Build a DIY Radio Telescope Using Roof Flashing and an Empty Paint Thinner Can

After his friend spent some time learning about radio telescopes, IEEE Spectrum editor David Schneider wondered how big of a telescope would he need to see anything of interest. It turns out it’s not that large — about 20-inches across. Schneider spent less than $130 and built a DIY radio telescope that is capable of detecting the motion of the Milky Way galaxy’s spiral arms. His first approach began with a used satellite TV dish and coffee can centered on the dish’s focus, acting as a waveguide.

Unfortunately, the can was too small for the wavelength Schneider was looking for- 21 centimeters, which is the wavelength of neutral hydrogen emissions, and what astronomers use to map the location and motion of space gas. After a few Google searches, Schneider settled on creating a horn antenna, utilizing an empty can of paint thinner and some aluminized foam board insulation, which he scrapped when he found the board couldn’t conduct electricity.

After ditching the aluminized foam board, Schneider found success with aluminum flashing (roofing material) and HVAC tape, which he fashioned into the antenna horn. He then added a waveguide pin to the inside of the can using an N-type coaxial bulkhead connector, which he then connected a Nooelec NESDR SMArt XTR SDR dongle and SAWbird SAW filter and ultra-low noise amplifier. The SAW filter allowed Schneider to zero in on the 1420MHz signal needed to track neutral hydrogen emissions, while the dongle provided the power to boost the amplifier.

The Nooelec NESDR dongle came bundled with free HDSDR software that Schneider used to detect the neutral hydrogen line on ‘first light,’ or first use of the telescope. Schneider wrote a complete walkthrough on how he built his DIY radio telescope in his IEEE Spectrum article for those interested in recreating his project.