VOLTCRAFT DOV series

[2N3055]

What is actual purchase price of the scope ( 2 and 4 channel) with VAT at this time?

[Aldo22]

It seems hopeless to me.
The signal looks fine, so I'm wondering if this could be a firmware bug.
Very strange.

Don't give up....
Please try the following:
1. Press the Default button and confirm
2. Then set the channel where the square wave is input back on (turn the other channels off)
3. Set the time base to 500 ns
4. Turn on FFT, leave it as is.
5. Now press “Autoset” in the FFT menu

What does it look like then?

If I follow your instructions (almost) to the letter, this is what it looks like (10MHz square):

[Martin72]

Here's what it looks like on my scope:
1) After restoring factory defaults, set to usable values.
2) FFT enabled, with no changes made to it#
3) “Autoset” pressed in the FFT menu.

It would be good if others could confirm or refute this.

@2N3055: No matter how much, it's too much.

[Aldo22]

Here's what it looks like on my scope:
1) After restoring factory defaults, set to usable values.
2) FFT enabled, with no changes made to it#
3) “Autoset” pressed in the FFT menu.

OK, thanks.
But what else could it be besides a firmware difference?
The 10 MHz signal looks fine, so what else could be going wrong?

[2N3055]

Here's what it looks like on my scope:
1) After restoring factory defaults, set to usable values.
2) FFT enabled, with no changes made to it#
3) “Autoset” pressed in the FFT menu.

OK, thanks.
But what else could it be besides a firmware difference?
The 10 MHz signal looks fine, so what else could be going wrong?

Try different frequency... 11Mhz for instance... Or try setting FG until scope shows exactly 10MHz..

[Aldo22]

What is actual purchase price of the scope ( 2 and 4 channel) with VAT at this time?

2Ch: 149.- at Conrad Germany
4Ch: 199.- at Conrad Germany
and far too much in other countries.

[Aldo22]

Try different frequency... 11Mhz for instance... Or try setting FG until scope shows exactly 10MHz..

Thanks, but how does that help me?
-> Screenshot at 11 MHz

The funny thing is that it actually works a little bit; it just looks completely different from Martin's.
I probably would have just accepted it if I hadn’t seen Martin’s screenshots.

It’s also particularly strange that the signals are always at -90dB (see Y cursor).
What does that tell me?

[KungFuJosh]

What sig gen are you using, and what output level?

What sig gen and output level is @Martin72 using?

[Aldo22]

What sig gen are you using, and what output level?

What sig gen and output level is @Martin72 using?

I've tried a few different ones.
This image here is from the NanoVNA with the MS5351. About 350 mVpp.

[atrophicinterludes]

What is actual purchase price of the scope ( 2 and 4 channel) with VAT at this time?

If you buy from Voelkner (part of Conrad) and use a coupon, the total prices including VAT and shipping currently come to €128.55 and €173.55 for the 2-channel and 4-channel variants, respectively.

I believe you also get a 2-year warranty extension if you subscribe to their newsletter.

[Martin72]

What sig gen and output level is @Martin72 using?

I first fed in the signal from the Bodnar pulser, which can also be seen in the FFT; the last examples were taken with an SDG6000X.
(+14 dBm, 50 Ω)

As for the firmware, as I mentioned, I took my first FFT images with my first Voltcraft unit, without updating the firmware

[KungFuJosh]

What sig gen are you using, and what output level?

What sig gen and output level is @Martin72 using?

I've tried a few different ones.
This image here is from the NanoVNA with the MS5351. About 350 mVpp.

So what's the put your signal at? @Martin72's signal was at +14dBm. My guess is that you'd have to adjust the sensitivity of the FFT if the scope can handle that, or try a higher signal level.

ETA: Are you using 50Ω termination?

[Martin72]

We can do it another way, Aldo.
What sources do you have available? I'll try to replicate them in terms of waveform, level, and frequency.
To be able to compare anything, the conditions have to be reasonably similar.

[Aldo22]

We can do it another way, Aldo.
What sources do you have available? I'll try to replicate them in terms of waveform, level, and frequency.
To be able to compare anything, the conditions have to be reasonably similar.

I really appreciate your help, but I'm becoming more and more convinced that there's something wrong with my device or the firmware version. 

Anyway, here's my suggestion:
12.50 MHz at 4 Vpp with coax and a 50-ohm load = approx. 2 Vpp.
OK? 6.25 MHz would work as well.

[Martin72]

OK, got it...

[Aldo22]

OK, got it...

Different rise-time! 

And now?

[2N3055]

As long as input is not overdriven (as it is not) level should not change shape of "skirts" on bins..

It is either different window or some RBW setting or something is wrong.
This is exactly where Rigol had (and still to some extent still has) a problem with FFT implementation...

So devices are software incomplete, OEM does not support it directly, there are numerous problems, including signal integrity problems...
Voltcraft supports it to some extent, but good luck fixing FW problems via intermediary.....

If this was simple scope that has only basic functions (very basic math for instance) but has simple stuff working right, for 150-180 € it would be cheap alternative to Fnrisi...
But it is not working right. In some aspects even Fnrisi works better, it seems....

As for normal price they are asking usually, you would have to be mental to buy it... This special price is only for Germany and some other special destinations. Conrad lists it for more than 400€+VAT...
More expensive than DHO800 and same as SDS800xHD.....

[2N3055]

OK, got it...

Different rise-time! 

And now?

Different rise time will change amplitude of higher harmonics. It has no influence to the shape of bins on lower frequencies itself.

[Martin72]

And now?

Switch on FFT, press Autoset.
After that, I played around with the span a bit and, of course, adjusted the time base.
But first, I used Autoset, and then it should have turned out like in my picture.

[Aldo22]

I can see something with these settings below.
Also strange: when you select “Mode Average,” the Vpp is halved in the automatic measurements.

[Martin72]

@2N3055:

The scope would be OK at the listed price RIGHT NOW if the 200 mV glitch were fixed.
Otherwise, it’s way too expensive and not worth recommending, because at the original price it’s too close to a DH800—and that’s significantly better.
It might be worth the price if the software were halfway up to par, but it isn’t.
It’s partially buggy and far too lacking in features.
Plus, the support is absolutely terrible.
No, €200–250 would be OK, but definitely not anything above that, because no improvements in terms of OS/UI are to be expected.

[Martin72]

With these settings, I can see something:

Same window (Hanning)?

[Aldo22]

With these settings, I can see something:

Same window (Hanning)?

No, Hamming. With Hanning, the dB levels drop even lower, so I can't see much anymore.

[Martin72]

I'm a kid at heart...
https://www.youtube.com/shorts/x6YUCSFR0DU

With Hanning, the dB levels drop even lower, so I can't see much anymore.

Then something is definitely wrong.

[Aldo22]

I'm a kid at heart...
https://www.youtube.com/shorts/x6YUCSFR0DU

By the way, you can also create an MP4 directly in the scope.
Swipe down from the top of the screen, then tap the hard-to-see camera icon and confirm to start

Then something is definitely wrong.

I think so too.
The question is simply whether it's a hardware issue or a firmware issue.