Category Archives: RTLSDR

Successful reception of the Yutu landing

Yesterday the Chang’e3 spacecraft andt the Yutu rover was landing successfuly. I was start to track the moon since the 18:30 to the 22:30 UTC. And I was listen Yutu from the start of my window and the signal was over 15dB of SN at 1Hz of BW. The frequency of the rover is 8462.08000MHz with the moon doppler of -0.6Hz/s of aprox. The signal was easy to listen in the earphones, and sounds like a some kind of morse.

For this event I was setup two receivers, as main a AOR AR5000 and Rfspace SDR14. As second receiver a rtl-sdr doongle with r820t tuner and baudline.

Yutu rover, using AR5000 + SDR14

Yutu rover using rtl-sdr + baudline

The command line to use rtlsdr with baudline was:

rtl_fm -g 44 -d0 -f$1 -s 250000 -F -U | ./baudline.static -stdin -samplerate 250000 -channels 1 -session rtlsdr1chUSB0 -basefrequency $1

Yutu rover using rtlsdr + baudline

Now you can listen how sounds the data stream from Yutu. A short audio record of the signal demodulated:

RTLSDR Coherence first test

The first test to see the coherence of two rtlsdr in realtime consist in do a cross-correlation of the two dongles, the cross-correlation is a measure of similarity of two signals.

To do the test I used baudline and tuned to a local VOR/DME. Here in the first picture can see some coherence of the two dongles using one antenna to every rtlsdr:

RTLSDR baudline cross-correlation with 2 antennas

Here the result if disconnect one antenna:

RTLSDR baudline cross-correlation with 1 antenna disconnected

RTLSDR Coherence setup

After the nice videos that Juha Vierinen has shared, looks that some people is interested in use multiple rtlsdr coherent for radar applications for example. I’m starting my experiments with this setup:

RTLSDR Cohernt setup

My setup consist in two rtlsdr dongles with r820t tunner with the xtal removed, connected to a PTS-160 Synthsesizer tunned at 28.8 MHz and locked to 10 MHz GPS reference.

SDR & RadioAstronomy rack

With coherence using radar mehtods, you can get cool images like:

Perseids shower using graves radar

The past agoust I was build a passive radar to detect the Perseids meteor shwoer . The most easy way is locate a very away transmiter and try to se the echoes produces by the meteors ionizacion.

Perseids meteor Graves radar

To do the detector I used a rtlsdr receiver tuned to the Graves radar at 143.050 MHz, a ground planae VHF antenna and Baudline to display the scatters. Putting all toghetther using this script: