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Siglent SDS800X HD Review & Demonstration Thread

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Performa01:
I don't expect the original sample data to reveal the true cause, which is already registered in Siglents internal bug list.

In short: a problem can arise whenever the FFT sample rate is not equal to the acquisition sample rate. There seems to be an exception for the 1:2 ratio.

In this particular test case, you can try using constant sample rate of 250 MSa/s and then, with 5 Mpts record length, the FFT will use 125 MSa/s, resulting in the smallest possible RBW at 50 MHz, without excessive spurious signals:


SDS824X HD_FFT_C50M_S1M_Sa250_125

gf:

--- Quote from: Performa01 on May 11, 2024, 05:04:19 pm ---I don't expect the original sample data to reveal the true cause, which is already registered in Siglents internal bug list.
In short: a problem can arise whenever the FFT sample rate is not equal to the acquisition sample rate. There seems to be an exception for the 1:2 ratio.

--- End quote ---

If it is already a well-know and accepted bug, then there is not need to investigate further.

markone:

--- Quote from: Performa01 on May 11, 2024, 05:04:19 pm ---I don't expect the original sample data to reveal the true cause, which is already registered in Siglents internal bug list.

--- End quote ---

Good to know, this is exactly what I was hoping to with my lame post activity  :)

So now we can officially say that there is some margin of improvement in FFT performance, could you "disclose" if we will see something in regard with the incoming FW release?

Martin72:

--- Quote from: Martin72 on May 11, 2024, 03:00:53 pm ---The RBW can only be achieved by manually setting the sample rate in the menu.
If you leave the settings on Auto, you get a different value - which RBW is the "right" one for a 50Mhz signal and 1Mhz span (50k, 10k)?
For example, if I leave the SDS3034X HD as it is, I have approx. 700Hz RBW, but also no "problems" with the signal display.

--- End quote ---

Was this question too stupid ?  :D
Edit:Pics(1M,50k,10K)..

joeqsmith:

--- Quote from: Performa01 on May 08, 2024, 05:58:39 pm ---...
The commonly agreed industry standard for the maximum acceptable input VSWR is 1.5:1, which is equivalent to 14 dB return loss.
...

--- End quote ---

I've never heard of such a standard.  Could you provide a reference?  If you are making measurements, 1.5 seems really high. 

Looking at the manual for my LeCroy 7200, they spec the VSWR at 1.2, BW is 4GHz with a 125pSec transition for 50mV and up.  Isolation is 60dB min at 1GHz.

I recently looked at SJL's sampling scope and verified the port match.


--- Quote from: SJL-Instruments on January 13, 2024, 03:00:49 am ---
--- Quote ---Wasn't sure how good your port match is. 
--- End quote ---
Not the best, to be honest: -17 dB @ 3 GHz (although we don't characterize this on a per-unit basis).
We have a design with better matching (-30 dB) at the cost of 2x noise floor. We opted for the lower-noise design, since you can get essentially the same results with a 6 dB attenuator (but not the other way around).

--- End quote ---

Once you get up to 5GHz, the return loss is around -7 and you really need to add an attenuator to improve it. 

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