Re: [time-nuts] fast switching quiet synthesizer
br...@ko4bb.com said: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. What does fast switching mean in the context of a DDS? What does the spectrum of a DDS look like if I switch back and forth between 2 frequencies at 1 KHz? Or what question should I be asking? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
Although the DDS settles rapidly there some filter settling time is required. These systems are combinations of DDS and direct synthesis with microsecond or sub microsecond settling. Bruce. On October 8, 2014 at 3:52 AM Hal Murray hmur...@megapathdsl.net wrote: br...@ko4bb.com said: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. What does fast switching mean in the context of a DDS? What does the spectrum of a DDS look like if I switch back and forth between 2 frequencies at 1 KHz? Or what question should I be asking? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
It might be worth looking at Holzworth. They make a range of single and multi channel synthesisers covering different levels of phase noise and switching speed. http://www.holzworth.com/ Regards, Garry Date: Tue, 07 Oct 2014 10:02:55 -0700 From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] fast switching quiet synthesizer Message-ID: 54341cbf.9080...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. The transfer of any controlled technology contained in or attached to this email is covered by the “Open General Export Licence (Technology for Military Goods)”, granted by the United Kingdom Secretary of State. The information contained in this email is provided as a personal communication of the sender and, as such, is not binding on Pascall Electronics Ltd unless the intended recipient has been notified by signed postal or fax communication that the sender is authorised to commit Pascall Electronics Ltd on the subject matter concerned. The contents of this email are confidential to the intended recipient at the email address to which it has been addressed. It may not be disclosed to or used by anyone other than this addressee, nor may it be copied in any way. If received in error, please contact Oli Poole, at opo...@pascall.co.uk, quoting the name of the sender and the addressee and then delete it from your system.___ ___ 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] fast switching quiet synthesizer
On 10/8/14, 12:52 AM, Hal Murray wrote: br...@ko4bb.com said: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. What does fast switching mean in the context of a DDS? How long does it take to load the new phase increment in? I suppose one can distinguish between load and set/settle time, and for a DDS the latter is one clock. (although for DDSes that include post NCO filtering for spur reduction/movement, there might be a longer transient, depending on the kind of filter) What does the spectrum of a DDS look like if I switch back and forth between 2 frequencies at 1 KHz? Or what question should I be asking? It would look like a phase continuous FSK signal. If you switch fast (e.g. at rates comparable to the shift), then the spectrum gets quite complex.) (this was basically the basis of the Yamaha FM synthesis approach for music synthesizers.. it produces a very rich spectrum with lots of overtones and intermod products and can produce very natural sounding notes) ___ 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] fast switching quiet synthesizer
We've been using/testing an AD9912 eval-kit board. It can take 10MHz input and has an internal 66x PLL and VCO for a 660MHz DDS sample-clock (just out of spec actually, vco is min 700MHz if I read the datasheet correctly). ... Anders PS. I could be tempted to join in if someone wants to make a PCB for these chips - would save significantly compared to eval-boards.. Hi Anders, See also the cute little AD9913 PCB that Bert made for the group earlier this year: http://leapsecond.com/pages/ad9913/ /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
Hi On Oct 8, 2014, at 3:52 AM, Hal Murray hmur...@megapathdsl.net wrote: br...@ko4bb.com said: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. What does fast switching mean in the context of a DDS? Not much at all. Your DDS clock will be something like 1 GHz and it will “switch frequency (actually it switches phase)” on a clock edge. You probably can’t load a billion updates a second through the update port. People do indeed load millions of updates a second.The DDS is quite happy to “follow” the updates. It’s one of the ways to get a clean(er) 10 MHz reference signal out of a DDS on a GPSDO. What does the spectrum of a DDS look like if I switch back and forth between 2 frequencies at 1 KHz? Since it is phase coherent FSK with instantaneous phase change, it’s pretty much a textbook spectrum. Lots of energy at the switch points. It’s likely closer to the textbook than anything you can get out of a conventional (non DDS) signal generator. Or what question should I be asking? Is that waveform (and it’s spurs) OK in the application or not. Only Jim knows for sure … Bob -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
On 10/8/14, 7:21 AM, Bob Camp wrote: Hi On Oct 8, 2014, at 3:52 AM, Hal Murray hmur...@megapathdsl.net wrote: br...@ko4bb.com said: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. What does fast switching mean in the context of a DDS? Not much at all. Your DDS clock will be something like 1 GHz and it will “switch frequency (actually it switches phase)” on a clock edge. You probably can’t load a billion updates a second through the update port. People do indeed load millions of updates a second.The DDS is quite happy to “follow” the updates. It’s one of the ways to get a clean(er) 10 MHz reference signal out of a DDS on a GPSDO. What does the spectrum of a DDS look like if I switch back and forth between 2 frequencies at 1 KHz? Since it is phase coherent FSK with instantaneous phase change, it’s pretty much a textbook spectrum. Lots of energy at the switch points. It’s likely closer to the textbook than anything you can get out of a conventional (non DDS) signal generator. Or what question should I be asking? Is that waveform (and it’s spurs) OK in the application or not. Only Jim knows for sure … It's a Stepped frequency CW radar..you make amplitude and phase measurements at a series of frequencies, then do an inverse FFT to transform to the time/range domain.. just like a VNA doing time domain measurements. It's a flavor of FMCW radar like used in radar altimeters. The system is basically a homodyne (think cops radar speed gun), so you're detecting the received signal by mixing it with the transmitted signal and looking mostly at the phase. Close in phase noise tends to cancel since ranges of 1000 meters are only 6 microsecond delay. Likewise, close in spurs tend not to have a lot of effect. I've used a bluetooth transmitter as the source for a very short range (few meters) experiment. The PSK modulation on the BT cancels itself out. The real issue is that you want as much time on target as you can get. So if you're stepping every 1 millisecond, and you have to wait 300 microseconds to settle, you're really only measuring for 700 microseconds, so you're giving up SNR (assuming fixed Tx power, Rx noise figure, etc.) There is an alternate architecture we want to experiment with where the receive LO is offset from the transmit frequency by a small amount: this shifts the detected signal away from baseband, so you don't have to deal with DC offsets in the I/Q detection, and in fact, you can use a single mixer instead of a quadrature demodulator. These systems have outputs in audio frequencies, so going to offset rather than baseband also means you can use one ADC instead of two. That would make the eventual system smaller, lighter, cheaper, etc. (with the increased complexity of the offset oscillator and mixers). And finally, the ultimate range resolution of a stepped frequency radar is determined by the number of steps. But you need a certain time at each frequency to make the measurement (SNR driven, mostly), and if you want to deal with a target that is moving (aren't most), you need to have the entire step sequence be fast enough that the target hasn't moved too much in that interval. So the ability to do multiple frequencies at the same time is desirable (if you have 4 transmitters, and 4 receivers, you can have 4 times the number of steps/second) There's an interesting tradeoff among all the various system parameters: how accurate is the step frequency (small errors are like noise and spread the target out), how many steps (sets the number of resolution bins), what's the bandwidth (sets the size of a bin), what is the ambiguity range (if you have 3 MHz steps, and 100 steps, then you have 0.5 meter resolution, but the bins repeat every 50 meters, so a target at 105 meters looks like it's at 5 meters). You can also do cool stuff like run two sequences simultaneously, one with big steps (good range resolution, but short ambiguity) and one with small steps (large unambiguous range), or non-uniform sequences (e.g. spacing the frequencies with log steps). And, of course, there's no particular reason you need to step in any particular order, or even that the frequencies be exactly the same on each group of steps, so you can use pseudo random schemes to do code division multiple access. One case where good phase noise (and low Adev) is important is when you're doing it bistatic: you don't have that sample of the transmitted signal to use as the LO for the receiver. Now, the transmitter and receiver oscillator noise is important, and if you're doing the usual baseband detection, the close in noise is in band for the signal you're detecting. That's where the offset frequency approach comes in handy. But still, you're ultimately making a phase measurement between transmitted and received signal, so the two separated sources have to be phase
Re: [time-nuts] fast switching quiet synthesizer
On Wed, Oct 8, 2014 at 3:52 AM, Hal Murray hmur...@megapathdsl.net wrote: br...@ko4bb.com said: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. What does fast switching mean in the context of a DDS? What does the spectrum of a DDS look like if I switch back and forth between 2 frequencies at 1 KHz? Or what question should I be asking? The bare AD DDS chips do textbook-perfect phase-continuous FSK quite nicely. This is not the same as phase-coherent. AD does have some good app notes on implementing phase coherent FSK. Tim. ___ 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] fast switching quiet synthesizer
On 10/7/2014 10:02 AM, Jim Lux wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. Possibly overkill, but Agilent has a very state of the art arbitrary waveform generator that is light years ahead of anything else. It uses a chip with the internal codename Griffin that was developed in the department I worked in at Agilent until I retired in March. IIRC, the complete price for the generator in a box is about $60K. You didn't mention budget constraints, but this is an off the shelf solution vs who knows how much of your time. 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] fast switching quiet synthesizer
On Tue, 07 Oct 2014 17:18:19 -0400, S. Jackson via time-nuts wrote: Hi Anders, in the absence of a true phase noise analyzer the next best thing is to use one of the Agilent 856x analyzers with the phase noise measurement software plug-in. Wouldn't a used E4406A do it , they're going quite cheap ? John Miles says it's quite good , despite it's 10Mhz span. http://tinyurl.com/o7fhwl6 I even think i read he mentioned -140dB somewhere. Ahh: http://tinyurl.com/myg5ra9 I think his site is down atm. , but here is an url for google's cached version. http://tinyurl.com/ppz85qf CFO Denmark ___ 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] fast switching quiet synthesizer
You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Cheers, Magnus On 10/07/2014 07:02 PM, Jim Lux wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? Ultimately, I'm looking at output frequencies in single digit GHz, but something that can be mixed/multiplied up will work just fine. I'm looking for something that is off the shelf-ey as much as possible. Using surplus gear is ok, because I really only need 3 or 4 channels and that might be scroungeable, but spending hours wiring up weird adapters or locating connectors that haven't been made since 1943 is something I'd like to avoid. ___ 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] fast switching quiet synthesizer
In message 54341cbf.9080...@earthlink.net, Jim Lux writes: Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? DDS is by far the easiest, but the question is if it is clean enough. Some of the HP generators which go cheap-ish in eBay are pretty agile too. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] fast switching quiet synthesizer
Jim I am not sure if this will meet your requirement for hygene but google Trinity Power Inc (Bob Yarbrough) he has a unit that was featured in EDN some time around a year ago. I doesnt switch fast enough at present but that could be altered. the problem might be that I think it is a PLL Rather than a DDS. But might be worth a look I know the PTS I have a couple of earlier Wavetek- Rockland units ...one TTL and one GPIB also an Adret 201 which uses the same technique. Alan G3NYK - Original Message - From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 07, 2014 6:02 PM Subject: [time-nuts] fast switching quiet synthesizer At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? Ultimately, I'm looking at output frequencies in single digit GHz, but something that can be mixed/multiplied up will work just fine. I'm looking for something that is off the shelf-ey as much as possible. Using surplus gear is ok, because I really only need 3 or 4 channels and that might be scroungeable, but spending hours wiring up weird adapters or locating connectors that haven't been made since 1943 is something I'd like to avoid. ___ 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] fast switching quiet synthesizer
Hi Consider that stepping every ms means settling in much less than that. If you need 100 us settling, a pair of synthesizers is probably the only way to go. Use some sort of modulator / switch between them to keep the key clicks from driving you nuts. Bob On Oct 7, 2014, at 1:02 PM, Jim Lux jim...@earthlink.net wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? Ultimately, I'm looking at output frequencies in single digit GHz, but something that can be mixed/multiplied up will work just fine. I'm looking for something that is off the shelf-ey as much as possible. Using surplus gear is ok, because I really only need 3 or 4 channels and that might be scroungeable, but spending hours wiring up weird adapters or locating connectors that haven't been made since 1943 is something I'd like to avoid. ___ 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] fast switching quiet synthesizer
I have two versions of the ADF4351 dds. One is the AD eval board, and the other the TPI synthesizer (http://www.rf-consultant.com/calibrated-signal-generator/) at $280 that might do the job. The latter device performs well. It will be as good as the 4351, I think. It has a programmable attenuator. A good price. Requires a Healthy! USB port. Don Magnus Danielson You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Cheers, Magnus On 10/07/2014 07:02 PM, Jim Lux wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? Ultimately, I'm looking at output frequencies in single digit GHz, but something that can be mixed/multiplied up will work just fine. I'm looking for something that is off the shelf-ey as much as possible. Using surplus gear is ok, because I really only need 3 or 4 channels and that might be scroungeable, but spending hours wiring up weird adapters or locating connectors that haven't been made since 1943 is something I'd like to avoid. ___ 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. -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.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] fast switching quiet synthesizer
jim...@earthlink.net said: I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Timing on Ethernet is as good as RS-232 if you have a point to point link rather than a huge network full of crappy software. I'd worry more about USB within the Prologix. It might be fun to do the experiment. Can you get a scope on one of the GPIB signals and something like a modem control signal on a PC that sends the packet? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
On Tue, Oct 7, 2014 at 8:32 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. We've been using/testing an AD9912 eval-kit board. It can take 10MHz input and has an internal 66x PLL and VCO for a 660MHz DDS sample-clock (just out of spec actually, vco is min 700MHz if I read the datasheet correctly). Output looks like so: http://www.anderswallin.net/wp-content/uploads/2013/12/Fout100M_Span400M.bmp DDS output is 0 to 2-400MHz with a resolution of ~few uHz since it has a 48-bit tuning word. We're programming it with an arduino+eth-shield using modbus-ethernet. Changing frequency over ethernet takes about 60ms, but it could be much much faster directly over SPI if you know the desired frequencies beforehand and store them on the arduino. zoom-in shows spurs at 50kHz http://www.anderswallin.net/wp-content/uploads/2013/12/Fout100M_Span500k.bmp The spurs improve when using the DDS with an external 1GHz sample-clock (internal PLL+VCO on the DDS-chip disabled). We produced it from 10MHz with an ADF4350 eval-board: http://www.anderswallin.net/wp-content/uploads/2014/03/100MHz_AD9912_internal_vs_external_PLL.jpg AD must use some niceexpensive spectrum-analyzer to produce that figure with a -100 dBm noise floor! :) even with the eval-boards there's a fair bit of building: multiple powersupplies, cables, enclosure, etc. Anders PS. I could be tempted to join in if someone wants to make a PCB for these chips - would save significantly compared to eval-boards.. ___ 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] fast switching quiet synthesizer
What is your definition of low noise / purity ? DDS and low noise take some pretty good engineering. What is the min frequency ? What is the step size ? As to PTS's it took me around an hour to make a cable write the C code to convert to its interface needs. If I had not lost the documentation I'd send it to you. If your looking for new, look on the web a Microwave Journal's web site http://www.microwavejournal.com/ and a couple of the military mags http://www.militaryaerospace.com/index.html for example. How many steps in a test run ? An 8645A can do 4K step at a time. But alas it is a pretty old instrument, Kesight recommends the E8257D but starting price is over $33K On Tue, Oct 7, 2014 at 10:32 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Cheers, Magnus On 10/07/2014 07:02 PM, Jim Lux wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? Ultimately, I'm looking at output frequencies in single digit GHz, but something that can be mixed/multiplied up will work just fine. I'm looking for something that is off the shelf-ey as much as possible. Using surplus gear is ok, because I really only need 3 or 4 channels and that might be scroungeable, but spending hours wiring up weird adapters or locating connectors that haven't been made since 1943 is something I'd like to avoid. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
Hi Anders, in the absence of a true phase noise analyzer the next best thing is to use one of the Agilent 856x analyzers with the phase noise measurement software plug-in. By chance I had looked at Ebay over the weekend and those two can be had for around $3500 these days (with an 8561E). Still a lot of $$, but it will give you a nice improvement over the Rigol spectrum analyzer and still be 5x cheaper than the lowest cost commercial PN analyzer.. Its really cool to have a good SA of course, so the PN option just comes as a bonus in my opinion. Attached is a sample plot of what that PN output would look like at 100MHz from a reasonable DDS output. The noise floor is about -135dBc/Hz. bye, Said In a message dated 10/7/2014 13:44:31 Pacific Daylight Time, anders.e.e.wal...@gmail.com writes: The spurs improve when using the DDS with an external 1GHz sample-clock (internal PLL+VCO on the DDS-chip disabled). We produced it from 10MHz with an ADF4350 eval-board: http://www.anderswallin.net/wp-content/uploads/2014/03/100MHz_AD9912_interna l_vs_external_PLL.jpg AD must use some niceexpensive spectrum-analyzer to produce that figure with a -100 dBm noise floor! :) ___ 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] fast switching quiet synthesizer
In message 20141007200046.02aa9406...@ip-64-139-1-69.sjc.megapath.net, Hal Mu rray writes: Timing on Ethernet is as good as RS-232 if you have a point to point link rather than a huge network full of crappy software. That is a truth with an almost uncountable number of footnotes... If we're only talking about timing in 99% of the cases, then yes, but that last one percent will make you tear your hair out. We did 20 microsecond jitter on 10GE for the ESO ELT adaptive optics prototype, and that was seriously pushing things near the edge. Five microseconds is trivially possible with a good $20 RS232 cable. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] fast switching quiet synthesizer
Jim, This reminds me of a project I did back in the early1990's. (Hopefully we have advanced a bit since then.) It used a bunch of quad latches, some 74138's, a UART, and an RS232 converter. It drove a PTS 40. The UART used the first 4 bits for BCD frequency and the last four bits to address which decade on the PTS. It was for a frequency hopping amateur radio project that I never finished but that part worked as hoped. As far as radar frequecy hopping, I spent several years in the US Air Force where our X band radar magnatrons were tuned hydraulically. 3000 PSI on a slug in the maggie tuned it very fast! Al, retired, mostly At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. ___ 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] fast switching quiet synthesizer
Hi Don, Jim, that is the one I was refering to, It has a VCO as the source (all part of the AD4351) but I think your description of the unit is more accurate that mine. Contact him directly he is keen to contact new areas and hobbyists. There are two units one is a source with 4 output levels, I believe he sells that on eBay at $280 but direct contact may get you a better deal. There is a version with a calibrated attenuator but this has FM capability which adds to the VCO control and may not be good for PN. I think this sells for $340. Robert Yarbrough rob...@rf-consultant.com (blame me for airing his ID :-)) ) Alan G3NYK - Original Message - From: Don Latham d...@montana.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, October 07, 2014 9:19 PM Subject: Re: [time-nuts] fast switching quiet synthesizer I have two versions of the ADF4351 dds. One is the AD eval board, and the other the TPI synthesizer (http://www.rf-consultant.com/calibrated-signal-generator/) at $280 that might do the job. The latter device performs well. It will be as good as the 4351, I think. It has a programmable attenuator. A good price. Requires a Healthy! USB port. Don Magnus Danielson You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Cheers, Magnus On 10/07/2014 07:02 PM, Jim Lux wrote: At work, I'm putting together a multichannel stepped frequency CW radar breadboard, and I'm looking for something to serve as a source that I can step quickly. I'm looking at stepping every millisecond or so. Right now, I use a Ardunino type microcontroller driving a serial DAC driving a VCO, but that's a bit wonky and noisy, although it's easy to get the step timing right on. The spectral purity is, shall we say, downright ugly. Since I'm going to be doing precision ranging with this, the spectral purity has to be reasonably good (not 1E-15 at 1000 seconds good, fortunately).. I was thinking about a PTS synthesizers (beloved of time-nuts for all kinds of reason), and they're nice because they are quiet, and switch really fast (microseconds). However, they all seem to have BCD or GPIB interfaces (only). Sure, I can code up something on an Arduino or other microcontroller to drive the BCD on the PTS, but maybe there's something else out there that might work as well? And is already off the shelf. I could hook a Prologix on the back of a PTS with GPIB, and hit it over the ethernet, but I'm not sure I'd be able to get the steps to occur when I want them (ethernet and determinism do not go well together). Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? Ultimately, I'm looking at output frequencies in single digit GHz, but something that can be mixed/multiplied up will work just fine. I'm looking for something that is off the shelf-ey as much as possible. Using surplus gear is ok, because I really only need 3 or 4 channels and that might be scroungeable, but spending hours wiring up weird adapters or locating connectors that haven't been made since 1943 is something I'd like to avoid. ___ 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. -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 www.lightningforensics.com www.sixmilesystems.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] fast switching quiet synthesizer
On 10/7/14, 10:28 AM, Poul-Henning Kamp wrote: In message 54341cbf.9080...@earthlink.net, Jim Lux writes: Maybe some DDS in a box product? That will take my nice clean 10 MHz reference? DDS is by far the easiest, but the question is if it is clean enough. Yes, probably clean enough (I can pick steps where the spurs are less obnoxious, if nothing else). The real question is whether someone makes a dds in a box or whether I'd have to get Eval boards, power supplies, and cobble up a controller and a box. Some of the HP generators which go cheap-ish in eBay are pretty agile too. ___ 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] fast switching quiet synthesizer
On 10/7/14, 10:32 AM, Magnus Danielson wrote: You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Yes, virtually all of them have a load input of some form (I'm familiar with the AD98xx and AD99xx ones, and they certainly do). What I'd really like, though is something at a slightly higher level of integration (for which I am willing to pay.. it's a time vs money thing). Does someone sell a DDS in a box with connectors, etc. I need a tuning range, for now, of around 3.1 to 3.4 GHz, so any of the 1 GHz DDSes can generate something that I could mix up with a 2.8-3 GHz LO (which I have), although I'd have to be careful about images. Or I can run the few hundred MHz out of the DDS into a doubler/tripler, then mix up. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Not a problem, I think I have a 10 in to 100 MHz out set of bricks from Wenzel (x5 and x2) from a previous project ___ 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] fast switching quiet synthesizer
Hi The output spectrum of some DDS’s is pretty rich. You may find that a 1 GHz DDS can be filtered to operate directly over the 3.1 to 3.4 GHz. Bob On Oct 7, 2014, at 7:36 PM, Jim Lux jim...@earthlink.net wrote: On 10/7/14, 10:32 AM, Magnus Danielson wrote: You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Yes, virtually all of them have a load input of some form (I'm familiar with the AD98xx and AD99xx ones, and they certainly do). What I'd really like, though is something at a slightly higher level of integration (for which I am willing to pay.. it's a time vs money thing). Does someone sell a DDS in a box with connectors, etc. I need a tuning range, for now, of around 3.1 to 3.4 GHz, so any of the 1 GHz DDSes can generate something that I could mix up with a 2.8-3 GHz LO (which I have), although I'd have to be careful about images. Or I can run the few hundred MHz out of the DDS into a doubler/tripler, then mix up. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Not a problem, I think I have a 10 in to 100 MHz out set of bricks from Wenzel (x5 and x2) from a previous project ___ 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] fast switching quiet synthesizer
On 10/7/14, 12:43 PM, Anders Wallin wrote: We've been using/testing an AD9912 eval-kit board. It can take 10MHz input and has an internal 66x PLL and VCO for a 660MHz DDS sample-clock (just out of spec actually, vco is min 700MHz if I read the datasheet correctly). Output looks like so: http://www.anderswallin.net/wp-content/uploads/2013/12/Fout100M_Span400M.bmp DDS output is 0 to 2-400MHz with a resolution of ~few uHz since it has a 48-bit tuning word. We're programming it with an arduino+eth-shield using modbus-ethernet. Changing frequency over ethernet takes about 60ms, but it could be much much faster directly over SPI if you know the desired frequencies beforehand and store them on the arduino. That's what we do now.. We actually use Teensy 3.1s, but same idea.. Store the table in the Teensy and use it to clock it out. And it's pretty easy to synchronize multiple Arduinos/Teensys to the sub microsecond level using interrupts But then there's the building boards and cables and putting it in a box. If I have to build 3 or 4 of these (or a half dozen) it's realistically a couple weeks work (which I'm paying a substantial sum for) by the time you find the box and connectors in the catalog, order it from Digikey/Mouser/Allied/Newark, get the holes drilled in it, mount the boards, etc. If I can just BUY something off the shelf that does it, that would be great. For instance, MiniCircuits (and others) have what are essentially a PLL-VCO in a box running off USB. But they a) don't have real fast settling time b) aren't easy to synchronize That's why I was thinking PTS or something else. even with the eval-boards there's a fair bit of building: multiple powersupplies, cables, enclosure, etc. And those AD parts run HOT, and they're temperature sensitive. I remember all sorts of hassles with the AD9854 on the early Flex-Radio units (a fan blowing on the part helps). ___ 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] fast switching quiet synthesizer
On 10/7/14, 1:19 PM, Don Latham wrote: I have two versions of the ADF4351 dds. One is the AD eval board, and the other the TPI synthesizer (http://www.rf-consultant.com/calibrated-signal-generator/) at $280 that might do the job. The latter device performs well. It will be as good as the 4351, I think. It has a programmable attenuator. A good price. Requires a Healthy! USB port. Don How fast does it settle? (it's a VCO-PLL, so the loop filter is probably the rate limiting step) How well can you synchronize the changes. USB is no problem. ___ 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] fast switching quiet synthesizer
On 10/7/14, 4:43 PM, Bob Camp wrote: Hi The output spectrum of some DDS’s is pretty rich. You may find that a 1 GHz DDS can be filtered to operate directly over the 3.1 to 3.4 GHz. Oh, clever idea.. Yes.. there is substantial harmonic content, and one could easily arrange to have more. And I've got boxes full of bandpass filters. ___ 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] fast switching quiet synthesizer
Jim, Bob Yarbrough's built units do 50 to 4400MHz, +10dBm and input for external 10MHz ref signals, though has an internal 10MHz TCXO. It sounds worth a try if it can be programmed to step fast enough, min step size is 1kHz (from memory). Alan G3NYK - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Wednesday, October 08, 2014 12:36 AM Subject: Re: [time-nuts] fast switching quiet synthesizer On 10/7/14, 10:32 AM, Magnus Danielson wrote: You should be able to use DDS test-boards and by timing your last write, you should be able to time the frequency jump. The STEL-1173 takes 6 bytes, but writing the last one latches all 6 bytes over to a single 48 bit word. I expect that other DDSes have the same distinct transfer-phase if you only look in the datasheet for the details. Yes, virtually all of them have a load input of some form (I'm familiar with the AD98xx and AD99xx ones, and they certainly do). What I'd really like, though is something at a slightly higher level of integration (for which I am willing to pay.. it's a time vs money thing). Does someone sell a DDS in a box with connectors, etc. I need a tuning range, for now, of around 3.1 to 3.4 GHz, so any of the 1 GHz DDSes can generate something that I could mix up with a 2.8-3 GHz LO (which I have), although I'd have to be careful about images. Or I can run the few hundred MHz out of the DDS into a doubler/tripler, then mix up. Some of the modern DDSes can take 10 MHz directly and step it up internally before hitting the DDS core, but it may be that you need to synthesize a higher clock from the 10 MHz first. Not a problem, I think I have a 10 in to 100 MHz out set of bricks from Wenzel (x5 and x2) from a previous project ___ 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] fast switching quiet synthesizer
Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. Aeroflex (www.aeroflex.com/ASCS) do 250ns settling time synthesisers. Bruce On October 7, 2014 at 7:52 PM Jim Lux jim...@earthlink.net wrote: On 10/7/14, 1:19 PM, Don Latham wrote: I have two versions of the ADF4351 dds. One is the AD eval board, and the other the TPI synthesizer (http://www.rf-consultant.com/calibrated-signal-generator/) at $280 that might do the job. The latter device performs well. It will be as good as the 4351, I think. It has a programmable attenuator. A good price. Requires a Healthy! USB port. Don How fast does it settle? (it's a VCO-PLL, so the loop filter is probably the rate limiting step) How well can you synchronize the changes. USB is no problem. ___ 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] fast switching quiet synthesizer
http://gmcatalog.kratosepd.com/index.cfm?act=prodsforgroupgrp=45 http://ams.aeroflex.com/ASCS/micro-ASCS-prods-synthesizers.cfm are the relevant webpages Bruce On October 7, 2014 at 11:06 PM br...@ko4bb.com br...@ko4bb.com wrote: Kratos (www.kratosepd.com) do fast switching synthesiser subsystems that can be locked to a reference.. Aeroflex (www.aeroflex.com/ASCS) do 250ns settling time synthesisers. Bruce On October 7, 2014 at 7:52 PM Jim Lux jim...@earthlink.net wrote: On 10/7/14, 1:19 PM, Don Latham wrote: I have two versions of the ADF4351 dds. One is the AD eval board, and the other the TPI synthesizer (http://www.rf-consultant.com/calibrated-signal-generator/) at $280 that might do the job. The latter device performs well. It will be as good as the 4351, I think. It has a programmable attenuator. A good price. Requires a Healthy! USB port. Don How fast does it settle? (it's a VCO-PLL, so the loop filter is probably the rate limiting step) How well can you synchronize the changes. USB is no problem. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] fast switching quiet synthesizer
On 10/7/14, 2:26 PM, Poul-Henning Kamp wrote: In message 20141007200046.02aa9406...@ip-64-139-1-69.sjc.megapath.net, Hal Mu rray writes: Timing on Ethernet is as good as RS-232 if you have a point to point link rather than a huge network full of crappy software. That is a truth with an almost uncountable number of footnotes... If we're only talking about timing in 99% of the cases, then yes, but that last one percent will make you tear your hair out. We did 20 microsecond jitter on 10GE for the ESO ELT adaptive optics prototype, and that was seriously pushing things near the edge. Five microseconds is trivially possible with a good $20 RS232 cable. Yes indeed.. And in my case, I have (or can make) a sync line, so I'd only trust USB/Ethernet to load the number and want to have a hardware execute now ___ 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.
