I will take the opportunity now to stop and review where I am with the Satellite Tracking project that my older son and I started several years ago. In 2009 we recorded several passes of a now decommissioned amateur radio satellite named HAMSAT (VO-52). With attention to the timing accuracy of the recording, I was able to estimate slant range from the receiver to the satellite as a function of time using a simple Doppler Shift model. I have then recently developed a Python script to estimate the actual location (eg. latitude/longitude of the ground track, altitude, and azimuth/elevation) of the satellite given the range/time data from three ground stations of known latitude and longitude.
The project now has some momentum in the direction of a real test sometime in the future raising the question of what radio receivers I should consider. My son has suggested the use of Software Defined Radio, a concept I like very much because it is in line with one of the unstated goals of most of my projects to do as much as you can with as little financial cost as possible. A month or so ago he mentioned Gnu Radio and a hardware device known generically as a DVB-T Dongle based on a Realtek RTL2832U circuit. The interface between GNU Radio and the dongle uses the RTL_SDR codebase as discussed at http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/ and http://sdr.osmocom.org/trac/wiki/rtl-sdr. I invested $25 to see if I could make it work. It is not a plug and play device and it does take a little work to get it operating so I am documenting what I had to do as a blog post here.
Acquiring and installing the NooElec NESDR Mini 2
While there are a lot of DVB-T dongles available, I purchased the NooElect NESDR Mini 2 on Amazon plus a PL-259 pigtail for it. Dongles from some suppliers take a long time to ship and defective devices are reportedly common.
I am programming this project in Python and decided that the best platform for the project was Linux so I installed the radio on a Dell Vostro notebook with 2 GB RAM and a 2 GHz Intel core duo processor running a brand new installation of XUbuntu 14.04 LTS. After reading several websites it looked like most pointed to osmocomSDR. There is a lot of information there. I have extracted only what I did to get up and running. My inexperience with Linux will become evident.
I downloaded the software as a package release as described on the website and extracted the archive. I tried to build the software following the instructions at osmocomSDR but the build threw several dependency errors. Save yourself some time and install these before you start.
Here is the build sequence using cmake:
sudo make install
cmake was not installed so I did a
sudo apt-get install cmake
and tried again. This time the error was that the libusb1.0 library was not installed. The osmocomSDR website very explicitly says this is required. In my previous experience with Linux I have used the synaptic package manager to download things like this but it is no longer installed by default. Most of this stuff could have been install from that…I have installed it now, after the fact. I downloaded the build package for libusb1.0 from SourceForge and extracted it. It threw an error in the configure step that libudev was not installed. I installed it from the Ubuntu Software center.
After that the build as described on osmocomSDR went smoothly to completion.
The installed codebase has several command line programs so I ran the first one described on the website
rtl_fm -f 96.3e6 -M wbfm -s 200000 -r 48000 – | aplay -r 48k -f S16_LE
I was greeted by the gentle hiss of a radio that was tuned to dead air. I exited and edited the command to
rtl_fm -f 95.3e6 -M wbfm -s 200000 -r 48000 – | aplay -r 48k -f S16_LE
our local FM station. This time I was greeted by the local high school girls basketball game at the some kind of state championship or something. I must admit that I was never so happy to hear a basketball game as I was this one.
Then I installed a SDR called GQRX from the Ubuntu Software Center. After fooling with the controls (mainly the receiver gain which is set to automatic by default) I got it working too…the blue LED in the lower right is the dongle. Shown here tuned to a nearby repeater for our regional NPR station.
Finally, I downloaded Gnu Radio from the Ubuntu Software Center and prepare to build the rtl_sdr source block for it. I ran the Gnu Radio Companion first though and was surprised to find the Osmocom rtl_sdr block already there. I had installed Gnu Radio on another identical install of XUbuntu and there were no sources shown.
Here is a screen shot of Gnu Radio Companion ready to build a radio based on the rtl_sdr dongle. I will describe that too once I figure out how to do it.