A twenty hour drift scan of the Milky Way showing the 1420 MHz signature of hydrogen clouds.

Description

Example scripts for doing simple hydrogen line radio astronomy on the Raspberry Pi using inexpensive equipment easily availble online. These do not comprise a good general-purpose "out of the box" solution, but should provide a useful template for those looking to do the same.

This approach is based on an excellent tutorial from the RTL-SDR Blog [1], but uses an inexpensive Raspberry Pi for data acqusition instead of a Microsoft Windows PC. This allows for a more trivial external location and continuous capture of the desktop to record results.

Contents

• take_baseline.sh : Script for collecting baseline data (must be run before hydrogen_obvs.py, with 50 Ohm terminator attached to LNA input instead of antenna)
• hydrogen_obvs.py : Script that collects power spectrum data and refreshes a plot
• timelapse.sh : Script to create timelapse of desktop (adjust per-second framerate and resolution with --framerate and -s options)

Detailed view of hardware used for this experiment.

Rough Software Setup Guide

Acquire hardware as per Reference 1, selecting an SDR with a software-togglable bias-T, and an LNA powered via bias-T.

1. Install Raspbian on a Raspberry Pi, setup to be "headless" (also change default username/password)
2. Log in via ssh to Raspberry Pi and install xrdp to enable remote desktop logins
3. Log in to Rapsberry Pi via Microsoft Remote Desktop
4. Install rtl-sdr software as per Reference 2
5. Install rtl_power_fftw command line tool via Reference 3
6. Install Stellarium app, set to appropriate location/time, toggle alt-az coordinate grid and point toward zenith
7. Install matplotlib Python package
8. Connect 50 Ohm terminator to antenna input of LNA and acquire baseline data with take_baseline.sh script
9. Re-connect antenna and run hydrogen_obvs.py script to begin data acquisition and display
10. Run timelapse.sh to begin capturing a timelapse movie of desktop

References

[1] https://www.rtl-sdr.com/a-good-quickstart-guide-for-rtl-sdr-linux-users/

[2] https://ranous.files.wordpress.com/2020/05/rtl-sdr4linux_quickstartguidev20.pdf

[3] https://github.com/AD-Vega/rtl-power-fftw