Over on his blog author Daniel Estevez has described how he's been listening to aircraft reflections from a 2.3 GHz 2W beacon. The beacon is 10km away from Daniels location and transmits a tone and CW identification at 2320.865 MHz. As aircraft fly nearby to his location Daniel was able to observe aircraft reflections of the beacon, and was able to match them with ADS-B position and velocity reports.
The hardware that he used was a LimeSDR and a 9dBi 2.4GHz planar WiFi antenna patch. By aiming the antenna away from the transmitter, and using his car as a shield to block the transmitter he was able to receive some reflections. Daniel recorded several reflections including one produced by a nearby car.
By combining his results with ADS-B data he was able to superimpose the results, and color aircraft tracks by either a negative or positive doppler shift which was observed from the reflection. By combining the ADS-B data with the time stamps, he was also able to mark the reflections from each aircraft.
In the thread the original poster used a standard hardware radio, but an RTL-SDR dongle or other software defined radio could also be used. He tuned to a strong analogue TV carrier and plotted the audio spectrograph in Spectrum Lab. If analogue TV is no longer available in your country other strong signals such as amateur radio beacons or radar signal carriers could also be used for aircraft scatter.
Below we show a small selection of some of the interesting images from page 9 of the thread, please see the actual thread for the rest. There is also more information and images contained in the other pages of the discussion thread too.