To be safe, I would use some attenuation externally.Thanks.
Unfortunately I don't have any SMA-SMA attenuators and I can imagine that some tinkering interferes with the signal.
dBm means power (like watts) right?
If I have no idea what the signal generator is doing, how do I measure it?
Do I measure the voltage and then calculate something against 50 ohms impedance?
Sorry for noob questions.
Certainly, you are able to adjust the output of a signal generator. The O-scope is what you can use to measure the output of the signal generator.
Perhaps the attached chart will help you.
For instance 0dbm = 1mW (milliwatt) = .224Vrms = .316Vp (Peak) = .632Vp-p (Peak to Peak). The scope we have been talking about can measure the frequency along with the Volts rms, peak or peak to peak.
It's hard to read the settings of your TinySA in the picture.
What is the level output set to on the TinySA? Did you adjust the level output as you increased the frequency or did it remain the same?Everything default: -7.0dBm
An no, I did not increase the level output of course.
I didn't change anything except the frequency.
Thank you!
Certainly, you are able to adjust the output of a signal generator. The O-scope is what you can use to measure the output of the signal generator.
Perhaps the attached chart will help you.
For instance 0dbm = 1mW (milliwatt) = .224Vrms = .316Vp (Peak) = .632Vp-p (Peak to Peak). The scope we have been talking about can measure the frequency along with the Volts rms, peak or peak to peak.Ah, thanks!
I wasn't so wrong that these values are calculated with reference to 50 ohms.
Then for a limit of +10dBm 707mV RMS would be the maximum, right?
Thank you!
Okay, I figured out the problem.
The scope cannot handle amplitudes higher than about 300mVrms and maintain bandwidth specs.
I retested the scope using your -7dbm (100mvRMS) settings and I got the same results you did. The bandwidth specs was much better. However, once I got above 300mVrms input level, the bandwidth dropped like a rock like in my initial test with 1Vrms.
Not sure why this is the case. Perhaps someone here with more knowledge can shed some light.
Using -7dbm input, I was able to get a 97Mhz bandwidth in normal mode. The waveform becomes a little shaky around 70Mhz but still useable.
Using the same -7dbm input in overclocking mode, I was able to achieve 120Mhz. Pretty impressive actually.
Okay, I figured out the problem.
The scope cannot handle amplitudes higher than about 300mVrms and maintain bandwidth specs.
I retested the scope using your -7dbm (100mvRMS) settings and I got the same results you did. The bandwidth specs was much better. However, once I got above 300mVrms input level, the bandwidth dropped like a rock like in my initial test with 1Vrms.
Not sure why this is the case. Perhaps someone here with more knowledge can shed some light.
Did you use sine wave in the tests?
And now there is also an explanation why there are such different opinions about the bandwidth: the amplitude.
Do you would say it works good up to the advertised frequency (18 MHz IIRC)?
Do you would say it works good up to the advertised frequency (18 MHz IIRC)?You know that I am not an expert, but I would say it works as I would expect it from my experience with the DSO2512.
It can keep up counting the frequency within the advertised bandwidth and has ~-3dB at 18MHz.
Maybe the amplitude drop comes bit earlier than his big brother's.
I've shown in the screenshots above that there is very little amplitude drop even at 90MHz in normal mode.
Beyond the advertised bandwidth, the frequency count is incorrect. That is the same with the DSO2512.
from my little experience, a square wave looks more or less decent up to 1/10 of the bandwidth.
It can be distinguished from a sine wave up to about 1/3 of the bandwidth.
That would be ~1.8MHz and ~6MHz for the DSO154 and that's what I'm seeing in the second video.
It is ~9.6MHz and ~40MHz for the DSO2512.
Thanks!
I agree. However I would like to know what our more experienced fellow forum members would have to say.
If, as said, DSO2512 does sample at 200/100 MSa/s and does sin(x)/x interpolation, that would add up with the results? 100/2.5 = 40 MHz.
However I doubt it's being tested with both channels activated?
Would be DSO2512 good enough to do some low-end but serious work or is it just a toy?
The 40 MHz you mentioned refer to the square wave. It is the state you see on the DSO154 at 6MHz.
The DSO2512 is specified with 500Ms/s. I guess in reality it is probably like this:
2 channel/standard mode: 200Ms/s
2 channel/OC mode:250Ms/s
1 channel/standard mode: 400Ms/s
1 channel/OC mode: 500Ms/s
OMG. I wouldn't say that square wave on DSO154 is useless at 6 MHz, but to me it's more disgusting than a bunch of phlegm. What a toothache. Please see FFT screenshots. At 6 MHz, only first higher odd harmonic fits into the bandwidth. So I think it's aliasing for sure.
OMG. I wouldn't say that square wave on DSO154 is useless at 6 MHz, but to me it's more disgusting than a bunch of phlegm. What a toothache. Please see FFT screenshots. At 6 MHz, only first higher odd harmonic fits into the bandwidth. So I think it's aliasing for sure.This is a square wave at 40MHz on the DSO2512.
I think it is clearly distinguishable from a sine.
This is the limit I'm talking about.
Above that, the square wave gets really ugly and at some point looks like a sine.
To me, DSO154 is good to do square waves up to 1 MHz. 2 MHz at most. Above that I consider it just "useable". Keeping my eyesight as good as age allows, and keeping any aches out of my head, matters.
EDIT: Can DSO2512 do math? Even if it's just ch1-ch2?
Matter is: do you see your waveform as stable as that while watching "live" your scope?
did you found the reason why it shows incorrect measurements? si5351 module has amplitude 1.5 Vpp, but all your screenshots never shows correct value. This is very strange, did you tested it at low frequency (1-2 MHz and below)?
Matter is: do you see your waveform as stable as that while watching "live" your scope?No, of course it dances nervously in this range.
But it shows - as smart people would say - the 3rd harmonic, if I'm not totally wrong.
And that is - if I'm not totally wrong - an indication of a certain bandwidth which has to bee 3x higher than the 1st harmonic.
So in case of the DSO2512 that would be 40Mhz->120MHz.
If I have misunderstood, please correct me.
Not sure what you mean exactly. It has some toy-FFT and an XY mode.
Didn't I said that it could turn out it's not that bad after all?
BTW a couple things have been learned while testing it.
FFT is a math function, and a much more complicated one than just to substract channel 2 from channel 1, I think. That substraction would be quite useful.
Why do you think it has to be 1.5Vpp?
I can only measure that with my (toy-) oscilloscope and if it shows 3.x Vpp, then I have to believe it.
If you look at the "Adafruit Si5351 Clock Generator Breakout" page: https://learn.adafruit.com/adafruit-si5351-clock-generator-breakout/wiring-and-test
When scrolling down you see three oscilloscope screenshots. They show similar Pk-Pk values, like 3.64 Volt @10.7KHz.
Yes, with dummy load and coax I get amplitudes in the range you mentioned, but since the signal is so ugly, there are higher Pk-Pk values.