Re: [time-nuts] 510 doubler
Ok, lets get real here. Temperature variations, could cause a phase shift but a very very slow one, the degree would depend on the Q of the filter, temperature coefficient of the crystal, and capacitor and how well it is isolated from turbulent air. I am not new to the game of making sensitive measurements using high Q filters. I would be more concerned with the phase changes due to the fractional Hz 1/f noise of the input threshold voltages of the FET's also any trigger circuit that may follow used to feed counters etc in instruments preceding and following the doubler. I am surprised that you aren't complaining about the sideband noise produced by the Brownian motion of nitrogen molecules inside the crystal case. In this case it is a 2 pole filter and once the phasing capacitor is adjusted the only the mechanical vibrational resonance of the crystal really counts. If you are interested in High Q resonators, phase shift, etc. you might want to take a look at Review of Scientific Instruments 60, 3035 (1989), Use of a helical resonator as a capacitive transducer in vibrating reed measurements where a helical resonator is used to measure the vibrations of small crystals with an sensitivity of 10e-7 Angstroms per square root Hertz bandwith. Also, take a look at citations in other papers and patents referencing this design. I just tried to describe a simple very pure sine wave doubler for your readers. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
On Tue, Feb 03, 2015 at 01:12:41AM -0500, Charles Steinmetz wrote: transformer into a 50 ohm load, the green trace results. This trace shows the simulated raw output, without any traps. Obviously, this is very much closer to a clean 10MHz signal than the rectified signal in Figure 1. Thank you for your explanation and graph. I got the point. The wave shaping is very impressive. Can you put in another graph the calculated difference to a pure sine wave? Best regards, Andrea Baldoni ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Bill wrote: Push-Push Jfet amplifier with parallel inputs and a Toroid output transformer, no secondary along with a simple filter using a 10 MHz series resonate crystal connected to one drain and an adjustable capacitor connected to the other would work fine. You connect the other ends of the two together and a loading resistor to ground. The capacitor is used to neutralize or null out the shunt capacitance of the crystal so that a capacitive path for the other frequencies , 5, 15, 20, etc is eliminated. I concur with what Bruce said regarding crystal filters (or any narrow bandpass filter) at the output frequency. More fundamentally, I'm not sure I understand your description of the circuit. You say it is a pair of FETs with parallel input and a transformer (autoformer) output. To me, that suggests the circuit pictured below (one feeds the sources in parallel, the other feeds the gates in parallel -- it doesn't make any difference in how the circuit operates). The usual push-push doubler feeds the FETs differentially, and takes the common-mode output. The diagrammed circuit reverses this -- it feeds the FETs in parallel (common-mode) and takes the 10MHz output differentially. As drawn, the circuit would have essentially no output at the input frequency or any of its harmonics (only that due to the mismatch between the FETs). The only signals it would amplify are uncorrelated signals -- i.e., the FETs' input noise voltages. A quick simulation confirmed no significant output at the input frequency or its harmonics for matched FETs. Simulating mismatched FETs produced a 5MHz signal rich in harmonics, but at a very low level and with no suppression of the 5MHz and its odd harmonics. I assume I misinterpreted your description and that you had a different circuit in mind, or that if you did have this circuit in mind I'm missing something about its operation. Can you please describe again what you had in mind, and how it generates 10MHz? Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Andrea wrote: Can you put in another graph the calculated difference to a pure sine wave? I'm not sure what you mean by the calculated difference to a pure sine wave. I already reported the amplitudes of all of the visible spurs (that is, the ones above the simulation noise floor), which define the departure from a pure 10MHz sine wave. I am attaching below the simulated spectrum analysis from which I took those reported amplitudes, if that helps. (There is no new data here, it is just graphical rather than tabular.) Again, this is from a simulation, and I purposely introduced 10mV of gate imbalance to model imperfectly-matched FETs. It is the raw output from the doubler, with no traps installed. The breadboard circuit performs similarly, although the 5MHz and 15MHz components are about 10dB lower from the breadboard than they are shown in this simulation (this depends on how well matched the FETs are -- I was able to get a better balance in real life than the imbalance I purposely introduced for this simulation). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Unfortunately that approach degrades the phase noise floor due to crystal dissipation limitations as well as degrading the phase noise in the flicker region due to the crystal itself,Not only is a clean (harmonic and subharmonic free) sine wave desirable so is low phase noise.Thermal drift of the crystal filter phase shift will also be problematic.Cascaded low Q filters suffer less from this than a single high Q filter. A low pass filter combined with series resonant shunt traps will have fewer issues with phase instability at 10MHz than using a 10MHz bandpass filter. Bruce On Wednesday, 4 February 2015 9:53 AM, Fuqua, Bill L wlfuq...@uky.edu wrote: Push-Push Jfet amplifier with parallel inputs and a Toroid output transformer, no secondary along with a simple filter using a 10 MHz series resonate crystal connected to one drain and an adjustable capacitor connected to the other would work fine. You connect the other ends of the two together and a loading resistor to ground. The capacitor is used to neutralize or null out the shunt capacitance of the crystal so that a capacitive path for the other frequencies , 5, 15, 20, etc is eliminated. Then follow up with your linear class A amplifier. The loading on the output of the crystal filter will determine it's Q and is not real critical, but should be perhaps around 10-100 times the series resistance of the crystal. Since most readily available crystals are not exactly on frequency a lower Q, higher R would be desired, but that will not greatly affect the 5 MHz or undesired harmonic attenuation. Perhaps one or two kHz bandpass would be just about right. Just don't overdrive the crystal. Also, for the price of $1 or less you may get 10 or so for further experimentation. This combination of doubler and crystal filter should provide a very nice sinewave output 73 Bill wa4lav ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Whilst the output signal of the barely class A JFET amplifier has a lower unwanted harmonic content and thus requires less filtering to achieve a given suppression of unwanted harmonics and/or subharmonics, the question of the flicker phase noise penalty incurred by the barely class A amplifier approach remains unresolved. Bruce On Tuesday, February 03, 2015 01:12:41 AM Charles Steinmetz wrote: Andrea wrote: But, what is the advantage between it and a couple of diode- connected transistors with a full A-class (more linear, so less spurs) amplifier in front of it? If it's so, why use a nonlinear (or barely linear) gain stage to rectify? Using just one stage means in general less phase noise output (but with probably more spurs that can be filtered out), versus a more stage linear amplifier (perhaps with strong negative feedblack) followed by a rectifier? I replied: The barely Class A push-push doubler does not rectify the signal -- it creates the second harmonic because of the primarily second-order transfer characteristics of the JFETs. The design goal is to map the DC bias and the input signal to the portion of the FETs' characteristic curve that has the best fit to a second-order transfer function, while at the same time holding noise below the design requirement. Perhaps some pictures would be helpful (see below). Figure 1 (top) shows an ideal full-wave rectified sine wave, similar to what is produced by a full-wave diode rectifier, a bipolar transistor push-push doubler, or a FET doubler driven into pinchoff (Class B). Obviously, it is extremely rich in harmonics. The second harmonic of the output (doubled) frequency is only 14dB below the desired signal, and a series of even harmonics stretches as far as the eye can see, diminishing only very slowly with increasing harmonic number. (In practice, there will be a HF rolloff that makes things slightly better. However, there will also be odd-order components, which an ideal full-wave rectifier would not produce.) Figure 2 (bottom) shows waveforms from the simulation of my barely Class A push-push doubler, using a matched pair of J111 FETs (J310s perform almost identically, with the appropriate change in the bias resistor). I purposely introduced a 10mV gate voltage imbalance in the simulation to model imperfect matching. The red and magenta traces are the currents in the two FETs, showing a primarily second-order transfer characteristic. When these currents are added by the push-push connection and put through a 4:1 (turns ratio) transformer into a 50 ohm load, the green trace results. This trace shows the simulated raw output, without any traps. Obviously, this is very much closer to a clean 10MHz signal than the rectified signal in Figure 1. The 5MHz component is ~40dB below the desired 10MHz signal. This depends strongly on how well the FETs are matched and on the layout and shielding. J111s or J310s from the same lot, matched to within 1mV, should do better than this (the 5MHz component from my breadboard circuit is below -45dBc, without any traps). The other visible distortion products, and their levels, are: 15MHz-75dBc 20MHz-45dBc 25MHz-100dBc 30MHz-75dBc 35MHz-100dBc (all figures are approximate). The breadboard circuit performs similarly (the 15MHz component is about 10dB lower from the breadboard, so I needed traps only at 5, 20, and 30MHz to get all spurious responses below -80dBc). As I noted before, the barely Class A circuit is not materially noisier than a FET push-push doubler that is run into Class AB or B, but it has MUCH lower spurious outputs and, therefore, does not need the sort of aggressive filtering the Class AB/B circuits need, avoiding the increase in phase noise and other problems associated with aggressive filters. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Bruce wrote: Whilst the output signal of the barely class A JFET amplifier has a lower unwanted harmonic content and thus requires less filtering to achieve a given suppression of unwanted harmonics and/or subharmonics, the question of the flicker phase noise penalty incurred by the barely class A amplifier approach remains unresolved. I posted the resolution a few days ago. As I said then, I adjusted the bias and input parameters of my breadboard doubler to match the conditions under which the FETs are operated in the doubler posted on your site, and measured the change in noise (including in the flicker region). The noise decreased by a fraction of a dB. Accordingly, I conclude that the barely class A doubler's noise, including flicker noise, is within a fraction of a dB of a Class AB doubler using the same FETs that you consider optimized. I also explained then why this result should come as no surprise (one FET in a Class AB or B doubler will not be contributing noise when it is cut off -- but that coincides with the other FET being at or near full current, so the total noise is dominated by the noise of the full-current FET and the benefit due to the cut-off FET is insignificant). There may be quieter FETs with lower flicker noise corners available that have similar medium-cutoff characteristics and are, therefore, suitable for this use -- but for the reasons I have given, I believe that similar relative noise relationships between barely Class A and Class AB doublers using such FETs would hold for them, as well. NOTE: For anyone simulating JFET circuits, be aware that many available JFET models do not model flicker noise at all, and many of those that do are wildly inaccurate at simulating noise in the flicker region. As always, there is no substitute for building and measuring the circuit. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Andrea wrote: But, what is the advantage between it and a couple of diode-connected transistors with a full A-class (more linear, so less spurs) amplifier in front of it? If it's so, why use a nonlinear (or barely linear) gain stage to rectify? Using just one stage means in general less phase noise output (but with probably more spurs that can be filtered out), versus a more stage linear amplifier (perhaps with strong negative feedblack) followed by a rectifier? I replied: The barely Class A push-push doubler does not rectify the signal -- it creates the second harmonic because of the primarily second-order transfer characteristics of the JFETs. The design goal is to map the DC bias and the input signal to the portion of the FETs' characteristic curve that has the best fit to a second-order transfer function, while at the same time holding noise below the design requirement. Perhaps some pictures would be helpful (see below). Figure 1 (top) shows an ideal full-wave rectified sine wave, similar to what is produced by a full-wave diode rectifier, a bipolar transistor push-push doubler, or a FET doubler driven into pinchoff (Class B). Obviously, it is extremely rich in harmonics. The second harmonic of the output (doubled) frequency is only 14dB below the desired signal, and a series of even harmonics stretches as far as the eye can see, diminishing only very slowly with increasing harmonic number. (In practice, there will be a HF rolloff that makes things slightly better. However, there will also be odd-order components, which an ideal full-wave rectifier would not produce.) Figure 2 (bottom) shows waveforms from the simulation of my barely Class A push-push doubler, using a matched pair of J111 FETs (J310s perform almost identically, with the appropriate change in the bias resistor). I purposely introduced a 10mV gate voltage imbalance in the simulation to model imperfect matching. The red and magenta traces are the currents in the two FETs, showing a primarily second-order transfer characteristic. When these currents are added by the push-push connection and put through a 4:1 (turns ratio) transformer into a 50 ohm load, the green trace results. This trace shows the simulated raw output, without any traps. Obviously, this is very much closer to a clean 10MHz signal than the rectified signal in Figure 1. The 5MHz component is ~40dB below the desired 10MHz signal. This depends strongly on how well the FETs are matched and on the layout and shielding. J111s or J310s from the same lot, matched to within 1mV, should do better than this (the 5MHz component from my breadboard circuit is below -45dBc, without any traps). The other visible distortion products, and their levels, are: 15MHz-75dBc 20MHz-45dBc 25MHz-100dBc 30MHz-75dBc 35MHz-100dBc (all figures are approximate). The breadboard circuit performs similarly (the 15MHz component is about 10dB lower from the breadboard, so I needed traps only at 5, 20, and 30MHz to get all spurious responses below -80dBc). As I noted before, the barely Class A circuit is not materially noisier than a FET push-push doubler that is run into Class AB or B, but it has MUCH lower spurious outputs and, therefore, does not need the sort of aggressive filtering the Class AB/B circuits need, avoiding the increase in phase noise and other problems associated with aggressive filters. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Push-Push Jfet amplifier with parallel inputs and a Toroid output transformer, no secondary along with a simple filter using a 10 MHz series resonate crystal connected to one drain and an adjustable capacitor connected to the other would work fine. You connect the other ends of the two together and a loading resistor to ground. The capacitor is used to neutralize or null out the shunt capacitance of the crystal so that a capacitive path for the other frequencies , 5, 15, 20, etc is eliminated. Then follow up with your linear class A amplifier. The loading on the output of the crystal filter will determine it's Q and is not real critical, but should be perhaps around 10-100 times the series resistance of the crystal. Since most readily available crystals are not exactly on frequency a lower Q, higher R would be desired, but that will not greatly affect the 5 MHz or undesired harmonic attenuation. Perhaps one or two kHz bandpass would be just about right. Just don't overdrive the crystal. Also, for the price of $1 or less you may get 10 or so for further experimentation. This combination of doubler and crystal filter should provide a very nice sinewave output 73 Bill wa4lav ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Andrea wrote: I see. This configuration is in effect a common gate B-class (or AB, or barely A) amplifier and the rectification is a side effect. But, what is the advantage between it and a couple of diode-connected transistors with a full A-class (more linear, so less spurs) amplifier in front of it? It is the rectification that causes the gross nonlinearities, not the amplification. So no matter how linear an amplifier you make, the diodes (or Class B or AB amplifier) will cause gross nonlinearities that we do not want. Furthermore, transistors have both even- and odd-order distortion products, while JFETs have predominantly second-order products. So JFETs naturally tend to produce the second harmonic, while transistors also produce the odd-order products we are trying to avoid (as well as higher even-order products). I know that the circuit originates at NIST and thus there surely IS an advantage. Are it trading more spurs (that you can cancel out with filtering) for less phase noise (that you cannot recover anymore)? I do not know precisely how the NIST circuit is biased, and as far as I know it is not general knowledge among time nuts -- so any substantive response would be conjecture. I don't even know if NIST still uses it. There are a few things to know -- NIST historically settles on something that works well enough, then sticks with it for a long time (until the phenomena they are trying to measure get distinctly better than their instruments). NIST has lots of considerations besides pure performance, such as power consumption and fitting into old form factors, so they do not necessarily have the best possible solutions, even when they have just designed the next generation. So, what we know for sure is that the JFET push-push doubler worked well enough for NIST's purposes when it was designed. That does not mean improvements weren't possible. Adding negative feedback linearize further the barely Class A amplifier; so, it's good to sacrifice part of the gain of the push-push stage to reduce flicker noise (and thus add less phase noise) and at the same time spurs. But it is the natural second-order distortion of the JFETs that makes it a particularly good way to build a push-push doubler. We don't *want* to linearize it! If it's so, why use a nonlinear (or barely linear) gain stage to rectify? Using just one stage means in general less phase noise output (but with probably more spurs that can be filtered out), versus a more stage linear amplifier (perhaps with strong negative feedblack) followed by a rectifier? The barely Class A push-push doubler does not rectify the signal -- it creates the second harmonic largely because of the device characteristic. The design goal is to map the bias and input to the portion of the FETs' characteristic curve that has the best fit to a second-order transfer function, while at the same time holding noise down below the noise budget. That is why medium-cutoff FETs like the J111 and J310 are the best choices, not sharp-cutoff FETs like 2SK369 and BF862. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Whilst input frequency related spurs can be significantly reduced with a suitable filter incorporating a sufficient number of series tuned traps plus a low pass filter, phase noise once incurred cannot be reduced by such means. The ultimate measure of performance of the phase noise performance of a frequency doubler is the input referred residual phase noise both for the noise floor and the flicker phase regions. The Wenzel JFET frequency doubler implementation (based on the NIST design) has a specified input referred residual phase noise of -155dBc/Hz @ 10Hz -178dBc/Hz @100kHz. for a 5MHz input signal. http://www.wenzel.com/wp-content/uploads/LNHD.pdf A BJT variant of the same circuit has an input referred residual phase noise for a 5MHz input -159dBc/Hz @ 10Hz offset -180dBc/Hz @ 100KHz offset If I have interpreted Adrian's measurements correctly see: http://www.timeok.it/files/high_performance_frequency_doublerv13.pdf. It would be interesting to compare these figures with the measured residual phase noise of other frequency doublers such as Gerard's JFET doubler using BF862's and the proposed near class A JFET based frequency doubler. Bruce On Tuesday, January 27, 2015 02:25:54 PM Charles Steinmetz wrote: Andrea wrote: Now I have some 5MHz DOCXO. I have started to experiment with them and I would like to build a frequency doubler. * * * By the way, I see that really many of the 10MHz reference out there, are in effect doubled 5MHz ones so build a doubler seems reasonable for me. One thing to watch for is the 5MHz leakage component. If you are going to use the 10MHz standard for time-nuts experiments, the 5MHz component needs to be WAY down ( -80dBc) or you will get funny periodic ripples in stability plots. Despite having two 5MHz traps, one recently published design suppresses the 5MHz component only about 52dB below the 10MHz output, and the 20MHz and 30MHz components are also only -50 to -55dB. For this reason (and some others, see discussions over the last several months in the archives) I prefer a doubler built with a quadrature hybrid coupler and a balanced mixer. There is a write-up here: http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/4_App_ Notes_an d_Articles/Frequency_doubler_quadrature_DBM.pdf I recently revived an old, stalled project to develop a JFET push-push doubler for use at 5MHz (see schematic below). FETs with very high transconductance and very small pinchoff voltage (what a tube designer would call a sharp cutoff characteristic) (e.g., 2SK369, BF862, etc.) are attractive on first look because they can operate with lower conversion loss or even some conversion gain. However, they are not well suited for doubler duty for two reasons: (i) their characteristics have a very short range of 2nd-order curvature, so in order to keep noise down they must be driven into regions of higher-order distortion and therefore generate lots of spurious energy; and (ii) they are devilishly hard to match well enough to suppress the input frequency feedthrough. Note that you also need to put enough voltage on the FET drains to get them well into the saturation region -- a Vcc of 5v is not enough. Again, the penalty is lots of spurious energy. So, the lower conversion loss of sharp-cutoff FETs is not the benefit it might at first appear to be -- it is much easier to add gain after the doubler than to remove unwanted spurious mixing products. The design below uses medium-cutoff FETs and a Vcc of 15v (I found that J111 and J310 work best and can be matched sufficiently with a one-point match; 2N4416 and others also work, but are fussier and would benefit from a 2- or 3-point match). At an input of 500mVrms, their long 2nd-order characteristic is used efficiently to generate 10MHz with relatively little spurious energy. I had no problem finding one or more FET pairs matched to within 1mV, given 20 devices from the same lot (YMMV). With properly adjusted traps at 5, 20, and 30MHz, all spurious responses were below -80dBc. The inductors can be commercial RF parts with Q of 200 or so (I used some high-quality through-hole RF inductors I had on hand -- I doubt any SMD inductors will work). The trap capacitors should be C0G/NP0 ceramics for the bulk of the capacitance, plus very small trimmers (I used 27pF, 27pF, and 100pF plus 0.2--6pF glass piston trimmers). I wound the two transformers on Mix-61 toroid cores (each winding is 20 turns on a FT37-61 core -- the inductance is a little lower than called out). Mini-Circuits parts (or equivalents) may also work. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Not a good idea to use a bandpass filter even a crystal filter as such a filter has a relatively large phase shift tempco.The flicker phase noise of the filter crystal will degrade the output signal flicker phase noise significantly.Another issue is that the maximum crystal current will limit the maximum signal input to the crystal filter and thus degrade the output phase noise floor over that achievable using other approaches. Bruce On Wednesday, 28 January 2015 11:19 PM, Alberto di Bene dib...@usa.net wrote: On 1/27/2015 11:57 PM, Bruce Griffiths wrote: /The only viable solution is to use better filtering of the output of a switching multiplier./ What about filtering the doubler output with a 10 MHz xtal ? 73 Alberto I2PHD --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
On Fri, Jan 30, 2015 at 07:35:34PM +0100, Gerhard Hoffmann wrote: As usual, it depends. If you want absolutely deep notches, it is easy with the usual molded chokes to produce craters at 5 and 15 MHz that meet at 10 MHz, even producing some loss there. Hello. Let me sum up everything and please correct me: the square-law characteristic of devices should be avoided, so the configuration of the doubler must be some sort of ideal full wave rectifier it's better to use diode-connected transistors like the 2N because they are less noisy than Schottky diodes at frequency 40MHz (what about the normal P-N diodes?) matching is very important, so monolithic doubles or quadruples could be the right choice, provided their other characteristics are compatible and the substrate connection is not a problem bandpass filtering must be avoided because of added unwanted temperature-dependent phase shifts, so harmonic suppression should be obtained by notch filtering the notch filters could be made using quartz resonators but their high impedance versus LC ones should be taken into account and, anyway, it's difficult to find exactly tuned quartz (particularly for the higher harmonics because of the overtone cut) - the sharpness of quartz filtering is not needed anyway because the harmonics are distant enough for LC filters (what about ceramic resonators?) I add some questions. I saw that most of the doublers out there are using a center tapped transformer to obtain +-180 while the Racal circuit use a single ended input / balanced output transistor discrete differential amplifier, thus combining phase splitting with gain and impedance matching (but not isolation). That configuration should be avoided because the transformer is normally a better matched splitter? On the base of many considerations, the Racal circuit is flawed in many parts; it's anyway good enough for the counters it was designed for or the better performance of other doublers will show up? Best regards, Andrea Baldoni ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
I wrote: In both cases, when the FETs are conducting they are operating as common-source linear amplifiers, NOT as switches. should be, common gate linear amplifiers Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
On 1/29/2015 5:41 PM, Alexander Pummer wrote: And the narrow notch for the harmonic is not required anyway, since the fundamental is fare enough, therefore a high Q LC trap will work better, also with the setting of the biasing af the active devices the Alex KJ6UHN When I designed the 5071A RF chain, I used five cascaded frequency doublers to go from 10 MHz to 320 MHz. I definitely used traps to reduce the 10, 30, and 40 MHz spurs (using 10-20 MHz as an example). It was no easy thing because I could only use coils of moderate Q (less than 50) and I needed at least 80 dB suppression. You might wonder why I needed to reduce 40 MHz spurs in the 20 MHz output. It turns out (little known fact) that the if I drove the 20-40 MHz doubler with 20 MHz contaminated with 40 MHz harmonics, it would degrade the spectral purity of the 40 MHz output. Strange but true. The 5071 filters are basically cascaded notch filters, as opposed to band pass filters. Doing this allowed me to have zero adjustments. Previous atomic clocks used narrow high-Q filters that had to be tuned up, and were temperature sensitive. The production engineers had to constantly stay on top of these filters because they were so temperamental. OTOH, the 5071 filters just work. There was never even a production change to them AFAIK. The key to getting the notch filters to work was to use 2% components, and use two coils and or two capacitors together to get around the fact that the standard values are quantized to 10%. Additionally, I measured each tank circuit in situ on the PC board and tweaked it to take into account the de facto board parasitics. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Am 30.01.2015 um 02:41 schrieb Alexander Pummer: And the narrow notch for the harmonic is not required anyway, since the fundamental is fare enough, therefore a high Q LC trap will work better, also with the setting of the biasing af the active devices the spures could be reduced to [ just observe the output with a spectrum analyzer and set the bias of one site to minimum harmonics, there will be no common optimum for all harmonics, but a good compromise could be achieved ] As usual, it depends. If you want absolutely deep notches, it is easy with the usual molded chokes to produce craters at 5 and 15 MHz that meet at 10 MHz, even producing some loss there. The harmonics are gone, then. At the -3dB point of a resonator we have 45° phase shift, now calculate how many ps delay that is at 10 MHz and then speculate on temperature stability. On MY doubler board, Amidon toroids are in the layout, too, and I have written that they are good enough. They are hard to get. I have heard that Amidon is really Micrometals, but have no cross reference. A good alternative would be Siemens K1 pot cores, but they are much too big and probably only NOS. But everybody can get 5 and 15 MHz crystals for 35 cents. BTW, this is the spectrum of a Morion MV89A that happenes to be on my table: https://picasaweb.google.com/lh/photo/4UEjkc8uy_vkE5nTUR0BEdMTjNZETYmyPJy0liipFm0?feat=directlink 10 dB external attenuator. Could use some filtering, too. regards, Gerhard ps My two BF862 are quite different. delta Vsource = 100mV. Changing that would be the cheapest improvement. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
And the narrow notch for the harmonic is not required anyway, since the fundamental is fare enough, therefore a high Q LC trap will work better, also with the setting of the biasing af the active devices the spures could be reduced to [ just observe the output with a spectrum analyzer and set the bias of one site to minimum harmonics, there will be no common optimum for all harmonics, but a good compromise could be achieved ] 73 Alex KJ6UHN On 1/29/2015 2:16 PM, Richard (Rick) Karlquist wrote: On 1/28/2015 11:28 AM, Charles Steinmetz wrote: Gerhard wrote: It is a different game when you want to notch away sub/harmonics. One problem with using crystals as traps (notch filters) is that the series resistance of a crystal is several orders of magnitude higher than that of a good series-resonant LC -- generally in the 50-100 ohm range. So, although the notch is very narrow, it will not be very deep unless it is in a high-impedance circuit. For example, in a 50 ohm It is very straightforward to use LC networks to transform the impedance of the crystal to a much lower value and get around this problem. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
I had forgotten about one quite promising candidate -- the THAT300 matched monolithic quad. I have some of those, too. I'll put it on the to-do list. To the best of my knowledge, they do not have reverse protection diodes across the B-E junctions (I've never had any reason to check). Best regards, Charles I wrote: Once upon a time, Motorola made monolithic quad BJTs -- but I'm not aware of any matched quads similar to 2Ns at this time. Gerhard replied: There still are MAT04 HFA3046-3096-3127-3128 if duals are enough: SSM2220 MAT12 also mat02, mat03, maybe SSM2110 [probably meant SSM2210? also, there is SSM2212] I had thought of these, but unfortunately, all of the AD parts (MAT and SSM) -- which otherwise look promising -- have reverse diodes across the B-E junctions, which rules them out as diode substitutes. The HFA parts are small-geometry, ultra-high frequency devices (Ft = 8GHz for the NPNs), not at all like 2Ns. It is doubtful they would have the low flicker noise of s. They are monolithic, so they should be pretty well matched, but only the differential pair in the 3046 is actually specified for matching -- and you couldn't use both of the diff pair in a ring structure because of the common cathodes. The 3127 would be the part to try. I have some, so maybe I'll try them (but I'm not hopeful). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
On 1/28/2015 11:28 AM, Charles Steinmetz wrote: Gerhard wrote: It is a different game when you want to notch away sub/harmonics. One problem with using crystals as traps (notch filters) is that the series resistance of a crystal is several orders of magnitude higher than that of a good series-resonant LC -- generally in the 50-100 ohm range. So, although the notch is very narrow, it will not be very deep unless it is in a high-impedance circuit. For example, in a 50 ohm It is very straightforward to use LC networks to transform the impedance of the crystal to a much lower value and get around this problem. Rick Karlquist N6RK ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
On 1/27/2015 11:57 PM, Bruce Griffiths wrote: /The only viable solution is to use better filtering of the output of a switching multiplier./ What about filtering the doubler output with a 10 MHz xtal ? 73 Alberto I2PHD --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Bruce wrote: Using the square law characteristic will inevitably increase the phase noise floor particularly in the flicker region with respect to just using the switching characteristic of a JFET, diode or BJT (non saturated). Even FETs with very large transconductance and low pinchoff voltage do not switch cleanly in a push-push mixer -- there is always plenty of square-law behavior to add flicker noise. So the difference is not really all that great. Furthermore, in practice whatever difference there is will be swamped in many (if not most) cases faced by amateur time nuts by the much larger phase noise of their sources. There are always tradeoffs. The only viable solution is to use better filtering of the output of a switching multiplier. For the reasons given above, I disagree that a switching multiplier is the only viable solution for amateur time nuts. For NIST, possibly. But not for amateur time nuts. Given a dirty multiplier such as a push-push doubler with 2SK369s or BF862s, the only way to get the fundamental and distortion products at 30MHz and below down to suitable levels for critical work is to use a high-Q 10MHz filter plus a series of traps. The high-Q 10MHz filter brings its own low frequency stability problems. There are always tradeoffs. If you intend to use a diode ring based mixer configuration diode connected (collector shorted to base) npns such as 2N222's are significantly quieter (as shown by NIST) than schottky diodes for frequencies below 40MHz or so. Yes, that is well known. However, the transistors need to be well matched or, once again, you end up with spurious products that are hard to remove without causing collateral damage. (I speak from experience -- I have built mixers that way.) This is mitigated to a large extent with matched diode rings as used in diode DBMs. The advantage at 10Hz with 2Ns is only 2 or 3 dB over a good Schottky ring, so unless one is comparing better sources than most amateur time nuts have access to, it will be lost in the source noise (note also that there is a crossover, above which the s are about 10dB worse). Given the relatively small potential gain and the effort required to match four 2Ns to sufficient accuracy not to do more harm than good, I believe this is an exercise best left to those who know they need the modest advantage (again, not many of us amateur time nuts). Once upon a time, Motorola made monolithic quad BJTs -- but I'm not aware of any matched quads similar to 2Ns at this time. [Several manufacturers still claim to make MPQs, but those are not monolithic and not matched.] There are always tradeoffs. Notwithstanding theoretical objections, the described circuit works very nicely and performs substantially better than most time nuts need. I presume that when one is willing to afford sources that require better performance, one will (1) know that, and (2) also be willing to afford an expensive doubler that meets that need. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit2nd ed. 1994)
Andrea, an answer your original Toko data question below. Message: 12 Date: Tue, 27 Jan 2015 16:53:07 +0100 From: Andrea Baldoni erm1ea...@ermione.com To: time-nuts@febo.com Subject: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit2nd ed.1994) cut some stuff Finally I found that a (fairly) complete Toko catalog existed, it was sold by Cirkit in '94 and it's not available anymore. Someone has it in PDF form, or want to borrow it to me to scan it? Best regards, Andrea Baldoni I had a look at the BEC catalogues and they have the same Toko data, rather than scan 60 pages or so. You can get what you want with the WayBack machine (web archive) to see old Toko data online right now at the archived www.bec.co.uk site, try this for a starter: http://web.archive.org/web/20041129173623/http://217.34.228.137/PG800/8var/p25.htm I think BEC (Bonex Electronic Components) followed on from CirKit but don't remember if there was a formal connection between the companies or not. Hope that helps, this method to find old data is frequently. David -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Am 28.01.2015 um 00:59 schrieb Alberto di Bene: On 1/27/2015 11:57 PM, Bruce Griffiths wrote: /The only viable solution is to use better filtering of the output of a switching multiplier./ What about filtering the doubler output with a 10 MHz xtal ? 73 Alberto I2PHD In a correctly designed oscillator, the close-in phase noise is determined by the crystal only and it's generally accepted that there are 20 dB differences from a single batch. Our data support that. Only 10% are really good. If you filter with a crystal that is in resonance it will impress its own phase noise on the signal-to-be-filtered, and the odds are that you lose. Also, crystal dissipation should be only in the 100s of uW max. Using it to filter a 10 dBm signal probably will do harm. It is a different game when you want to notch away sub/harmonics. The power levels of the harmonics are much lower and the crystal does not resonate on the resonator frequency. If you mis-tune a trap, it won't deliver its notch but it will leave all other frequencies alone. A LC series circuit that produces a crater of 15 % center frequency could have more global effects if mis-aligned. When playing with the notch filters for my doubler I got the idea that one could use them to filter away sideband noise even at the 16 dBm level. One would have to be careful not to tune a notch over the carrier, but stay away 100 Hz to some KHz. That might bring an oscillator from quite good to impressive over a limited offset range. I have made a filter board for a dozen notch crystals. That could be populated with the 90% losers from oscillator production. There is also an offset generator from JPL IIRC where they divide 100 MHz down to 10 KHz, subtract that from the 100 MHz with a single sideband mixer and use the 99.99 MHz for a DMTD system. Here one could use the notch filter array to get rid of the residual carrier wrong sideband. DDS-free. But I have no time to follow that in the moment. :-( 73, Gerhard, DK4XP ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit2nd ed. 1994)
I think another spinoff from Cirkit was Mainline Electronics of Leicester. They also mostly disappeared (though I have wondered if they still trade as the ebay seller anonalouise, who seems to have similar stock). Mainline Electronics seems to exist as a Russian website, and it looks as though they have something similar to the Toko range : http://mainline-group.ru/product-category/coil_transform/moulded/ Barend Hendrikson http://barendh.home.xs4all.nl/Indexeng.htm also has a useful range of RF components. On Wed, Jan 28, 2015 at 10:00 AM, David t_list_1_o...@braw.co.uk wrote: Andrea, an answer your original Toko data question below. Message: 12 Date: Tue, 27 Jan 2015 16:53:07 +0100 From: Andrea Baldoni erm1ea...@ermione.com To: time-nuts@febo.com Subject: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit2nd ed.1994) cut some stuff Finally I found that a (fairly) complete Toko catalog existed, it was sold by Cirkit in '94 and it's not available anymore. Someone has it in PDF form, or want to borrow it to me to scan it? Best regards, Andrea Baldoni I had a look at the BEC catalogues and they have the same Toko data, rather than scan 60 pages or so. You can get what you want with the WayBack machine (web archive) to see old Toko data online right now at the archived www.bec.co.uk site, try this for a starter: http://web.archive.org/web/20041129173623/http://217.34. 228.137/PG800/8var/p25.htm I think BEC (Bonex Electronic Components) followed on from CirKit but don't remember if there was a formal connection between the companies or not. Hope that helps, this method to find old data is frequently. David -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Gerhard wrote: It is a different game when you want to notch away sub/harmonics. One problem with using crystals as traps (notch filters) is that the series resistance of a crystal is several orders of magnitude higher than that of a good series-resonant LC -- generally in the 50-100 ohm range. So, although the notch is very narrow, it will not be very deep unless it is in a high-impedance circuit. For example, in a 50 ohm circuit (50 ohms looking each way, so 25 ohms at the node) you will be lucky to get 3dB of attenuation. To get 40dB of suppression, the nodal impedance would need to be at least 5k ohms, perhaps even 10k ohms -- and the high impedance adds noise, which means there is a phase noise penalty. Another problem is that the narrow notches are prone to sliding off frequency with small temperature changes. Also, while a 5MHz trap crystal will almost certainly be a fundamental-mode resonator, that will probably not be true at, say, 30MHz -- so a 30MHz trap would most likely have a notch at or near the desired output frequency. Made with good, high-Q RF inductors (forget SM parts), an LC trap is generally preferable to a crystal trap. There is still some temperature sensitivity, but the greater width is much more forgiving. At the same time, the Q is high enough that you don't have to worry about effects 5MHz away when you are trapping frequencies of 30MHz and below. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
I wrote: Once upon a time, Motorola made monolithic quad BJTs -- but I'm not aware of any matched quads similar to 2Ns at this time. Gerhard replied: There still are MAT04 HFA3046-3096-3127-3128 if duals are enough: SSM2220 MAT12 also mat02, mat03, maybe SSM2110 [probably meant SSM2210? also, there is SSM2212] I had thought of these, but unfortunately, all of the AD parts (MAT and SSM) -- which otherwise look promising -- have reverse diodes across the B-E junctions, which rules them out as diode substitutes. The HFA parts are small-geometry, ultra-high frequency devices (Ft = 8GHz for the NPNs), not at all like 2Ns. It is doubtful they would have the low flicker noise of s. They are monolithic, so they should be pretty well matched, but only the differential pair in the 3046 is actually specified for matching -- and you couldn't use both of the diff pair in a ring structure because of the common cathodes. The 3127 would be the part to try. I have some, so maybe I'll try them (but I'm not hopeful). Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit2nd ed. 1994)
This site is quite helpful. I happened to pick up several toko kits last years and the data is here. Thank you On Wed, Jan 28, 2015 at 5:00 AM, David t_list_1_o...@braw.co.uk wrote: Andrea, an answer your original Toko data question below. Message: 12 Date: Tue, 27 Jan 2015 16:53:07 +0100 From: Andrea Baldoni erm1ea...@ermione.com To: time-nuts@febo.com Subject: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit2nd ed.1994) cut some stuff Finally I found that a (fairly) complete Toko catalog existed, it was sold by Cirkit in '94 and it's not available anymore. Someone has it in PDF form, or want to borrow it to me to scan it? Best regards, Andrea Baldoni I had a look at the BEC catalogues and they have the same Toko data, rather than scan 60 pages or so. You can get what you want with the WayBack machine (web archive) to see old Toko data online right now at the archived www.bec.co.uk site, try this for a starter: http://web.archive.org/web/20041129173623/http://217.34. 228.137/PG800/8var/p25.htm I think BEC (Bonex Electronic Components) followed on from CirKit but don't remember if there was a formal connection between the companies or not. Hope that helps, this method to find old data is frequently. David -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Am 28.01.2015 um 01:57 schrieb Charles Steinmetz: (again, not many of us amateur time nuts). Once upon a time, Motorola made monolithic quad BJTs -- but I'm not aware of any matched quads similar to 2Ns at this time. [Several manufacturers still claim to make MPQs, but those are not monolithic and not matched.] There still are http://www.analog.com/static/imported-files/data_sheets/MAT04.pdf http://www.intersil.com/content/dam/Intersil/documents/hfa3/hfa3046-3096-3127-3128.pdf if duals are enough: http://www.analog.com/static/imported-files/data_sheets/SSM2220.pdf , http://www.analog.com/static/imported-files/data_sheets/MAT12.pdf also mat02, mat03, maybe SSM2110, I have used most of them :-) https://picasaweb.google.com/103357048842463945642/LowNoisePreamplifiers?authuser=0feat=directlink regards, Gerhard ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit 2nd ed.1994)
Hi Andrea I have here a Cirkit 2nd edition Toko catalogue dated 1993 (a firm local to me I dealt with quite a lot) The cat is in good condition but it is 128 pages and a glued spine so scanning risks breaking it up. However the 10k range occupies just one page and if the part adjacent to the spine does not copy well all you will lose is the 100off price column (and I dont think you can buy them for that now 20 years on :-)) ) Give me a little time and I will do you a scan of the page, and mail it direct as a PDF. I might actually have some new Toko coils in the component drawers but they may not be 10K. However I also have a lot of 5MHz OCXOs including Racal an Toyocom so I might have something useful if you dont find a source nearer to you. Best Wishes Alan G3NYK - Original Message - From: Andrea Baldoni erm1ea...@ermione.com To: time-nuts@febo.com Sent: Tuesday, January 27, 2015 3:53 PM Subject: [time-nuts] 510 doubler and old Toko RF catalogue (Cirkit 2nd ed.1994) Hello All. Now I have some 5MHz DOCXO. I have started to experiment with them and I would like to build a frequency doubler. I already saw the very nice circuit from Gerhard Hoffmann for the Lucent, I saw some diode circuits from Wenzel (my oscillators output around 1.5Vpp loaded, too scarce for diodes alone; I used a 1:2 transformer just to try and I obtained the 10MHz but not good for anything) and I saw the doubler circuit Racal Dana used in some counters I attached. I would like to build something like one of those; it's a full wave rectifier made by a differential amplifier and two diodes, followed by a 10MHz amp/filter chain much like the IF of FM radios (with AGC too!). I don't know if it's adequate for serious use; I also saw the Z3811-80007 doubler board used in Z3815A and Z3805A according to the seller, much more modern and surely better, but I have not its schematic. Someone knows it? I have bought one of the Racal units, just to have the opportunity to fiddle with an already working one; I identified the IF transformers used there and are Toko common 10.7MHz Q=80 unit. They are not built anymore but it's possible to find similar ones in Internet; however it happens to me frequently to need information about the old Toko 10K series and there is not any comprehensive source. I saw I share this frustration with many people in the electronics newsgroups. Finally I found that a (fairly) complete Toko catalog existed, it was sold by Cirkit in '94 and it's not available anymore. Someone has it in PDF form, or want to borrow it to me to scan it? By the way, I see that really many of the 10MHz reference out there, are in effect doubled 5MHz ones so build a doubler seems reasonable for me. Best regards, Andrea Baldoni ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Andrea wrote: Now I have some 5MHz DOCXO. I have started to experiment with them and I would like to build a frequency doubler. * * * By the way, I see that really many of the 10MHz reference out there, are in effect doubled 5MHz ones so build a doubler seems reasonable for me. One thing to watch for is the 5MHz leakage component. If you are going to use the 10MHz standard for time-nuts experiments, the 5MHz component needs to be WAY down ( -80dBc) or you will get funny periodic ripples in stability plots. Despite having two 5MHz traps, one recently published design suppresses the 5MHz component only about 52dB below the 10MHz output, and the 20MHz and 30MHz components are also only -50 to -55dB. For this reason (and some others, see discussions over the last several months in the archives) I prefer a doubler built with a quadrature hybrid coupler and a balanced mixer. There is a write-up here: http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/4_App_Notes_and_Articles/Frequency_doubler_quadrature_DBM.pdf I recently revived an old, stalled project to develop a JFET push-push doubler for use at 5MHz (see schematic below). FETs with very high transconductance and very small pinchoff voltage (what a tube designer would call a sharp cutoff characteristic) (e.g., 2SK369, BF862, etc.) are attractive on first look because they can operate with lower conversion loss or even some conversion gain. However, they are not well suited for doubler duty for two reasons: (i) their characteristics have a very short range of 2nd-order curvature, so in order to keep noise down they must be driven into regions of higher-order distortion and therefore generate lots of spurious energy; and (ii) they are devilishly hard to match well enough to suppress the input frequency feedthrough. Note that you also need to put enough voltage on the FET drains to get them well into the saturation region -- a Vcc of 5v is not enough. Again, the penalty is lots of spurious energy. So, the lower conversion loss of sharp-cutoff FETs is not the benefit it might at first appear to be -- it is much easier to add gain after the doubler than to remove unwanted spurious mixing products. The design below uses medium-cutoff FETs and a Vcc of 15v (I found that J111 and J310 work best and can be matched sufficiently with a one-point match; 2N4416 and others also work, but are fussier and would benefit from a 2- or 3-point match). At an input of 500mVrms, their long 2nd-order characteristic is used efficiently to generate 10MHz with relatively little spurious energy. I had no problem finding one or more FET pairs matched to within 1mV, given 20 devices from the same lot (YMMV). With properly adjusted traps at 5, 20, and 30MHz, all spurious responses were below -80dBc. The inductors can be commercial RF parts with Q of 200 or so (I used some high-quality through-hole RF inductors I had on hand -- I doubt any SMD inductors will work). The trap capacitors should be C0G/NP0 ceramics for the bulk of the capacitance, plus very small trimmers (I used 27pF, 27pF, and 100pF plus 0.2--6pF glass piston trimmers). I wound the two transformers on Mix-61 toroid cores (each winding is 20 turns on a FT37-61 core -- the inductance is a little lower than called out). Mini-Circuits parts (or equivalents) may also work. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 510 doubler
Using the square law characteristic will inevitably increase the phase noise floor particularly in the flicker region with respect to just using the switching characteristic of a JFET, diode or BJT (non saturated).The only viable solution is to use better filtering of the output of a switching multiplier.If you intend to use a diode ring based mixer configuration diode connected (collector shorted to base) npns such as 2N222's are significantly quieter (as shown by NIST) than schottky diodes for frequencies below 40MHz or so. Bruce. On Wednesday, 28 January 2015 8:25 AM, Charles Steinmetz csteinm...@yandex.com wrote: Andrea wrote: Now I have some 5MHz DOCXO. I have started to experiment with them and I would like to build a frequency doubler. * * * By the way, I see that really many of the 10MHz reference out there, are in effect doubled 5MHz ones so build a doubler seems reasonable for me. One thing to watch for is the 5MHz leakage component. If you are going to use the 10MHz standard for time-nuts experiments, the 5MHz component needs to be WAY down ( -80dBc) or you will get funny periodic ripples in stability plots. Despite having two 5MHz traps, one recently published design suppresses the 5MHz component only about 52dB below the 10MHz output, and the 20MHz and 30MHz components are also only -50 to -55dB. For this reason (and some others, see discussions over the last several months in the archives) I prefer a doubler built with a quadrature hybrid coupler and a balanced mixer. There is a write-up here: http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/4_App_Notes_and_Articles/Frequency_doubler_quadrature_DBM.pdf I recently revived an old, stalled project to develop a JFET push-push doubler for use at 5MHz (see schematic below). FETs with very high transconductance and very small pinchoff voltage (what a tube designer would call a sharp cutoff characteristic) (e.g., 2SK369, BF862, etc.) are attractive on first look because they can operate with lower conversion loss or even some conversion gain. However, they are not well suited for doubler duty for two reasons: (i) their characteristics have a very short range of 2nd-order curvature, so in order to keep noise down they must be driven into regions of higher-order distortion and therefore generate lots of spurious energy; and (ii) they are devilishly hard to match well enough to suppress the input frequency feedthrough. Note that you also need to put enough voltage on the FET drains to get them well into the saturation region -- a Vcc of 5v is not enough. Again, the penalty is lots of spurious energy. So, the lower conversion loss of sharp-cutoff FETs is not the benefit it might at first appear to be -- it is much easier to add gain after the doubler than to remove unwanted spurious mixing products. The design below uses medium-cutoff FETs and a Vcc of 15v (I found that J111 and J310 work best and can be matched sufficiently with a one-point match; 2N4416 and others also work, but are fussier and would benefit from a 2- or 3-point match). At an input of 500mVrms, their long 2nd-order characteristic is used efficiently to generate 10MHz with relatively little spurious energy. I had no problem finding one or more FET pairs matched to within 1mV, given 20 devices from the same lot (YMMV). With properly adjusted traps at 5, 20, and 30MHz, all spurious responses were below -80dBc. The inductors can be commercial RF parts with Q of 200 or so (I used some high-quality through-hole RF inductors I had on hand -- I doubt any SMD inductors will work). The trap capacitors should be C0G/NP0 ceramics for the bulk of the capacitance, plus very small trimmers (I used 27pF, 27pF, and 100pF plus 0.2--6pF glass piston trimmers). I wound the two transformers on Mix-61 toroid cores (each winding is 20 turns on a FT37-61 core -- the inductance is a little lower than called out). Mini-Circuits parts (or equivalents) may also work. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] 510 doubler and old Toko RF catalogue (Cirkit 2nd ed. 1994)
Hello All. Now I have some 5MHz DOCXO. I have started to experiment with them and I would like to build a frequency doubler. I already saw the very nice circuit from Gerhard Hoffmann for the Lucent, I saw some diode circuits from Wenzel (my oscillators output around 1.5Vpp loaded, too scarce for diodes alone; I used a 1:2 transformer just to try and I obtained the 10MHz but not good for anything) and I saw the doubler circuit Racal Dana used in some counters I attached. I would like to build something like one of those; it's a full wave rectifier made by a differential amplifier and two diodes, followed by a 10MHz amp/filter chain much like the IF of FM radios (with AGC too!). I don't know if it's adequate for serious use; I also saw the Z3811-80007 doubler board used in Z3815A and Z3805A according to the seller, much more modern and surely better, but I have not its schematic. Someone knows it? I have bought one of the Racal units, just to have the opportunity to fiddle with an already working one; I identified the IF transformers used there and are Toko common 10.7MHz Q=80 unit. They are not built anymore but it's possible to find similar ones in Internet; however it happens to me frequently to need information about the old Toko 10K series and there is not any comprehensive source. I saw I share this frustration with many people in the electronics newsgroups. Finally I found that a (fairly) complete Toko catalog existed, it was sold by Cirkit in '94 and it's not available anymore. Someone has it in PDF form, or want to borrow it to me to scan it? By the way, I see that really many of the 10MHz reference out there, are in effect doubled 5MHz ones so build a doubler seems reasonable for me. Best regards, Andrea Baldoni ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
