Rogol 1054Z actual bandwidth - Page 1
Forum section: electronics / beginners

author: rad400
author_rank: Contributor
timestamp: October 31, 2017, 01:01:23 am
content: When a Rigol DS1054Z 50Mhz scope is updated to a 100Mhz, do you really get an improvement in the bandwidth?. At 100MHZ are you down only 3db or considerably more?

author: MarkF
author_rank: Super Contributor
timestamp: October 31, 2017, 01:29:32 am
content: The 3dB bandwidth for the DS1104Z 100MHz scope is approx 160Mhz.The 3dB bandwidth for the DS1074Z 75MHz scope is approx 90Mhz.

author: rstofer
author_rank: Super Contributor
timestamp: October 31, 2017, 01:41:12 am
content: Quote from: rad400 on October 31, 2017, 01:01:23 amYou need to watch Dave's video on the subject. There are two filters on the front end of each channel. One for 50 MHz bandwidth and one for 100 MHz bandwidth. The choice is made by the firmware. If it thinks it is a 50 MHz scope, it chooses the 50 MHz filter. If it thinks is is a 100 MHz scope it chooses the 100 MHz filter. That's why tweaking the scope settings make a difference.Set to 100 MHz, the scope has been tested and found to have rather more than 100 MHz of bandwidth to -3 dB. I don't recall the number but it's up around 150 MHz.

author: ebclr
author_rank: Super Contributor
timestamp: October 31, 2017, 04:26:28 am
content: 1054Z hacked go far away from 100 Mhz, at least 130 Mhz without attenuation, and +- 200 Mhz with attenuation

author: Fungus
author_rank: Super Contributor
timestamp: November 01, 2017, 06:43:01 pm
content: Quote from: rad400 on October 31, 2017, 01:01:23 amYes.Quote from: rad400 on October 31, 2017, 01:01:23 amThe 3dB point is usually around 130MHz (as measured by several people here).

author: Fungus
author_rank: Super Contributor
timestamp: November 01, 2017, 06:45:16 pm
content: Quote from: ebclr on October 31, 2017, 04:26:28 amYou can still see 300MHz+ signals on one, although very attenuated, obviously.

author: rhb
author_rank: Super Contributor
timestamp: December 20, 2017, 12:49:27 am
content: How about a screen shot of a sweep generator feeding a "hacked" scope? Has anyone posted that?

author: xrunner
author_rank: Super Contributor
timestamp: December 20, 2017, 01:20:56 am
content: Quote from: rhb on December 20, 2017, 12:49:27 amFstart?Fstop?

author: rstofer
author_rank: Super Contributor
timestamp: December 20, 2017, 01:52:58 am
content: Quote from: xrunner on December 20, 2017, 01:20:56 amI suppose something less than 50 MHz for those who don't think the original bandwidth has changed. Say 10 MHz?QuoteNo point in going beyond 200 MHz because it is pretty well establised that the -3dB point is around 130 MHz.I have no idea if those values are realistic...

author: xrunner
author_rank: Super Contributor
timestamp: December 20, 2017, 03:10:28 am
content: Quote from: rstofer on December 20, 2017, 01:52:58 amI don't strictly have an RF sweep generator, but I might be able to cobble together something, if another member doesn't beat me to it.

author: kahe40
author_rank: Contributor
timestamp: December 20, 2017, 02:40:49 pm
content: here a sweep 50M to 500M with 10M step, you see those spikes every 10M.Rigol is not fast enough, but Micsig and Siglent show them clearly.Center of Grid is around 225M, so you get an idea of BW and Freq.Micsig goes down very fast, Siglent is the best of alland Rigol has a linear degree, like a triangle.Rigols 5ms are too short for the entire sweep (or user error?),but I tried to make it comparable.Sweep was done with RF-Explorer-SigGen,yes, maybe it is a toy but better than nothing...Micsig TO1104https://ibb.co/hTupS6Rigol 1074Z hackhttps://ibb.co/mf2b76Siglent 1202XEhttps://ibb.co/cMZCfRedit: have not found out, how to post pictures with iPad, sorry

author: bingo600
author_rank: Super Contributor
timestamp: December 20, 2017, 05:18:33 pm
content: I measured mine to around 134Mhz , for the 3dB markDS1054Z (100Mhz Hacked)/Bingo

author: xrunner
author_rank: Super Contributor
timestamp: December 20, 2017, 07:03:46 pm
content: Quote from: rstofer on December 20, 2017, 01:52:58 amHere's my data. First up is from 10 MHz to 150 MHz. The -3dB point is where the cursors on the right intersect, about 130 MHz.Second is from 10 MHz to 500 MHz, again where the cursors intersect is -3dB @ 130 MHz. But certainly the scope can easily display signals in excess of 500 MHz.Note: Using TG output of a Rigol DS815 triggered externally, some amplitude anomalies are expected. The TG output was set to 0 dBm into 50 ohms at the scope.

author: rhb
author_rank: Super Contributor
timestamp: December 21, 2017, 01:31:02 am
content: The Rigol has a very strange response. It looks like a filter skirt with the corner frequency below 50 MHz.

author: Fungus
author_rank: Super Contributor
timestamp: December 21, 2017, 05:38:06 am
content: Quote from: kahe40 on December 20, 2017, 02:40:49 pmWhat sort of settings are these?Rigol has 1GSa/s and 24M pts.Quote from: rhb on December 21, 2017, 01:31:02 amJust a display artifact from the settings, nothing to do with frequency response.

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 21, 2017, 07:23:05 am
content: Quote from: rhb on December 20, 2017, 12:49:27 amQuote from: xrunner on December 20, 2017, 07:03:46 pmno, beyond 500MHz, you will see aliased signal...

author: xrunner
author_rank: Super Contributor
timestamp: December 21, 2017, 01:38:34 pm
content: Quote from: Mechatrommer on December 21, 2017, 07:23:05 amYes, if you don't care about amplitude or frequency accuracy. 900 MHz signal shown below, is displayed quite nicely. The amplitude and frequency you would measure with the scope will be wrong, but that's not the point.

author: scopeman
author_rank: Frequent Contributor
timestamp: December 21, 2017, 03:34:10 pm
content: Hello,You should re-run this test with a known good 50 ohm feed through termination and start with a 50KHz signal with six divisions ofsignal and increase the frequency to the point where you have 4.2 divisions of signal and repeat this for each attenuation setting to get a better idea of what the bandwidth of the scope itself is.Sam"scopeman"

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 21, 2017, 03:48:07 pm
content: Quote from: xrunner on December 21, 2017, 01:38:34 pmthats called 100MHz garbageQuote from: xrunner on December 21, 2017, 01:38:34 pmif the point is try to make out something from garbage, then yes i get your point.

author: xrunner
author_rank: Super Contributor
timestamp: December 21, 2017, 04:05:02 pm
content: Quote from: Mechatrommer on December 21, 2017, 03:48:07 pmYou aren't understanding the point I'm making. It's not garbage - it's a signal, it's useful information. If you want to trace a signal on a boardto see if it existsthen it's just fine for that above ~130 MHz. The signal is very easy to view on the DS1054Z hundreds of MHz higher than it's bandwidth limit (which is simply the -3dB point - not where it completely stops working).

author: rhb
author_rank: Super Contributor
timestamp: December 21, 2017, 06:46:56 pm
content: To paraphrase Harry Calahan, "A man's got to know his scope's limitations." Unfortunately, many people are held by economic considerations in a state of ignorance. The linear loss of amplitude on the Rigol, *is* a serious issue if you're trying to measure the rise time of a pulse.Thank you to those who have provided screenshots. I'd like to suggest, though, that you document the signal generator used. There are two terms in the equation.It would be very interesting to see a head to head of a hacked DS1054Z vs a DS1104Z using a top tier signal generator.

author: stlspartan
author_rank: Newbie
timestamp: November 09, 2019, 01:23:44 am
content: (sorry for posting on an old thread) I was chasing a ~124 Mhz noise signal on my hacked 100 Mhz DS1054z and came here and read through the thread and watched the videos.Conclusions:1) The scope has full 3db bandwidth out to ~130 Mhz. Nice!2) When I hear "bandwidth "and "3 db down" I think of filters. So when folks said the 3db down point of the scope was ~130Mhz I assumed it would be rolling off at 6db/octave or faster. But what I gather from the photos and videos is that it isn't as simple as that with a system like a digital scope. It seems that there is a plateau and that the scope maintains considerable response out to 200 Mhz.I know that uncalibrated response isn't as good as something you can measure with - but for me this is a delightful finding - that I can see a lot of waveform information to 200Mhz on my crazy cheap scope.

author: radiolistener
author_rank: Super Contributor
timestamp: November 09, 2019, 02:59:08 am
content: 3 dB bandwidth will be better, but things are not so easy to evaluate it by taking into account only 3 dB bandwidth.It depends on your goal. Sometimes smaller 3 dB bandwidth will be even better.

author: rhb
author_rank: Super Contributor
timestamp: November 09, 2019, 10:51:04 pm
content: Perhaps you should google "aliasing".The Nyquist for the DS1054Z displaying 3-4 channels is 125 MHz. So if the response is only -3 dB at 130 MHz there is a *lot* of garbage if you do an FFT. Not that Rigol has a usable FFT implementation. But even if you pull data from the scope and use Octave all you will get is garbage.The reality is that sampling at 250 MSa/s, anything over 70 MHz is corrupted by aliasing and excessively sharp roll off. If the filter rolls off fast enough to prevent aliasing you get really large overshoot on a step function.Buy a <40 ps square wave generator from Leo Bodnar and test the Rigol with that. Then consider what it it tells you.My LeCroy DDA-125 has a 1.5 GHz BW sampling at 2 GSa/s in 4 channel mode. Everything above 500 MHz is garbage if you do an FFT. But it *really* does have a < 233 ps rise time. IIRC I measured 226 ps with 20% overshoot as specified in the datasheet. Don't try to check a trace for ringing with that.Reg

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2019, 02:26:49 am
content: Quote from: rhb on November 09, 2019, 10:51:04 pmYou're allowed to turn channels off for critical measurements though.(or just to check if there's a radical change in the display...)

author: Tepe
author_rank: Frequent Contributor
timestamp: November 10, 2019, 10:39:54 am
content: Quote from: rhb on November 09, 2019, 10:51:04 pmAnd for the DS1104Z?

author: tooki
author_rank: Super Contributor
timestamp: November 10, 2019, 11:18:42 am
content: Quote from: Tepe on November 10, 2019, 10:39:54 amSame. There’s no difference in the hardware. The 1104Z just comes with the 100MHz analog filter enabled instead of the 50 or 70MHz one.

author: radiolistener
author_rank: Super Contributor
timestamp: November 10, 2019, 01:29:45 pm
content: Quote from: tooki on November 10, 2019, 11:18:42 am100 MHz filter leads to worse aliases than 50 or 70 MHz one. So 100 MHz will have even worse aliases.

author: tooki
author_rank: Super Contributor
timestamp: November 10, 2019, 04:32:09 pm
content: Quote from: radiolistener on November 10, 2019, 01:29:45 pmWhile that is true, my answer is 100% correct. The question was what the Nyquist frequency was. And it’s absolutely unchanged at 125MHz (1/2 of the 250MS/sec sample rate), regardless of what filter is ahead of it. And there is no hardware difference between the three models — they differ only in which filter the firmware enables.

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2019, 07:59:08 pm
content: Quote from: Tepe on November 10, 2019, 10:39:54 amThe same - it's the exact same hardware.Remember that with 2 channels on, Nyquist is 250Mhz and with 1 channel it's 500Mhz. Hence my comment about turning off one of the other channels if something is really critical. You can always get a good display on the DS1054Z, it's just something you need to be aware of when you're using the scope with all channels enabled (ie. that any Gibbs phenomenon will be more pronounced, etc.)Back in reality: You'll find your probing technique is far more critical for reducing artifacts than this problem is.

author: rhb
author_rank: Super Contributor
timestamp: November 10, 2019, 09:37:03 pm
content: Has anyone actually determined that there are 3 analog anti-alias filters? It seems quite unlikely. I'd expect the change to be in the FPGA. It certainly is in the Instek GDS-2000E scopes.I've not sat down to work out the implications of aliasing if you stay in the time domain and don't do trace interpolation.I did verify that my LeCroy DDA-125/LC648DLX display of a <40 ps step function does not change whether I am sampling at 2 GSa/s, 4 GSa/s or using the random Interleaved Sampling mode.Reg

author: rstofer
author_rank: Super Contributor
timestamp: November 10, 2019, 10:49:28 pm
content: Dave did a teardown and pointed out a Varicap to select between 100 MHz and 50 MHz - around 21:51

author: Fungus
author_rank: Super Contributor
timestamp: November 10, 2019, 11:51:55 pm
content: Quote from: rhb on November 10, 2019, 09:37:03 pmYes. It connects/disconnect different capacitors to the the analog input circuitry depending on the bandwidth option in the firmware.Quote from: rhb on November 10, 2019, 09:37:03 pmNope.Quote from: rstofer on November 10, 2019, 10:49:28 pmHe also did a reverse engineer of the input circuitry:

author: tooki
author_rank: Super Contributor
timestamp: November 11, 2019, 01:52:53 am
content: Quote from: rhb on November 10, 2019, 09:37:03 pmYep. All of us that have answered you have done so based on actual knowledge of this hardware, not speculation. The DS1xx4Z series has been dissected and discussed to death here on eevblog, such that practically none of its operating principles and design is unknown.Also, they’re not antialiasing filters per se. They're just bandwidth limits. Since all of them are below Nyquist, they’re not just there for antialiasing. Also, it’s 4 of them: 100, 70, 50, and 20MHz. The first three are used to capture consumer surplus (i.e. enable multiple price points), while the 20MHz is the user-selectable bandwidth limit.

author: rstofer
author_rank: Super Contributor
timestamp: November 11, 2019, 06:27:03 pm
content: Quote from: Fungus on November 10, 2019, 11:51:55 pmTo cut to the chase, look around 32:00 where Dave describes exactly how the bandwidth selection works.This firmware selection of 50, 70, 100, 20 MHz is a settled issue. It's shown in the schematic, it's proven by testing, it's settled!