Products > Test Equipment

Siglent SDS800X HD Review & Demonstration Thread

<< < (71/87) > >>

Martin72:
Nice. :-+
"Fun" fact:
The different modes (Average, Max Hold) are not available with the "normal" FFT from Lecroy.
You have to buy them with the "Spectrum Analyzer" option....

EEVblog:

--- Quote from: Martin72 on May 06, 2024, 05:24:54 pm ---Today, at work...
Lecroy Waverunner 9054(8bit), HDO6034A(12bit).
FFT with 100khz span, source Siglent SDG1062X, 50Mhz, 0dBm, 50Ohm.

Maybe we should have the last pages separated and moved to a new thread, title suggestion "FFT comparison and settings".


--- End quote ---

Split from which post exactly?

Martin72:
Hi Dave,

Start with this please:
https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/msg5483791/#msg5483791

electronics hobbyist:

--- Quote from: Martin72 on May 04, 2024, 07:51:08 pm ---
--- Quote ---0 dBm 1 MHz carrier, AM modulated with sine wave 10Khz / 100%, sourced by SDG2042x
--- End quote ---

In addition, you have changed the window to "Blackman" and manually reduced the sample rate to 10MSa/s,  to complete the settings...
Then I get the same result.
I don't know if these are the right settings.
In any case, anything below -72dBm can be doubted as to whether it actually exists.
Possibly these "artifacts" below this threshold are faded out in the DHO, unfortunately I don't have any more to investigate this.

--- End quote ---

The comparison chart of this keysight shows that the SDG output has these frequencies.

Performa01:
50 Ω Termination and probing

I sometimes see discussions about 50 Ω termination at the scope inputs. Some seem to believe that scopes with switchable 50 Ω inputs are just a luxury, that can easily be replaced by an external through-terminator or a BNC-T with end terminator.

Even though I’ve often commented on this very topic already, I want to repeat it here with especially the SDS800X HD in mind.

The commonly agreed industry standard for the maximum acceptable input VSWR is 1.5:1, which is equivalent to 14 dB return loss. This tolerates 4 % power reflection with its associated amplitude errors. It goes without saying that oscilloscopes with properly designed switchable 50 Ω inputs, like the SDS2000X series and anything above from Siglent, provide a VSWR ≤1.5:1 up to and beyond their full bandwidth.

Now let’s have a look at all these emergency solutions, like external through-terminators and BNC-T with end termination, which all have a perfect VSWR of 1:1 up to 250 MHz when not connected to anything.

First let’s connect the ancient hp10100C through-terminator to a real scope input, like the 1 MΩ // 17 pF in case of the SDS824X HD:


hp10100C_SDS824X HD_VSWR_73M

The VSWR reaches 1.5:1 at 73 MHz. Beyond that, we’ll have to face substantial linear distortion.

Here’s another test with the through-terminator RS-456-150-50Ω, which is the Tyco part B35 X13 • 999 X99, connected to the SDS824X HD:


RS-456-150-50Ω_SDS824X HD_VSWR_78M

The VSWR reaches 1.5:1 at 78 MHz, hence is a tad better than the venerable hp10100C.

Finally, the BNC-T with 50 Ω end terminator connected to the SDS824X HD:


BNC-T50_SDS824X HD_VSWR_78M

The VSWR reaches 1.5:1 at 78 MHz, hence its effect is the same as the RS-456-150-50Ω.

Just for orientation, here’s the VSWR-plot up to 3 GHz for the hp10100C not connected to anything:


hp10100C_VSWR_1157M

The VSWR reaches 1.5:1 at 1157 MHz, hence would be useless for higher bandwidth oscilloscopes. By contrast, here’s the VSWR-plot up to 1.2 GHz for the SDS2504X HD and its 50 Ω input path:


SDS2504X HD_V200mV_VSWR_1130M

Here the VSWR reaches 1.5:1 at 1130 MHz, which is very similar to the hp through-terminator alone. Now, at the latest, it should become clear that 50 Ω input mode is more than just a resistor switched across the input connector. I do not have any SDS1000X HD here, but would not be surprised if its VSWR was similar to the SDS2000X HD.

An oscilloscope without 50 Ω inputs is fine as long as you stick to the supplied probes, but circuit loading might become a problem at relatively low frequencies like 20 MHz already. Passive x10 “high impedance” probes with e.g. 10 pF tip capacitance represent a 200 Ω load impedance at 80 MHz after all. On the other hand, it can only perform up to some 80 MHz without noticeable linear distortion when using direct coax connection.

Conclusion:Whenever you plan to do serious work at higher frequencies, then you should consider an oscilloscope with proper 50 Ω inputs. In order to avoid expensive active probes, you should better design appropriate 50 Ω test points into your prototype circuit.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod