Signal Quality of "Budget" Waveform Generators - Page 1
Forum section: electronics / testgear

author: TurboTom
author_rank: Super Contributor
timestamp: December 18, 2019, 12:07:14 pm
content: Since I've been tampering recently a lot with different AWGs, and also some inquiries on that concern appeared on the forum, I thought it may be worth looking at the signal quality of these "budgetary" instruments.The three generators that I was able to compare are no real "el-cheapos" but far from high-end devices. They are:- Rigol DG811 (~240EUR incl. VAT), hacked to believe it's a DG992 (~1070EUR incl. VAT) but calibrated only up to ~70MHz- Rigol DG4102 (~950EUR incl. VAT), hacked to a DG4202 version (~2000EUR incl. VAT) and fully calibrated- Siglent SDG6022X (~1560EUR incl. VAT), hacked to an SDG6052X (~5500EUR incl. VAT) and fully calibratedBoth the prices of the base version spread considerably as well as the models that they were made to believe they are by hacking. I'm aware that the opinions if the hacked models can be actually considered to perform the same as the "true" higher versions, differ considerably. In case of the DG811 / DG992 it surely doesn't due to the lack of calibration over the full frequency range. Yet, the hacked DG811 still meets Rigol's "Performance Verification Guide" specification for the DG992!The DG4000 series is an older model that is equipped with 14bit DACs while the other two have 16bit DACs installed. Sampling rates are 250MSa/s (DG811), 500MSa/s (DG4102) and 2.4GSa/s (SDG6022X).I compared the harmonics (the strongest that is, usually second or third) of a sine wave on CH1, 10MHz and 60MHz at levels of 0dBm, +10dBm and the maximum possible level (short of +24dBm on all devices @ 10MHz, +12dBm @ 60MHz on the DG811 and +18dBm @ 60MHz for the two bigger instruments.Some findings were quite peculiar: Since the output drivers in all the instruments are switched to different configurations, depending on the selected output level, and at lower levels even complete amplifiers in the signal chain are bypassed, the distortion levels don't necessarily monotonously rise with increasing output power. For example, the DG811 appears to have a "sweet spot" at 10MHz / +10dBm where it provides its lowest distortion. The DG4102 in general appears to provide quite a clean output signal at low levels, outperforming the other two instruments despite its 14bit DACs while the SDG6022X competes best at high output levels.Also regarding the measurements some interesting findings could be made: I used a DSA815 to analyze the signals. This instrument easily tolerates mixer levels of -10dBm, but this is only half the truth. If I want the mixer to be sufficiently linear in order to be able to evaluate harmonic distortion levels in the range of -70~-80dBc and not just to measure the mixer-induced distortion, I've got to reduce the mixer level to -25dBm. With a maximum attenuation of 30dB in the DSA815's front end, and signal levels of up to approx. 24dBm, this requires an additional attenuator of 20dB that I wired in-line with the SA's input. To still get the necessary low noise floor, the RBW had to be set to 1kHz...3kHz (which means looooong sweep times with averaging).Anyway, for those interested in the details, I attached 18 screenshots of the tests. If someone wants to add similar tests of other instruments (DG1000Z, SDG2000x, maybe some Feeltech or Uni-T measurements, or on the other end Keysight, TEK or R&S), this lineup may actually turn into a good overview of what users may expect in certain price ranges of AWGs (signal-quality-wise).Thanks,Thomas

author: tautech
author_rank: Super Contributor
timestamp: December 21, 2019, 10:19:05 am
content: Other models to come when they are back in stock.SSG3021X RF genimprovedto 3.2 GHz model. $ 2549 (SSG3032X $ 4009)Above 17 dBm gets flagged as possibly unlevel so used as max output for these tests.Spectrum analyser = SVA3032XN-N cable = 6GHz rated Siglent N-N-6LNO external attenuation used.Averages = 5RBW/VBW settings selected to reduce noise floor to show harmonics if any.

author: TurboTom
author_rank: Super Contributor
timestamp: December 21, 2019, 12:08:38 pm
content: Thank you tautech, it's quite interesting to compare the performance of a proper RF generator to the function generators from my tests. Of course, the upper frequency range cannot be covered by the AWGs, with the SDG6052X somewhat "in between", maxing out at 500MHz. But level-wise, the RF gen wins hands down at the higher frequencies.I'm a little bit surprised of the relatively poor harmonic distortion charateristics of the RF gen at the low end, but considering that the output signal is generated by (probably multiple) mixing operations of a baseband signal with one or more LO signals, and filtering after the final mixer / amplifier probably isn't adaptive (don't know for sure in case of the SSG3000X), that's what one could expect.Since I lmited my tests to the two frequencies 10MHz and 60MHz (basically due to the limitation of the "majority" of AWGs and also previous inquiries), I may later add some tests of the SDG6000X covering its higher frequency capabilities for comparison with the SSG.Cheers,Thomas

author: bd139
author_rank: Super Contributor
timestamp: December 21, 2019, 12:23:56 pm
content: Interested to see a FY6900 compared.

author: TheBay
author_rank: Unknown
timestamp: December 21, 2019, 01:29:10 pm
content: Interesting thread.I'm about to order a function generator today. But I really cannot decide what budget one to get, I can't seem to find comparisons of the models i'm interested in.I'm getting close to order the SDG1032X as I'm told it's better than the Rigol DG800 series, however no one seems to say why the Siglent is better and on paper the Rigol 800 series appears to be better and is extremely tempting especially as I can get a DG811 for £200 and "Hack" it to dual channel with more bandwidth.Or I can get a Aim TTI TG2512A for the same price as the Siglent SDG1032X, but no idea if the TG2512A is any good and surpassed by newer designs. Also its limited to 25MHz which is an issue as I need at least up 30MHz.

author: Performa01
author_rank: Super Contributor
timestamp: December 21, 2019, 03:09:29 pm
content: True RF signal generators aren't exactly known for having low harmonic distortion; harmonic levels up to 30dBc (at certain conditions) are not at all uncommon, even for expensive instruments.Here I present the measurements for the Anritsu MG3633A, which is a high performance signal generator from the late 90s. Its key features were super low phase noise, high output level and fast switching speed.30dB external attenuators were inserted for all tests, so 30dB have to be added to get the true carrier levels.Here's the measured data:MG3633A_THD_A30dB_10MHz_0dBm-----------------------------1,10.000000 MHz,-30.07 dBm2,20.000000 MHz,57.96 dBc3,30.000000 MHz,58.43 dBc4,40.000000 MHz,64.02 dBc5,50.000000 MHz,67.53 dBcMG3633A_THD_A30dB_10MHz_10dBm-----------------------------1,10.000000 MHz,-20.15 dBm2,20.000000 MHz,60.63 dBc3,30.000000 MHz,57.27 dBc4,40.000000 MHz,63.39 dBc5,50.000000 MHz,67.06 dBcMG3633A_THD_A30dB_10MHz_20dBm-----------------------------1,10.000000 MHz,-10.20 dBm2,20.000000 MHz,52.50 dBc3,30.000000 MHz,40.03 dBc4,40.000000 MHz,49.71 dBc5,50.000000 MHz,58.60 dBcMG3633A_THD_A30dB_60MHz_0dBm-----------------------------1,60.000000 MHz,-30.12 dBm2,120.000000 MHz,61.34 dBc3,180.000000 MHz,43.56 dBc4,240.000000 MHz,56.74 dBc5,300.000000 MHz,57.76 dBcMG3633A_THD_A30dB_60MHz_10dBm-----------------------------1,60.000000 MHz,-20.15 dBm2,120.000000 MHz,63.06 dBc3,180.000000 MHz,44.38 dBc4,240.000000 MHz,54.84 dBc5,300.000000 MHz,60.27 dBcMG3633A_THD_A30dB_60MHz_20dBm-----------------------------1,60.000000 MHz,-10.14 dBm2,120.000000 MHz,39.09 dBc3,180.000000 MHz,36.63 dBc4,240.000000 MHz,47.54 dBc5,300.000000 MHz,55.93 dBcMG3633A_THD_A30dB_500MHz_0dBm-----------------------------1,500.000000 MHz,-30.34 dBm2,1.000000 GHz,43.92 dBc3,1.500000 GHz,48.43 dBc4,2.000000 GHz,65.41 dBc5,2.500000 GHz,60.77 dBcMG3633A_THD_A30dB_500MHz_10dBm------------------------------1,500.000000 MHz,-20.42 dBm2,1.000000 GHz,45.02 dBc3,1.500000 GHz,45.83 dBc4,2.000000 GHz,63.40 dBc5,2.500000 GHz,60.10 dBcMG3633A_THD_A30dB_500MHz_20dBm------------------------------1,500.000000 MHz,-10.64 dBm2,1.000000 GHz,24.39 dBc3,1.500000 GHz,23.58 dBc4,2.000000 GHz,39.52 dBc5,2.500000 GHz,57.74 dBcPlease note that the 20dBm test was made just for fun; levels above 17dBm are uncalibrated, yet I used the higher level because the amplitude was still well within spec. Distortion at these high levels is another story though.The screenshots for the individual measurements are attached.

author: TurboTom
author_rank: Super Contributor
timestamp: December 21, 2019, 03:21:21 pm
content: Interesting findings: Since the harmonics of @tautech's measurements of his SSG3000X on his SVA3000X appeared a little high to me, I wanted to look at more detail into the measurement setup effects on the results.I've neither got an SSG3000X nor an SVA3000X, but the RF section of the latter should be somewhat related to the SSA3000X which can be found in my basement messFor a first, general comparison with the measurements of my introductory post of this thread, I used the SSA to measure the harmonics of my DG4000 @ 10MHz 0dBm which appears to be the cleanest AWG source I've got. Here the original screenshot of the DSA815 again:This measurement has been done with an external (SMA-through) attenuator of 20dB and an internal attenuation of 5dB, i.e. the mixer level of the DSA815 was -25dBm and the input level -20dBm, which appears to be a good setup as the low harmonic level of -75dBc shows.And now my attempt to rearrange that with the SSA3000X:Whatever I tried, I wouldn't get closer than 5dB of the highest harmonic (in this case the second) to what I was able to measure with the Rigol SA. The measurement shown represents approximately the "sweet spot", more attenuation doesn't help, and even a little less raises the third harmonic well above -70dBc.Anyway, this is still quite acceptable but shows that the mixer level is a very critical parameter if harmonic measurements a done. But also the input level is critical as I had to find out now!May basic objective was to duplicate @tautech's measurement of his SSG3000X, set to 17dBm @ 10MHz:So I got my source with the lowest distortion at that settings which is (surprise, surprise...) the Rigol DG800/900!Here's the best measurement that I got of it on the SSA3000X, taken with an external attenuation of 40dB and an internal one of 5dB:As listed in the marker table the first harmonic is at almost -70dBc.Since the SSA's internal attenuator ranges up to 51dB, I thought I can get the same result without the 40dB of external attenuation. Well, not exactly...:That is an almost 18dB worse second harmonic level! I wonder what causes this distortion, it basically has got to be related to the first semiconductor switches that route the input to the additional 20dB attenuator in the SSA's input circuitry.Finally I reduced the internal attenuation by another 5dB to replicate @tautech's settings but still got the worst (2nd) harmonic about 10dB better than he with his SSG3000X as the source:It's quite interesting to see that the 3rd harmonic increased by more than 12dB from just reducing the attenuation by 5dB!So I've also got to learn that when doing quantitative measurements over wide dynamic ranges, it's very important to keep an eye on both input as well as mixer levels. At least so when working with "budget instruments" like the Siglent or Rigol SAs. I'm sure an HPAK, TEK, RS ... boat anchor or decent more current model won't perform as bad since there are probably "real" switches in the input section that won't produce that much harmonics.Regarding the SSG3000X, I'm afraid the harmonic levels that @tautech was able to measure, are probably quite real since the SVA-induced harmonics (if it's comparable to the SSA that is) are probably 10dB lower...

author: bd139
author_rank: Super Contributor
timestamp: December 21, 2019, 03:55:48 pm
content: To note the Rigol DG1022Z harmonic performance is better than the DG800 and all the siglent generators. One reason I was using one as an RF signal generator. Output attenuator was poo though.

author: Performa01
author_rank: Super Contributor
timestamp: December 21, 2019, 06:20:14 pm
content: As another example for a true RF signal generator, here are the measurements for the ancient Rohde & Schwarz SMS2 with 1040MHz option. This is a fully analog PLL synthesizer and smallest frequency step is 100Hz.30dB external attenuators were inserted for all tests, so 30dB have to be added to get the true carrier levels.Here's the measured data:SMS2_THD_A30dB_10MHz_0dBm-----------------------------10.000000 MHz,-29.89 dBm20.000000 MHz,46.30 dBc30.000000 MHz,57.18 dBc40.073344 MHz,67.40 dBc50.000000 MHz,65.45 dBcSMS2_THD_A30dB_10MHz_10dBm-----------------------------10.000000 MHz,-19.89 dBm20.000000 MHz,46.58 dBc30.000000 MHz,57.11 dBc40.000000 MHz,70.70 dBc50.000000 MHz,67.29 dBcSMS2_THD_A30dB_60MHz_0dBm-----------------------------60.000000 MHz,-30.05 dBm120.000000 MHz,46.29 dBc180.000000 MHz,48.75 dBc240.000000 MHz,64.10 dBc299.964634 MHz,68.41 dBcSMS2_THD_A30dB_60MHz_10dBm-----------------------------60.000000 MHz,-20.05 dBm120.000000 MHz,46.62 dBc180.000000 MHz,50.03 dBc240.000000 MHz,66.94 dBc299.999763 MHz,75.49 dBcSMS2_THD_A30dB_500MHz_0dBm-----------------------------500.000237 MHz,-30.54 dBm1.000000 GHz,54.70 dBc1.500001 GHz,54.19 dBc2.000094 GHz,65.70 dBc2.499999 GHz,68.18 dBcSMS2_THD_A30dB_500MHz_10dBm------------------------------500.000237 MHz,-20.51 dBm1.000000 GHz,55.38 dBc1.500001 GHz,54.79 dBc2.000001 GHz,63.73 dBc2.500001 GHz,71.46 dBcThe screenshots for the individual measurements are attached.

author: Performa01
author_rank: Super Contributor
timestamp: December 21, 2019, 07:00:53 pm
content: Quote from: TurboTom on December 21, 2019, 03:21:21 pmDistortion products usually scale with the fundamental signal level by their order.For example, if you increase the signal by 1dB, then the fundamental will rise by 1dB as expected, 2nd order distortion products rise by 2dB, 3rd order products by 3dB.In theory, increasing the signal level by 5dB should increase the third harmonic by 15dB, but of course in a real world experiment there are limits to that rule...Quote from: TurboTom on December 21, 2019, 03:21:21 pmYes, the distortion does not appear to be particularly low, but it is certainly quite acceptable. We have to accept that we cannot have a distortion-free general purpose singal source, hence it makes little difference if a distortion product is 40dBc or 60dBc - except when we need a signal source secifically for low distortion measurements (where we need additional filters anyway).The RF performance is nothing special, but in line with many other general purpose RF signal generators, hence good enough for most common tasks. The SSG comes with high output power without additional cost on top of that.

author: TheBay
author_rank: Unknown
timestamp: December 21, 2019, 10:10:16 pm
content: I use an old Motorola R-2010D (R-2001D) Communications System Analyser for RF stuff, it will go up to 1GHzI wonder how it fares with any modern "Budget" equipment, it was a great bit of kit back in the day and still does everything I need it to, but its a bit of a heavy beast and a pain if I need to move it around the workshop or take to somewhere.Would be interesting to see how that compares too.

author: TurboTom
author_rank: Super Contributor
timestamp: December 21, 2019, 11:38:36 pm
content: Quote from: Performa01 on December 21, 2019, 07:00:53 pmSo very true...Did some more testing of my SDG6000X at 150, 300 and 500MHz. Nothing spectacular, as expected possible maximum level decreases considerably and at the same time harmonics increase. The output stage is just pretty much at its limits.And then I stumbled over my really ugly Hantek HDG2002B that (once again) somehow lost its calibration (...as if that matters...) and the knob of the incremental encoder that had been treated with this "smooth" coating (rubberization?) turned sticky like on all that cheap gear with the built-in obsolescenseThere are times that I really hate that capitalism! Had to dispose of a completely functional "ghetto blaster" and a very nice, high power battery drill (otherwise perfectly good) among other things due to this crap. I just don't buy stuff with this surface treatment anymore. But I'm diverging...Whatsoever, at 10MHz it performs okay-ish while at 60MHz, though it's got to be my AWG with the highest output level at that frequency, it is a real nightmare with a forest of non-harmonic (spurious) and harmonic signals. Once again, screenshots attached.Cheers,Thomas

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: December 22, 2019, 02:50:45 am
content: Very interesting results. Has anyone tried looking at non-round frequencies, like 13.3 MHz?

author: Performa01
author_rank: Super Contributor
timestamp: December 22, 2019, 08:34:45 am
content: Quote from: TurboTom on December 21, 2019, 11:38:36 pmVery true and this is also a good opportunity to confirm your test results, which are consistent with my measurements within a few dB. Any deviations can be attributed to manufacturing tolerances of the output amplifiers, I guess.Just as a particular example, here's my test result for 500MHz at 0dBm output:SDG6052X_THD_A30dB_500MHz_0dBm------------------------------1,500.000237 MHz,-30.10 dBm2,1.000001 GHz,41.28 dBc3,1.500001 GHz,35.56 dBc4,2.000001 GHz,69.49 dBc5,2.500002 GHz,76.66 dBcOnce again, 30dB external attenuation. Image attached.

author: Performa01
author_rank: Super Contributor
timestamp: December 22, 2019, 08:37:32 am
content: Quote from: maxwell3e10 on December 22, 2019, 02:50:45 amHere you have it for the Siglent SDG6052X.30dB external attenuation have to be added to get the true carrier level.SDG6052X_THD_A30dB_13.3MHz_0dBm-------------------------------13.300000 MHz,-29.93 dBm26.600000 MHz,65.46 dBc39.900000 MHz,70.89 dBc53.200000 MHz,69.31 dBc66.559102 MHz,83.30 dBcSDG6052X_THD_A30dB_13.3MHz_10dBm--------------------------------13.300000 MHz,-19.96 dBm26.600000 MHz,58.95 dBc39.900000 MHz,68.39 dBc53.200000 MHz,69.98 dBc66.500000 MHz,78.03 dBcSDG6052X_THD_A30dB_13.3MHz_20dBm--------------------------------13.300000 MHz,-9.97 dBm26.600000 MHz,54.32 dBc39.900000 MHz,53.19 dBc53.200000 MHz,68.35 dBc66.500000 MHz,63.53 dBcSDG6052X_THD_A30dB_13.3MHz_24dBm--------------------------------13.300000 MHz,-5.95 dBm26.600000 MHz,53.63 dBc39.900000 MHz,50.25 dBc53.200000 MHz,63.26 dBc66.500000 MHz,57.39 dBc

author: TurboTom
author_rank: Super Contributor
timestamp: December 22, 2019, 12:28:56 pm
content: On my SDG6022X, recent tests showed that channel 2 has at least 2dB lower distortion over the whole frequency range than channel 1. It's not much but maybe still worth mentioning. Hence, on instruments with multiple channels, it may be worthwhile to take a look at all of them.Anyone who could add in some data of one of the typical low-end AWGs (price-wise that is) like the Feeltech or recent Uni-T units? I would love to see a comparison!

author: Performa01
author_rank: Super Contributor
timestamp: December 22, 2019, 01:36:47 pm
content: I used to own an UNI-T UTG2062A, which was (and still is) not exactly cheap at ~ €480,- excl. tax.After a few years of moderate use it died for no reason (doesn't switch on anymore) and I just have no time and cannot be bothered to troubleshoot the thing.I have no distortion measurement results in my archive, but as far as I remember it performed flawlessly in line with the other AWGs already shown in this thread (even at 60MHz the distortion was fairly decent).I do have a comparison of the phase noise though, see the following screenshot:Noise_MG3633A_SDG6052X_UTG2062AThis compares the Anritsu MG3633A (magenta), which is THE reference when it comes to phase noise for a RF signal generator, the Siglent SDG6052X (cyan) and the UNI-T UTG2062A (yellow).It can be seen that there is no noticable difference between the Anritsu and the Siglent (a detailed phase noise plot reveals the differences and the Anristu is still vastly better, especially at close carrier offsets and at higher frequencies), but at the same time it becomes immediately clear that the UNI-T just cannot play in the same league.

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2019, 08:19:01 am
content: Quote from: TurboTom on December 21, 2019, 03:21:21 pmGood idea to cross examine our results.So using the same signal generator settings as before but this time with reduced internal SA attenuation as I've added an external 10dB N type attenuator.Previous using internal attenuation. 10 MHz, 0 dB from SSG3000XNow with 10 dB external attenuation, reduced internal attenuation, Ref level offset adjustment (cancelling out external attenuation) and screenshot image changed to Normal in Display settings.One will presume the differences in amplitude measurement accuracy can be attributed to the cheap external attenuator.

author: Performa01
author_rank: Super Contributor
timestamp: December 23, 2019, 09:33:22 am
content: Quote from: tautech on December 23, 2019, 08:19:01 amThings aren't always straight forward...Never change more than one parameter at the same time, otherwise results are not guaranteed to be comparable anymore.You changed three parameters at the same time:Signal level (by means of an external 10dB attenuator)Internal attenuation from 25dB to 20dBReference level from 5dBm to 10dBmBy changing the reference level, the automatic RF/IF gain of the analyzer will very likely make up for that, i.e. the total gain might become 5dB higher.While the input signal is 10dB lower, the reduced internal attenuation will make it 5dB higher again. Now add the 5dB higher gain to this calculation and you end up with the exact same (1st or at least 2nd) mixer level as before (and very similar intermodulation products).The even order harmonic distortion of the internal attenuators as discovered by TurboTom appear to be always an issue, unless the internal attenuation is set to zero. So I would not expect a noticable difference in distortion levels because of just changing the internal attenuation by 5dB.

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2019, 10:04:42 am
content: Quote from: Performa01 on December 23, 2019, 09:33:22 amYet themeasuredresult is just 1.3dB different for the first harmonic and other than amplitude and Ref level changes the only difference in HW used is the addition of a 10dB external attenuator and Ref Level offset to null the attenuators impact from a measured result.Where TurboTom had difficulty getting 5dB agreement in measurement I just wanted to demonstrate what might be possible with a different setup......not trying to prove anything as it's just an educational exercise.Following soon is a look at the SSG3000X Low Frequency BNC output........

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2019, 10:45:05 am
content: SSG3000X LF BNC output.1 MHz max frequency and waveforms available are sine wave and 20 kHz max for square wave, saw-tooth and triangle waveforms.Max output = 3Vp-pSVA1032X Only Internal attenuation engagedSiglents 1 GHz rated BNC cable with BNC-N type adapter.

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2019, 11:53:55 am
content: NIB $499 SDG2042X checked and updated with latest FW and now ready for dispatch.SVA1032XSiglent's 1 GHZ rated BNC cable and N-BNC adapter. Again, NO external attenuation.Note, SDG2042X max output levels are frequency dependant.

author: TurboTom
author_rank: Super Contributor
timestamp: December 23, 2019, 12:26:28 pm
content: Thanks @ tautech for these tests. The SDG2000X looks really nice at low signal levels (0dBm), about three to six decibels better than the (my) SDG6000X, depending on the frequency. Yet, at higher output levels, it seems the latter one wins hands down.

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2019, 08:12:33 pm
content: Quote from: TurboTom on December 23, 2019, 12:26:28 pmYes at ~70dB down for the first harmonic was pleasing to see yet my tests were of a stock unit not one that has been improved to 120 MHz. Maybe a member with a SDG2122X can provide us with 60 and 100 MHz results.Also there are members with SDG1032X and improved to SDS1062X that could chime in with their investigations of signal harmonics which would complete the picture of the current AWG offerings from Siglent.I hope they do as it will be some weeks before I have more in stock.

author: tautech
author_rank: Super Contributor
timestamp: December 29, 2019, 11:59:52 pm
content: The 'budget' SAG1021 25 MHz USB powered and controlled AWG module for Siglent DSO's.Instruments usedSDS1104X-E FFT Peak Hold (with external Tek 50 ohm feedthrough)SVA1032XFrequencies tested; 10 and 20 MHz @ 1V p-p as SAG1021 controlled from SDS1104X-E does not have a dB amplitude output facility.EEVblog not playing nice with attachments so edits to come.........

author: 0culus
author_rank: Super Contributor
timestamp: December 30, 2019, 12:17:06 am
content: Quote from: Performa01 on December 22, 2019, 01:36:47 pmThis is not quite correct. It is indeed very good at larger deviations from the carrier, but the HP 8662/8663 (my back is groaning just thinking about how heavy these units are) is quite a bit better closer to the carrier, going by quoted specs on the datasheets. Unfortunately, the Anritsu sheet seems to have a problem with the reproduction of the SSB phase noise plot...it's fuzzy and nearly impossible to read, but a rough guess shows that that 8662 is considerably better at small deviations.However, like most things in life, it's a trade-off...as I understand it you're better off with two sources that are good at different things than having to try to have both in one.

author: tautech
author_rank: Super Contributor
timestamp: December 30, 2019, 11:09:09 am
content: Quote from: beanflying on December 30, 2019, 10:39:19 amYep.Summary of events:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/msg2850078/?topicseen#msg2850078

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 03, 2020, 04:55:41 pm
content: I recently played with using an oscilloscope as a spectrum analyzer. On Owon XDS3062A scope with 12 bit resolution and 500MHz sample rate I can get pretty good noise floor of about 140 dB/Hz. I compared the noise floor level of several generators I have at home: FeelTech 6600, PTS 160, Owon generator build into the scope and a simple analog GW generator.10 MHz 2Vpp sine wave12.3456789 MHz sine waveZoom on the peakPTS generators are known for low noise. In my measurements the white noise is -130 dBc/Hz, somewhat shy of the spec of -135dBc/Hz. Surprisingly, FeelTech generator has even lower white noise, about -138 dBc/Hz. It has more spurs, though. The analog generator GFG-8019 also has pretty low white noise, but much stronger harmonics.The measurements also show limitations of the XDS3062A ADC. The huge peaks around 25 MHz are due to the oscilloscope. Also close-in phase noise is limited by the scope as well, since it's the same for all generators. I locked PTS frequency to the scope clock by using its build-in generator to provide a 10 MHz reference for the PTS. FeelTech generator is unmodified and has no clock locking mechanism.

author: Sighound36
author_rank: Frequent Contributor
timestamp: May 04, 2020, 08:52:46 am
content: Just saw this threadLater I will compare some FG I have including a opened up 822 (plus rebuilt power supply) Tek 3100, a R&S plus an Agilent 4403 on a RTSA see if that throws up some surprises.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 05, 2020, 05:26:02 pm
content: I haven't played with too many spectrum analyzers, but from what I've seen most of them don't have very high dynamic range. So resolving white noise at -135dBc/Hz is not that trivial. I was kind of surprised that I can do it with just a low-cost scope.

author: THDplusN_bad
author_rank: Regular Contributor
timestamp: December 17, 2021, 11:38:35 am
content: Good day,I find this topic quite interesting...I have analysed the square signal quality of my Rigol DG811/922 signal generator. Firmware version 2.06.00.01.Measurement setup:* 1.25 Vpp signal from Rigol DG922 1 kHz square wave from output 1* Tektronix TDS 5054 oscilloscope used, Aircell 5 BNC-cable 1 meter length into the TDS, 50 Ohm terminated in oscilloscope* Measurements with sin x/x interpolation:Rise time 8.4 ns, overshoot: 3.3%, manual measurement of overshoot with cursors: 104 mV or 4.2%* Measurements with linear interpolation (preferred for these type of measurements):Rise time 8.3 ns, overshoot: 3.3%, manual measurement of overshoot with cursors: 100 mV or 4%* See the two screenshots attached.Overall, that's really not bad for a budget function generator that was upgraded to 100 MHz...Cheers,THDplusN_bad