SDRuno, dBm levels incorrect in Main SP window during playback

[FrancoisD]

When using SDRuno to play an I/Q file recorded from an RSP2pro with SDRuno,
the displayed spectral representation can be off (sometimes) tens of dBm's.

For example, a noise floor recorded around -140 hovers around -116 during playback.

It seems some (necessary) underlying settings are not saved along with the WAV file to ensure accurate playback.


The workaround I found is to make a recording to reset settings prior to playback:

1 - In the Main window, press the Opt button and set the input to the RSP.
2 - In the Main window, set SR, Dec and Gain to what was used at the time of the desired recording.
3 - In the Recorder window, make a new recording. A few seconds suffice.
4 - Stay in SDRuno and proceed to play your old recording.

I am running SDRuno 1.22 on Windows 7 and Windows 8.1 machines.

Thank you SDRplay for these wonderful devices and the great software.

François
Granby, QC, Canada

[Tech_Support]

Hello Francois,
All SDR programs receive an I/Q stream from the ADCs and so all magnitude information is referred initially to the ADC input. To convert this to an antenna referred power level, the software uses a combination of the RSP gain setting values and calibration tables to calculate what the equivalent antenna port input power levels are.
If you simply start SDRuno and play a WAV file, the software has no way of knowing what the gain levels were when the file was recorded and so the calculated power will be incorrect.
When you switch back to the RSP and set the gain settings to the correct values and then switch back to the WAV file as an input, SDRuno has the gain settings stored and so is able to perform the correct calculation to convert the ADC input level to an antenna referred power level.

Sincerely

SDRplay Tech_Support

[FrancoisD]

Thank you very much, Tech_Support,

All experimenters take note: better write down those settings in your notebook for future reference.

Maybe someday, some of that could be recorded as WAV Metadata by the program itself.

François

[FrancoisD]

Key statement is "When you switch back to the RSP and set the gain settings to the correct values and then switch back to the WAV file as an input"

There is no need to <record>, simply run the RSP briefly with the same settings as the old recording to achieve valid results.

Apologies to SDRplayers.

François