I have some nice gadgets handy, such as R820T dongle for RTL-SDR, nice WW2 gun-mount 3m dish, s53mv preamp and a S57UUU paprika-feed. Let's try to do some radio-astronomy experiments, with this hardware it should be possible to find the 21cm hydrogen line first.

I had some trouble finding software for spectrum display with long averageing window, or better to say something that would run with my version of gnuradio and on Ubuntu Linux 12.04. The simple_ra only runs with gnuradio 3.6 and i was not able to compile it on my latest version (3.7).

Marko S57UUU sugested to write my own software (it's obvious, since he got  ERAC FFT-DSP award), so i started writing code and while searching for some copy/paste stuff i found an interesting project  - rtlizer software by OZ9AEC developed for a beaglebone. I tried to run and compile it on my system and it worked immediately, it is very clean and simple, so i only added averageing and gain control.

I have put the sources here lana.hamradio.si/~s57ra/images/astronomy/software/rtlizer.tar.gz

Just compile it (./compile) and run (./run.sh).

Depending on GTK you have on the system, you might have to un/comment the line in compile script. I am using ubuntu 12.04 and i had to install gtk-devel package:

sudo apt-get install libgtk-3-dev

Run the spectrum analyzer with window size parameters as:
rtlizer 640x360+0+0   

commands while running:
F1 - print various data about receiver in terminal window
F2 - toggle AGC (auto/manual)
F3 - decrease gain
F4 - increase gain
TAB - increase averageing
SHIFTTAB - decrease averageing
LEFT - decrease fq
RIGHT - increase fq
PGDWN - decrease fq 100MHz
PGUP - increase fq 100MHz
KEYUP - increase BW
KEYDN - decrease BW
ENTER - exit app.

The 3m dish is quite narrow, so i had to find a way how to catch the radio source in a Swan constellation. When i used it for the 5.7GHz Moonbounce i just mounted a camera and a noise meter to track the moon,.. but a decade later, there is a nice gadget on my mobile phone, a software called SkEye, so i just placed my phone to the back of my aluminium dish, calibrated it on a noise source (sun) and voila, precision tracking is now available ;). While tweaking hardware, the swan flew away down to the horizont, and the next target was Orion. I managed to get a first clearly visible hydrogen line there. 

Hydrogen line is clearly visible, antenna pointed towards ORION.


osmocom_fft picture of orion Hydrogen line. DC spike in center.

tracking the objects in the sky with a mobile phone

Allignment with the SUN

S57UUU & his Paprika-feed, broadband from 1.2-1.5 GHz


mounted paprika-feed