Re: [time-nuts] Sysclock source for AD9912
Anders You can set the overall PLL divider to any even value between 4 and 66 as there is a fixed /2 prescaler preceding the programmable divider, so with a 20MHz reference (from a 10MHz source) set the overall divider to 50 to give 1GHz - not sure if you set N to 50 or 25 in the Eval. software, but it's easy to do. regards Grant Anders wrote :- Thanks for all replies so far! It looks like I will play around with the evaluation board some more, and see if I can get the on-chip PLL to behave better. The settings with 2x edge-detector and 60x PLL were the only ones I could find where the output frequency setting in the software corresponded to the actual output frequency - hence I tested only with 10MHz x120 = 1200 MHz sysclock. I have asked about this on the AD forum, but no replies yet. If that doesn't work the suggested ADF4351 (or similar) evaluation board looks like the most straightforward option. thanks, Anders ___ 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] sysclock source for AD9912 DDS?
Anders I've used the AD9912 Eval board with great success - spurs with the on-chip clock multiplier were -60dBc, IIRC, maybe better. My guess is that you are pushing the on-chip VCO too high - do you really need a 1200MHz system clock? The AD9912 is only specified for a sys. clock of 1000MHz, and the on-chip VCO is also only specified to 1000MHz - yes, I know that the Eval software allows other values, but the VCO actually has quite a narrow frequency range (10%) in order to improve phase noise, and uses switchable on-chip inductors to select the correct output frequency range, the highest being 900-1000MHz. I'd be surprised if it locks at 1200MHz. First thing is to try a 1000MHz clock. regards Grant Hodgson From: Anders Wallin anders.e.e.wal...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] sysclock source for AD9912 DDS? I've tested the AD9912 evaluation board: http://www.anderswallin.net/wp-content/uploads/2013/12/dds_test_2013-12-30.png I want to use it with a 10MHz external input clock, but it looks like the on-board PLL that generates a 1200MHz sample clock from my input isn't that great, since I get strong side-bands on the output that are only 18-20 dB down from the fundamental. So it looks like I need to supply a clean 800-1000MHz clock to the DDS to get a clean output. Any ideas/suggestions for generating this from a 10 MHz sine? Driving the DDS system clock from an expensive RF generator (e.g. HP 8648A) would be possible but I'd prefer a PLL from 10MHz if it's doable simply/cheaply. Anders ___ 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] GPS antenna??
Alan As has already been stated by others, if the purpose of the GPS signal is for a GPSDO, then putting an active patch next to a SW facing window should work fine. No need to re-radiate. You only need to receive 1 satellite in order to get a timing signal - more satellites will give better (lower) jitter/ADEV, but if you just want an accurate frequency source for a counter or signal generator then the setup you describe should be fine. If that's the case, then it might be worth taking a Rubidium source as a higher-performance back-up than the GPSDO in holdover, although some GPSDOs are more equal than others in holdover performance. regards Grant Quoting time-nuts-requ...@febo.com: Hi all an interesting problem you may have encountered, I want to use a GPS frequency standard inside a building with no opening windows (opening windows are known as air conditioning in the UK :-)) ) This is part of a two day amateur microwave conference so we should have the expertise. I intend to try and pass the signal through a a double glazed glass window unit (hopefully not metalised) using a couple of patch antennas. The outer GPS antenna is active so will need a 5v supply via an inserter. Inner patch active, outer patch passive to avoid problems of feedback. Main antenna can be shielded from the coupling either physically or with a slab of absorber. Has anyone tried this? does it work?.any gotchas? Thanks Alan G3NYK ___ 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] 40MHz source
Dave I think you're going down the right road with the Chris Bartram transceiver. My suggestion for a 40MHz source would be to take a 10MHz source and feed it into two successive doublers, with a bit of inter-stage and post-stage buffering and filtering. Frequency doublers can be very simple indeed - as simple as a full-wave rectifier. It's the sort of thing that somebody in the local radio club might be interested in building, even if they are afraid of the 'scary' microwave stuff. Lot's of possibilities for experimentation there. As for a 10MHz source - I'd be tempted to go for either a good quality OCXO, or maybe a GPSDO such as the Trimble Thunderbolt (which has a fairly good 10MHz OCXO inside it). Many Rubidium sources are designed for medium-long term stability, at the expense of close-in phase noise, and that might be a problem in this application, as the 10MHz oscillators in many rubidium sources don't have as low phase noise as the 10MHz oscillators in the good GPSDOs. A good quality 10MHz frequency standard will also have other uses in the lab, of course. To answer Jim's question - 'inside the box' is an LTC6946-3 integrated Frac-N PLL/VCO with an o/p at 5GHz, then feeding into a sub-harmonic mixer to get to 10GHz. The PLL uses a 40MHz reference, which I believe is also the PLL comparison frequency. I think that the supplier might be reluctant to change the software to use a lower comparison frequency, but I haven't asked. The loop bandwidth of the PLL is somewhere in the 10kHz-20kHz range, so any close-in phase noise from the reference will get multiplied up to the final frequency, hence the need for a reference with good phase noise. regards Grant Subject: [time-nuts] Are there any rubidiums programmahttps://mail.google.com/mail/?shva=1#inboxble to 40 MHz? I'm possibly looking for a 40 MHz source and I know some of the rubidiums are programmable. But can any of the affordable ones be programmed to work at 40.0 MHz? I was looking for a source to drive this 144 MHz - 10 GHz transceiver. http://www.chris-bartram.co.uk/products.html The TCXO oscillator is off the board and a separate item, but costs ?40 and then one ideally wants to lock that to a more precise source. The oscillator will lock to an external 10 MHz source, but then one needs to buy both a 10 MHz rubidium as well as this 40 MHz TCXO. Hence I was wondering if there was a cheaper more compact solution, which just used a rubidium, and dispensed with a TCXO. Dave ___ 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] GPS at 60,000 feet
GPS has already flown in space several times; one of the well-publicized occurrences is when NASA sponsored an experiment to put a 6-channel Trimble receiver on the ill-fated AO-40 amateur radio satellite which launched in 2000. This satellite had a highly elliptical orbit, with perigee of 1000km and apogee of 6 km - well outside the GPS constellation. The GPS experiment was one of the first experiments to be tested on this satellite and some useful results were obtained before the satellite was lost due to technical failures in 2004. The results of the experiment have been published :- ftp://goes.gsfc.nasa.gov/pub/chesters/goesref/Moreau_GPS.pdf and http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030025378_2003025844.pdf Just google AO-40 GPS for more information. regards Grant On 01/02/2013 14:16, time-nuts-requ...@febo.com wrote: Message: 6 Date: Fri, 01 Feb 2013 06:14:04 -0800 From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Subject: Re: [time-nuts] GPS at 60,000 feet Message-ID: 510bcdac.8080...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed On 1/31/13 1:09 PM, Chris Albertson wrote: I know for sure my handheld Garmin works at 27000 feet, at 530mph... ...I was actually surprised it worked up there. It made me wonder what the actual limits are. What are the limits of your hand held unit or what are the limits of GPS in general. I think GPS works as long as you are under the orbit of the satellites. The company I used to work for placed GPS on some low orbit spacecraft, so say roughly 200 miles up and 18,000 mph but I'd guess most hand held units would not work in those conditions GPS will even (maybe) work at the Moon: with a gain antenna pointed back at earth.. you're looking at the satellites on the opposite side of the earth radiating around the limb. I don't know that anyone has actually tried it but it's certainly been analyzed to death. The potential problem with a handheld GPS in space (depending on where you are) would be whether you can keep track of the constellation and acquire new s/v's fast enough with lots o'Doppler. You already have to deal with the Doppler from the S/Vs buzzing around at 3-4 km/sec. Whether your receiver can handle the extra 7 km/sec Doppler in LEO is a good question. 7 km/sec is about 20 ppm, and I suspect that the receiver can already deal with that much change in the oscillator frequency. It might be doppler rate that it would have a hard time with (because the designer cranked down on the loop bandwidth for noise reasons) What are those folks flying GPS on CubeSats using? ___ 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] Is there any way to use a TIC to measure time of reflection on a PCB?
Dave Couple of thoughts here :- 1) A 'real' TDR measurement would require a pulse generator with a fast rise/fall time. The faster the rise/fall, the better. A directional coupler could be used to separate the forward and reflected signals, or you may be able to get away with a 3dB splitter and use the forward pulse to start the TIC and the reflected pulse to stop it. However - this will only give you a measurement of the propagation time of the pulse - using the VNA with a short at the end of the microstrip (as has already been described) would give a much better result. So yes, you could use a TIC, but you would need a pulse generator and you wouldn't have a better measurement than that already. Actually, a fast 'scope would be better than a TIC as you would be able to see the shape of the reflected pulse, which is somewhat more useful than a simple time measurement. 2) Given that the student doesn't have the TDR option on his VNA, it would be possible to simulate this using Matlab, Mathcad or one of the other analysis packages which are now freely available. The formatted data (in the frequency domain) from the VNA can be read via GPIB, inverse FFT'ed, time-gated and FFT'ed back into the frequency domain. Excellent learning task for a keen student. regards Grant ___ 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] Thermal noise contribution to phase noise
Joe Nobody is suggesting that KTB noise is revised. Bruce's original post quoted two articles that state that the thermal contribution to the phase noise floor of a carrier signal is -177dBm/Hz, not -174dBm/Hz. These papers also state that there is an equal contribution of amplitude noise which also equals -177dBm/Hz. So the total thermal noise floor of a carrier signal is -174dBm/Hz - half of which contributes to amplitude noise, half of which contributes to phase noise. The quoted articles go some way to demonstrating that by both theory and measurement. regards Grant -- Message: 4 Date: Fri, 18 Jan 2013 23:52:37 -0500 From: Joe Leikhim jleik...@leikhim.com To: time-nuts@febo.com Subject: Re: [time-nuts] Thermal noise contribution to phase noise Message-ID: 50fa2695.1030...@leikhim.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed I have just sent off an e-mail to David Howe of NIST Metrology requesting clarification about this assertion that KTB is revised -3dB. ___ 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] 5120A and PM signal
Filip What exactly are you trying to measure? A phase-modulated carrier will have an infinite number of sidebands spaced at the modulating frequency, the amplitude of the sidebands gradually reducing away from the carrier. The amplitude of the 1st pair of sidebands (closest to the carrier) is a function of the modulation index. In your case the 10MHz carrier signal has it's phase modulated by +/- 1 rad, at a rate of 10kHz. Note that the level of the carrier is itself a function of the modulation - i.e. as you change the level of the peak deviation, the level of the carrier will change. With 1 rad deviation, the carrier will be approx. 2.3dB down compared to with no modulation. So, if you want to measure the phase noise of the 2024, then you should turn off the modulation. Are you getting confused about the dBc/Hz measurement? 'dBc' means 'dB relative to the carrier' - that's why it's called dBc. dBc/Hz is usually used for noise measurements only, and means the level of noise, relative to the un-modulated carrier (in dB), if measured in a 1Hz bandwidth, at a given offset from the carrier. The level of modulation sidebands is independent of measurement bandwidth. I may have missed something here - please could you give more details of what you are trying to do? regards Grant Date: Mon, 14 Jan 2013 11:35:02 +0100 From: Filip Amator filip.ama...@gmail.com To: time-nuts@febo.com Subject: [time-nuts] 5120A and PM singal Message-ID: cabztljcz+vht+ehijzgm0uky_lio9yzphogxngmg7yap4rt...@mail.gmail.com Content-Type: text/plain; charset=ISO-8859-1 Hello, I made a simple measurement using Symmetricon 5120A phase noise measurement set and a Marconi 2024 signal generator and I don't understand the results. I measured the phase noise of 10 MHz signal with 1 Rad phase modulation at 10 kHz, and I got from mesurement peak at 10 kHz with level about -26dBc/Hz. According to the current definition of dBc/Hz, the value of -26dBc/Hz should be considered as a -26dB of modulation relative to 1 Rad. But I would expect that the peak level will be at 0 dBc at 10 kHz. Does anyone knows how to explain this difference? Filip Ozimek -- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 102, Issue 51 ** ___ 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] Orbital time-delayed angular momentum
If the signal is delayed in time by the dish, then there will be no phase coherency, and it is the phase coherent properties of a parababoid that make it the most commonly used type of reflector for microwave signals. A direct analogy between optical signals propogating in a fiber and RF signals propogating in free space is not possible - the best analogy would be to compare light in a fibre with RF in a circular waveguide - which somwehat limits the applications of orbital angular momentum for RF/microwave systems. regards Grant From: Michael Baker mp...@clanbaker.org To: time-nuts@febo.com Subject: Re: [time-nuts] Orbital time-delayed angular momentum phasing???!! Message-ID: 5008c114.2090...@clanbaker.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Time-nutters-- Didier Juges asked: What does that do to the focussing properties of the dish? I have seen several descriptions of how the dish needs to be shaped in order to develop the orbital time-delayed angular momentum signal and still achieve an integral focus point. I am not sure that I can describe it, but as I understand it, the dish is not just split and bent into a cork-screw, but that the surface of the dish is also continuously shaped so as to provide a good focus It is just that the signal striking parts of the dish which are increasingly displaced along the axis of the bore-sight are time delayed more or less with respect to other surfaces of the dish. The only way I can see for this to work is for the dish surface to deviate from a true parabolic shape incrementally as each particular area is displaced closer or further away from the focal point. It is a little hard to visualize and a lot harder to find the right words to adequately describe! Mike Baker --- ___ 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] HP 53310A modulation domain analyzer
Jose As with most things, it depends. The 53310A was designed and marketed at the RF design community where there was a need to be able to display parameters such as settling time of PLLs and to display frequency-based modulation modes in the time domain. To this end, the 53310A is a superb instrument. It performs these functions by acting as a time interval counter, but has the rather interesting feature of a very large display, combined with X and Y markers. It can be used as a stand-alone TIC - I'm not sure how it performs against other, more popular TICs, such as the SR620, HP5370, CNT-90 etc. etc. From memory the single-shot resolution is about an order of magnitude worse than the 5370 - that may, or may not, be relevant to you. The 53310A is not generally regarded as an easy instrument to use, certainly by RF engineers familiar with 'classic' user interfaces such as on HP spectrum and network analysers. However, the 53310A has a very useful Auto Scale feature, which for repetitive waveforms tends to work very well IMHO - simply connect the signal to be analysed, and the 53310A works out X and Y scaling factors and DC offset/trigger levels. From that point it is easy to apply markers and zoom functions, and otherwise tweak the parameters that were auto-set. The one thing that the 53310A won't do as-is, is display ADEV or related parameters - to do this you would need to download measured data and post-process using a PC, just as with most other TICs. I've never had to use histograms, std dev etc., but my use has been primarily for PLL measurements. Option 31 is highly desirable and well worth paying a bit extra for. Nice instrument, bit quirky to use. regards Grant Does anyone use an HP 53310A modulation domain analyzer (it is like an oscilloscope for frequency - displays frequency in Y and time in X, also does histograms, stdev, etc.) What are gotchas, drawbacks and advantages using it as a counter, stability measurements instead of a simple counter? It certainly is a nice tool for rf debug of sweepers, plls, etc. Ebay has a nice one, with 2.5GHz option 031 for 750 or best offer. -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Phase noise measurement (was - no subject)
Mark You've come to the right place - well, that is if you want to devote a significant amount of your life in the pursuit of ever-more accurate time and frequency measurements If you've only got one source then you need to use the frequency discriminator method (aka delay line method) of phase noise measurement. Basically you take the output of the source, split it in two, delay one of the signals, re-combine the two and then measure the resultant signal on a base-band spectrum analyser. There are loads of references to this on the web, which describe the method in more detail, including :- The Art of phase noise measurement - Dieter Scherer and HP Application Note AN270-2 both available from John Miles web site www.thegleam.com/ke5fx/gpib/pn.htm The references at the end of these articles, especially the HP ones, are particularly useful. The operating manual for the HP 11729B or 11729C Carrier Noise Test Set is also highly recommended. Yes, there's some maths, you need to understand the relationship between phase and frequency measurements, but you don't necessarily need ALL the theory that most of the papers give - don't give up just because of a few differential equations :) The limitation of the frequency discriminator method is that the noise floor of the measurement system is often worse than the DUT, especially if your DUT is very good, and it's even worse if you're trying to measure close-in noise. The Sherer article gives a good graph illustrating this. If you're trying to measure the phase noise of the oscillator inside a Tbolt then I don't think that a frequency discriminator will be sensitive enough, although I might be wrong. Despite what you said, you might want to consider buying an HP 10811 oscillator or similar which you could use in a phase detector measurement system which is likely to give superior results. Hope that helps regards Grant Mark wrote :- My new GPSDO leaves me with the question of how do I measure the phase noise of what is by far the best oscillator I own... without buying a better one to compare it to. That question is what brought me to time-nuts. I'm starting to read some papers on oscillator characterization that are collected together in a technical note from NIST that a co-worker pointed me towards, but some of them are giving me a math-induced headache. ___ 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] Low cost 6+ GHz Prescaler
Samuel Mini-Circuits ADCH-80A is very good and reasonably priced. Coilcraft also make a couple of very wideband chokes, but cheap - they are not. regards Grant PS : I'm looking for a source for RF chokes (MMIC Power stage) useable from DC to 8+ GHz. ___ 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] Low cost 6+ GHz Prescaler
I've used the RFMD NBB300/310 and they are excellent up to 14GHz. The NLB300 and NLB310 are in plastic packages and are somewhat cheaper than the NBBs, but have similar gain characteristics. They don't do strange things when compressed; I've driven them right up to the abs. max i/p power level and they survive, and I don't see any evidence of harmonic problems when driving a Hittite HMC364 /2 prescaler. They do exactly what it says on the datasheet. regards Grant Hodgson RFMD seems to produce some nice MMIC, for example the NBB-300 (http://www.rfmd.com/CS/Documents/Nbb-300.pdf), but I never used a RFMD amplifier. I used Agilent/Avago MMIC since years with great results, but always with frequencies no more than 3 GHz. Anyone have some experience with DC-8/12 GHz MMIC and which's the best ? ___ 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] Notes on the Driscoll VHF Overtone Crystal Oscillator
I've had several discussions with Chris Bartram about this and similar VHF oscillators. My understanding is that Chris' variant of this particular Driscoll osc. has been designed specifically for low close-in phase noise, and that is why the phase-shift network has a low-pass response (to try and reduce flicker noise) rather than the more common high-pass network. The NE688xx was chosen for the active devices due to it's claimed low flicker noise; the flicker noise parameters are actually specified on the datasheet for the NE68833 - which is quite unusual. The high Ft may not be desirable, but it seems that is the price to pay for low flicker noise. I've built a couple of oscillators similar to Chris Bartram's design at around 116MHz, albeit with the more conventional 'high-pass' phase shift network, and they seem to perform quite well - certainly no sign of spurious high frequency oscillation, but that may be a function of PCB layout. I'm not aware of anyone yet measuring the close-in phase noise of the Bartram variant of this oscillator, and that's really the only way to verify or otherwise that the new topology gives any advantage in terms of close-in phase noise, compared to a similar, low cost design using similar crystals. BTW I've tried simulating the phase noise of this oscillator using ADS, but wasn't able to get meaningful results from the simulator, and on this occasion Agilent technical support were not able to resole the issues either. Maybe Microwave Office or Ansoft Designer would yield better results, but I haven't tried them. (LT Spice is unable to simulate phase noise of oscillators). regards Grant An inductor in series with the 220 ohm emitter resistor will improve the phase noise floor. In theory, yes. But already with only 220 Ohms, Q3 will oscillate wildly at a few hundred MHz. The mechanism is this: Somewhat hot RF transistor NE688, collector at RF ground, emitter at high-ish impedance --- When you measure into the base, you see a negative resistance in series with a few pF. Using a transistor with a higher ft than necessary in an oscillator circuit isnt usually a good idea. ___ 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] DIY Frequency extension for HP Agilent
Samuel The NLB-300 and NBB-300 series MMICs from RFMD work very at up to 13GHz or so, certainly far better than a Mini-circuits ERA- whose gain will start to roll off at higher frequencies. Designing a broadband gain stage to work up to 12GHz+ may not be as easy as it seems. However it is made somewhat easier by the use of broadband chokes from the likes of Mini-Circuits, wideband inductors from Coilcraft and broadband capacitors from ATC - to name but three - there may be others as well. The 4-stage amplifier used by HP not only increases the signal level, it increases the slew rate (V/uSec) at lower frequencies. It's not just about signal level, it's about getting fast edges. The Hittite HMC363 /8 is a great IC, using static flip-flops, and will work all the way down to DC - IF the edges are fast enough. Ironically it may be the case that the lower frequency limit presents more of a challenge than the higher frequency limit. regards Grant ___ 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] Tbolt with Palisade
The antenna will be mounted outside with a reasonably clear view to the horizon from east-south-west. But there are times when there could be a lot of RF in the area - I design and build high power VHF and UHF PAs, amongst other things, and one of the attractions of the quality GPS antennas is the fact that they have a built in filter. But I might try one of the cheap patch antennas as a start with a view to upgrading at some point in the future. regards Grant Nigel Wrote :- - Hi Grant I think this really does depend on where you are, satellites in view etc, and what level of performance you're actually looking for. I have a few different timing antennas but have found these don't give very reliable reception indoors. Until I can get these mounted outdoors I have been having good results on various receivers using some small Trimble magnetic patch antennas, specified 26dB gain, attached to a steel plate and sitting on a shelf inside a one level timber framed house on the west coast of Scotland. These came via a buy it now from the usual place at $21 for 10 about a year ago. Driving a pair of Thunderbolts with these and comparing them with an HP 53132A counter, either one as reference and the other as input, once locked I see variations of just a few places around zero in the 10th decimal place. I have used this test on any two units selected from four with consistent results. Not a very scientific test perhaps, and nothing else measured, but as regards frequency at least I don't think they're suffering too much from their lesser antennas:-) regards Nigel GM8PZR -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Tbolt with Palisade?
Robert Thanks, looks like the hassle factor is greater than the fun factor on this one :( Guess I'll have to start a search for an HP58532A, VIC-100, Vaisala or similar. I don't think a cheapy £4 patch antenna will give the same performance. regards Grant Hi Grant, Keep the Palisade as it is. It's got a useful 1 PPS output. Also it's almost impossible to open the case without destroying it. The two halves are epoxyed together with a very good joint geometry! There is no obvious way to get to the antenna output. If you want to hack something, have a look for one of the Vaisalla GPS radiosondes. They have a nice Bi-Helix antenna, LNA and filter. But even a simple patch on a ground plane will do. Robert G8RPI. ___ 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] Tbolt with Palisade?
Does anybody know how difficult it would be to use just the antenna + LNA part of a Trimble Palisade? Have Tbolt but no antenna. I can get a Palisade for much less than a proper GPS antenna. Coax length would be about 20 feet, connected to the output of the Palisade's LNA (or output filter if fitted). Only possible problem I envisage is that the Palisade LNA will probably have less gain than say a 58532A. However, the latter is designed for long cable runs; I'm guessing that this unusual arrangement might work with a fairly short cable run. Powering the Palisade LNA shouldn't be too difficult me thinks. regards Grant ___ 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] Close-in phase noise question...
Brian Thanks for the details. There are a number of problems with crystal filters. A crystal filter will have a finite bandwidth, and at offsets less than half the bandwidth the filter won't have a significant effect on the phase noise. For example the 40MHz xtal filter used in the 8662A has a bandwidth of 6kHz (according to the service manual), so phase noise at less than 3kHz offset will not be affected. For your application you would need a filter with a very narrow bandwidth indeed - maybe 50Hz or so. Ignoring the manufacturing issues of such a device, there could be problems with temperature sensitivity and microphony. These problems could of course be overcome, but I'm not convinced that a crystal filter would give an overall benefit in this application, given that the primary goal is to achieve leading-edge close in phase noise. The MSA1105 has better phase noise than I thought, but I'd still be tempted to change one or both of the passive doubler/buffer stages to an active doubler, if the figures for the NIST active doubler are correct. regards Grant ___ 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] Close-in phase noise question...
Brian Could you give some more details? I think alternative solutions to MMICs at 5 and 10MHz would give much lower phase noise. Bruce's web pages have a number of designs that will get the 5MHz reference up to 20MHz in 2 stages :- http://www.ko4bb.com/~bruce/FrequencyMultipliers.html Another approach would be to use op-amps instead of MMICs, op-amps with a low flicker corner frequency should give lower close in noise than a MMIC, but probably won't be as good as a discrete solution. regards Grant Looking for comment here... The background: I'm working on a sub mm-wave LO chain for a ham radio application. While chasing issues of close-in phase (ie: within 1KHz of RF carrier) by peeling the layers of the onion, I'm starting to question the performance of the MMICs that are used as buffers and amps following my Wenzel reference OCXOs. Question(s): Should any MMIC be allowed to be driven close to compression or into compression when striving for best close-in noise? I know and have seen the NF of a MMIC degrade while in compression, but my target right now is close-in noise rather than broadband noise. My design, in summary, takes 5MHz up to 630GHz via several multipliers and PLL stages. -Brian ___ 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] DMTD mixer question
Jim Figures such as -200dBc/Hz probably relate to the phase noise figure of merit which some PLL suppliers like Nat. Semi, Hittite and AD use to compare various PLL offerings. These figures are normalised to a 1Hz comparison frequency and unity division ratio; to get a prediction of PLL phase noise within the loop bandwidth you need to scale for both comparison frequency and division ratio. This FOM is somewhat crude, as it doesn't take into account flicker noise, amongst other things, and loses accuracy with very high comparison frequencies. Banerjee goes into more detail about this subject. regards Grant --snip-- I seem to recall seeing a number like -190dBc/Hz or -200dBc/Hz for these hot stuff PFDs, but I can't recall where, maybe Banerjee's PLL book? --snip-- ___ 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] US Shipping Was huntron tracker advice
There are companies that provide a 'real' USA mail address and then forward the items on, overseas. Google 'US address' and 'USA address'. regards Grant ___ 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] 53310A help
Does anybody know how to use the signal source that comes with the HP 53310A Modulation Domain Analyser? The MDA is fine, but I don't have a manual for the signal source, and there seems to be nothing coming out of it - and yes, I checked the battery. There's no mention of how to use the signal source in the 53310A manual. regards Grant Hodgson ___ 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] Low phase noise digital divider (in 600MHz to10MHz area)
Anders One option is to use just the programmable divider part of a PLL IC, such as those from National Semiconductors or Analog Devices. Or, use a Hittite HMC394 programmable counter preceded by a fast /2 flip flop. The PLLs will need serial programming via a micro-controller or other logic device; the HMC394 uses parallel programming so is easier to implement. Neither the PLLs nor the HMC394 counter need external edge conditioning - they will work with sine wave inputs. These solutions won't give you as good a phase noise performance as a regenerative divider, but if you want something that you can just plug together then they will work for relatively little effort. And you don't need to worry about -ve supply voltages which some ECL devices need. regards Grant From: Anders Time [EMAIL PROTECTED] Subject: [time-nuts] Low phase noise digital divider (in 600MHz to10MHz area) To: time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1 Have been locking around for a good article on how to design a good Low phase noise digital divider(in 600MHz to 10MHz area), but the have not found any good literature. Today most people talk about regenerative dividers, but are a rather complex subject. Does anyone have experience in what logic family that have the lowest noise TTL, AC, HC, F etc? What is the upper limit for ECL diviers? My first idea was to use ECL to divide down to 100MHz area and then to use lower noise TTL to go down to 10MHz. What about edge-conditioning circuit at divider input? Have seen people talk about it, but no info what it does? Thanks Anders ___ 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] Spec An for phase noise measurements
Matt It depends on what you want to measure. If all you want to do is measure the relatively close-in phase noise of (say) a single-loop PLL, then an 8560 is fine - I know, because that's what I used for some time. But if you want to measure the noise floor of a VCO, PLL or other source then even the best spec. an. just does not have enough dynamic range, so other techniques have to be employed, such as the down-conversion techniques that have been discussed here recently. There's a circuit on the Wenzel website for a suitable PLL/LNA that will do most of the downconversion, just add a suitable mixer and off you go. I was seriously looking at building one until an 11729B popped up for a price I couldn't refuse. The only problem with building one is the time - your choice as to whether you want to build/buy. And it also depends on how close to the carrier you want to get - most 8590 series analysers go down to 9kHz, if you down-converted and want to get closer than that then you will indeed need another analyser. There is an option on the 8560s that take the lower frequency limit down to 30Hz, which is close enough for most applications. Beware the options on the 8560 - option 103 replaces the nice OCXO with a cheaper TCXO; the stability and accuracy with opt 103 should be fine for most uses, but due to the poorer stability of the TCXO, you lose the 1Hz Resolution bandwidth which may or may not be a problem. Just check exactly what options you are getting in advance. However, option 103 was cheaper, which tipped the balance for me; I can use an external 10MHz reference if I want greater stability and accuracy, but I still can't get the 1Hz RBW ! Also check the frequency range if you want to go above 22GHz - the 8563E will definitely go to 26.5GHz; some, but not all, 8653As stop at 22GHz. I love the 8560s, they are an order of magnitude better than the 8590s for serious RF work. regards Grant Matt wrote :- Message: 1 Date: Mon, 21 Jan 2008 11:20:03 -0800 From: Matt Ettus [EMAIL PROTECTED] Subject: [time-nuts] Spec An for phase noise measurements To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=ISO-8859-1 I am considering getting a new spectrum analyzer so I can make better phase noise measurements than with my 8596E. I've looked at the 8566B and the 8562 and 8563 since I need coverage to at least 6 GHz. The 8566 is huge and ancient, though, so I think I'm leaning away from that one. Anybody have other suggestions? Some of the Advantest units seem to be reasonably priced on ebay, but it is hard to figure out what their phase noise performance is. Also, what is the difference between the A, B, and E models on the 8560 series? The A models are much cheaper on ebay. Thanks, Matt ___ 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] xtal oscillator phase noise
Henk ten Pierick wrote: --snip-- It showed to be very difficult to come lower than what I have now. If can be the crystal. How can I decide? As an absolute minimum, you need to know the crystal dynamic (or motional) parameters - the crystal supplier should be able to provide these. If not, you can measure them on a network analyser whilst you look for another crystal supplier. Then you should be able to simulate the phase noise of the oscillator using a harmonic balance or similar method as used in Microwave Office, Genesys, ADS, Ansoft Desginer, QUCS etc. Failing that, a small-signal (linear) open-loop analysis would at least give an estimate of the loaded Q, which can be used to predict phase noise - but ignoring flicker noise. Some SPICE-based simulators might be able to help. --snip-- I used the BC375 for the low Rbb' and assume that the noise corner must be low as a result of that. Is this not true? There are many different types of noise - the base bulk resistance of a transistor contributes to shot noise, which is close to being 'white' - i.e. equal magnitude /Hz at all frequencies. This does not have a significant effect on phase noise at offsets close to the carrier, and at 30Hz offset the flicker noise dominates. Flicker noise is not 'white' noise - flicker noise increases at a rate of 1/f, or 10dB/decade as the offset frequency is reduced, and simply choosing a transistor with low Rbb' is not sufficient - the noise mechanisms are different. For an 11MHz oscillator I would use 2N5179s as advocated by Rick for both the sustaining amplifier and the limiter - this is a very popular transistor for oscillators in this frequency range. I'd be surprised if the BC375 generated less noise than the 2N5179. This would mean changing the circuit topology to use an NPN transistor instead of the BF450 which is PNP. At 11MHz, most crystal oscillators use parallel resonant crystals, although some are series resonant, such as the excellent Driscoll oscillator which is capable of the performance you desire with a suitable crystal. I was aware that most lower frequency circuits are parallel resonant. I used series in class A because I thought is was better, it is easier to use the current though the xtal. Is there a fundamental difference between parallel ore series w.r.t performance? Not really, it's the circuit topology determines whether a parallel or series resonant crystal is used. Your circuit appears to be a variant of the Driscoll oscillator, which usually uses a series resonant crystal and is capable of exceptionally high performance, however there are a number of differences in your circuit, which I've never seen before, although I can't claim to be an expert oscillator designer. Circuit simulation is a good (no - essential) starting point, and would give you a good idea of the relative merits of the features of your circuit. --snip-- I do normally not have access to a FSUP but borrowed the instrument for two weeks. To my luck it has the B60 option and I used this of coarse. There must be a reason for my employer to buy this fantastic tool. Henk OK, but given that the noise level is currently way above the noise floor of the FSUP, using cross-correlation doesn't add anything - it just slows down the measurement. Cross-correlation would only be of benefit to reduce the noise floor of the instrument if/when the phase noise of the oscillator has been reduced enough to justify it - it can seriously slow down the measurement. regards Grant ___ 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] xtal oscillator phase noise
Henk Two things will dominate if you want such a low phase noise spec.:- the loaded Q of the oscillator circuit, and the flicker corner frequency of the sustaining amplifier transistor. To get a high loaded Q you need a crystal with a high unloaded Q - maybe 100 000 or more - this isn't difficult to achieve from a good crystal manufacturer, but you can't expect any old crystal to work. And the rest of the oscillator circuit should not load the crystal too much, otherwise the loaded Q, and thus phase noise, will suffer. Good crystal manufacturers will provide the necessary measurements of series resistance, motional inductance (or capacitance, or unloaded Q - doesn't matter which) and static capacitance. Lesser crystal manufacturers - don't. Also the flicker corner frequency of the transistor needs to be as low as possible. Generally speaking, at offsets below the flicker corner frequency you will get 30dB/decade, above the flicker corner frequency you should get 20dB/decade, or flat, depending on the level of the phase noise floor. If you can find a transistor with a lower corner frequency, the flicker noise will be reduced. In fact, this is one of the dominant parameters when choosing a transistor as an oscillator - any old transistor can be made to oscillate, but to do so with a low flicker corner frequency is not so easy, and the corner frequency is usually a function of bias current. At 11MHz, most crystal oscillators use parallel resonant crystals, although some are series resonant, such as the excellent Driscoll oscillator which is capable of the performance you desire with a suitable crystal. Then you have the added problem of the FSUP. It's a superb instrument, but it has it's limitations. The FSUP data sheet states a phase noise spec. of -130dBc at 10Hz offset for a 10MHz signal, which gives a resulting sensitivity of -127dBc - 3dB worse than what you are trying to achieve. You would need option B60 (cross correlation) to significantly reduce the effect of the internal source by (say) 15db or so. regards Grant Henk wrote :- Hello, Some questions on xtal oscillator phase noise. Attached the measurement result of my series resonant xtal oscillator. It is a class A, ibias 5 mA, Ixtal 1 mArms. Transistor selected for low Rbb' 20 Ohm, Ft 100MHz. Reference voltage 5V from an ADR445, filtered with 10uF folie cap. Phase noise target -130dBc at 10Hz. 1. Is series resonant better or easier to engineer than parallel resonant? 2. Where should I have 20 dB/decade and where 30 B/decade? 3. Some suggestions for the next 25dB? 4. Is there more to learn from the attached picture? regards, Henk ___ 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] Super Regulator links
Torex make some very nice low noise regulators; the XC6204 series has been around for some years now and appears to offer much lower noise levels than the 723 :- http://www.torex-europe.com/products/range/125 Click on 'Technical Diagrams' to see the noise plot of the 3V part - sub 1uV /rtHz at all frequencies above 100Hz. One has to assume that the noise specification for the uA723 is per rtHz, in which case the Torex part has lower noise. The uA723 has higher ripple rejection though. The Torex XC6204 is specifically intended for noise-critical applications such as oscillators, PLLs and the like - it's not really a general purpose regulator like the 723. Torex parts are available in the UK (and maybe elsewhere) from Farnell, other distributors also stock them. I suspect that lower noise regulators are now available. regards Grant John Miles wrotre :- What are some of your favorite low-noise regulators? When I made the remark about the uA723, I was specifically thinking of its performance compared to the LT1762. With Cref=5 uF, the uA723's output noise voltage is rated at 2.5 uV from 100 Hz to 10 kHz. The LT1762, which seems to be among Linear's quietest parts, is rated at 20 uV from 100 Hz to 100 kHz, with external bypassing that places most of the noise at lower frequencies. Snake oil or not, that's 18 dB less noise from the 723. There are various hacks like Wenzel's that can clean up after a noisy regulator, but if there are quieter fully-integrated solutions out there I'd like to hear about them. Posted back to the list in case there are other views on the subject... -- john, KE5FX ___ 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] Prologix 3478A
Chuck et al I connected my Prologx 3.12 to the 3478A, ran 7470.exe and the 3478A's TLK icon came on straight away, with the RMT icon coming on a few seconds later. Repeated it for good measure with the same result. 7470.exe reported an error saying that it was talking to unsupported device '0.43700E.00' or something similar so the Prologix was getting some data from the 3478A. Looks like the Prologix adapter is OK. regards Grant Hi Grant, It is an axiom of the GPIB world that if a device gets addressed, it will sit up at attention and wait for commands. The 3478A shows that it is waiting by lighting up a couple of annunciators on the bottom row of the LCD that you never see otherwise. All you have to do to test whether the Prologix can work with your 3478A is address it. So, if you change the 3478A's address to match your HP analyzer's, and then run John's program, you should see these annunciators light up. The 3478A won't do anything useful that way, but it will prove that it hears the Prologix, something mine can't do. -Chuck Harris Grant Hodgson wrote: Chuck I've got a Prologix 3.12 and a 3478A; I've only ever used the former with John Ms. s/w and HP analysers. I'll happily test it with the 3478A if you give me some simple instructions for a simple XP user. regards Grant ___ 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] Osc. Phase Noise Article
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY But watch out for the mistakes in some of the equations - e.g. the right hand side of eqn 2 is wrong, but eqn 3 is correct, and eqn 9 is wrong. Don't know if there are any other mistakes, but it's a good article so far - haven't finished reading it yet, I can only take so much trig. in one day. regards Grant Message: 3 Date: Tue, 25 Sep 2007 08:30:49 -0700 From: Had [EMAIL PROTECTED] Subject: [time-nuts] Osc. Phase Noise Article To: time-nuts-febo.com time-nuts@febo.com Message-ID: [EMAIL PROTECTED] Content-Type: text/plain; charset=us-ascii; format=flowed In the current (September) issue of the Microwave Journal there is a pretty comprehensive article Oscillator Phase Noise: Theory and Prediction. It may viewed on the Microwave Journal Web site at www.mwjournal.com. Page 178 for the print version. Best to all, Had ___ 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] Neat toys on eBay for PN measurement
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] John Don't know if you got an answer, but this is my understanding :- The 11729B needs to have an external 640MHz reference input for measurements above 1280MHz. The 11729C has a SAW-based 640MHz oscillator built-in, but it can take an external 640MHz reference signal if one is available, such as from the 8662A. The spec. for the 11729C internal 640MHz osc is not as good as that of the 8662A at offsets of up to about 20kHz or so, but at offsets above 50kHz the 11729C SAW is better than the 8662A's xtal osc. AFAIK, there is no physical difference between an 8662A with and without option 03. All this option does is mean that somebody has done an extra set of measurements on the 640MHz reference output to confirm that it did indeed meet the spec. There was also an option H40 which had an even lower noise 10MHz reference which reduced the phase noise at offsets up to about 100Hz by 8dB for both the main output and the 640MHz reference output. Also, the 640MHz reference input to the 11729 does not have to be phase locked - as long as it does not drift at a rate outside the 11729's PLL hold-in range then it will work. The 11729's PLL will pull the signal generator to compensate for drift in either of the two reference inputs (640MHz and/or external signal generator). I've got an 11729B, but no 8662A, so I've started working on the design of a very-low phase noise 640MHz source based on an 80MHz crystal osc. But until that's ready, I've still been able to make measurements below 1280MHz without the external reference input. The Racal 9087 is a suitable reference signal generator up to 1.3GHz, which can be phase locked, and at offsets greater than about 1kHz it actually has lower phase noise than the 8662A. Other low-noise generators are also avaialble... And for those that can't resist tinkering with the fine offerings from the HP labs, I've been wondering if it would be possible or practical to replace the internal Step-Recovery Diode comb generator in the 11729B/C with one of the Non-Linear Transmission Line comb generators from Picosecond Pulse Labs. PsPL are quoting a 15-20dB reduction in phase noise for their NTL comb generator compared to an SRD. Seems almost too good to be true; don't know how much they cost for one-offs but it would be interesting to see if it could be used to reduce the residual phase noise of the 11729. regards Grant John Miles wrote :- That's something I meant to ask you about, Rick, as a follow-up to an old Usenet post of yours from 1995. From looking over the block diagram in the 11729B-1 app note, it appears that there is no reason why you couldn't feed any sufficiently-clean 640 MHz signal in. Obviously, you want to drive it with the cleanest source you can find, but I don't see any other constraints. But some of the 8662As did not have the optional (003) specified SSB phase noise for rear-panel output feature, including mine. They all seem to have provided a 640 MHz output at an unused internal SMB jack, though. Is there something special about the reference multiplier section in an option-3 8662A that actually improves the noise level available at this jack? I'd already added a BNC jack to the rear panel to bring the 640 MHz clock out in anticipation of buying or building a downconverter, and I expect it will work OK with this 11729C, but I am not sure whether I should expect the fully-characterized option-3 noise performance, or something worse. Any thoughts on that? From your Usenet post I understand that there is supposed to be a feature that lets you turn the built-in 640 MHz SAW filter into an oscillator in case an 8662A isn't available, but I also understand that this is really only a utility/test function. If there's no way to phase-lock the resulting SAW oscillator, I can see why. -- john, KE5FX ___ 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] Neat toys on eBay for PN measurement
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] The 8662A derrives it's 640MHz o/p from a (very) good 10MHz crystal osc. which is then doubled 6 times and filtered at the 40MHz and 160MHz stages with crystal filters. The problem with using so many multipliers is that the noise floor increases at every doubler stage, which is why the filters are necessary to reduce the the noise floor down to something close to thermal. An alternative is to use a higher frequency crystal osc., such as 80MHz. I guess that this is what Wenzel would do for a 640MHz osc, as 160MHz crystals would probably be 7th overtone which have lower Q and therefore higher phase noise than 80MHz 5th OT xtals. That's the route that I'm exploring at the moment, and I think it should be possible to get close to the performance that Wenzer quote. A crystal filter at 160MHz would be a bounus, an inverted MESA xtal filter at 320MHz or a SAW filter at either 320MHz or 640MHz would be better still, but I think this would start to add serious $$$ for small quantities. An 80MHz crystal osc. would probably have worse phase noise very close-in (100Hz or less) but better far out and with a lower noise floor, compared to a 10MHz osc. But as I'm not testing radars, I'm not after the ultimate close-in performance, I'm more interested in the performance at 3kHz-1MHz. regards Grant John Miles wrote: Picosecond Pulse Labs quoted me $1,000 for one of the NLTL comb generators a couple of years ago. They are nice parts, no question about it, and substantially better than SRD multipliers. In quantity, they would be cheaper, since I was just asking them for a one-off price to some random guy with a credit card. However, the residual noise floor of the 11729x is still lower than its absolute spec when driven by an 8662A's 640 MHz output (see page 42 of 11729B-1). So unless you plan to use a quieter 640-MHz driver than an option-3 8662A, there seems little benefit in improving its comb generator. Likewise, the noise at the 8662A's main output still limits the floor of at least some microwave measurements with the 11729. That said, I am trying to get a price quote out of Wenzel for a 640 MHz ULN OCXO: http://www.wenzel.com/pdffiles1/Oscillators/ULN_130_to_650.pdf This is the only OTS source I can find that's substantially cleaner than the 'typical' figures quoted for the 8662A's 640-MHz output. It would sure be nice to install one of these as an an internal source in the 11729, and drive its electrical tuning line from the quadrature PLL. -- john, KE5FX ___ 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] Low noise frequency multiplication
Stephen It seems there are indeed many ways to kill a cat. More ways than you could imagine... IMHO, a 100MHz PLL is likely to give the best results, and is very easy to implement. A 100MHz crystal oscillator should give very low phase noise and spur levels; crystals are readily available and there are quite a few circuits around. Crystal oscillators running at 100MHz or so are widely used by radio hams for multiplication up to microwave frequencies so the phase noise and spur levels has to be low to start with, which a VCXO can achieve. Crystal oscillators can easily be disciplined with a varactor diode. Various PLL configuations exist to do this and the loop bandwidth is very narrow so the phase noise will not be degraded significantly by the PLL. There are other ways as well, but my vote would be for the VCXO as above. regards Grant ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] time-nuts Digest, Vol 29, Issue 86
Stephan --snip-- I prefer phase detectors which is more continous such as mixers, XOR or S-R style phase detectors. In this case the phase detector is purely digital so I guess the loop filter could also be a purely digital IIR filter (or something?) I guess the only limitation is the frequency at which the digital system could run. Going back through this thread, it seems you want to lock a 100MHz OCXO to a 10MHz reference, which is itself disciplined to PPS. By far the easiest solution would be to discipline the 100MHz OCXO directly to the PPS - this will have negligible impact on the OCXO's phase noise and is a simple, reliable method - the Luis Cupido design will work very well for example, and there are other designs. regards Grant ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Wikipedia Dual-modulus Prescaler item
Dunno if it's still relevant, but the Wikipedia article on dual-mode prescalers is confusing, to say the least. Here's a much better description, written by a master of explaining the complicated to the uninitiated in simple terms - Dean Banerjee :- http://www.national.com/AU/files/PLL_Building_Blocks.pdf regards Grant Hodgson ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
