Interpolation Issue in Log Sweep Mode (and some other functional feature requests)

[njyq2008]

Hi, Jankae!
Thank you so much for developing such an extraordinary open-source project!
I would like to share my feedback with you.

1. Interpolation Issue in Log Sweep Mode
   When using the Log sweep in VNA mode, I observed that the measurement results in the low-frequency range seem to have interpolation issues after calibration, leading to inaccurate data. I wonder if this is due to algorithmic limitations or if there are plans to optimize this aspect. If you need more details or test data, I would be happy to assist.

2. Suggestion for Max Hold Function in SA Mode
   The SA mode is quite useful. However, adding a 'max hold' function might significantly enhance its practicality in applications like EMC troubleshooting. I hope you can consider adding this feature in a future version :)

3. Support for Reverse Frequency Sweep in VNA Mode
   I have a specific testing scenario that requires the VNA to sweep from high frequency to low frequency. Currently, LibreVNA only supports sweeping from low to high frequency as limited by the GUI itself. I was wondering if it would be possible to add an option for reverse sweeping in the future? This would be very helpful for my current project needs.

Once again, thank you for your work and dedication!

[jankae]

Hi and thank you very much for the feedback.

1. This is a known issue in the latest release, see also the discussion here: https://groups.io/g/LibreVNA-support/topic/114223721#msg3846
   It is already fixed in the development builds and if you do not want to wait for the next release, you can download the latest build here: https://github.com/jankae/LibreVNA/actions/runs/17359871272

2. That feature already exists, you can find it in the trace edit dialog:
   
   I still do not recommend the LibreVNA for EMC troubleshooting, at least not when the exact amplitude matters. The hardware is primarily a VNA and the spectrum analyzer function is rather limited.

3. The LibreVNA itself should already support that although I have never tested it so far. As far as I know the only thing preventing you from doing a reverse sweep is the GUI because it enforces stop frequency >= start frequency. Could you tell me a little bit about your application and why that feature is required?

[njyq2008]

Thank you so much for your prompt and detailed response! I'll try the latest firmware!

Regarding the reverse frequency sweep, my current research focuses on low-dimensional material nanodevices, which exhibit nonlinear effects under high driving forces. The ability to sweep from high to low frequency is crucial for studying hysteresis effects in these devices, as the hysteretic behavior often manifests differently during forward and reverse sweeps. This feature would allow us to characterize such phenomena more comprehensively.