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Bode plotter: huge distortions at certain frequencies
Posted: Sat Dec 29, 2018 3:54 pm
by mark_dammer
I notice that the Bode plot is showing crazy results at certain frequency ranges. Using the standard calibration setup I am getting jumping amplitude and phase at these ranges (see attached plot):
17 - 27 MHz
47 - 51 MHz
53 - 56 MHz
Is this known behaviour and are there any workarounds for this problem ?
I tried both the Bode plotter app that come with the RedPitaya and the one on the Marketplace. Both show the same distortions.
Re: Bode plotter: huge distortions at certain frequencies
Posted: Wed Sep 11, 2019 2:19 pm
by redpitaya
Please give more details on what you are measuring and how.
This shows how it should look and work
https://www.redpitaya.com/f136/bode-analyzer
at the same time , more details you can find in this documentation
https://redpitaya.readthedocs.io/en/lat ... light=bode
It seems you might have some pins set up the wrong way, we will see.
In the case you cannot share details here, please hit me up on
support@redpitaya.com
Re: Bode plotter: huge distortions at certain frequencies
Posted: Sat Oct 10, 2020 9:37 am
by NL_Toontje
I have the same problem with the STEM 125-14 v1.0 (OS 0.99-48).
I want to measure a LPF, but when calibrating it already goes wrong.
According the manual I connect IN1, IN2 and OUT1 together with the jumpers in the LV position.
The result of the calibration run is attached as well.
What do I do wrong?
Re: Bode plotter: huge distortions at certain frequencies
Posted: Thu Oct 22, 2020 3:50 pm
by bma
Hi,
You may have to add a 50ohm in front of the ADC.
Re: Bode plotter: huge distortions at certain frequencies
Posted: Mon Nov 16, 2020 3:53 pm
by redpitaya
Yes, please add 50Ohm terminations via a T-sma connector on IN1 and IN2
Re: Bode plotter: huge distortions at certain frequencies
Posted: Thu Nov 19, 2020 1:26 pm
by redpitaya
Black Friday 2020 is here!