RIGOL DG1022 sweep signal amplitude problem

[greasemonkey]

This is a 1Vpp, 3 second sweep of a sine signal (1Hz to 20MHz). The oscilloscope is in roll mode.



As you can see the amplitude starts dropping after 10MHz and at 20MHz it is 720mVpp. Is this normal? Could someone reproduce it?

Thing I have checked:
- The transmission line is 50Ohm terminated.
- When it is not sweeping the signal is 1Vpp at 20MHz
- The firmware is the latest

[duckduck]

As you can see the amplitude starts dropping after 10MHz and at 20MHz it is 720Vpp. Is this normal? Could someone reproduce it?

You are not crazy.

EDIT:

This isn't some aliasing issue with the scope. When the timebase is set to something more common, say 100nS, it is possible to see the sine wave shrink in the vertical dimension (voltage) as the frequency approaches 20MHz (when the DG1022 is set to sweep). In static frequency mode, changing the frequency on the DG1022 (using the rotary encoder) from 1 Mhz to 20 MHz in 1 MHz steps results in the output remaining between 1.01 Vpp - 1.03 Vpp.

TEST SETUP:

Rigol DG1022
Firmware version: 00.02.00.06.00.02.07

CH1 output set to 50 Ohm
Sine wave, 1Vpp
Sweep:
    Start: 1Hz
    Stop: 20MHz
    Time: 3s

Rigol DG1022, channel 1 --> Amphenol 50 Ohm BNC-BNC cable, 36" (~1 meter) --> Amphenol 50 Ohm BNC-BNC terminator --> Rigol DS1202Z-E

[greasemonkey]

Thank you duckduck. So it seems to be a ...feature. 

Can anyone try it on another waveform generator? A DG800 maybe? Or a Siglent?

[duckduck]

Well, now it's a good excuse for you to buy a new signal generator. Maybe give the competition a try? The SDG830 looks pretty: NA https://siglentna.com/waveform-generators/sdg800-series-functionarbitrary-waveform-generators/ EU https://www.siglent.eu/product/1139868/siglent-sdg830-30mhz-function-arbitrary-waveform-generator and is not too pricey at an MSRP of USD269 / €199 w/o VAT. Make sure to post a screen-grab of the sweep for us!

Fortunately, this DG1022 issue is not much of a problem for me since 99.9% of my work is from 20Hz - 20,000Hz, and the Rigol DG1022's sweep is pretty flat within that range. I am working on a mouse-scrambler for the garage which sweeps around 34kHz, but it just needs to be sine-wavish-ish and the output level just needs to be "loud". Even so, that's not outside of my core interest of audio, I'm just moving up(?) to small-mammal audio.

Image: 20Hz-20,000Hz sweep. Sweep period 1s.

[greasemonkey]

Well, now it's a good excuse for you to buy a new signal generator.

Don't worry about that. When it comes to TE we can all find excuses to justify a new buy to ourselves (don't try to convince the wife though. Always keep separate bank accounts  )

Maybe give the competition a try?

I kind of had my eyes on the DG811. It's hard to beat that 16bit 100MHz combination.

That being said the DG1022 is still a solid generator and has really covered my needs all these years. I maybe used the sweep function 4-5 times. I mostly use arbitrary waveforms up to 100kHz. I even wrote a python script recently and I can now load any mathematical function to it from the USB port.

It would be interesting to see how other waveform generator behave. Searching the internet did not return any interesting results about this problem.

[duckduck]

Maybe give the competition a try?

I kind of had my eyes on the DG811. It's hard to beat that 16bit 100MHz combination.

The DG811 is especially interesting for two reasons:

1) It is hackable:

Got my DG811 past week.

It came with FW 2.05. Backup. Direct downgrade to FW 1.8. Magic disk done on Linux with mkfs.vfat and dd. SN and MODIF done with pyvisa-py and A-B USB cable. Applied finish_upgrade_2.04. Direct upgrade to 2.06. It shows DG992 and correct serial number in System info.

Thank you all guys 

2) It is supported by Sigrok:
https://sigrok.org/wiki/Supported_hardware#Function_generators

That being said the DG1022 is still a solid generator and has really covered my needs all these years. I maybe used the sweep function 4-5 times. I mostly use arbitrary waveforms up to 100kHz. I even wrote a python script recently and I can now load any mathematical function to it from the USB port.

I agree that it is hard to beat the bang/buck of the DG1022 for my purposes (hobby audio electronics) when purchased used for ~USD120.

[Gary350z]

I verified this problem on my Rigol DG1022. It is the same as desccribe by greasemonkey and duckduck.

I tried the same test on my Siglent SDG2122X Arbitrary Waveform Generator and it works properly.

[Gary350z]

I am working on a mouse-scrambler for the garage

What is a mouse-scrambler?

[duckduck]

I am working on a mouse-scrambler for the garage

What is a mouse-scrambler?

A handful of cheap modules thrown into a box together to annoy mice. I am reminded that I should fuse this thing so it doesn't burn the house down. I know they sell stuff like this but I want to set the frequency and and output level.

Photocell controlled dusk-to-dawn power-switch --> wall-wart SMPS --> 34kHz sine wave generator --> audio amplifier --> piezo tweeters