative measurements. One person is using a vector voltmeter instead of an oscilloscope for the voltage measurements, and that is a very worthwhile modification. > > On page 7, calibration, you mention to disconnect the circuitry to the test > socket and switch. If I understand, that would mean I would take my measurements > prior to installing C4, Q6, R14, R15 and Q5. In my prior test sets I used a > 2-pin .100" male header with a shorting jumper as the test switch to minimize > stray capacitance and plan to do the same here. > No, you should make the calibration test with everything in place. Install ALL of the components, with C10 mounted right on the switch and your 2-pin headers on the board (BTW - nice modification). Use short wires (less stray inductance) from the switch and test socket to the board and headers. > > My other question regards T1 as I plan on using a T37-43 core with a trifilar > 10 turn winding, 2 turns in series to form the secondary. Do you see any problem > with that? > That's a good way to go about making your own, but you can probably get by with fewer turns though it's not importatnt. I made my own with 4 turns of trifilar #32 in a BLN-43-2402 binocular core. > > Thanks again for the paper and I'll await your comments. > Go for it. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3343	2009-07-26 17:13:23	Phil Sittner	Re: Measuring Crystal Parameters
Chris- I came across another question while laying the board out. Caps C5 and C11 appear to be redundant. Is there a specific placement intended here? Phil ----- Original Message -----
3344	2009-07-26 17:35:08	Chris Trask	Re: Measuring Crystal Parameters
> > I came across another question while laying the board out. Caps C5 and > C11 appear to be redundant. Is there a specific placement intended here? > Yes, One should go near the base of Q2 and the other at the cold end of the T1 secondary. Also, you can improve the performance of the test set by using MPS6521 and MPS6523 transistors in place of the 2N4123 and 2N4125, respectively. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3345	2009-07-27 21:52:04	Wes Hayward	Re: Measuring Crystal Parameters
Hi Phil, Chris, and gang, Well I finally went and did it. This experiment has been on my "must do" list for a while now and I figured that this was the time to get it done. I took some crystals and measured them with a variety of methods to see what looked reasonable and how the methods compared. The base, my "standard" if you will, is the N2PK VNA. Wonderful box! After measurements on a crystal with that, I looked at the same crystal with the methods put forth in EMRFD and in an earlier posting here. I looked at crystals at 4.0, 5.0, 10.0, and 11.06 MHz. Bottom line is that the G3UUR methods are amazingly good. Not only do they produce results that are pretty close to the VNA produced crystal parameters, but when the resulting data is used to design a crystal filter, it comes out just as simulated. Errors in Lm range from 1 to 10 % when comparing the VNA to the oscillator produced results. The information is in a report
3347	2009-07-28 20:51:47	Wes Hayward	Re: Measuring Crystal Parameters
Hello again, all, I have updated the piece that was mentioned yesterday, for I took some more data. None of the conclusions have changed. The new url is http://w7zoi.net/Comparing_Quartz_Crystal_Measurement_Methods.pdf As I got more data on crystals that I had measured in the past, I noticed an anomaly with some of the 5 MHz data. Specifically, I found that the Q numbers I was getting with the VNA were much lower than what I had remembered. I wondered: could my memory be that far off? After all, that is part of this geezerism thing. Anyway, I continued to do Q measurements. It finally all made more sense when I started to wonder about the RF power level. Wondering if I was hitting the crystal a bit on the hard side, I inserted a 14 dB pad between the VNA and the bridge, re-calibrated, and repeated the measurement. What had been a Q of 75K jumped to 147K. In another case, I saw 93K with about 0 dBm applied to the bridge and 321K with -14 dBm applied. I would be questioning my measurements if I had not seen similar things in the past. I encountered a similar behavior many years ago when fighting with some crystal filter problems related to spectrum analyzers. In that case, we were seeing gain compression in a narrow crystal filter that we did not see with wider filters. So, the moral is to be careful when measuring crystal Q. Incidentally, drive level seemed to have little to do with the motional numbers that were predicted. There seemed to be some impact, but it was within the scatter of the measurements. 73, Wes w7zoi
3351	2009-07-29 07:02:36	ehydra	Re: Measuring Crystal Parameters
Hm. Maybe the quartz was already depressed. See "Dissipation in the quartz" here: http://translate.google.de/translate?u=http%3A%2F%2Fwww.oliverbetz.de%2Fquarz%2Fquarz.htm&sl=de&tl=en&hl=de&ie=UTF-8 - Henry -- ehydra.dyndns.info Wes Hayward schrieb: > Incidentally, drive level seemed to have little to do with the motional numbers that were predicted. There seemed to be some impact, but it was within the scatter of the measurements. >
3352	2009-07-29 07:36:40	Chris Trask	Re: Measuring Crystal Parameters
> > Anyway, I continued to do Q measurements. It finally all made > more sense when I started to wonder about the RF power level. > Wondering if I was hitting the crystal a bit on the hard side, > I inserted a 14 dB pad between the VNA and the bridge, > re-calibrated, and repeated the measurement. What had been a > Q of 75K jumped to 147K. In another case, I saw 93K with about > 0 dBm applied to the bridge and 321K with -14 dBm applied. > I ran into similar problems with drive level, but it had more to do with harmonic distortion in the oscillator rather than overdriving the crystal. Chris
3353	2009-07-29 08:00:22	joop_l	Re: Measuring Crystal Parameters
> Anyway, I continued to do Q measurements. It finally all made more sense when I started to wonder about the RF power level. Wondering if I was hitting the crystal a bit on the hard side, I inserted a 14 dB pad between the VNA and the bridge, re-calibrated, and repeated the measurement. What had been a Q of 75K jumped to 147K. In another case, I saw 93K with about 0 dBm applied to the bridge and 321K with -14 dBm applied. > Ai, my MiniVNA methods use the Q (-3dB points) for the determination of the Lm and Cm. If drive level has such a huge impact, then I suppose the Lm values can be very inaccurate. When I find the time I should test with some attenuation between generator and crystal. The method is from Jim Kortge, K8IQY. It uses the crystal as passband device in 12.5 ohm setting (4:1 transformers). My drive level is about -6 or -7dBm. Joop
3354	2009-07-29 08:16:42	Chris Trask	Re: Measuring Crystal Parameters
> > Ai, my MiniVNA methods use the Q (-3dB points) for the > determination of the Lm and Cm. If drive level has such a > huge impact, then I suppose the Lm values can be very > inaccurate. When I find the time I should test with some > attenuation between generator and crystal. > The IEC standard fixture for testing crystals is described in: <http://www.cliftonlaboratories.com/Documents/Assembly and Usage Notes for Crystal Test Fixture.pdf> Chris
3356	2009-07-29 10:05:27	timshoppa	Re: Measuring Crystal Parameters

3357	2009-07-29 10:11:14	Chris Trask	Re: Measuring Crystal Parameters
> > > > > > > > > Ai, my MiniVNA methods use the Q (-3dB points) for the > > > determination of the Lm and Cm. If drive level has such a > > > huge impact, then I suppose the Lm values can be very > > > inaccurate. When I find the time I should test with some > > > attenuation between generator and crystal. > > > > > > > The IEC standard fixture for testing crystals is described in: > > > > <http://www.cliftonlaboratories.com/Documents/Assembly and Usage Notes for Crystal Test Fixture.pdf> > > How, in practice, does using the 12.5 ohm crystal driving impedance differ > from using a 50 ohm pad in front as shown in EMRFD Fig 3.34? It already > recommends a maximum drive level to the crystal of -30dBm. > > Most of the cheapo 4-10 MHz crystals I measure have series resistances > between 10 and 15 and 20 and 30 ohms. I suppose a lower ohm driving > impedance would be more convenient if I were dealing with higher-Q, lower > ESR crystals. > The 12.5 ohm impedance is the standard for the industry set by IEC, and my guess is that the resistive pads are more easily reproduced than transformers plus they have far fewer parasitics. In the full IEC fixture, there are a couple of trimmer capacitors that correct for the high frequency cutoff. I don't have a copy of the formal IEC publication about this, and that's where you would find the reasoning behnd it all. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3358	2009-07-29 11:01:36	Chris Trask	Re: Measuring Crystal Parameters
> > > > > Anyway, I continued to do Q measurements. It finally all made > > more sense when I started to wonder about the RF power level. > > Wondering if I was hitting the crystal a bit on the hard side, > > I inserted a 14 dB pad between the VNA and the bridge, > > re-calibrated, and repeated the measurement. What had been a > > Q of 75K jumped to 147K. In another case, I saw 93K with about > > 0 dBm applied to the bridge and 321K with -14 dBm applied. > > > > I ran into similar problems with drive level, but it had more to > do with harmonic distortion in the oscillator rather than overdriving > the crystal. > There's some useful information regarding the drive level when measuring crystal parameters: Gufflet, N., "Quatrz Crystal Resonators," KVG Quarts Crystal Technology http://www.kvg-gmbh.de/fileadmin/Bilder/TechInfo/Quarz/IntroductionQuartz.pd f Rose, D., "Load Resonant Measurement of Quartz Crystals," Saunders and Associates, 1998 http://www.saunders-assoc.com/datasheets/paper/paper.pdf Saunders, J.L., "Drive Level Effects on Transmission Measurements of AT Overtone Resonators," Proceedings 6th Annual Quartz Crystal Conference, 1984 Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3365	2009-07-29 19:44:45	Phil Sittner	Re: Measuring Crystal Parameters
Wes- That's a really good piece of work. I've finished building my smd version of Chris's oscillator (it has a problem yet to be found) and am anxious to compare the results. I too have had some issues when trying to measure small values of capacitance with the AADE bridge and came up with a very simple solution. I use a short piece (about 1 foot) of cheap twin conductor speaker cable, not unlike what you find at Radio Shack. It has a nice molded jacket and you fan out the far end, zero the bridge, then tack solder the cable to what needs measuring. It works quite well. If you have an interest I'll share the results of using Chris's method. 73's, Phil kd6rm ----- Original Message -----
3366	2009-07-29 19:51:07	ashhar_farhan	Re: Measuring Crystal Parameters
on a slightly removed note, how can we any of these methods to measure the overtone parameters? i suppose that only motional capacitance will change in the overtone modes. using the g3UUR's method the oscillator's phase shift will have to be 360 degrees at the overtone frequency. - farhan
3367	2009-07-29 20:07:49	Chris Trask	Re: Measuring Crystal Parameters
> > on a slightly removed note, how can we any of these methods to measure > the overtone parameters? > > i suppose that only motional capacitance will change in the overtone > modes. using the g3UUR's method the oscillator's phase shift will have > to be 360 degrees at the overtone frequency. > In a full model of the crystal, each overtone frequency consists of the same series resistor, capacitor, and inductor as for the fundamental. They are all connected in parallel. One of the papers I mentioned earlier shows this full model. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3370	2009-07-30 04:44:36	joop_l	Re: Measuring Crystal Parameters

3371	2009-07-30 06:55:51	john lawson	Re: Measuring Crystal Parameters
Good morning Phil and all. I have read with great interest the helpful replies from your post on the question of Rs measurements to arrive at the crystal's Q from Wes, Chris as well as others. I. too, was looking for a better way to arrive at the Q of the crystal being measured along with the use of my G3UUR oscillator. Wes reminded us in his paper he posted a couple of days ago about the Trap Method for measuring the Q of a crystal as outlined in Chapter 7 of EMRFD. After using some LC oscillators for my measurements, I simply did what I had been thinking about for months and built a VXO with buffering followed by a 5 element LP filter, some 50 pads to arrive at -17 dBm to drive the crystal in the test fixture, while monitoring the ouput for the dip on Bob Kopski's version of Wes's Power Meter.... I then did the math to come up with the needed Q. In my case, it ended up being a very easy, direct way for me to arrive at the needed Q information. John Lawson, K5IRK
3375	2009-07-30 09:50:20	Ashhar Farhan	Re: Measuring Crystal Parameters
chris, joop, if the overtone mode is modeled as having the same motional inductance as the fundamental crystal, then all that remains to be done is recalculate the motional capacitance for the overtone modes as being 1/9th, 1/25th and 1/49th of the fundamental motional capacitance isn't it? - farhan
3376	2009-07-30 10:40:04	Chris Trask	Re: Measuring Crystal Parameters
> > if the overtone mode is modeled as having the same motional inductance > as the fundamental crystal, then all that remains to be done is > recalculate the motional capacitance for the overtone modes as being > 1/9th, 1/25th and 1/49th of the fundamental motional capacitance isn't > it? > Where did you get the impression that each overtone has the same motional inductance? In every piece of literature that I've seen, each one is unique (ie - different), just as each motional capacitance and resistance is unique for each overtone. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3377	2009-07-30 11:07:02	Wes Hayward	Re: Measuring Crystal Parameters
Hi Farhan, Joop, Chris, and gang, Re the overtone crystals. This was briefly mentioned in EMRFD, Fig 4.27. Of course this model is simplified in that it does not include spurious responses. This crystal modeling game is the same as semiconductor modeling. We start with something simple and then start refining it, adding nonlinear behavior to the core model and layer upon layer of packaging parasitic L, C, and R. Often the original basic model is lost in the complexity. The N2PK machine is essentially a computer controlled pair of frequency synthesizers (DDS) that drive an output port and an internal DC receiver. The receiver is configured so that you measure the receiver input port response in amplitude and in phase with respect to the source. The port impedances are 50 Ohms. The simplest measurement is just the frequency response through a network. If you elect to add a bridge to the VNA, you get a result which is the complex (amplitude and phase) reflection coefficient. That gets converted to impedance by the internal software. Like so many (read as "all") network analyzers, the essence is in the calibration. As was pointed out, there is a VERY ACTIVE Yahoo Group that deals with the N2PK analyzer. There were numerous impedance bridges that were on the market in the past. These generally had "stuff" in them allowing the user to directly read impedance in real and imaginary form. The detected output was used only as a null indicator. That is, one tuned the knobs on the bridge to zero it for both real and imaginary parts of the impedance. In contrast, the usual VNA that is used with a bridge still has an output that is a reflection coefficient, which is then converted to impedance with mathematics. These more recent methods are more consistent with swept measurements. It is extremely interesting to go back and look at the old bridge circuits and the methods that they used. Old app notes from General Radio were wonderful in this regard. Who knows? There may be a Yahoo Group for these old instruments. It is easy enough to look at low overtones with the N2PK VNA. All that's required is to program the VNA to look at the overtone frequencies. But the N2PK instrument only goes up to 60 MHz. This will catch a lot of the 3rd overtone VHF crystals, but not the critical 5th and higher overtones that are usually above 60 MHz. There are schemes that extend the frequency range of the N2PK instrument. Paul describes transverters on his web site. Just Google "N2PK" or look at the Group. Paul has also been looking at frequency multipliers with mixed results. Years ago I built a 25 MHz overtone oscillator to look at a sack of 3rd overtone crystals that I had picked up. This variation of the G3UUR method was less than satisfactory, but I didn't spend much time with it, so don't condemn the concept. I suspect that insertion of a simple resonator in the Trask variation of the Butler oscillator would allow it to operate nicely at overtones. Experiments are in order. The motional elements in the model tend to differ mainly in motional capacitance as overtones are encountered, leaving the motional inductance constant. But this is merely a first order model. Not all overtone crystals are exact in this regard. Assuming a constant LM would probably be a reasonable starting approximation for use in building crystal filters. A simple model says nothing of Q, and assumptions can be dangerous. I recall having measured a crystal Q of a mere 50,000 at 3.3 MHz . This was a surprise, for the same crystal had a Q of near a million at 10 MHz. Crystal frequencies are not predictable. The 3rd overtone frequency is often very close to 3x the fundamental. But there are sometimes dramatic differences. Bottom line plan on measuring the parts for best results. 73, Wes w7zoi
3378	2009-07-30 11:19:12	joop_l	Re: Measuring Crystal Parameters
> > Where did you get the impression that each overtone has the same > motional inductance? In every piece of literature that I've seen, each one > is unique (ie - different), just as each motional capacitance and resistance > is unique for each overtone. > I had to search again so these might not be the best examples. http://rfdesign.com/mag/ramon.pdf It is implied at the bottom of page 32. Actually it says Cn = C1 / n^2 With F = 1 / (2pisqrt(LC)) and L = 1 / (C * (F2pi)^2) and Ln = 1/ (Cn * (Fn2pi)^2) thus Ln = 1/ (C1/n^2 * (F1n2pi)^2) thus Ln = 1/ (C1 (F12pi)^2) ;is the same for every n http://www.am1.us/Papers/U11625%20VIG-TUTORIAL.PDF Page 3-23 The formula is different: C1 = r' * Cn / n^3 where r' = f1 / fn if it would have said r' = fn / f1, then the formulas would match the other article. But I am pretty sure I read it elsewhere too. It just does not fit my own measurements. But a lower drive level might bring more clarity. Do you have articles that state something totally different? I would be interested. Joop
3379	2009-07-30 11:26:18	joop_l	Re: Measuring Crystal Parameters

3380	2009-07-30 12:40:03	victorkoren	Re: Measuring Crystal Parameters
I have found two places that refer to the overtone xtal parameters in the technical literature: 1)"Design of crystal and other harmonic oscillators" by Benjamin Parzen (Paragraph 3.2.4.1): "In the equivalent circuit exptended to represent the family of overtones associated with the fundamental, Co C1 L1 and R1 are unchanged in value but Cn = C1 / N^2." 2)"Foundations of oscillator circuit design" by Guillermo Gonzales (Paragraph 4.4, Crystal characteristics): "The overtone element values are calculated using Ln = L Cn = C/n^2 " (L,C are the fundamental frequency motional parameters) This is what I found in a short search. Indeed it seems that in first order at least, The motional inductance of an overtone is identical to the motional inductance of the fundamental while the motional capacitance decreases by the square of the overtone order. Victor - 4Z4ME
3381	2009-07-30 13:17:22	Chris Trask	Re: Measuring Crystal Parameters
> I have found two places that refer to the overtone xtal parameters in the > technical literature: > > 1)"Design of crystal and other harmonic oscillators" by Benjamin Parzen > (Paragraph 3.2.4.1): > "In the equivalent circuit exptended to represent the family of overtones > associated with the fundamental, Co C1 L1 and R1 are unchanged in value but > Cn = C1 / N^2." > > 2)"Foundations of oscillator circuit design" by Guillermo Gonzales > (Paragraph 4.4, Crystal characteristics): > "The overtone element values are calculated using > Ln = L > Cn = C/n^2 " > (L,C are the fundamental frequency motional parameters) > > This is what I found in a short search. > Try something more up to date, such as: http://www.am1.us/Papers/U11625%20VIG-TUTORIAL.PDF Page 3-23 gives a far better approximation of the overtone model parameters, and none of them are identical. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3382	2009-07-30 13:19:56	joop_l	Re: Measuring Crystal Parameters
I measured a couple of crystals to look at motional parameters per fundamental and overtones plus at two different drive levels. Two crystals were measured: 100MHz 3rd OT and 200MHz 9th OT. Above fundamental the Cp was neutralized with a parallel resonance LC. A second measurement of both was done with a 10dB attenuator after the generator. Generator output -2.5 @ 30MHz, -2.5@100MHz, -4.5 @ 160MHz My xtal fixture contains 4dB attenuator and 4:1 transformers on both sides. Roughly max xtal level -6.5 @ 30MHz, -6.5@100MHz, -8.5 @ 160MHz Results: 100Mhz xtal =========================== 33MHz: Ls = 1.293759 mH, Cs = 17.677113 fF, Rs = 4.51 Ohm, Q = 60012 100MHz: Ls = 1.412943 mH, Cs = 1.792847 fF, Rs = 16.68 Ohm, Q = 53219 166MHz: Ls = 1.074538 mH, Cs = 0.848610 fF, Rs = 69.39 Ohm, Q = 16216 100Mhz xtal 10dB attenuated =========================== 33MHz: Ls = 1.135663 mH, Cs = 20.137836 fF, Rs = 4.71 Ohm, Q = 50392 100MHz: Ls = 1.533813 mH, Cs = 1.651560 fF, Rs = 20.18 Ohm, Q = 47756 166MHz: Ls = 1.232540 mH, Cs = 0.739822 fF, Rs = 80.91 Ohm, Q = 15953 200Mhz xtal =========================== 22MHz: Ls = 2.725901 mH, Cs = 18.876546 fF, Rs = 4.30 Ohm, Q = 88274 66MHz: Ls = 2.748298 mH, Cs = 2.074455 fF, Rs = 8.57 Ohm, Q = 134321 110MHz: Ls = 2.392983 mH, Cs = 0.857497 fF, Rs = 13.15 Ohm, Q = 127083 155MHz: Ls = 1.917052 mH, Cs = 0.546095 fF, Rs = 19.87 Ohm, Q = 94302 200Mhz xtal 10dB attenuated =========================== 22MHz: Ls = 2.387415 mH, Cs = 21.552760 fF, Rs = 3.94 Ohm, Q = 84556 66MHz: Ls = 2.686533 mH, Cs = 2.122141 fF, Rs = 9.23 Ohm, Q = 121867 110MHz: Ls = 2.374893 mH, Cs = 0.864027 fF, Rs = 15.83 Ohm, Q = 104756 155MHz: Ls = 2.417492 mH, Cs = 0.433049 fF, Rs = 23.97 Ohm, Q = 98566 Only a single measurement of each was done. So I cannot tell how repeatable they are. Initial impression is that the 200MHz crystal does seem to follow the rule of thumb rather well that Lm is similar for the overtones. The 100MHz crystal does this to a lesser extend. The order of magnitude is similar though. The two drive levels do not seem to give a general shift towards some behavior. Joop - pe1cqp
3383	2009-07-30 13:28:08	joop_l	Re: Measuring Crystal Parameters
I see I left some 'dB' out. Corrected section: Generator output -2.5dBm @ 30MHz, -2.5dBm @ 100MHz, -4.5dBm @ 160MHz My xtal fixture contains 4dB attenuators and 4:1 transformers on both sides. Roughly max xtal level -6.5dBm @ 30MHz, -6.5dBm @100MHz, -8.5dBm @ 160MHz All are 10dB less of course in the second round using the attenuator. Joop - pe1cqp
3384	2009-07-30 19:46:25	Ashhar Farhan	Re: Measuring Crystal Parameters
chris and others, wow! i never cease to amaze at how much little experiments can illuminate! thanks chris, joop, for this round. the motional inductance, as per the literature (i have only access to the net and some pdfs) is modeled after the crystal mass where as the capacitance is changed as the number of standing waves across the physical bounds of the crystal. so, as per joop's measurements, it is indeed the motional capacitance that changes its magnitude while the inductance varies in percentages. first, can we then assume that the G3UUR method will give us at least starting values to tune up a ladder filter that works in overtone mode? an ominous indication is that the series resistance shows the filter could have higher losses than a fundamental one. second, will we also require bandpass tuned to the overtone frequency in the input of the ladder filter? how else can we prevent the ladder filter from responding to other modes (spurious and overnote) ? - farhan
3385	2009-07-30 19:53:22	Ashhar Farhan	Re: Measuring Crystal Parameters
this might be of interest in the discussions (refer to page 73 of pdf below): http://www.am1.us/Papers/U11625%20VIG-TUTORIAL.PDF The motional inductance prediction as L(1n) is given in the equation. which can be approximate to remain the same in the overtones. - farhan
3386	2009-07-30 20:31:11	Ivan Makarov	Re: Measuring Crystal Parameters
Hi Wes, do you think the RF-IV method can be used for crystal Q measurements? I think you were copied on communication of measuring of Q for coils/caps using Paul N2PK's RF-IV sensor design, which showed good results. http://www.n2pk.com/VNA/RFIV_Single_%20Detector_Switch_%20and_%20Sensors_V1c.pdf Thks, Ivan VE3iVM ----- Original Message -----
3387	2009-07-30 23:03:11	joop_l	Re: Measuring Crystal Parameters

3388	2009-07-31 05:48:15	victorkoren	Re: Measuring Crystal Parameters
Chris, First, the Gonzales book is from 2007 so it is certainly not outdated. Second, in the tutorial you mentioned (in page 73) it seems that there is an error: r' is defined as f1/fn. It seems to me that it should be r'=fn/f1 and then r' is very close to n, the overtone number (The overtone frequency is very close to the harmonic frequency). If it is so, putting n instead of r' in the equations you will get exactly what the other books say, that Cn~C1/n^2 and Ln=L1 . Victor - 4Z4ME
3389	2009-07-31 07:20:09	Harold Smith	Re: Measuring Crystal Parameters
Here's an idea, which might not be practical: to built a filter using overtone crystals without worrying about the fundamental response, mix the overtones. Use some third overtones and some fifth, for instance. The fundamentals wouldn't even be close. You'd almost certainly have to custom order those crystals, of course, since the odds of finding such a set in your junkbox are pretty long. Just a thought... de KE6TI, Harold
3390	2009-07-31 09:01:49	Chris Trask	Re: Measuring Crystal Parameters
> >Second, in the tutorial you mentioned (in page 73) it seems that >there is an error: >r' is defined as f1/fn. It seems to me that it should be r'=fn/f1 >and then r' is very close to n, the overtone number (The overtone >frequency is very close to the harmonic frequency). If it is so, >putting n instead of r' in the equations you will get exactly what >the other books say, that Cn~C1/n^2 and Ln=L1 . > You're attempting to force a desired conclusion. The overtone frequencies are not sufficiently close to the harmonic frequencies so that your approximation would survive close scrutiny. What you're suggesting might be suitable for a very rough approximation, but not useful for more demanding circumstances. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3391	2009-07-31 16:34:12	victorkoren	Re: Measuring Crystal Parameters
Chris, I am not forcing a conclusion. Please download an updated (2004) of the same tutorial you posted written by John Vig
3394	2009-08-01 07:50:58	Chris Trask	Re: Measuring Crystal Parameters
> > I am not forcing a conclusion. Please download an updated (2004) of the same > tutorial you posted written by John Vig from: > http://www.pwgdev.com/~datasheets/Vig-tutorial%208.5.2.0.ppt > See below slide 75 (similar to page 73 in the older tutorial) that its written: > > "In the last row, the r' is the ratio between the fundamental mode and the n-th > overtone frequencies. For example, when comparing the parameters of a 10 MHz > fundamental mode and a 10 MHz 3rd overtone (of similar design), r' = 1, and when > comparing the parameters of a 10 MHz fundamental mode resonator when excited at > the fundamental mode, and when excited at the 3rd overtone frequency, i.e., at > ~30 MHz, r' = 3." > > This shows that my guess that r' is the overtone number (when comparing fundamental > to overtone frequency of the same crystal) is right, and then Cn~C1/n^2 and Ln=L1 . > That's entirely invalid. The equations are for the parameters for the same crystal, not two different ones. You're now trying to continue to force the conclusion by saying that since since the fundamental frequency for one crystal is 10MHz and the third overtone for the second crystal is 10MHz, the value of r' for the second crystal is exactly 3 without knowing what the fundamental frequency for the second crystal is. That is exactly what you have said here. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3395	2009-08-01 16:11:52	Wes Hayward	Re: Measuring Crystal Parameters
Hi All, This whole exchange has become extremely interesting. Esoteric, perhaps, but still interesting. After Chris' comment yesterday where he was questioning the idea of a constant motional L with overtone number, I started digging in the references I had in my library. My standard reference on crystal related things, the book by Bottoms, had nothing on the subject. I could not find anything else that really supported my contention. So I was pleased when Joop and Victor both offered references and data to support the idea that was in EMRFD. I remembered having seen something to support the idea at one time or another and also recall having done some related measurements on some 5th overtone crystals at both 100 MHz and 125 MHz that were used in spectrum analyzer LO applications. But I didn't recall having done any comparative measurements on HF crystals that would normally be used in fundamental mode filter applications. So, it was back to the lab. This in itself brought some complications. I encountered trouble making the program xtal2.exe work with the VNA on overtone frequencies, at least with some crystals. It worked in some other cases, but not all. My final solution was to do a Smith Chart plot of the VNA data at the appropriate frequencies. The series resistance at resonance is then directly read from the place where the plot crosses the horizontal line of pure resistance. The motional inductance is calculated from the rate of change of reactance with frequency at resonance. This is illustrated in a short note on my web site. Go to http://w7zoi.net/ and then to the designs and experiments section. This note was generated merely to illustrate that reactance slope is a viable way to obtain Lm. So, what were the results? Two crystals were investigated and both were interesting. They were both from batches I've used to build crystal filters. Neither had a constant motional L in going from fundamental to third overtone operation. Not even close! In fact, I saw a dramatic increase in Lm with overtone for these two crystals. Here's some data where Lm(xtal) is obtained with the normal VNA program and Lm(SC) is from the Smith Chart plot using reactance slope. Xtal F Lm(xtal) Lm(SC) R Q 1 4.00 0.1427 0.145 23.5 155K 1 12 0.671 0.628 592 85K 2 5 .09836 0.1017 19.7 170K 2 15 ---- 0.7677 123 588K I never could get the 3rd overtone of the 5 MHz crystal to work in the VNA program xtal2.exe. However, the series and parallel resonances were very close to each other, which is a probable reason for the difficulty. The data above is not the whole story. There is a significant difference between 3 x the fundamental frequency and the third overtone frequency. Clearly from the chart, we can't even come close to guessing a motional L at an overtone after characterizing a crystal at the fundamental, at least with the two rocks I examined. Constant Lm with overtone number may be a viable model for some crystal types, but not for these. The extremely high Q observed with the third overtone of the 5 MHz rock was encouraging. However, it is probably not all that useful for filters owing to the very high Lm. This puts it in the same league as the little cylinder crystals, which suffer a similar problem, which makes filter realization very difficult. I've heard the axiom that any scientific investigation worth its salt will generate as many questions as it does answers. I think we must have arrived with this crystal study! 73, Wes w7zoi
3396	2009-08-01 17:15:10	Chris Trask	Re: Measuring Crystal Parameters
> > This whole exchange has become extremely interesting. Esoteric, perhaps, but > still interesting. > > After Chris' comment yesterday where he was questioning the idea of a constant > motional L with overtone number, I started digging in the references I had in > my library. My standard reference on crystal related things, the book by > Bottoms, had nothing on the subject. I could not find anything else that > really supported my contention. So I was pleased when Joop and Victor both > offered references and data to support the idea that was in EMRFD. > <> Parzen shows the complete fundamental/overtone model on p. 84. He provides very little discussion of the overtone frequencies, instead repeating the gross approximation that the nth overtone is n times the fundamental. This approximation is the source of a considerable amount of discord lately. Bottom at least goes into some detail about the mathematical derivation of the overtone frequencies, then states that they are approximately n times the fundamental. He shows, to some small degree, that the deviation from the overtones not being integral multiples of the fundamental is due to the thickness of the resonator. Buchanan ("Handbook of Piezoelectric Crystals for Radio Equipment Designers"), doesn't even make mention of ovvertones. Nor do any of the other almost dozen texts and additional literature that I have. > > So, what were the results? Two crystals were investigated and both were > interesting. They were both from batches I've used to build crystal filters. > Neither had a constant motional L in going from fundamental to third overtone > operation. Not even close! In fact, I saw a dramatic increase in Lm with > overtone for these two crystals. Here's some data where Lm(xtal) is obtained > with the normal VNA program and Lm(SC) is from the Smith Chart plot using > reactance slope. > With two sets of independent test data at our disposal, it's safe to say that the modal inductances are not identical and the overtone frequencies are not integral multiples. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3397	2009-08-01 19:53:24	Wes Hayward	Re: Measuring Crystal Parameters
Hello again, all, My last posting contained a table, but it is essentially unreadable. It was OK when composed in WORD. I have uploaded a "file" titled "Posting_3395_table.jpg" that should be quite readable. Also, the errata for EMRFD now contains an item for page 4.15 about this issue. 73, Wes w7zoi
3398	2009-08-02 02:19:02	joop_l	Re: Measuring Crystal Parameters

3399	2009-08-02 03:10:07	Ashhar Farhan	Re: Measuring Crystal Parameters
on a related note, in my other obsession as guitarists (i am the worst guitarist i have ever known) we aspire to play harmonics. the way it is done is quite simple, theoretically. we lightly hold a finger to that part of the string where the standing wave's node ought to be and then pluck it quickly (impluse excitation). depending upon where the finger was placed, an overtone is generated. usually these overtone frets are marked on the guitar by white spots. however, a very frustrating aspect of this overtone mode of oscillations is that harmonics do not always fall within the scale the guitar is tuned to! they are always off by a few beats. this results in quite a confusion. eric clapton, once asked about who he would vote in the coming elections, said 'i will vote for anyone who can invent an automatic guitar harmonics tuner'. there is, thus, more to harmonics than just the length of the waves. something to do with the boundary conditions, i guess. - farhan
3400	2009-08-02 07:02:54	Chris Trask	Re: Measuring Crystal Parameters
> >on a related note, in my other obsession as guitarists (i am the worst >guitarist i have ever known) we aspire to play harmonics. > >the way it is done is quite simple, theoretically. we lightly hold a >finger to that part of the string where the standing wave's node ought >to be and then pluck it quickly (impluse excitation). depending upon >where the finger was placed, an overtone is generated. usually these >overtone frets are marked on the guitar by white spots. however, a >very frustrating aspect of this overtone mode of oscillations is that >harmonics do not always fall within the scale the guitar is tuned to! >they are always off by a few beats. this results in quite a confusion. >eric clapton, once asked about who he would vote in the coming >elections, said 'i will vote for anyone who can invent an automatic >guitar harmonics tuner'. > I've seen/heard performers do that, and it adds an interesting dimension to the performance. Chris Chris
3401	2009-08-02 09:19:37	Chris Trask	Re: Measuring Crystal Parameters
> > > > > This whole exchange has become extremely interesting. Esoteric, > > perhaps, but still interesting. > > > > After Chris' comment yesterday where he was questioning the idea > > of a constant motional L with overtone number, I started digging > > in the references I had in my library. My standard reference > > on crystal related things, the book by Bottoms, had nothing on > > the subject. I could not find anything else that really > > supported my contention. So I was pleased when Joop and Victor > > both offered references and data to support the idea that was in > > EMRFD. > > > > <> > I've exhausted my own library, Google, and IEEE Xplore on this subject and have nothing more to add. I have a good backlog of literature to download at the university library, so tomorrow I'll take a trek over there and use the INSPEC search engine to see what else is available. I'm especially curious to determine the source of Vig's overtone parameter equations. They may be the result of original work by him, but it's difficult to say as he doesn't cite any references. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3402	2009-08-02 12:24:32	ehydra	Re: Measuring Crystal Parameters
Chris ist right. The ratio depends mostly on crystal cut and processing parameters. It can vary to a very extend. It may help, that the circuit model for monopole and dipole antennas is almost the same! regards - Henry -- ehydra.dyndns.info Chris Trask schrieb: > > With two sets of independent test data at our disposal, it's safe to say > that the modal inductances are not identical and the overtone frequencies > are not integral multiples. >
3403	2009-08-02 12:36:49	ehydra	Re: Measuring Crystal Parameters
joop_l schrieb: > We tend to look at overtones from the electronics side. But since the crystal has a mechanical motion it might be interesting to look at a similar effect in musical instruments. This usenet thread mentions what happens with a piano: > http://groups.google.nl/group/sci.electronics.design/browse_thread/thread/22a35328f1d2d358/d8befaad4f9cce64#d8befaad4f9cce64 > Antoher manifestication of the same phaenomen. In general: It is not a good idea to use a crystal in overtone or subtone mode if it is designed for baseband frequency. And the other way around is the same. I read that several times in various references. And even got the problem on the desk with a old Narva 27.12MHz quartz. It is without datasheet but offered as 27.12MHz. But it is a overtone quartz resonating somewhere at 9MHz! With the right oscillator it will be pressed to 27.12MHz and indeed, I repaired the rc car of my youngster with such a crystal. I think the quartz was mechanical killed by dropping the remote transmitter several times on hard ground. Now the car is controllable much longer range than before! (china product) This quartz shows 'in a lot of severals' more variant resonating frequency if it is NOT on it's designed-frequency. As expected! So, don't make it! - Henry -- ehydra.dyndns.info
3404	2009-08-03 06:13:24	victorkoren	Re: Measuring Crystal Parameters
One more input: The book :"Practical RF Circuit Design for Modern Wireless Systems: Passive circuits" ... By Rowan Gilmore, Les Besser. In page 400 is written: "The crystal can be modeled at a higher overtone by a separate R-L-C motional arm set to resonate at that frequency. If N denotes the Nth overtone ,then we may model that resonance with: Cn = Cm / N^2 for modes where the resonant frequency is determined by the thickness of crystal between the plates. It follows therefore that since the resonant frequency increases by a factor of N: Ln = Lm and since the motional R-C time constant (approximately) independent of frequency, Rn = Rm * N^2 " Note that it mentions that this is good only for modes where the resonant frequency is determined by the thickness of crystal between the plates, so there might be some dependence on the mechanical characteristics like the way the crystal is being held etc, and that might make some frequency and motional parameters change. The book can be found in Google books, Just google the book name. Victor - 4Z4ME
3405	2009-08-03 08:30:58	Chris Trask	Re: Measuring Crystal Parameters
> > Note that it mentions that this is good only for modes where the resonant > frequency is determined by the thickness of crystal between the plates, so > there might be some dependence on the mechanical characteristics like the > way the crystal is being held etc, and that might make some frequency and > motional parameters change. > In other words, they're openly admitting that the approximations is not entirely valid, which is what we've been saying here for over a week now. Since we have a more accurate derivation available by way of Vig, there is no reason to continue using the approximation as a crutch. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3406	2009-08-03 09:33:10	victorkoren	Re: Measuring Crystal Parameters
Vig's derivati
3407	2009-08-03 10:33:51	victorkoren	Re: Measuring Crystal Parameters
Wes, When you did the overtone frequency measurements, did you connect an inductor in parallel to cancel the influence of Co (parallel capacitance)
3408	2009-08-03 12:12:56	Wes Hayward	Re: Measuring Crystal Parameters
Hi Victor, and gang, No, I didn't add anything to the crystals other than to solder the leads to an SMA connector. That was then attached to my bridge with an SMA "un-barrel." That short line was present during OSL calibration, so should not be part of the data. In the later measurements, I have been grounding the metal crystal can, at the tweaking of w4zcb. Two more crystals were examined yesterday, both extremely interesting. The first was an old FT-243. These are the things that plugged into our old novice transmitters that kept us on the right frequency in spite of ourselves. The one I examined was marked 7100 and was a type Z2 manufactured by Pierson Radio. The N2PK crystal program (xtal2.exe) worked fine on the fundamental, but produced nothing at the third overtone. Sweeps yielded an explanation. A Smith Chart display of a 2 kHz region showed a sweep with two series resonances that were nearly identical. The real spurious response is not well established, although we assume it is the upper one. This sweep has been posted as a file named "third_overtone_with_spur". The fundamental mode had a motional L of .01579 H and a Q of 68K. The parallel C was only 2.5 pF. This makes sense when one examines the interior of one of these crystals. The quartz is only contacted at the corners of the rectangular blank. The two resonances related to the third overtone had the following properties, extracted from the SC display: First resonance: 20.76 Ohms, Lm=.02302H, Q=148K. Second resonance (spur?): 40.94 Ohms, Lm=.04051 H, Q=133K. I have a bunch of these crystals, left from the mid 1960s. I used some of these rocks in a 15 meter QRP rig (QST, April, 1968) where I operated the crystals in the third overtone mode and they worked great. It was an easy way to get on a new band and produced my first DX with less than a watt of output. The frequencies were very close to 3X the fundamental (perhaps half a kHz at 21 MHzwho knew exactly back in the day) and I don't recall any problems with the transmitter hopping from one frequency to a spur. The oscillator was keyed without any observed difficulty. I regularly monitored my signal in the receiver at that time and don't recall hearing anything at other frequencies. I have used crystals with strong spurs in other situations. They usually just oscillate on one frequency (the main one) so long as the spur strength is just a few dB below the main response. The other crystal examined yesterday was one of the 10 MHz high Q third overtone jobs mentioned in earlier posts. This rock is in a glass HC-6 package and is in vacuum. This part was manufactured by Colorado Crystal. The quartz disc is about 0.5 inch in diameter with gold plating over the center to a diameter of 0.33 inch or so. There was no problem in getting good data with the VNA and the program xtal2.exe. Smith Chart sweeps produced data that was virtually identical to that from the program. At the 10 MHz third overtone, the motional L was 0.110 H, parallel C was 5.99 pF, and Q=710K. (The internal spec for this crystal was a Q of 650K, so this one would have passed. Most parts were better than this.) The fundamental mode measurement suggested a very ordinary crystal. The series frequency of 3.3466 MHz was not 1/3 of the OT, but was just in the general region. The fundamental mode Q was a very modest 73K. But the motional L was 0.103 H, which is close to the same as the overtone. I think I'm about ready to put this subject to rest, at least for a while. This has been an interesting one! 73, Wes w7zoi
3420	2009-08-03 15:40:05	joop_l	Re: Measuring Crystal Parameters
Wes, Were did you find your beautiful 10MHz crystal? Joop
3421	2009-08-03 19:44:15	Wes Hayward	Re: Measuring Crystal Parameters
Hi Joop, et al, Yea, that crystal is a gem. This one came from Tektronix surplus. This crystal was used in a number of their 70s and 80s era spectrum analyzers. Three of them are used in an oven to form a filter with a bandwidth of 30 Hz, which is amazing at 10 MHz. They were used in some other filters in various spectrum analyzers. Also kicking around from Tek surplus are some color burst crystals that are truly stellar in performance, outgrowths of Tek TV efforts. 73, Wes w7zoi
3427	2009-08-04 09:08:50	joop_l	Re: Measuring Crystal Parameters

3430	2009-08-04 12:52:57	joop_l	Re: Measuring Crystal Parameters

3432	2009-08-05 05:31:34	timshoppa	Re: Measuring Crystal Parameters

3433	2009-08-05 05:55:32	w4zcb	Re: Measuring Crystal Parameters
I'm moderately interested in measurements of crystals intended for use in the 70MHz and 100MHz filters common in upconverting radios these days. Isn't this where the thread started before it degenerated into hagiography? Tim. You pay a price for a radio that is "general coverage" upconverting. Increased phase noise from the high frequency oscillator. Every japanese offering is upconverting and every one of them is inferior to down converting radios WRT reciprocal mixing. I've owned a couple in nearly 60 years, and tested and evaluated many more. By far, the worst radio Ten Tec ever produced was their general coverage "Paragon" with it's 70 MHz first IF. My neighbor and nemisis who owned one was an untenable force when we operated on the same band, and even he admitted that my signal cleaned up remarkably when he got rid of it. W4ZCB BTW, I purchased a pair of Ten Tecs 75 MHz crystal filters many years ago and never used them. If you plan on making something at that frequency, they're yours for an address.. (Authors who use long words are vaingloriously ostentatious.)
3796	2009-11-21 09:12:38	Phil Sittner	Re: Measuring Crystal Parameters
Chris- Several months ago I built your design of the crystal test set and could not get the loop to work, in fact, I inserted a potentiometer in the base circuit of Q3 and used it to bias the oscillator and then made my measurements but I was still perplexed as to why I could not make the loop work. I believe there is a small typo on your schematic. The mod I made was relative to C7, R14 and the primary of T1. I currently have C7 couple between the base of Q5 and the emitter of Q4; and R14 is in series with the primary of T1 and also ties to the base of Q5. Is this the way the circuit should be configured or have I missed something? regards, Phil kd6rm ----- Original Message -----
3797	2009-11-21 11:09:23	Chris Trask	Re: Measuring Crystal Parameters
> > Several months ago I built your design of the crystal test set and could not > get the loop to work, in fact, I inserted a potentiometer in the base circuit > of Q3 and used it to bias the oscillator and then made my measurements but I > was still perplexed as to why I could not make the loop work. I believe there > is a small typo on your schematic. The mod I made was relative to C7, R14 and > the primary of T1. I currently have C7 couple between the base of Q5 and the > emitter of Q4; and R14 is in series with the primary of T1 and also ties to > the base of Q5. > > Is this the way the circuit should be configured or have I missed something? > The circuit works exactly as shown in the schematic. What you have done is double the open loop gain while upseting the impedance balance of the test fixture. Hook it up the way shown and then check the control voltage at the base of Q3. It should be somewhere between ground and Vcc/2. Somehow, you're not getting enough control current to the differential pair, and if that voltage is close to Vcc, then you need to check the load between Q2 and Q4, as that sets the maximum loop gain. Also check the value of R7. If it's higher than the 120 ohms shown, then you will also have insufficient loop gain. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _
3798	2009-11-21 11:11:40	Chris Trask	Re: Measuring Crystal Parameters
> > Several months ago I built your design of the crystal test set and could > not get the loop to work, in fact, I inserted a potentiometer in the base > circuit of Q3 and used it to bias the oscillator and then made my > measurements but I was still perplexed as to why I could not make the > loop work. I believe there is a small typo on your schematic. The mod I > made was relative to C7, R14 and the primary of T1. I currently have C7 > couple between the base of Q5 and the emitter of Q4; and R14 is in series > with the primary of T1 and also ties to the base of Q5. > > Is this the way the circuit should be configured or have I missed > something? > The circuit works exactly as shown in the schematic. What you have done is double the open loop gain while upseting the impedance balance of the test fixture. Hook it up the way shown and then check the control voltage at the base of Q3. It should be somewhere between ground and Vcc/2. Somehow, you're not getting enough control current to the differential pair, and if that voltage is close to Vcc, then you need to check the load between Q2 and Q4, as that sets the maximum loop gain. Also check the value of R7. If it's higher than the 120 ohms shown, then you will also have insufficient loop gain. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _

Message

Date

From

Subject

3339

2009-07-26 10:17:29

Phil Sittner

Measuring Crystal Parameters

I've been using the G3UUR method for establishing the Lm and Cm parameters of crystals as documented by Wes's work. The only downfall of this method is that it doesn't (at least it's not obvious to me) establish Rs that's needed for establishing the Q factor. There is also the K6OLG's method, using a test set designed by the late W1FB, as shown in the Jan. 1990 QST using a substitution method to establish Rs and a similar method shown by Wes in his May 1982 QST article. I built the W1FB jig and obtained an approximate +/- 10% difference in calculated values. Finally, I came across an article presented by Kortage, K8IQY, at Atlantacon and built his test fixture as well but used SMD components in an attempt to minimize all stray values. And finally, after reading the dialog of this group, I adapted an SMD version of Wes's 17Jan2002 test oscillator, a modified version of the classic G3UUR test oscillator. The correlation between the two SMD versions is quite close-most results are within 3%. But the question still remains, is there a method using the G3UUR fixture to establish Rs, and consequently the Q?

regards,
Phil KD6RM

[Non-text portions of this message have been removed]

3340

2009-07-26 11:40:03

Chris Trask

Re: Measuring Crystal Parameters

>
> I've been using the G3UUR method for establishing the Lm and Cm parameters
> of crystals as documented by Wes's work. The only downfall of this method
> is that it doesn't (at least it's not obvious to me) establish Rs that's
> needed for establishing the Q factor.
>

>
> But the question still remains, is there a method using the G3UUR fixture
> to establish Rs, and consequently the Q?
>

No. To measure Rs properly you need to make the measurements where the
crystal is operating in the series mode. The G3UUR test set is actually
making measurements in the parallel mode with a Colpitts oscillator, however
the two voltage divider capacitors are so large that the series and parallel
mode frequencies are only a 100Hz or so apart. A Pierce oscillator operates
between the series and parallel modes. One of the very few oscillator
topologies that uses the crystal in a series mode is the circuits devised by
Butler, a variation of which which I used in my crystal parameter test set:

http://www.home.earthlink.net/~christrask/Paper008.html

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3341

2009-07-26 16:13:10

Phil Sittner

Re: Measuring Crystal Parameters

Chris-

I'm intrigued by your paper and wish to thank you for forwarding it. In fact, I'm going to build your design in smd and have a couple of questions regarding the calibration.

On page 7, calibration, you mention to disconnect the circuitry to the test socket and switch. If I understand, that would mean I would take my measurements prior to installing C4, Q6, R14, R15 and Q5. In my prior test sets I used a 2-pin .100" male header with a shorting jumper as the test switch to minimize stray capacitance and plan to do the same here.

My other question regards T1 as I plan on using a T37-43 core with a trifilar 10 turn winding, 2 turns in series to form the secondary. Do you see any problem with that?

Thanks again for the paper and I'll await your comments.

73's
Phil
KD6RM

----- Original Message -----

3342

2009-07-26 16:56:45

Chris Trask

Re: Measuring Crystal Parameters

>
> I'm intrigued by your paper and wish to thank you for forwarding it. In

fact,

> I'm going to build your design in smd and have a couple of questions

regarding

> the calibration.
>

Let us know how it works out. Others have built it and it sees regular
use. It is a bit intensive, but I wanted to be able to make good,
quantitative measurements. One person is using a vector voltmeter instead
of an oscilloscope for the voltage measurements, and that is a very
worthwhile modification.

>
> On page 7, calibration, you mention to disconnect the circuitry to the

test

> socket and switch. If I understand, that would mean I would take my

measurements

> prior to installing C4, Q6, R14, R15 and Q5. In my prior test sets I used

> 2-pin .100" male header with a shorting jumper as the test switch to

minimize

> stray capacitance and plan to do the same here.
>

No, you should make the calibration test with everything in place.
Install ALL of the components, with C10 mounted right on the switch and your
2-pin headers on the board (BTW - nice modification). Use short wires (less
stray inductance) from the switch and test socket to the board and headers.

>
> My other question regards T1 as I plan on using a T37-43 core with a

trifilar

> 10 turn winding, 2 turns in series to form the secondary. Do you see any

problem

> with that?
>

That's a good way to go about making your own, but you can probably get
by with fewer turns though it's not importatnt. I made my own with 4 turns
of trifilar #32 in a BLN-43-2402 binocular core.

>
> Thanks again for the paper and I'll await your comments.
>

Go for it.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3343

2009-07-26 17:13:23

Phil Sittner

Re: Measuring Crystal Parameters

Chris-

I came across another question while laying the board out. Caps C5 and C11 appear to be redundant. Is there a specific placement intended here?

Phil

----- Original Message -----

3344

2009-07-26 17:35:08

Chris Trask

Re: Measuring Crystal Parameters

>
> I came across another question while laying the board out. Caps C5 and
> C11 appear to be redundant. Is there a specific placement intended here?
>

Yes, One should go near the base of Q2 and the other at the cold end of
the T1 secondary.

Also, you can improve the performance of the test set by using MPS6521
and MPS6523 transistors in place of the 2N4123 and 2N4125, respectively.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3345

2009-07-27 21:52:04

Wes Hayward

Re: Measuring Crystal Parameters

Hi Phil, Chris, and gang,

Well I finally went and did it. This experiment has been on my "must do" list for a while now and I figured that this was the time to get it done. I took some crystals and measured them with a variety of methods to see what looked reasonable and how the methods compared. The base, my "standard" if you will, is the N2PK VNA. Wonderful box! After measurements on a crystal with that, I looked at the same crystal with the methods put forth in EMRFD and in an earlier posting here. I looked at crystals at 4.0, 5.0, 10.0, and 11.06 MHz.

Bottom line is that the G3UUR methods are amazingly good. Not only do they produce results that are pretty close to the VNA produced crystal parameters, but when the resulting data is used to design a crystal filter, it comes out just as simulated. Errors in Lm range from 1 to 10 % when comparing the VNA to the oscillator produced results.

The information is in a report

3347

2009-07-28 20:51:47

Wes Hayward

Re: Measuring Crystal Parameters

Hello again, all,

I have updated the piece that was mentioned yesterday, for I took some more data. None of the conclusions have changed. The new url is http://w7zoi.net/Comparing_Quartz_Crystal_Measurement_Methods.pdf As I got more data on crystals that I had measured in the past, I noticed an anomaly with some of the 5 MHz data. Specifically, I found that the Q numbers I was getting with the VNA were much lower than what I had remembered. I wondered: could my memory be that far off? After all, that is part of this geezerism thing.

Anyway, I continued to do Q measurements. It finally all made more sense when I started to wonder about the RF power level. Wondering if I was hitting the crystal a bit on the hard side, I inserted a 14 dB pad between the VNA and the bridge, re-calibrated, and repeated the measurement. What had been a Q of 75K jumped to 147K. In another case, I saw 93K with about 0 dBm applied to the bridge and 321K with -14 dBm applied.

I would be questioning my measurements if I had not seen similar things in the past. I encountered a similar behavior many years ago when fighting with some crystal filter problems related to spectrum analyzers. In that case, we were seeing gain compression in a narrow crystal filter that we did not see with wider filters.

So, the moral is to be careful when measuring crystal Q. Incidentally, drive level seemed to have little to do with the motional numbers that were predicted. There seemed to be some impact, but it was within the scatter of the measurements.

73, Wes
w7zoi

3351

2009-07-29 07:02:36

ehydra

Re: Measuring Crystal Parameters

Hm. Maybe the quartz was already depressed.
See "Dissipation in the quartz" here:
http://translate.google.de/translate?u=http%3A%2F%2Fwww.oliverbetz.de%2Fquarz%2Fquarz.htm&sl=de&tl=en&hl=de&ie=UTF-8

- Henry

--
ehydra.dyndns.info

Wes Hayward schrieb:

> Incidentally, drive level seemed to have little to do with the motional numbers that were predicted. There seemed to be some impact, but it was within the scatter of the measurements.
>

3352

2009-07-29 07:36:40

Chris Trask

Re: Measuring Crystal Parameters

>
> Anyway, I continued to do Q measurements. It finally all made
> more sense when I started to wonder about the RF power level.
> Wondering if I was hitting the crystal a bit on the hard side,
> I inserted a 14 dB pad between the VNA and the bridge,
> re-calibrated, and repeated the measurement. What had been a
> Q of 75K jumped to 147K. In another case, I saw 93K with about
> 0 dBm applied to the bridge and 321K with -14 dBm applied.
>

I ran into similar problems with drive level, but it had more to do with harmonic distortion in the oscillator rather than overdriving the crystal.

Chris

3353

2009-07-29 08:00:22

joop_l

Re: Measuring Crystal Parameters

> Anyway, I continued to do Q measurements. It finally all made more sense when I started to wonder about the RF power level. Wondering if I was hitting the crystal a bit on the hard side, I inserted a 14 dB pad between the VNA and the bridge, re-calibrated, and repeated the measurement. What had been a Q of 75K jumped to 147K. In another case, I saw 93K with about 0 dBm applied to the bridge and 321K with -14 dBm applied.
>

Ai, my MiniVNA methods use the Q (-3dB points) for the determination of the Lm and Cm. If drive level has such a huge impact, then I suppose the Lm values can be very inaccurate. When I find the time I should test with some attenuation between generator and crystal.

The method is from Jim Kortge, K8IQY. It uses the crystal as passband device in 12.5 ohm setting (4:1 transformers). My drive level is about -6 or -7dBm.

Joop

3354

2009-07-29 08:16:42

Chris Trask

Re: Measuring Crystal Parameters

>
> Ai, my MiniVNA methods use the Q (-3dB points) for the
> determination of the Lm and Cm. If drive level has such a
> huge impact, then I suppose the Lm values can be very
> inaccurate. When I find the time I should test with some
> attenuation between generator and crystal.
>

The IEC standard fixture for testing crystals is described in:

<http://www.cliftonlaboratories.com/Documents/Assembly and Usage Notes for Crystal Test Fixture.pdf>

Chris

3356

2009-07-29 10:05:27

timshoppa

Re: Measuring Crystal Parameters

3357

2009-07-29 10:11:14

Chris Trask

Re: Measuring Crystal Parameters

>
> >
> > >
> > > Ai, my MiniVNA methods use the Q (-3dB points) for the
> > > determination of the Lm and Cm. If drive level has such a
> > > huge impact, then I suppose the Lm values can be very
> > > inaccurate. When I find the time I should test with some
> > > attenuation between generator and crystal.
> > >
> >
> > The IEC standard fixture for testing crystals is described in:
> >
> > <http://www.cliftonlaboratories.com/Documents/Assembly and Usage Notes

for Crystal Test Fixture.pdf>

>
> How, in practice, does using the 12.5 ohm crystal driving impedance differ
> from using a 50 ohm pad in front as shown in EMRFD Fig 3.34? It already
> recommends a maximum drive level to the crystal of -30dBm.
>
> Most of the cheapo 4-10 MHz crystals I measure have series resistances
> between 10 and 15 and 20 and 30 ohms. I suppose a lower ohm driving
> impedance would be more convenient if I were dealing with higher-Q, lower
> ESR crystals.
>

The 12.5 ohm impedance is the standard for the industry set by IEC, and
my guess is that the resistive pads are more easily reproduced than
transformers plus they have far fewer parasitics. In the full IEC fixture,
there are a couple of trimmer capacitors that correct for the high frequency
cutoff. I don't have a copy of the formal IEC publication about this, and
that's where you would find the reasoning behnd it all.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3358

2009-07-29 11:01:36

Chris Trask

Re: Measuring Crystal Parameters

>
> >
> > Anyway, I continued to do Q measurements. It finally all made
> > more sense when I started to wonder about the RF power level.
> > Wondering if I was hitting the crystal a bit on the hard side,
> > I inserted a 14 dB pad between the VNA and the bridge,
> > re-calibrated, and repeated the measurement. What had been a
> > Q of 75K jumped to 147K. In another case, I saw 93K with about
> > 0 dBm applied to the bridge and 321K with -14 dBm applied.
> >
>
> I ran into similar problems with drive level, but it had more to
> do with harmonic distortion in the oscillator rather than overdriving
> the crystal.
>

There's some useful information regarding the drive level when measuring
crystal parameters:

Gufflet, N., "Quatrz Crystal Resonators," KVG Quarts Crystal
Technology

http://www.kvg-gmbh.de/fileadmin/Bilder/TechInfo/Quarz/IntroductionQuartz.pd
f

Rose, D., "Load Resonant Measurement of Quartz Crystals,"
Saunders and Associates, 1998

http://www.saunders-assoc.com/datasheets/paper/paper.pdf

Saunders, J.L., "Drive Level Effects on Transmission Measurements
of AT Overtone Resonators," Proceedings 6th Annual Quartz
Crystal Conference, 1984

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3365

2009-07-29 19:44:45

Phil Sittner

Re: Measuring Crystal Parameters

Wes-

That's a really good piece of work. I've finished building my smd version of Chris's oscillator (it has a problem yet to be found) and am anxious to compare the results. I too have had some issues when trying to measure small values of capacitance with the AADE bridge and came up with a very simple solution. I use a short piece (about 1 foot) of cheap twin conductor speaker cable, not unlike what you find at Radio Shack. It has a nice molded jacket and you fan out the far end, zero the bridge, then tack solder the cable to what needs measuring. It works quite well. If you have an interest I'll share the results of using Chris's method.

73's,
Phil
kd6rm

----- Original Message -----

3366

2009-07-29 19:51:07

ashhar_farhan

Re: Measuring Crystal Parameters

on a slightly removed note, how can we any of these methods to measure the overtone parameters?

i suppose that only motional capacitance will change in the overtone modes. using the g3UUR's method the oscillator's phase shift will have to be 360 degrees at the overtone frequency.

- farhan

3367

2009-07-29 20:07:49

Chris Trask

Re: Measuring Crystal Parameters

>
> on a slightly removed note, how can we any of these methods to measure
> the overtone parameters?
>
> i suppose that only motional capacitance will change in the overtone
> modes. using the g3UUR's method the oscillator's phase shift will have
> to be 360 degrees at the overtone frequency.
>

In a full model of the crystal, each overtone frequency consists of the
same series resistor, capacitor, and inductor as for the fundamental. They
are all connected in parallel. One of the papers I mentioned earlier shows
this full model.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3370

2009-07-30 04:44:36

joop_l

Re: Measuring Crystal Parameters

3371

2009-07-30 06:55:51

john lawson

Re: Measuring Crystal Parameters

Good morning Phil and all.

I have read with great interest the helpful replies from your post on the question of Rs measurements to arrive at the crystal's Q from Wes, Chris as well as others. I. too, was looking for a better way to arrive at the Q of the crystal being measured along with the use of my G3UUR oscillator. Wes reminded us in his paper he posted a couple of days ago about the Trap Method for measuring the Q of a crystal as outlined in Chapter 7 of EMRFD. After using some LC oscillators for my measurements, I simply did what I had been thinking about for months and built a VXO with buffering followed by a 5 element LP filter, some 50 pads to arrive at -17 dBm to drive the crystal in the test fixture, while monitoring the ouput for the dip on Bob Kopski's version of Wes's Power Meter.... I then did the math to come up with the needed Q. In my case, it ended up being a very easy, direct way for me to arrive at the needed Q information. John Lawson, K5IRK

3375

2009-07-30 09:50:20

Ashhar Farhan

Re: Measuring Crystal Parameters

chris, joop,

if the overtone mode is modeled as having the same motional inductance
as the fundamental crystal, then all that remains to be done is
recalculate the motional capacitance for the overtone modes as being
1/9th, 1/25th and 1/49th of the fundamental motional capacitance isn't
it?

- farhan

3376

2009-07-30 10:40:04

Chris Trask

Re: Measuring Crystal Parameters

>
> if the overtone mode is modeled as having the same motional inductance
> as the fundamental crystal, then all that remains to be done is
> recalculate the motional capacitance for the overtone modes as being
> 1/9th, 1/25th and 1/49th of the fundamental motional capacitance isn't
> it?
>

Where did you get the impression that each overtone has the same
motional inductance? In every piece of literature that I've seen, each one
is unique (ie - different), just as each motional capacitance and resistance
is unique for each overtone.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3377

2009-07-30 11:07:02

Wes Hayward

Re: Measuring Crystal Parameters

Hi Farhan, Joop, Chris, and gang,

Re the overtone crystals. This was briefly mentioned in EMRFD, Fig 4.27. Of course this model is simplified in that it does not include spurious responses. This crystal modeling game is the same as semiconductor modeling. We start with something simple and then start refining it, adding nonlinear behavior to the core model and layer upon layer of packaging parasitic L, C, and R. Often the original basic model is lost in the complexity.

The N2PK machine is essentially a computer controlled pair of frequency synthesizers (DDS) that drive an output port and an internal DC receiver. The receiver is configured so that you measure the receiver input port response in amplitude and in phase with respect to the source. The port impedances are 50 Ohms. The simplest measurement is just the frequency response through a network. If you elect to add a bridge to the VNA, you get a result which is the complex (amplitude and phase) reflection coefficient. That gets converted to impedance by the internal software. Like so many (read as "all") network analyzers, the essence is in the calibration. As was pointed out, there is a VERY ACTIVE Yahoo Group that deals with the N2PK analyzer.

There were numerous impedance bridges that were on the market in the past. These generally had "stuff" in them allowing the user to directly read impedance in real and imaginary form. The detected output was used only as a null indicator. That is, one tuned the knobs on the bridge to zero it for both real and imaginary parts of the impedance. In contrast, the usual VNA that is used with a bridge still has an output that is a reflection coefficient, which is then converted to impedance with mathematics. These more recent methods are more consistent with swept measurements. It is extremely interesting to go back and look at the old bridge circuits and the methods that they used. Old app notes from General Radio were wonderful in this regard. Who knows? There may be a Yahoo Group for these old instruments.

It is easy enough to look at low overtones with the N2PK VNA. All that's required is to program the VNA to look at the overtone frequencies. But the N2PK instrument only goes up to 60 MHz. This will catch a lot of the 3rd overtone VHF crystals, but not the critical 5th and higher overtones that are usually above 60 MHz.

There are schemes that extend the frequency range of the N2PK instrument. Paul describes transverters on his web site. Just Google "N2PK" or look at the Group. Paul has also been looking at frequency multipliers with mixed results.

Years ago I built a 25 MHz overtone oscillator to look at a sack of 3rd overtone crystals that I had picked up. This variation of the G3UUR method was less than satisfactory, but I didn't spend much time with it, so don't condemn the concept. I suspect that insertion of a simple resonator in the Trask variation of the Butler oscillator would allow it to operate nicely at overtones. Experiments are in order.

The motional elements in the model tend to differ mainly in motional capacitance as overtones are encountered, leaving the motional inductance constant. But this is merely a first order model. Not all overtone crystals are exact in this regard. Assuming a constant LM would probably be a reasonable starting approximation for use in building crystal filters. A simple model says nothing of Q, and assumptions can be dangerous. I recall having measured a crystal Q of a mere 50,000 at 3.3 MHz . This was a surprise, for the same crystal had a Q of near a million at 10 MHz. Crystal frequencies are not predictable. The 3rd overtone frequency is often very close to 3x the fundamental. But there are sometimes dramatic differences. Bottom line plan on measuring the parts for best results.

73, Wes
w7zoi

3378

2009-07-30 11:19:12

joop_l

Re: Measuring Crystal Parameters

>
> Where did you get the impression that each overtone has the same
> motional inductance? In every piece of literature that I've seen, each one
> is unique (ie - different), just as each motional capacitance and resistance
> is unique for each overtone.
>

I had to search again so these might not be the best examples.
http://rfdesign.com/mag/ramon.pdf
It is implied at the bottom of page 32.
Actually it says Cn = C1 / n^2

With F = 1 / (2*pi*sqrt(LC))
and L = 1 / (C * (F*2*pi)^2)
and Ln = 1/ (Cn * (Fn*2*pi)^2)
thus Ln = 1/ (C1/n^2 * (F1*n*2*pi)^2)
thus Ln = 1/ (C1 * (F1*2*pi)^2) ;is the same for every n

http://www.am1.us/Papers/U11625%20VIG-TUTORIAL.PDF
Page 3-23
The formula is different:
C1 = r' * Cn / n^3
where r' = f1 / fn
if it would have said r' = fn / f1, then the formulas would match the other article.

But I am pretty sure I read it elsewhere too. It just does not fit my own measurements. But a lower drive level might bring more clarity.

Do you have articles that state something totally different?
I would be interested.

Joop

3379

2009-07-30 11:26:18

joop_l

Re: Measuring Crystal Parameters

3380

2009-07-30 12:40:03

victorkoren

Re: Measuring Crystal Parameters

I have found two places that refer to the overtone xtal parameters in the technical literature:

1)"Design of crystal and other harmonic oscillators" by Benjamin Parzen (Paragraph 3.2.4.1):
"In the equivalent circuit exptended to represent the family of overtones associated with the fundamental, Co C1 L1 and R1 are unchanged in value but Cn = C1 / N^2."

2)"Foundations of oscillator circuit design" by Guillermo Gonzales (Paragraph 4.4, Crystal characteristics):
"The overtone element values are calculated using
Ln = L
Cn = C/n^2 "
(L,C are the fundamental frequency motional parameters)

This is what I found in a short search.
Indeed it seems that in first order at least, The motional inductance of an overtone is identical to the motional inductance of the fundamental while the motional capacitance decreases by the square of the overtone order.
Victor - 4Z4ME

3381

2009-07-30 13:17:22

Chris Trask

Re: Measuring Crystal Parameters

> I have found two places that refer to the overtone xtal parameters in the
> technical literature:
>
> 1)"Design of crystal and other harmonic oscillators" by Benjamin Parzen
> (Paragraph 3.2.4.1):
> "In the equivalent circuit exptended to represent the family of overtones
> associated with the fundamental, Co C1 L1 and R1 are unchanged in value

but

> Cn = C1 / N^2."
>
> 2)"Foundations of oscillator circuit design" by Guillermo Gonzales
> (Paragraph 4.4, Crystal characteristics):
> "The overtone element values are calculated using
> Ln = L
> Cn = C/n^2 "
> (L,C are the fundamental frequency motional parameters)
>
> This is what I found in a short search.
>

Try something more up to date, such as:

http://www.am1.us/Papers/U11625%20VIG-TUTORIAL.PDF

Page 3-23 gives a far better approximation of the overtone model parameters,
and none of them are identical.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3382

2009-07-30 13:19:56

joop_l

Re: Measuring Crystal Parameters

I measured a couple of crystals to look at motional parameters per fundamental and overtones plus at two different drive levels.
Two crystals were measured: 100MHz 3rd OT and 200MHz 9th OT.
Above fundamental the Cp was neutralized with a parallel resonance LC.
A second measurement of both was done with a 10dB attenuator after the generator.

Generator output -2.5 @ 30MHz, -2.5@100MHz, -4.5 @ 160MHz
My xtal fixture contains 4dB attenuator and 4:1 transformers on both sides.
Roughly max xtal level -6.5 @ 30MHz, -6.5@100MHz, -8.5 @ 160MHz

Results:

100Mhz xtal
===========================
33MHz: Ls = 1.293759 mH, Cs = 17.677113 fF, Rs = 4.51 Ohm, Q = 60012
100MHz: Ls = 1.412943 mH, Cs = 1.792847 fF, Rs = 16.68 Ohm, Q = 53219
166MHz: Ls = 1.074538 mH, Cs = 0.848610 fF, Rs = 69.39 Ohm, Q = 16216

100Mhz xtal 10dB attenuated
===========================
33MHz: Ls = 1.135663 mH, Cs = 20.137836 fF, Rs = 4.71 Ohm, Q = 50392
100MHz: Ls = 1.533813 mH, Cs = 1.651560 fF, Rs = 20.18 Ohm, Q = 47756
166MHz: Ls = 1.232540 mH, Cs = 0.739822 fF, Rs = 80.91 Ohm, Q = 15953

200Mhz xtal
===========================
22MHz: Ls = 2.725901 mH, Cs = 18.876546 fF, Rs = 4.30 Ohm, Q = 88274
66MHz: Ls = 2.748298 mH, Cs = 2.074455 fF, Rs = 8.57 Ohm, Q = 134321
110MHz: Ls = 2.392983 mH, Cs = 0.857497 fF, Rs = 13.15 Ohm, Q = 127083
155MHz: Ls = 1.917052 mH, Cs = 0.546095 fF, Rs = 19.87 Ohm, Q = 94302

200Mhz xtal 10dB attenuated
===========================
22MHz: Ls = 2.387415 mH, Cs = 21.552760 fF, Rs = 3.94 Ohm, Q = 84556
66MHz: Ls = 2.686533 mH, Cs = 2.122141 fF, Rs = 9.23 Ohm, Q = 121867
110MHz: Ls = 2.374893 mH, Cs = 0.864027 fF, Rs = 15.83 Ohm, Q = 104756
155MHz: Ls = 2.417492 mH, Cs = 0.433049 fF, Rs = 23.97 Ohm, Q = 98566

Only a single measurement of each was done. So I cannot tell how repeatable they are.
Initial impression is that the 200MHz crystal does seem to follow the rule of thumb rather well that Lm is similar for the overtones. The 100MHz crystal does this to a lesser extend. The order of magnitude is similar though.

The two drive levels do not seem to give a general shift towards some behavior.

Joop - pe1cqp

3383

2009-07-30 13:28:08

joop_l

Re: Measuring Crystal Parameters

I see I left some 'dB' out. Corrected section:

Generator output -2.5dBm @ 30MHz, -2.5dBm @ 100MHz, -4.5dBm @ 160MHz
My xtal fixture contains 4dB attenuators and 4:1 transformers on both sides.
Roughly max xtal level -6.5dBm @ 30MHz, -6.5dBm @100MHz, -8.5dBm @ 160MHz

All are 10dB less of course in the second round using the attenuator.

Joop - pe1cqp

3384

2009-07-30 19:46:25

Ashhar Farhan

Re: Measuring Crystal Parameters

chris and others,

wow! i never cease to amaze at how much little experiments can
illuminate! thanks chris, joop, for this round.

the motional inductance, as per the literature (i have only access to
the net and some pdfs) is modeled after the crystal mass where as the
capacitance is changed as the number of standing waves across the
physical bounds of the crystal. so, as per joop's measurements, it is
indeed the motional capacitance that changes its magnitude while the
inductance varies in percentages.

first, can we then assume that the G3UUR method will give us at least
starting values to tune up a ladder filter that works in overtone
mode? an ominous indication is that the series resistance shows the
filter could have higher losses than a fundamental one.

second, will we also require bandpass tuned to the overtone frequency
in the input of the ladder filter? how else can we prevent the ladder
filter from responding to other modes (spurious and overnote) ?

- farhan

3385

2009-07-30 19:53:22

Ashhar Farhan

Re: Measuring Crystal Parameters

this might be of interest in the discussions (refer to page 73 of pdf below):
http://www.am1.us/Papers/U11625%20VIG-TUTORIAL.PDF

The motional inductance prediction as L(1n) is given in the equation.
which can be approximate to remain the same in the overtones.

- farhan

3386

2009-07-30 20:31:11

Ivan Makarov

Re: Measuring Crystal Parameters

Hi Wes,

do you think the RF-IV method can be used for crystal Q measurements? I
think you were copied on communication of measuring of Q for coils/caps
using Paul N2PK's RF-IV sensor design, which showed good results.

http://www.n2pk.com/VNA/RFIV_Single_%20Detector_Switch_%20and_%20Sensors_V1c.pdf

Thks,
Ivan
VE3iVM

----- Original Message -----

3387

2009-07-30 23:03:11

joop_l

Re: Measuring Crystal Parameters

3388

2009-07-31 05:48:15

victorkoren

Re: Measuring Crystal Parameters

Chris,
First, the Gonzales book is from 2007 so it is certainly not outdated.
Second, in the tutorial you mentioned (in page 73) it seems that there is an error:
r' is defined as f1/fn. It seems to me that it should be r'=fn/f1 and then r' is very close to n, the overtone number (The overtone frequency is very close to the harmonic frequency). If it is so, putting n instead of r' in the equations you will get exactly what the other books say, that Cn~C1/n^2 and Ln=L1 .
Victor - 4Z4ME

3389

2009-07-31 07:20:09

Harold Smith

Re: Measuring Crystal Parameters

Here's an idea, which might not be practical: to built a filter using
overtone crystals without worrying about the fundamental response, mix the
overtones. Use some third overtones and some fifth, for instance. The
fundamentals wouldn't even be close. You'd almost certainly have to custom
order those crystals, of course, since the odds of finding such a set in
your junkbox are pretty long.

Just a thought...

de KE6TI, Harold

3390

2009-07-31 09:01:49

Chris Trask

Re: Measuring Crystal Parameters

>
>Second, in the tutorial you mentioned (in page 73) it seems that
>there is an error:
>r' is defined as f1/fn. It seems to me that it should be r'=fn/f1
>and then r' is very close to n, the overtone number (The overtone
>frequency is very close to the harmonic frequency). If it is so,
>putting n instead of r' in the equations you will get exactly what
>the other books say, that Cn~C1/n^2 and Ln=L1 .
>

You're attempting to force a desired conclusion. The overtone frequencies are not sufficiently close to the harmonic frequencies so that your approximation would survive close scrutiny. What you're suggesting might be suitable for a very rough approximation, but not useful for more demanding circumstances.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3391

2009-07-31 16:34:12

victorkoren

Re: Measuring Crystal Parameters

Chris,
I am not forcing a conclusion. Please download an updated (2004) of the same tutorial you posted written by John Vig

3394

2009-08-01 07:50:58

Chris Trask

Re: Measuring Crystal Parameters

>
> I am not forcing a conclusion. Please download an updated (2004) of the

same

> tutorial you posted written by John Vig from:
> http://www.pwgdev.com/~datasheets/Vig-tutorial%208.5.2.0.ppt
> See below slide 75 (similar to page 73 in the older tutorial) that its

written:

>
> "In the last row, the r' is the ratio between the fundamental mode and the

n-th

> overtone frequencies. For example, when comparing the parameters of a 10

MHz

> fundamental mode and a 10 MHz 3rd overtone (of similar design), r' = 1,

and when

> comparing the parameters of a 10 MHz fundamental mode resonator when

excited at

> the fundamental mode, and when excited at the 3rd overtone frequency,

i.e., at

> ~30 MHz, r' = 3."
>
> This shows that my guess that r' is the overtone number (when comparing

fundamental

> to overtone frequency of the same crystal) is right, and then Cn~C1/n^2

and Ln=L1 .

>

That's entirely invalid. The equations are for the parameters for the
same crystal, not two different ones. You're now trying to continue to
force the conclusion by saying that since since the fundamental frequency
for one crystal is 10MHz and the third overtone for the second crystal is
10MHz, the value of r' for the second crystal is exactly 3 without knowing
what the fundamental frequency for the second crystal is. That is exactly
what you have said here.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3395

2009-08-01 16:11:52

Wes Hayward

Re: Measuring Crystal Parameters

Hi All,

This whole exchange has become extremely interesting. Esoteric, perhaps, but still interesting.

After Chris' comment yesterday where he was questioning the idea of a constant motional L with overtone number, I started digging in the references I had in my library. My standard reference on crystal related things, the book by Bottoms, had nothing on the subject. I could not find anything else that really supported my contention. So I was pleased when Joop and Victor both offered references and data to support the idea that was in EMRFD. I remembered having seen something to support the idea at one time or another and also recall having done some related measurements on some 5th overtone crystals at both 100 MHz and 125 MHz that were used in spectrum analyzer LO applications. But I didn't recall having done any comparative measurements on HF crystals that would normally be used in fundamental mode filter applications.

So, it was back to the lab. This in itself brought some complications. I encountered trouble making the program xtal2.exe work with the VNA on overtone frequencies, at least with some crystals. It worked in some other cases, but not all. My final solution was to do a Smith Chart plot of the VNA data at the appropriate frequencies. The series resistance at resonance is then directly read from the place where the plot crosses the horizontal line of pure resistance. The motional inductance is calculated from the rate of change of reactance with frequency at resonance. This is illustrated in a short note on my web site. Go to http://w7zoi.net/ and then to the designs and experiments section. This note was generated merely to illustrate that reactance slope is a viable way to obtain Lm.

So, what were the results? Two crystals were investigated and both were interesting. They were both from batches I've used to build crystal filters. Neither had a constant motional L in going from fundamental to third overtone operation. Not even close! In fact, I saw a dramatic increase in Lm with overtone for these two crystals. Here's some data where Lm(xtal) is obtained with the normal VNA program and Lm(SC) is from the Smith Chart plot using reactance slope.

Xtal F Lm(xtal) Lm(SC) R Q
1 4.00 0.1427 0.145 23.5 155K
1 12 0.671 0.628 592 85K
2 5 .09836 0.1017 19.7 170K
2 15 ---- 0.7677 123 588K

I never could get the 3rd overtone of the 5 MHz crystal to work in the VNA program xtal2.exe. However, the series and parallel resonances were very close to each other, which is a probable reason for the difficulty.

The data above is not the whole story. There is a significant difference between 3 x the fundamental frequency and the third overtone frequency. Clearly from the chart, we can't even come close to guessing a motional L at an overtone after characterizing a crystal at the fundamental, at least with the two rocks I examined. Constant Lm with overtone number may be a viable model for some crystal types, but not for these.

The extremely high Q observed with the third overtone of the 5 MHz rock was encouraging. However, it is probably not all that useful for filters owing to the very high Lm. This puts it in the same league as the little cylinder crystals, which suffer a similar problem, which makes filter realization very difficult.

I've heard the axiom that any scientific investigation worth its salt will generate as many questions as it does answers. I think we must have arrived with this crystal study!

73, Wes
w7zoi

3396

2009-08-01 17:15:10

Chris Trask

Re: Measuring Crystal Parameters

>
> This whole exchange has become extremely interesting. Esoteric, perhaps,

but

> still interesting.
>
> After Chris' comment yesterday where he was questioning the idea of a

constant

> motional L with overtone number, I started digging in the references I had

> my library. My standard reference on crystal related things, the book by
> Bottoms, had nothing on the subject. I could not find anything else that
> really supported my contention. So I was pleased when Joop and Victor

both

> offered references and data to support the idea that was in EMRFD.
>

<>

Parzen shows the complete fundamental/overtone model on p. 84. He
provides very little discussion of the overtone frequencies, instead
repeating the gross approximation that the nth overtone is n times the
fundamental. This approximation is the source of a considerable amount of
discord lately.

Bottom at least goes into some detail about the mathematical derivation
of the overtone frequencies, then states that they are approximately n times
the fundamental. He shows, to some small degree, that the deviation from
the overtones not being integral multiples of the fundamental is due to the
thickness of the resonator.

Buchanan ("Handbook of Piezoelectric Crystals for Radio Equipment
Designers"), doesn't even make mention of ovvertones. Nor do any of the
other almost dozen texts and additional literature that I have.

>
> So, what were the results? Two crystals were investigated and both were
> interesting. They were both from batches I've used to build crystal

filters.

> Neither had a constant motional L in going from fundamental to third

overtone

> operation. Not even close! In fact, I saw a dramatic increase in Lm

with

> overtone for these two crystals. Here's some data where Lm(xtal) is

obtained

> with the normal VNA program and Lm(SC) is from the Smith Chart plot using
> reactance slope.
>

With two sets of independent test data at our disposal, it's safe to say
that the modal inductances are not identical and the overtone frequencies
are not integral multiples.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3397

2009-08-01 19:53:24

Wes Hayward

Re: Measuring Crystal Parameters

Hello again, all,

My last posting contained a table, but it is essentially unreadable. It was OK when composed in WORD.

I have uploaded a "file" titled "Posting_3395_table.jpg" that should be quite readable.

Also, the errata for EMRFD now contains an item for page 4.15 about this issue.

73, Wes
w7zoi

3398

2009-08-02 02:19:02

joop_l

Re: Measuring Crystal Parameters

3399

2009-08-02 03:10:07

Ashhar Farhan

Re: Measuring Crystal Parameters

on a related note, in my other obsession as guitarists (i am the worst
guitarist i have ever known) we aspire to play harmonics.

the way it is done is quite simple, theoretically. we lightly hold a
finger to that part of the string where the standing wave's node ought
to be and then pluck it quickly (impluse excitation). depending upon
where the finger was placed, an overtone is generated. usually these
overtone frets are marked on the guitar by white spots. however, a
very frustrating aspect of this overtone mode of oscillations is that
harmonics do not always fall within the scale the guitar is tuned to!
they are always off by a few beats. this results in quite a confusion.
eric clapton, once asked about who he would vote in the coming
elections, said 'i will vote for anyone who can invent an automatic
guitar harmonics tuner'.

there is, thus, more to harmonics than just the length of the waves.
something to do with the boundary conditions, i guess.

- farhan

3400

2009-08-02 07:02:54

Chris Trask

Re: Measuring Crystal Parameters

>
>on a related note, in my other obsession as guitarists (i am the worst
>guitarist i have ever known) we aspire to play harmonics.
>
>the way it is done is quite simple, theoretically. we lightly hold a
>finger to that part of the string where the standing wave's node ought
>to be and then pluck it quickly (impluse excitation). depending upon
>where the finger was placed, an overtone is generated. usually these
>overtone frets are marked on the guitar by white spots. however, a
>very frustrating aspect of this overtone mode of oscillations is that
>harmonics do not always fall within the scale the guitar is tuned to!
>they are always off by a few beats. this results in quite a confusion.
>eric clapton, once asked about who he would vote in the coming
>elections, said 'i will vote for anyone who can invent an automatic
>guitar harmonics tuner'.
>

I've seen/heard performers do that, and it adds an interesting dimension to the performance.

Chris

Chris

3401

2009-08-02 09:19:37

Chris Trask

Re: Measuring Crystal Parameters

>
> >
> > This whole exchange has become extremely interesting. Esoteric,
> > perhaps, but still interesting.
> >
> > After Chris' comment yesterday where he was questioning the idea
> > of a constant motional L with overtone number, I started digging
> > in the references I had in my library. My standard reference
> > on crystal related things, the book by Bottoms, had nothing on
> > the subject. I could not find anything else that really
> > supported my contention. So I was pleased when Joop and Victor
> > both offered references and data to support the idea that was in
> > EMRFD.
> >
>
> <>
>

I've exhausted my own library, Google, and IEEE Xplore on this subject and have nothing more to add. I have a good backlog of literature to download at the university library, so tomorrow I'll take a trek over there and use the INSPEC search engine to see what else is available.

I'm especially curious to determine the source of Vig's overtone parameter equations. They may be the result of original work by him, but it's difficult to say as he doesn't cite any references.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3402

2009-08-02 12:24:32

ehydra

Re: Measuring Crystal Parameters

Chris ist right. The ratio depends mostly on crystal cut and processing
parameters. It can vary to a very extend.
It may help, that the circuit model for monopole and dipole antennas is
almost the same!

regards -
Henry

--
ehydra.dyndns.info

Chris Trask schrieb:

>
> With two sets of independent test data at our disposal, it's safe to say
> that the modal inductances are not identical and the overtone frequencies
> are not integral multiples.
>

3403

2009-08-02 12:36:49

ehydra

Re: Measuring Crystal Parameters

joop_l schrieb:

> We tend to look at overtones from the electronics side. But since the crystal has a mechanical motion it might be interesting to look at a similar effect in musical instruments. This usenet thread mentions what happens with a piano:
> http://groups.google.nl/group/sci.electronics.design/browse_thread/thread/22a35328f1d2d358/d8befaad4f9cce64#d8befaad4f9cce64
>

Antoher manifestication of the same phaenomen.

In general: It is not a good idea to use a crystal in overtone or
subtone mode if it is designed for baseband frequency. And the other way
around is the same.

I read that several times in various references. And even got the
problem on the desk with a old Narva 27.12MHz quartz. It is without
datasheet but offered as 27.12MHz. But it is a overtone quartz
resonating somewhere at 9MHz! With the right oscillator it will be
pressed to 27.12MHz and indeed, I repaired the rc car of my youngster
with such a crystal. I think the quartz was mechanical killed by
dropping the remote transmitter several times on hard ground. Now the
car is controllable much longer range than before! (china product)

This quartz shows 'in a lot of severals' more variant resonating
frequency if it is NOT on it's designed-frequency. As expected!

So, don't make it!

- Henry

--
ehydra.dyndns.info

3404

2009-08-03 06:13:24

victorkoren

Re: Measuring Crystal Parameters

One more input:
The book :"Practical RF Circuit Design for Modern Wireless Systems: Passive circuits" ... By Rowan Gilmore, Les Besser.
In page 400 is written: "The crystal can be modeled at a higher overtone by a separate R-L-C motional arm set to resonate at that frequency. If N denotes the Nth overtone ,then we may model that resonance with:

Cn = Cm / N^2

for modes where the resonant frequency is determined by the thickness of crystal between the plates. It follows therefore that since the resonant frequency increases by a factor of N: Ln = Lm and since the motional R-C time constant (approximately) independent of frequency,

Rn = Rm * N^2 "

Note that it mentions that this is good only for modes where the resonant frequency is determined by the thickness of crystal between the plates, so there might be some dependence on the mechanical characteristics like the way the crystal is being held etc, and that might make some frequency and motional parameters change.
The book can be found in Google books, Just google the book name.

Victor - 4Z4ME

3405

2009-08-03 08:30:58

Chris Trask

Re: Measuring Crystal Parameters

>
> Note that it mentions that this is good only for modes where the resonant
> frequency is determined by the thickness of crystal between the plates, so
> there might be some dependence on the mechanical characteristics like the
> way the crystal is being held etc, and that might make some frequency and
> motional parameters change.
>

In other words, they're openly admitting that the approximations is not
entirely valid, which is what we've been saying here for over a week now.
Since we have a more accurate derivation available by way of Vig, there is
no reason to continue using the approximation as a crutch.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3406

2009-08-03 09:33:10

victorkoren

Re: Measuring Crystal Parameters

Vig's derivati

3407

2009-08-03 10:33:51

victorkoren

Re: Measuring Crystal Parameters

Wes,
When you did the overtone frequency measurements, did you connect an inductor in parallel to cancel the influence of Co (parallel capacitance)

3408

2009-08-03 12:12:56

Wes Hayward

Re: Measuring Crystal Parameters

Hi Victor, and gang,

No, I didn't add anything to the crystals other than to solder the leads to an SMA connector. That was then attached to my bridge with an SMA "un-barrel." That short line was present during OSL calibration, so should not be part of the data. In the later measurements, I have been grounding the metal crystal can, at the tweaking of w4zcb.

Two more crystals were examined yesterday, both extremely interesting.

The first was an old FT-243. These are the things that plugged into our old novice transmitters that kept us on the right frequency in spite of ourselves. The one I examined was marked 7100 and was a type Z2 manufactured by Pierson Radio. The N2PK crystal program (xtal2.exe) worked fine on the fundamental, but produced nothing at the third overtone. Sweeps yielded an explanation. A Smith Chart display of a 2 kHz region showed a sweep with two series resonances that were nearly identical. The real spurious response is not well established, although we assume it is the upper one. This sweep has been posted as a file named "third_overtone_with_spur". The fundamental mode had a motional L of .01579 H and a Q of 68K. The parallel C was only 2.5 pF. This makes sense when one examines the interior of one of these crystals. The quartz is only contacted at the corners of the rectangular blank. The two resonances related to the third overtone had the following properties, extracted from the SC display: First resonance: 20.76 Ohms, Lm=.02302H, Q=148K. Second resonance (spur?): 40.94 Ohms, Lm=.04051 H, Q=133K.

I have a bunch of these crystals, left from the mid 1960s. I used some of these rocks in a 15 meter QRP rig (QST, April, 1968) where I operated the crystals in the third overtone mode and they worked great. It was an easy way to get on a new band and produced my first DX with less than a watt of output. The frequencies were very close to 3X the fundamental (perhaps half a kHz at 21 MHzwho knew exactly back in the day) and I don't recall any problems with the transmitter hopping from one frequency to a spur. The oscillator was keyed without any observed difficulty. I regularly monitored my signal in the receiver at that time and don't recall hearing anything at other frequencies. I have used crystals with strong spurs in other situations. They usually just oscillate on one frequency (the main one) so long as the spur strength is just a few dB below the main response.

The other crystal examined yesterday was one of the 10 MHz high Q third overtone jobs mentioned in earlier posts. This rock is in a glass HC-6 package and is in vacuum. This part was manufactured by Colorado Crystal. The quartz disc is about 0.5 inch in diameter with gold plating over the center to a diameter of 0.33 inch or so. There was no problem in getting good data with the VNA and the program xtal2.exe. Smith Chart sweeps produced data that was virtually identical to that from the program. At the 10 MHz third overtone, the motional L was 0.110 H, parallel C was 5.99 pF, and Q=710K. (The internal spec for this crystal was a Q of 650K, so this one would have passed. Most parts were better than this.) The fundamental mode measurement suggested a very ordinary crystal. The series frequency of 3.3466 MHz was not 1/3 of the OT, but was just in the general region. The fundamental mode Q was a very modest 73K. But the motional L was 0.103 H, which is close to the same as the overtone.

I think I'm about ready to put this subject to rest, at least for a while. This has been an interesting one!

73, Wes
w7zoi

3420

2009-08-03 15:40:05

joop_l

Re: Measuring Crystal Parameters

Wes,

Were did you find your beautiful 10MHz crystal?

Joop

3421

2009-08-03 19:44:15

Wes Hayward

Re: Measuring Crystal Parameters

Hi Joop, et al,

Yea, that crystal is a gem. This one came from Tektronix surplus. This crystal was used in a number of their 70s and 80s era spectrum analyzers. Three of them are used in an oven to form a filter with a bandwidth of 30 Hz, which is amazing at 10 MHz. They were used in some other filters in various spectrum analyzers. Also kicking around from Tek surplus are some color burst crystals that are truly stellar in performance, outgrowths of Tek TV efforts.

73, Wes
w7zoi

3427

2009-08-04 09:08:50

joop_l

Re: Measuring Crystal Parameters

3430

2009-08-04 12:52:57

joop_l

Re: Measuring Crystal Parameters

3432

2009-08-05 05:31:34

timshoppa

Re: Measuring Crystal Parameters

3433

2009-08-05 05:55:32

w4zcb

Re: Measuring Crystal Parameters

I'm moderately interested in measurements of crystals intended for use
in the 70MHz and 100MHz filters common in upconverting radios these
days.

Isn't this where the thread started before it degenerated into
hagiography?

Tim.

You pay a price for a radio that is "general coverage" upconverting.
Increased phase noise from the high frequency oscillator. Every
japanese offering is upconverting and every one of them is inferior to
down converting radios WRT reciprocal mixing. I've owned a couple in
nearly 60 years, and tested and evaluated many more. By far, the worst
radio Ten Tec ever produced was their general coverage "Paragon" with
it's 70 MHz first IF. My neighbor and nemisis who owned one was an
untenable force when we operated on the same band, and even he
admitted that my signal cleaned up remarkably when he got rid of it.

W4ZCB

BTW, I purchased a pair of Ten Tecs 75 MHz crystal filters many years
ago and never used them. If you plan on making something at that
frequency, they're yours for an address..

(Authors who use long words are vaingloriously ostentatious.)

3796

2009-11-21 09:12:38

Phil Sittner

Re: Measuring Crystal Parameters

Chris-

Several months ago I built your design of the crystal test set and could not get the loop to work, in fact, I inserted a potentiometer in the base circuit of Q3 and used it to bias the oscillator and then made my measurements but I was still perplexed as to why I could not make the loop work. I believe there is a small typo on your schematic. The mod I made was relative to C7, R14 and the primary of T1. I currently have C7 couple between the base of Q5 and the emitter of Q4; and R14 is in series with the primary of T1 and also ties to the base of Q5.

Is this the way the circuit should be configured or have I missed something?

regards,
Phil kd6rm

----- Original Message -----

3797

2009-11-21 11:09:23

Chris Trask

Re: Measuring Crystal Parameters

>
> Several months ago I built your design of the crystal test set and could

not

> get the loop to work, in fact, I inserted a potentiometer in the base

circuit

> of Q3 and used it to bias the oscillator and then made my measurements but

> was still perplexed as to why I could not make the loop work. I believe

there

> is a small typo on your schematic. The mod I made was relative to C7, R14

and

> the primary of T1. I currently have C7 couple between the base of Q5 and

the

> emitter of Q4; and R14 is in series with the primary of T1 and also ties

> the base of Q5.
>
> Is this the way the circuit should be configured or have I missed

something?

>

The circuit works exactly as shown in the schematic. What you have done
is double the open loop gain while upseting the impedance balance of the
test fixture.

Hook it up the way shown and then check the control voltage at the base
of Q3. It should be somewhere between ground and Vcc/2. Somehow, you're
not getting enough control current to the differential pair, and if that
voltage is close to Vcc, then you need to check the load between Q2 and Q4,
as that sets the maximum loop gain. Also check the value of R7. If it's
higher than the 120 ohms shown, then you will also have insufficient loop
gain.

Chris

,----------------------. High Performance Mixers and
/ What's all this \ Amplifiers for RF Communications
/ extinct stuff, anyhow? /
\ _______,--------------' Chris Trask / N7ZWY
_

3798

2009-11-21 11:11:40

Chris Trask

Re: Measuring Crystal Parameters

>
> Several months ago I built your design of the crystal test set and could
> not get the loop to work, in fact, I inserted a potentiometer in the base
> circuit of Q3 and used it to bias the oscillator and then made my
> measurements but I was still perplexed as to why I could not make the
> loop work. I believe there is a small typo on your schematic. The mod I
> made was relative to C7, R14 and the primary of T1. I currently have C7
> couple between the base of Q5 and the emitter of Q4; and R14 is in series
> with the primary of T1 and also ties to the base of Q5.
>
> Is this the way the circuit should be configured or have I missed
> something?
>