Re: Frequency shift when Airspy HF "DSP library" enabled

David J Taylor

Hello David,

this is due to linking with a more recent version of libairspyhf. Frequency correction is done via a library function (airspyhf_set_calibration). A lot of things are done in software with libairspyhf including precise LO correction via NCO. LO precise correction and other features like enhanced DC and IQ imbalance correction are optional and driven by activation of "DSP" feature which is linked to the "DSP" button in the UI that is active when background is orange.

For the other issue you mention that would require a core dump but I have no idea on how to get it and read it in Windows. However it is also necessary to know about the context and this is possible via the REST API and Swagger UI. When everything is set by default this is accessible via http://localhost:8091. Then you can click on Interactive Swagger UI documentation and access to Swagget UI.
- GET /sdrangel gives general information about the SDRangel instance, the devices and channels attached.
- GET /sdrangel/config lists all persistent values and presets. It can be large so you might be able to select only the preset in question.

In both cases clicking on "Try it out" and "execute" yields the JSON response in the "response body" box below.

With this information I can possibly try to reproduce the problem.

Brgds, Edouad.


Thanks, Edouard.

On the Airspy HF/Discovery, there should be no need for SDRangel to supply correction as the unit holds its calibration. What surprised me was that the shift was as much as it was (5 kHz), and that it was a constant shift almost independent of frequency. It's easy to live with.

OK on the crash. It /may/ be when a new preset is selected while the receiver is running. To start with, I'd like to know whether other Windows users are seeing this, or if it's just me!

David GM8ARV
SatSignal Software - Quality software for you
Email: david-taylor@...
Twitter: @gm8arv

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