Oscilloscope for fft functions - Page 1
Forum section: electronics / testgear

author: freebil
author_rank: Regular Contributor
timestamp: August 09, 2016, 05:12:42 am
content: Hello. I would like to buy an oscilloscope which will have a decent fft viewer. I read that ds1054z has poor fft functionality. So, siglent sds1000x is the next move?

author: scanlime
author_rank: Newbie
timestamp: August 09, 2016, 05:20:53 am
content: Not sure what your other scope requirements are, but I recently had a similar problem with my Rigol being useful for most things but somewhat lacking for FFTs and deeper captures. I recently bought the Analog Discovery 2, which had a surprisingly nice FFT. IMHO it isn't a replacement for a full bench scope, but if you mostly just need a better FFT occasionally, that may be worth looking into.

author: nugglix
author_rank: Regular Contributor
timestamp: August 09, 2016, 05:47:12 am
content: Hi!Have a look at that one:Compares a few scopes in terms of FFT.CheersEdit: And now I really need to go to work...

author: rf-loop
author_rank: Super Contributor
timestamp: August 09, 2016, 06:04:05 am
content: Quote from: freebil on August 09, 2016, 05:12:42 amIf you want Good FFT analyzer with oscilloscope functions also, it is not at all Rigol DS1000Z or Siglent SDS1000X.DS1000Z is entry level multipurpose toy what is not good in anything. But with its price it have lot of "things".SDS1000X is strong entry level oscilloscope (but only 2 channel + ext trig) with some totally unbeated oscilloscope functions in its price class.But if you want Good FFT, forget both, totally.All depends of course what specifications you have for FFT what you need. Define first exatly what you need, then look what equipment meet your needs. There is so many variables. Some one want good audio FFT with high resolution, fast speed and high dynamic range with very low base noise etc.. some may want good FFT for RF frequencies. In some audio cases perhaps some PC high quality sound card based solutions are quite good also.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: August 09, 2016, 06:21:31 am
content: Quote from: rf-loop on August 09, 2016, 06:04:05 amCompletely agree.QuoteSorry to reorder the quote, and emphasis from me. But, seriously?Edit: More emphasis on silly statements.

author: BravoV
author_rank: Super Contributor
timestamp: August 09, 2016, 06:54:21 am
content: Quote from: rf-loop on August 09, 2016, 06:04:05 amI think you better format the font with this kind of arrangement, much-much better.

author: rf-loop
author_rank: Super Contributor
timestamp: August 09, 2016, 07:25:33 am
content: Quote from: CustomEngineerer on August 09, 2016, 06:21:31 amSemi seriously.Rigol problem is high noise level, very poor sin(x)/x joke (explained here in forum several times and leads example to wrong levels). Trigger and delay time jitter quite high, possible origin partially from signal noise and partially poor clock aand perhaps also trigger position fine adjust iterpolation is poor. Slow UI. Poor user interface ergonomy including shared vertical control and small display. Poor intensity grading. Lack of true seqmented memory acguisition. Lack of always bacround working waveform history. (just some kind of quite slow frame recorder). Very unprofessional mask test what give very easy statistical random error in test result. (due to very different speed if mask test pass or fail). 1mV and 2mV/div are not true analog sensitivity.SDS1000Xmax 60kwfm/s average, max >400kwfm/s (quaranteed speed, not average or peak speed) in sequence (segmented memory)Full speed hardware based mask test.Always in backround continuous history recording up to 80000 last captured single waveforms. (stop and look what just previously happend)Down to 500uV/div full bandwidth true analog sensitivity low noise front end.Inputs 1Mohm / 50ohm.Separate vertical adjustments for channels.Sin(x)/x and line modes, both always draw trace via true raw sample points what are not flushed to toilet as Rigol do (starting from beginning with DS1052E, Rigol have this same joke where they flush out true data and supersede it with "fake nice draw using" (imho its betteer name is "smooth").I have used both. I have also purchased DS1000Z for one my project where need cheap scope standing alone collecting data including fact that if poor luck it can also damage. So I select this because it was cheap and have four channel. But, later I see it was wrong selection. All data nearly like from garbage generator due to noise and trig jitter.But, for many hobbyist, even if it is toy, it have lot of "things" and for many use - I did not say it is useless. If look how many features get with quite low price.... well, and if need cheap kitchen all in one multipurpose toy what can do tens of miracles but nothing well (we know these kitchen machines). This is like same, lot of things, it can do many things but nothing well. And many peoples buy.Toy is not here as synonym for unusable.

author: JPortici
author_rank: Super Contributor
timestamp: August 09, 2016, 07:58:40 am
content: What are you going to look at? what will the fft function be used for?you have to remember that most oscilloscopes use 8 bit ADC and every averaging/high res mode is actually software vodoo trying to guess what's going on between two LSBs, so the actual accuracy of the thing will be limited on a rigol just as it will be limited in a lecroy, keysight, R&SThis is an insteresting topichttps://www.eevblog.com/forum/testgear/fft-spectrum-analysis-reviewed/msg920781/

author: wraper
author_rank: Unknown
timestamp: August 09, 2016, 08:09:00 am
content: GW instek GDS-1000B series is the cheapest you can get with good FFT. BTW how it looks on the Dave's video is not how it will be with installed FFT app, it becomes separate FFT display, not together with waveform. So his complains about UI are not valid at current moment.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 09, 2016, 08:36:11 am
content: Quote from: JPortici on August 09, 2016, 07:58:40 amNot exactly. There's a big difference between the 'HiRes' (boxcar) modes used by most scopes vs ERES as used by LeCroy:http://teledynelecroy.com/doc/differences-between-eres-and-hiresIt's also far from "guessing", you do actually get a real increase in resolution.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 09, 2016, 09:31:46 am
content: Quote from: freebil on August 09, 2016, 05:12:42 amNo, not really. You have to understand that FFT is very processing intensive, probably amongst the most processing intensive applications on any modern scope. Neither Rigol nor Siglent1offer scopes that are powerful enough to do that properly.You didn't say what else you're looking for in a scope, so giving some recommendations is difficult. At the moment, the GW Instek GDS-1000B and GDS-2000E are the cheapest (and only) new entry-level scopes that offer decent FFT (1Mpts). Especially if you need more bandwidth I'd also consider some 2nd hand scopes (for example, my 600MHz Agilent Infiniium 8064A does FFT with up to 32Mpts).1Siglent also has the SDS3000 which is only sold in China and which was developed in co-operation with LeCroy (which sells it in the ROW as 'WaveSurfer 3000'), and this scope offers fast FFT up to 1Mpts.

author: Fungus
author_rank: Super Contributor
timestamp: August 09, 2016, 09:50:37 am
content: Quote from: freebil on August 09, 2016, 05:12:42 ama) Depending on when you read it, it might not be true any more (firmware update)b) Amuchbetter idea would be to get a spectrum analyzer. No entry level scope has what you'd call a "good' FFT viewer.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 09, 2016, 10:09:00 am
content: What about the PC software tool that was designed to give the Rigol scope "Spectrum Analyzer"-powers?http://hackaday.com/2012/10/10/giving-the-rygol-ds1052e-scope-a-spectrum-analyzer/Has anybody used this PC software tool?Note that this PC software tool was designed for the Rigol DS1052E.Is there also a version available for the Rigol DS1054Z?

author: nctnico
author_rank: Super Contributor
timestamp: August 09, 2016, 10:10:19 am
content: Quote from: wraper on August 09, 2016, 08:09:00 amIndeed. Currently GW Instek (GDS-1000B and GDS-2000E series) is king when it comes to FFT on an entry level oscilloscope. Peak search also allows you to show up to 10 frequency peaks in a list.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 09, 2016, 10:20:34 am
content: Can someone with a GW-Instek scope post a screenshot of this separate FFT display?

author: freebil
author_rank: Regular Contributor
timestamp: August 09, 2016, 12:03:24 pm
content: Thanks for the answers! Can a spectrum analyzer show voltage/time?

author: nctnico
author_rank: Super Contributor
timestamp: August 09, 2016, 01:51:40 pm
content: Quote from: freebil on August 09, 2016, 12:03:24 pmNot really although some can display the demodulated signal in the time domain. Tektronix has a series of MDO oscilloscopes (mixed domain oscilloscopes) which are both a spectrum analyser and oscilloscope in one device.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 09, 2016, 02:47:52 pm
content: Quote from: freebil on August 09, 2016, 12:03:24 pmSome SAs can show voltage or power over time (0Hz span), although its no replacement for a proper scope.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 03:09:00 pm
content: The R&S RTO has the best FFT I have seen so far in a scope in terms of usability and performance. It beats the even most modern Keysight scopes in terms of usability. I can post pics if some is interested. As expected, the RTO is not cheap.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 03:23:58 pm
content: here is pic of the 600MHz RTO 1004 in spectrum analysis mode.500MHz CW at the inputImportant note: in FFT mode you use it like a spectrum analyzer, meaning you will have a GUI that allows you to center freq, span, Res BW etc and the tome domain parameter like sampling rate etc are updated accordingly. Very convenient to use!Also, you may not care, but then RTO is one of the few scopes that retains the phase information of the FFT calculation. Many scopes throw the phase information away and only offer you the magnitude. As a result you can use the RTO for large dynamic range bode plot measurements plotting mag and phase response over freq.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 03:29:13 pm
content: attached a bode plot measured with the RTO and compared against network analyzer measurements E5061B

author: jjoonathan
author_rank: Frequent Contributor
timestamp: August 09, 2016, 03:34:57 pm
content: You beat me to the punch rfbroadband, I saw this thread yesterday and thought "I should link to info on the RTO to show what a non-toy fft looks like." I wish other vendors took the function half as seriously as R&S.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 03:45:10 pm
content: :-)

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 09, 2016, 04:21:55 pm
content: I don't see the point of the R&S RTO scope which costs much more than a Siglent spectrum analyzer that goes up to 3.2 GHz and a very decent digital oscilloscope together.It's for people who have too much money.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 04:51:40 pm
content: the combination of having a digital 16 bit MSO, a 4 channel scope and a SA in one box for cross domain analysis is a huge advantage.One can trigger in the frequency domain on masks and signals over a very large dynamic range, and then debug other related signals in the time domain and do decoding of signals on the 16 digital lines.I have a real high end spectrum analyzer next to the scope but the fact that you have a powerful FFT function and time domain analysis in one box is a huge advantage. I am using the built in SA of the scope more and more just because of the cross domain capability.And yes it not a scope that a hobbyist would purchase.

author: freebil
author_rank: Regular Contributor
timestamp: August 09, 2016, 05:55:36 pm
content: Does hantek dso5102p has better ftt than rigol ds1054z?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 09, 2016, 06:06:45 pm
content: Quote from: rfbroadband on August 09, 2016, 03:23:58 pmThat is nothing new, really. Even my old Agilent Infiniium 8000 comes with an 'SA' like interface (standard), and it has been a paid-for option (SPECTRUM) on LeCroy scopes since 2006. Like it is a paid-for option on your RTO (K18).QuoteAgain, that is nothing new. Pretty much every better high end scope has been doing phase for almost 20yrs now. My old 200Mhz WaveRunner LT could do that, and that scope came out in 1998. And again, my old Infiniium 8000 can do that, as pretty much every high-end scope I worked with that was made after 2000.The display representation looks nice, but I can't see anything really new here.Quote from: rfbroadband on August 09, 2016, 04:51:40 pmYou don't have a 16bit scope. You have an 8bit scope (8bit ADCs) with a 16bit software option for which R&S charges pretty much an arm and a leg, with all the associated limitations. It's not the same as a true 16bit scope, or even a true 12bit scope.Quote from: jjoonathan on August 09, 2016, 03:34:57 pmThey do. If you want to see some really sophisticated FFT then have a look at the Keysight Infiniium S.

author: rsjsouza
author_rank: Super Contributor
timestamp: August 09, 2016, 06:40:01 pm
content: Quote from: Wuerstchenhund on August 09, 2016, 06:06:45 pmI think he meant 16 digital inputs...

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 06:54:34 pm
content: the FFT option is free of charge with every RTO scope. The option K18 is an advanced Spectrum analysis option. The spectrum analysis is thus free in every standard config.I always find it difficult to review a product without having used it myself.I have used and owned various Tektronix, LeCroy, Agilent (Keysight) scopes over many years. When R&S did come out with the their first scope years ago, I have to admit I, did not even look at it. Once I got my hands on one and evaluated it I purchased one, immediately. At some point I gave a demo to a Keysight sales person and his silence (nope we can't do that, nope we can't do this) was priceless. He then arranged for Keysight to send a scope R&D/marketing guy from Colorado to visit my lab for feedback on their scopes. If I remember correctly, 80% of the > 1.5 hour session was spent on FFT and frequency domain measurements. He took lots of notes.Some technical marketing guy at R&S did his homework. It is the first scope where I use the FFT function on a regular basis, because a majority of the built scope FFT functions are indeed toy implementations.In summary, there a many fine scopes out there in the market. The FFT, SA analysis capability including measurement speed, dynamic range, FFT gating, noise floor etc.the RTO is outstanding. If someone is looking for a new scope for a work environment (not as a hobbyist due to cost) and wants frequency domain capability, I seriously suggest you at least evaluate the RTO.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 07:00:17 pm
content: rsjsouza,thank you. Certainly I meant 16 bits digital inputs for the MSO option.The HD option (that claims 16bit) is only a software option and it is not delivering 16bits. The HD option reduces the noise floor by ~9.5 dB, thus 1.5 ENOB. It is a useful option, but the marketing for the HD option is very misleading and I communicated that very clearly! to R&S.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 09, 2016, 07:13:34 pm
content: Quote from: rfbroadband on August 09, 2016, 06:54:34 pmThat's why the best way to evaluate a scope is to request a loaner for say a week so you can spend time with the scope yourself. Relying on that the sales droid knows how to operate and demo advanced functions can be pretty hit and miss, especially if it's a more sophisticated scope.QuoteGlad you like the RTO but none of the FFT implementations of other scopes in that class are "toy" implementations, and haven't been so for many years. If you as you said had LeCroy and Agilent/Keysight scopes before then you should have been aware that phase information is not thrown away, or that an SA like interface isn't something new, either.BTW, what's the max FFT size the RTO1000 can do? The R&S spec sheet doesn't seem to mention.QuoteThis, but I'd strongly suggest to also look at the Keysight Infiniium S. It's FFT is really good (and it can do up to 16 at the same time, vs only 4 with the RTO), and you get a true 10bit ADC on top of it.

author: rfbroadband
author_rank: Unknown
timestamp: August 09, 2016, 09:36:08 pm
content: sorry, I don't recall the max. FFT size.I looked at the Keysight Infiniium S for a few days a year ago. It has better jitter performance than the RTO, but the improved jitter was not that important to me.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 10, 2016, 05:10:38 am
content: Quote from: rfbroadband on August 09, 2016, 09:36:08 pmDoesn't the scope show how much memory it is using for FFT?QuoteIt's not just the lower jitter, it's better SFDR and SNR, faster ASICs, FFT with very large sample sizes and so on. Especially for FFT, there's currently no better scope in the 1 to 8 GHz class.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 10, 2016, 10:27:41 am
content: If you want to make your bench look professional, just get both an oscilloscope and a separate spectrum analyzer. The more test equipment, the better and the more impressive it will look. If your bench table is not big enough, go to Ikea and buy a bigger table. Mount an anti-static mat on top of the table to turn it in a work spaceHereby a quick calculation, to proof that it doesn't take 4000-6000 EUR to get good FFT at home:Siglent SSA3021X: 1500 EUR (supports up to 3.2 GHz after Werewolf mode)Rigol DS2072A: 750 EUR (supports up to 300 MHz after Riglol)Conclusion: For 2250 EUR you are set and have a 2 GS/s oscilloscope, a 3.2 GHz spectrum analyzer.I didn't count the Ikea table, as I assume your bench space is big enough for both devices =)You have plenty of budget left, so you could as well throw in a Siglent SDG2042X signal generator which got extremely good reviews! It supports up to 120 MHz sine waves.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 10, 2016, 11:38:43 am
content: Quote from: pascal_sweden on August 10, 2016, 10:27:41 amGreat idea! And hey, why not randomly place some wires, old PCBs and a few screwdrivers on there as well?It will look yuuuge, it will look beautiful, really, you'll see!QuoteI know the fact that someone talks about making a bench "look professional" should have been a clear indicator that there's very little real-world experience involved ('nuff said), and therefore its very likely futile to ask but:Please explain how a cheap B-brand scope with piss-poor FFT (2kpts?) and a cheap B-brand SA with a lowly max RBW of only 1MHz (according to the spec sheet) is an adequate replacement for a scope with proper FFT, including how this setup can be used to assess low frequency spectra from DC to 9kHz, or modern wideband signals with BW of multiple tens of MHz, both things which are a very common use for FFT in a good scope.

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 10, 2016, 12:22:37 pm
content: According to the specs (and verified by actual test users):10 Hz Minimum Resolution Bandwidth (RBW)

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 10, 2016, 01:05:36 pm
content: Quote from: pascal_sweden on August 10, 2016, 12:22:37 pmWell done for stating data that is completely irrelevantI was talking about themax RBW, which for the SSA3000X isn't 10Hz, it's 1MHz. And since you apparently don't understand why that is necessary, the RBW pretty much tells you how big a slice the SA can capture in one go. 1MHz, which btw is pretty poor even compared to many 30yr old boat anchor SAs, is absolutely insufficient to look at a modern wideband signal.I have to say it's truly mind boggling how you can always come up with some silly "alternative", usually involving some poor-spec B-brand kit, while being clearly completely oblivious to what the specs actually mean, how this stuff works and where its limitations are, or how it's actually used, and then conclude that this is an appropriate replacement for what was initially discussed.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: August 10, 2016, 01:11:07 pm
content: Quote from: Wuerstchenhund on August 10, 2016, 11:38:43 amAlso, fast events that require a frequency-domain digital phosphor display to catch. You could add a SDR and an upconverter to round out the B team, calibration is sure to give you hours of fun!

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 10, 2016, 01:28:01 pm
content: Wuerstchenhund, you seem a very bright person with years of experience in this industry area.I am sure you are too busy with your current work situation, but if you would start making YouTube movies, you would be very successful, and a lot of people out here would get a lot smarter with your help

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 10, 2016, 01:54:08 pm
content: Quote from: pascal_sweden on August 10, 2016, 01:28:01 pmThere are certainly a few things I think I do quite well but unfortunately being in front of a camera isn't one of them. I'm sure if I made YT movies then they'd make Uwe Boll's movies look like works of art in comparisonAlso, living in a country where houses and the rooms in them are generally already on the 'compact' side, my personal workshop is currently pretty cramped so I wouldn't really know where to record something (we'll probably move to some place where I shall find more spacious facilities, but that could take well another year or so).I'm also not really a video guy, and a lot of stuff can be explaned very well even in the format of a forum, supported by images (i.e. screenshots) where required.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2016, 12:33:14 am
content: Quote from: rfbroadband on August 09, 2016, 03:23:58 pmYay! \o/ (Amazingly enough, Dave's forum doesn't have the right emoticon.)Now what is the lowest end oscilloscope which returns phase information with its FFT instead of throwing it out?

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2016, 12:58:00 am
content: Quote from: Wuerstchenhund on August 09, 2016, 06:06:45 pmThe oldest DSOs which I know of which provide magnitude and phase from FFTs are the Tektronix TDS520 and TDS540 (with option 2F) released in 1992 and the DSA601 and DSA602 (11k series) released in 1990. Unfortunately Tektronix limited this feature to DSOs with bandwidths of 500 MHz and higher which I assume was for purposes of market segmentationI am always on the lookout for other examples which may have lower bandwidth but must be less expensive.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 11, 2016, 05:44:06 am
content: Quote from: David Hess on August 11, 2016, 12:33:14 amDifficult. I *believe* (don't have access to one at the moment to check) the LeCroy WaveSurfer 3000 can do phase, and this starts at 2ch 200MHz and $3k.With Keysight, none of the DSOX variants do phase so the "cheapest' one is the Infiniium DSO9064A (600MHz 4ch for $16k).With R&S, I think FFT phase starts with the RTE, of which the cheapest variant (RTE1022 200MHz 2ch) starts at roughly $6k.With Tek, the cheapest scope that offers phase seems to the the MDO4000 which for 4ch 200Mhz starts at $7k.I doubt any Rigol, Siglent (aside from the SDS3000 maybe) or GW Instek scope does phase.QuoteI'm pretty sure the old LeCroy 9300 Series (which if I remember right starts at 200MHz) could do phase, at least optional. I wonder what the FFT capabilities are for the 7200/7400 and 9400 Series from the '80s.There were a few other scopes (i.e. from HP) back then that did offer FFT but I can't remember if they could do phase or not.

author: The Electrician
author_rank: Frequent Contributor
timestamp: August 11, 2016, 09:08:19 am
content: Quote from: rfbroadband on August 09, 2016, 03:29:13 pmHow did you create these plots? I notice the horizontal scale is logarithmic; did you need the K18 option to do this?

author: borjam
author_rank: Unknown
timestamp: August 11, 2016, 09:33:45 am
content: Quote from: Wuerstchenhund on August 11, 2016, 05:44:06 amFrom the 9400 manualI imagine that Lecroy's approach at the time was: "let's display that FFT in every conceivable (and doable) way". Indeed it can be painfully slow if you select too many points (up to 20 seconds if I remember correctly) but it just does it.

author: rf-loop
author_rank: Super Contributor
timestamp: August 11, 2016, 10:01:56 am
content: Quote from: Wuerstchenhund on August 10, 2016, 01:05:36 pmWho need and who do not need over 1MHz RBW in normal sweeping SA.Many peoples still survive with example HP8560E and HP8590E series, example, And yes, they are old and yes, they are not even near state of art in any thing.I have used tens of years spectrum analyzers and I have never need over 3MHz but this is in my use. . Who need more, he buy what he need. There is not universal machine what is good in all things including price. For <2kEur and talking NEW equipments there is not many... Buyer need brain. He need know what he need and what he do not need and if he do not know what he need but still want buy, why he need buy any.it can ask why. Just for fun or decorate his work room. Most of people who Need SA also know what he need. So he do not need buy universal all in one all perfect machine. Oh..yes...I know these peoples who never know what they perhaps need tomorrow or next year or after ten year. I remember one people who was, and is still, in this trap. He still take pictures using film camera because next year come more features and some have this and that feature but it is too expensive but perhaps next year this is available also in reasonable price class. I believe he stay infinite without digital camera but all time he read reviews and compares and follow what new is coming and what all perhaps need...Sometimes, not always, also things can do with skills and using clever methods for jump over some limitations in equipments.Some may buy 30kEur measurement system when he is doing his telescope main mirror and some use 0.1 eur razor blade and candle. Both get same result in final. Other use brain and skills and do himself, second delegates thinking to machine but then he have head ache when he thing if machine result can trust.Btw, there is undocumented 3MHz RBW in SSA... Simple, if you need something what equipment do not have, then buy equipment what meet your needs. So extremely simple. If I need spectrum and SSA specifications etc meet my needs that's it. If I do not need 100MHz wide realtime analyzer for 6GHz then why need tell that SA noname is poor nad crap when it do not have it.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 11, 2016, 11:25:21 am
content: Quote from: rf-loop on August 11, 2016, 10:01:56 amMany people survive with less than a $1 per day. That doesn't suggest that this is worth emulating.And I'm really not sure why you bring up these old boat anchors into a discussion about FFT in a scope.QuoteGreat. I regularly need more than 3MHz BW, and while I have an SA that goes up to 20MHz RBW (Anritsu MS8609A) I regularly use FFT on my 8yr old scopes to look at wideband signals up to 160MHz.QuoteYes, in that class aren't many new scopes with good FFT (pretty much only the GW Instek GDS-1000B and GDS-2000E), and none which do phase.QuoteNot saying you're wrong but this isn't really relevant to the discussion. How about we focus on the topic?And I'd like to see how you "work around" the lack of proper bandwidth in your instrumentationQuoteSo if they have 3MHz RBW which works properly why is this even undocumented?But the real point which you so clearly missed was not if the SSA-X is 'crap' or not (I leave this for others to decide), the point was that the SSA-X was suggested as a perfect replacement for a scope with proper FFT. which it clearly isn't, because it's pretty useless for analyzing modern wideband signals due to it's very low max RBW.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 11, 2016, 11:28:10 am
content: Quote from: borjam on August 11, 2016, 09:33:45 amThanks!So even the old 9400 could do phase. That's pretty impressive for a scope from the mid-'80s.QuoteWell, at least you can get the data. Considering the performance of processors back then it's no surprise that it's slow.

author: borjam
author_rank: Unknown
timestamp: August 11, 2016, 01:21:39 pm
content: Quote from: Wuerstchenhund on August 11, 2016, 11:28:10 amOh I'm not criticizing it, quite the contrary! It runs on an ancient Motorola 68000.It reflects the mentality of a long gone era I think. The minimal FFT present nowadays in many oscilloscopes is just a checkbox feature. The people from Lecroy, on the other side, probably thought something like "let's sqeeze every possible bit ouf of this function". Probably their background in the Physics background helped as well.

author: David Hess
author_rank: Super Contributor
timestamp: August 12, 2016, 11:45:28 pm
content: Quote from: Wuerstchenhund on August 11, 2016, 05:44:06 amI will keep these in mind next time I go search for this feature in a new or old DSO, thanks.While not quite a substitute, the low performance but low cost USB oscilloscopes from Syscomp Electronic Design support network analysis using their built in function generators. This is another thing which would make me consider buying a new DSO but alas, none support even this.http://www.syscompdesign.com/Instruments_ep_42.html

author: Electric2000
author_rank: Newbie
timestamp: August 25, 2017, 02:46:37 am
content: What is the max fft point of rigol ds1054z?

author: tautech
author_rank: Super Contributor
timestamp: August 25, 2017, 02:57:33 am
content: As this is an older thread without mention of new models, SDS1202X-E should be mentioned with 1 Mpts FFT.

author: ruairi
author_rank: Frequent Contributor
timestamp: August 25, 2017, 03:09:05 am
content: Tautech,Perhaps you are not aware how much of a turnoff your relentless Siglent sales pitch is? It completely undermines the brand IMO and I have ruled out Siglent products because of it. The question above your post was about the FFT points on a Rigol,nothingto do with Siglent.Being diligent in answering Siglent related queries or correcting misinformation is good business, what you do is not.Ruairi

author: tautech
author_rank: Super Contributor
timestamp: August 25, 2017, 03:29:02 am
content: Quote from: ruairi on August 25, 2017, 03:09:05 amRuairi, I try to make posts that are informative and factual to the best of my ability.If I was to reply directly to E2000's post I would have quoted it specifically, instead I checked all posts in this thread and found 'up to date' info missing and simply added it, it was only that E2000's post brought this thread to my attention.Each and every viewer/reader/member will take my input in a different way and if you take some time to check my postings they cover all manner of subjects, that I also hope is reflected in my signature.FYI of the several 100's of Siglents units I have sold in the few years I've been a distributor only a very few are to EEVblog members so my efforts here can hardly be called self interest.

author: hendorog
author_rank: Super Contributor
timestamp: August 25, 2017, 03:32:10 am
content: Tautech is enthusiastic to be sure, but I don't think your comment is fair.The first thing I thought of when I saw "Oscilloscope for FFT" in my unread posts list, was that Siglent FFT picture as I know it has very nice FFT for the price.I came to the thread to point it out and saw he had beat me to it.

author: ruairi
author_rank: Frequent Contributor
timestamp: August 25, 2017, 05:17:14 am
content: Tautech,We'll have to agree to disagree on your approach. For me Daniel at Keysight to Rich at R&S are an example of what a company rep can bring to the forum, they always seem to arrive when needed but don't wedge their products in to every conversation. That predisposes me to their brands and I have gear from each company, your posts have the opposite effect for me.Hendorog - it's a personal opinion and I'm probably in the minority, I'm happy that you find Tautech's posts helpful.Apologies for the thread derail.Cheers,Ruairi

author: nctnico
author_rank: Super Contributor
timestamp: August 25, 2017, 07:28:54 am
content: GW Instek has a new MDO-2000E series which is geared towards FFT / frequency domain analysis.http://www.gwinstek.com/en-global/products/Oscilloscopes/Digital_Storage_Oscilloscopes/MDO-2000E_Series

author: MrW0lf
author_rank: Frequent Contributor
timestamp: August 25, 2017, 07:29:22 am
content: Quote from: Electric2000 on August 25, 2017, 02:46:37 am16k

author: Fungus
author_rank: Super Contributor
timestamp: August 25, 2017, 07:38:49 am
content: Quote from: MrW0lf on August 25, 2017, 07:29:22 amUnless you own an Ethernet cable and a PC, in which case the FFT size can be the entire memory of the 'scope.For serious FFT a dedicated spectrum analyzer will always beat a DSO for high frequencies and a $200 Analog Discovery will usually beat one at lower frequencies (it has a 14-bit ADC).And now we pass you to your regularly scheduled Picoscope fans...

author: MrW0lf
author_rank: Frequent Contributor
timestamp: August 25, 2017, 07:52:30 am
content: Quote from: Fungus on August 25, 2017, 07:38:49 amBTW did you ever considerwhyI like Picoscopes? Heres why:If there is no feature (like graphing phase between two signals) I can just take couple cups of coffee, and dream up some math formula that will settle the matter:https://www.picotech.com/support/topic31641.htmlGreen trace is phase(A,B). Work still in progress but shows certain promise that might be related to bode plotsHowever would not hurt if they finally implement anti-alias in analytical mode

author: Fungus
author_rank: Super Contributor
timestamp: August 25, 2017, 09:13:24 am
content: Quote from: MrW0lf on August 25, 2017, 07:52:30 amNot really, no.

author: b_force
author_rank: Super Contributor
timestamp: August 25, 2017, 11:37:23 am
content: What is good and what is poor?In 90% of the cases I see people using the wrong type of time window for what they are looking for and blame the equipment.It also depends on the bandwith you're looking for.

author: nctnico
author_rank: Super Contributor
timestamp: August 25, 2017, 03:42:28 pm
content: Quote from: Fungus on August 25, 2017, 07:38:49 amNo because a DSO shows the time and frequency domain together. Sometimes it is very usefull to see which part of a signal (time domain) influences which part of the frequency domain.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 26, 2017, 06:46:57 pm
content: Quote from: Fungus on August 25, 2017, 07:38:49 amNo, because the longest sequence a DS1054z can capture is 24Mpts (which is still quite a lot) so that's longest sequence you can use as a basis for FFT.Of course you could stitch together multiple acquisitions but then you'd introduce errors.Forget it. Somehow I read "..entire memory of the computer" instead of "...scope"Mea culpa!QuoteNo, not always. A decent lab-grade SA offers better dynamic range and overall RF performance, however capturing high BW signals is generally easier with a scope (which can use it's full analog BW) while the RBWs of a swept SA are a lot more limited (usually between 1MHz and 10MHz, with very few offering more than 10MHz) unless you use a newer high-end model.Quote from: nctnico on August 25, 2017, 03:42:28 pmTrue, but many better SAs can show the time domain as well, often even time and frequency domains together.

author: Fungus
author_rank: Super Contributor
timestamp: August 26, 2017, 07:25:02 pm
content: Quote from: Wuerstchenhund on August 26, 2017, 06:46:57 pmAnd 24Mpts is ... what percentage of the memory of the 'scope?

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: August 26, 2017, 08:04:00 pm
content: If you want to analyze signals in frequency domain and you are on budget , try software defined radio (sdr) on ebay. They come in all kinds of price ranges and with little effort they can make a usable signal analayzer.

author: shteii01
author_rank: Frequent Contributor
timestamp: August 26, 2017, 11:41:10 pm
content: Tek DSA601/602...

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 26, 2017, 11:46:05 pm
content: Even though it's probably not going to be it king of the hill, it's good to note that there is an application to do FFT externally with the DS1054Z. That way you can record with the oscilloscope, but do the heaving lifting with your computer. Also, newer firmware versions apparently have improved FFT.http://hackaday.com/2015/09/22/a-better-spectrum-analyzer-for-your-rigol-scope/

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 27, 2017, 02:21:07 pm
content: Quote from: shteii01 on August 26, 2017, 11:41:10 pmSeriously?http://w140.com/tekwiki/wiki/DSA600"FFT: complex, forward and reverse,max. 16384 points; windows: Rectangular, Bartlett, Hanning, Hamming, Blackman, Blackman-Harris..."

author: Kalvin
author_rank: Super Contributor
timestamp: August 27, 2017, 02:50:35 pm
content: Quote from: Karlo_Moharic on August 26, 2017, 08:04:00 pmHackRF (and clones) is quite inexpensive device going from 1MHz to 6GHz, and there are some FFT analyzer software available. For example thishttps://github.com/pavsa/hackrf-spectrum-analyzeris build for the spectrum analysis purposes. Even using a cheap SDR dongle can be used up to 1.7GHz. There are some SDR dongles which can go down to very low frequencies using so called direct sampling mode:http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/.However, the dynamic range will be around 48dB using these less expensive alternatives. So, depending on your budget there are some options how to proceed.As others have already pointed out, using a suitable PC software with the oscilloscope for analyzing the captured waveform will also be very handy. So, you do not have to select the oscilloscope per FFT, just make sure that you can get the samples out to PC.

author: David Hess
author_rank: Super Contributor
timestamp: August 27, 2017, 06:33:05 pm
content: Quote from: Wuerstchenhund on August 27, 2017, 02:21:07 pmTekwiki neglects to mention it but the 11K series also supports waveform math functions like differentiation and FFT magnitude *and* phase which together may be used to do vector network analysis using a step signal source. Averaging and filtering may be applied to the FFT instead of the time domain waveform. Math also allows the FFT magnitude display to be corrected for ENBW. The 11K series are the oldest DSOs that I know of which support these things.At some point I may still pick up one of these DSOs for the above but I would prefer a better option short of a new DSO that costs more than my car.

author: MikeP
author_rank: Regular Contributor
timestamp: August 28, 2017, 08:46:07 am
content: This is interesting thread. I asked a question about FFT in the RTB2000-thread. Unfortunately, the answer still is not present.Please explain - why I see so big difference in results? What settings need to be used? Why there is dependence from the THD level? In other words - the dependence from the settings decreases at a large THD.Now I use the rejector filter. These good old days!The RTB2000 is the great tool. But I can't use it.Thanks.Mike.

author: nctnico
author_rank: Super Contributor
timestamp: August 28, 2017, 09:10:02 am
content: FFT works best in sample mode. Averaging and high-res will filter the signal and peak detect adds extra noise. You also need to be aware of aliasing products at low samplerates especially when the FFT length is short so you can't have high samplerates (yes, 128kpts is short).

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: August 28, 2017, 09:58:07 am
content: Quote from: David Hess on August 27, 2017, 06:33:05 pmThey aren't. The LeCroy 9400A (which came out in 1985) supports these when soft option WP02 is installed, which allows advanced FFT up to 25kpts. The LeCroy 7200a modular scope (1989) should, too, although I don't know what the max FFT size is.QuoteIf you want to do some TDR stuff then there are quite a few low-cost options available. The LeCroy 9300 Series from the '90s supports the above features with the (now free) software options WP02 and WP03, while offering FFT up to 1Mpts. There are various models of the 9300 Series with different sample rates and bandwidths, most of which can be had for a few hundred dollars in working condition (although these days you can find the successor LC Series for similar money, with faster processing and FFT up to 8M).Also, there are TDR options for the HP 54120A/B/D sampling scope mainframes, one up to 20Ghz and one up to 50Ghz (scope and TDR mainframe are called 54120T). The scope frames are cheap, however the TDR heads are not but with some patience you can find working examples of scope + head for <£1200.

author: David Hess
author_rank: Super Contributor
timestamp: August 28, 2017, 02:25:46 pm
content: Quote from: nctnico on August 28, 2017, 09:10:02 amUnfortunately many DSOs do what you describe and apply averaging to the waveform before the FFT when what is desired is to average the FFT output.