Simple 2-channel coherent FM Receiver

Piotr Krysik has developed a GNU Radio block “Multi-RTL”. In this post we provide a very basic example how to use this block for the FM-Radio improvement.

Please see the coherent averaging post for more details about the SNR improvements using coherent receivers.

Moreover, the user Fabio writes in the RTL-SDR blog following comment: “Using multiple receivers could be interesting also to perform noise reduction. Combining samples over the same band could reduce the Gaussian Noise. Filtering out the signal from a reference receiver with the RF input terminated with a dummy load could be used to reduce system noise. Filtering out the signal from a reference receiver with reference antennas could be used to reduce other site specific noise. Would be nice to have such alternatives explored in a dynamic way, where you can trade sensitivity and bandwidth on the run.” Indeed, that can be very interesting experiments that we could make in the future.

The resulted sound was without delays or reverberations.

GNU Radio Schema

Channel delays estimation using Multi-RTL

No antenna connection

Antenna connected to the 1st receiver

Antenna connected to the 2nd receiver

Antennas connected to the both single channel receivers