Useful software related to pulsar detection.

NOTE: the files here have been scanned with Microsoft Security Essentials - but naturally it is *your* responsibility to scan them with *your* virus-checker before execution.

If you decide not to accept this responsibility then don't download them.

RTL_SDR Applications

Various applications designed to process the unsigned-byte I/Q file data captured from RTL2832 dongles.  A default sampling rate of 2M s/s (set by specifying a 2 MHz bandwidth for the device) is assumed as this would be the most common setting for Radio Astronomy observations.

Console Application: RTL_SDR_u8.exe

Design Purpose: To reduce the size of raw RTL_SDR I/Q observation files to allow easier exchange between interested parties for simple pulse integration activities.

A small console application which can be run from a DOS window in Windows. It converts RTL_SDR raw I/Q files into unsigned byte power samples with a chosen downsampling ratio.  As an example, choosing a downsample ratio of 100 reduces the file size by a factor of 200 - i.e. a 10 GB file becomes 50 MB.

Download the Windows console application executeable here (172 kB).

Usage: rtl_sdr_u8 inputfile.bin 100 - where 'inputfile.bin' is the raw RTL_SDR I/Q data file and '100' is the downsample ratio.  For this example, the converted data is written to a file with the filename 'ds100_inputfile.u8b'.  Note: running 'rtl_sdr_u8' without command-line parameters displays a usage message detailing this.

NOTE: the input file must reside in the same location as RTL_SDR_u8.exe.  That is, the input file name must not contain a path.  An error will occur if this is not adhered to.

It has been found, for most pulsars, that a downsample ratio of 100 is a good compromise between size reduction and preservation of data information.

Other Software

Unfortunately software written for amateur pulsar detection tends to be bespoke, i.e., specially made for an individual's particular hardware.  However, Peter East and Guillermo Gancio have collaborated to produce some very useful examples which should give a good guide to the principles involved.  Look for "Set 4 - Pulsars" on page 2 of "RTL SDR Large File Software Tools - Peter East, Guillermo Gancio".   These can be used on RTL-SDR raw I/Q data files.

 There is a link in that document to a *.ZIP file of the various source code listings (currently called "").

Some Examples of the Use of the Above Linked Software

A good example of 'folding software' is "rapulsar2.exe" available from the above-mentioned *.ZIP file.  Applying this to an RTL SDR raw I/Q data file (20150420_185141_1413405_157_100.bin - about 190 MB size) with the following command line parameters...

rapulsar2 20150420_185141_1413405_157_100.bin test.txt 2 256 89.39

...outputs a text file with three columns: time bin number (0 - 255), time bin value, number of samples in each time bin.

The above command line is called from a "Command Window" in a Windows machine.  The RTL SDR raw I/Q data file needs to reside in the same directory as the executable.

The output text file ("test.txt") can be imported into a spreadsheet and the first two columns can be plotted to get the pulse profile as shown on the right (period = 89.39 ms).

The RTL SDR raw I/Q data file (20150420_185141_1413405_157_100.bin - about 190 MB size) can be downloaded from here...

The raw data file was obtained from a 50 second observation of the Vela pulsar (J0835-4510) by the 26 metre diameter dish at IAR by Guillermo Gancio.

The source code for 'rapulsar2.exe' can be found in the *.ZIP file referenced above (currently called "").

The "RTL SDR Large File Software Tools" document resides on Peter's website, a site which contains a lot of useful radio astronomy information.

Thanks to Peter and Guillermo for making this information available.