KiwiSDR IQ data streams with >20.25 kHz bandwidth (5)

By now, gr-kiwisdr can coherently combine between 2 and 6 IQ data streams recorded from the same KiwiSDR.

Following an idea by WA2ZKD, the following test was made with DRM signals: three data streams were recorded, one centered on the DRM signal on 15120 kHz and two more centered on 15112.5 kHz and on 15127.5 kHz which were then coherently combined into a signal data stream. The GNURadio display is shown below:

Coherent combination of two IQ data streams using gr-kiwisdr.

Both, the WAV file centered on 15120 kHz, and the combined WAV file were successfully decoded by DREAM:

DREAM display

The SNR is comparable for both files, taking into account that it fluctuates by about ±0.5 dB:

DREAM waterfall display for the combined WAV file.

DREAM waterfall display for the WAV file recorded on the center frequency.

Only one slight difference was found in the SNR per carrier display: although the SNR per carrier is fluctuating quite a lot, for the combined WAV file there is a dip around the center which is not there for the WAV file recorded on the center frequency:

DREAM SNR per carrier display display for the combined WAV file.

DREAM SNR per carrier display for the WAV file recorded on the center frequency.