Choosing between entry-level 12-bit DSOs

[Mechatrommer]

this is +1 imho in rigol, lets not forget, the 2 scopes discussed here got pros and cons.

Since the Siglent can into 2 Gsa/s, it could potentially be modded to support at least 800 MHz single-channel bandwidth, if there are no further limitations in digital signal processing and/or software. I don't recall anyone mentioning or trying this though.

i posted this earlier in this thread, some people said its very rare case. now we have 2 person asking for it so i'm not so rare, lets wait HAM fellows (names with numbers and who build their own radio) to chime in what they have to say, cheers.

[gf]

The Rigol is applying the theory correctly and the Siglent can't possibly be doing an infinitely wide reconstruction, so... 

But you have the choice to implement either

• a truncated/windowed sinc filter with a n*sampe_rate...(1-n)*sample_rate transition band (symmetrical around 0.5*sample_rate),
• or an ordinary steep lowpass filter with a n*sampe_rate...0.5*sample_rate transition band,

where 0<n<0.5 (for example n=0.4).

Contrary to what you might intuitively believe, it's the latter which does what people here seem to expect when it comes to frequencies beyond the filter's reconstructability limit of n*sample_rate. But it requires more DSP resources.

[pdenisowski]

lets wait HAM fellows (names with numbers and who build their own radio) to chime in what they have to say

Depends on the kind of radio you're building (or operating)   In the United States, there are amateur allocations at 902 MHz and 1240 MHz, and some experimenters go even higher.

https://www.arrl.org/files/file/Regulatory/Band%20Chart/Band%20Chart%20-%2011X17%20Color.pdf

One of my commercially-produced radios (the Icom 9700) has 144, 440, and 1200 MHz,  Icom is also investigating making amateur transceivers for the 2.4 and 5.6 GHz ISM bands

https://www.icomjapan.com/api/download.php?page_id=66&fl=JTJGdXBsb2FkcyUyRmxwJTJGc2hmJTJGU0hGX3Byb2plY3Rfdm9sMV9lbmcucGRm

73, Paul, KO4LZ

[Mechatrommer]

nice story but anything 1GHz and above is not relating to this thread... 140,144,902MHz maybe related. if you have one of this https://www.ebay.com.my/itm/114448357711 it would be nice to see the signal in time domain... ymmv.

[Fungus]

iircsomeone stated dho800 only works on specific brand. i have few wifi adapter here, maybe later i will try. but still, its a few more steps to do... rather than plugin usb stick and hit capture button. ymmv.

It's literally the most common chipset/brand.

I never take the WiFi dongle out. Apart from the web interface you can save all screen captures, data dumps, etc., to the internal memory and accessed via ftp as if they were local files on my PC.

You also get correct date/time stamps on the files if it's connected to WiFi.

[KungFuJosh]

@KungFuJosh can you please set the scope to 500 Msa/s, low waveform acquisition rate (to make the TinySA's glitches less visible), low persistence, and record a video of a 30 seconds long frequency sweep from, say, 110 MHz to 270 MHz?

Coax connection with a 50 Ohm feed-through terminator, if possible, to make the test conditions the same as in my test.

It will be interesting to see at what frequencies (and at what ratio relative to the sampling rate) it will become first wobbly and then AM-like (if it will), to compare that to Rigol.

I'd love to play, but I don't have one of these scopes. I have an SDS2504X+ 500MHz scope. I can sweep up to 841MHz on my scope with the TinySA Ultra.

[shapirus]

I'd love to play, but I don't have one of these scopes. I have an SDS2504X+ 500MHz scope.

Well, it would still be an interesting data point. What's the lowest samples/sec rate it can do? The idea is to set it to the lowest sampling rate and connect it to a source that outputs a frequency sweep in the range from ~20% to ~60% of the sampling rate.

We can then speculate if the Siglent's 800 HD series have the same wave reconstruction implementation as yours, or not :).

I can sweep up to 841MHz on my scope with the TinySA Ultra.

It can actually output up to 5.4 GHz (or at least so the specs say), but it switches from sine to square wave above 800 MHz.

[Fungus]

I'd like to know what the Siglent does on a real AM waveform, too.

Feed in the 220MHz signal at 500MSamples/sec. but add some AM modulation and see if it reproduces it (eg. 16MHz modulator).

[KungFuJosh]

I'd love to play, but I don't have one of these scopes. I have an SDS2504X+ 500MHz scope.

Well, it would still be an interesting data point. What's the lowest samples/sec rate it can do? The idea is to set it to the lowest sampling rate and connect it to a source that outputs a frequency sweep in the range from ~20% to ~60% of the sampling rate.

We can then speculate if the Siglent's 800 HD series have the same wave reconstruction implementation as yours, or not .

I guess, if I feel like procrastinating something else, I could do that. We'll see. 😉

I can sweep up to 841MHz on my scope with the TinySA Ultra.

It can actually output up to 5.4 GHz (or at least so the specs say), but it switches from sine to square wave above 800 MHz.

I meant I get a clean sine wave up to 841MHz.

[BillyO]

I meant I get a clean sine wave up to 841MHz.

I've been able to do that that too.  Well, I only went to 840MHz.

[KungFuJosh]

I meant I get a clean sine wave up to 841MHz.

I've been able to do that that too.  Well, I only went to 840MHz.

I win. 😉

[shapirus]

I meant I get a clean sine wave up to 841MHz.

Ah, I see. Well, that's just one point in time, and the display persistence hides the deviation of the peaks from the real value. What we're interested in is observing dynamically how the waveform becomes wobbly as the signal frequency increases and gets closer to that point.

It's clearly better than the Rigol, though, which is much worse at 1/2.5x the sampling rate. I wonder how the SDS800X HD scopes perform in this scenario.

Here's, BTW, a 500 MHz sine wave captured at 1.25 GSa/s sampling rate:

[shapirus]

And here's 625 MHz. Just like the 500 MHz waveform, the scope fails to trigger on it when vertical scale is less than 2 mV/div, so I had to capture it at at least 2 mV/div in single trigger mode and then zoom in.

...frequency counter? What's that?

But hey. Really, I can see how modding the input low-pass filter can make sense.

[KungFuJosh]

I meant I get a clean sine wave up to 841MHz.

Ah, I see. Well, that's just one point in time, and the display persistence hides the deviation of the peaks from the real value. What we're interested in is observing dynamically how the waveform becomes wobbly as the signal frequency increases and gets closer to that point.

It's clearly better than the Rigol, though, which is much worse at 1/2.5x the sampling rate. I wonder how the SDS800X HD scopes perform in this scenario.

Here's, BTW, a 500 MHz sine wave captured at 1.25 GSa/s sampling rate:

You saw what a sweep looks like to 100MHz on mine (I did one with TinySA Ultra, and one with SDG2122X), but that's no challenge for my scope. I could do the extended range to show it get goofy if you want.

Every day I have to resist purchasing the SDS804XHD. It's so cheap I could get it just to mess with it...but I'd rather buy a 2nd 6.5 digit DMM. And long term I want at least the SDS3000XHD, if I can ever afford it.

[BillyO]

and the display persistence hides the deviation of the peaks from the real value.

Persistence will not hide the peaks, it will tend to broaden the trace to include both peaks and the troughs and everything in between over the period of persistence.  Maybe you are thinking of averaging?

[KungFuJosh]

Exactly. That's why I did 1s persistence to illustrate the glitches better over the limited framerate of the web console.

[shapirus]

and the display persistence hides the deviation of the peaks from the real value.

Persistence will not hide the peaks, it will tend to broaden the trace to include both peaks and the troughs and everything in between over the period of persistence.  Maybe you are thinking of averaging?

We're talking about the same thing, but from different perspective. Yes, the more the amplitude varies, the wider the trace at the peaks becomes. If we want to conveniently see the spread over a period of time, that's where persistence helps. It's like seeing min/max/avg values in the same place.

My screenshots in previous posts show an opposite approach, where a single capture shows how the scope interprets the wave at a single given acquisition.

[shapirus]

the limited framerate of the web console.

Yeah that can be an unpleasant obstacle to a demonstration of a frequency sweep. What's the frame rate, anyway? Is it worse than 30 fps?

[KungFuJosh]

the limited framerate of the web console.

Yeah that can be an unpleasant obstacle to a demonstration of a frequency sweep. What's the frame rate, anyway? Is it worse than 30 fps?

Yes, I assume it's around 15 fps, but I don't know. I wish they made the framerate selectable.

[shapirus]

Yes, I assume it's around 15 fps, but I don't know. I wish they made the framerate selectable.

Hmm... Can you fetch, decompile, modify, recompile and reinstall the web control app? :)

It's a linux-based system, right? I wonder if it's hackable like the DHO800/900 series is, with full access to the file system etc. The stock web control app on the Rigols has some stupid design choices, like the upscaling (in a lossy way!) of the video stream, using jpeg for screenshots and setting quality level below the highest possible for the video stream compression. I spent some time and fixed all of that to use higher quality settings, native resolution and png for screenshots, and it's much better now.

[KungFuJosh]

That's above my paygrade. 😉

[KungFuJosh]

I meant I get a clean sine wave up to 841MHz.

Ah, I see. Well, that's just one point in time, and the display persistence hides the deviation of the peaks from the real value. What we're interested in is observing dynamically how the waveform becomes wobbly as the signal frequency increases and gets closer to that point.

It's clearly better than the Rigol, though, which is much worse at 1/2.5x the sampling rate. I wonder how the SDS800X HD scopes perform in this scenario.

Here's, BTW, a 500 MHz sine wave captured at 1.25 GSa/s sampling rate:

I didn't get any wobble within normal range, and then I still don't get anything as crazy as what you showed in your screenshot. It mostly shrinks and the counter gets farther and farther off. Near the end before it resets, it looks a little wonkier.

Let me know if you want different parameters than what I've got here:


TSA Ultra set at 800MHz with a 10s 500MHz sweep.

[shapirus]

I didn't get any wobble within normal range, and then I still don't get anything as crazy as what you showed in your screenshot. It mostly shrinks and the counter gets farther and farther off. Near the end before it resets, it looks a little wonkier.

Yeah looks very reasonable. I think there's no doubt now that the signal processing algorithms are implemented much better in this scope than in the Rigol's DHO800/900.

Now, let's see if someone will be willing to repeat a similar test with the Siglent's SDS800X HD series :).