Problem with Siglent BODE II using SDS1204X-E and SDG2122X

[bnz]

I use the Siglent SDS1204X-E and SDG2122X with latest software.
I got strange looking results with BODE II when I use a span of about 100MHz (default settings apart of that). With small span of about 1MHz the plots did not look suspicious.

I ended in feeding the same signal in both inputs of the SDS and got the attached plot, with a continuous increasing gain of about 15dB over the span, instead of the expexted flat line. I tried a simple tee as well as a power splitter, different inputs at the SDS, different cables, ...  the plot remains the same.

Is there an bug at the Siglent side, or is there some setting I can mess up?

[tautech]

Maybe this excellent thread can help:
https://www.eevblog.com/forum/testgear/siglent-sds1x04x-e-bodeplot-ii-(sfra)-features-and-testing-(coming)/msg2453655/#msg2453655

[bnz]

OK I found the issue(s).

1. the chanle sampling the DUT input had the 20MHZ bandwith limiter enabled. Disabling that, the result, at least with the power splitter, was as expected. One can argue if that is a bug in BODE II, as Bode II controlls the inpus it should be aware of the bandwith limiter in conflict with the sweep span.

2. Without limiter but spliting with a tee only, the plot looked nearly as wrong as before. Adding a further tee with a 50Ohm terminator, made things looking good. Well, with using probes, this issue wil not happen.