30th Annual Report 2017-18

160 HornAntenna for 21cmHydrogenLine The 21cm hydrogen line is a spectral line emitted by atomic hydrogen. Since Hydrogen is the most abundant element in the universe, this makes the Hydrogen line very crucial in the field of Radio Astronomy. A horn antenna was designed for detecting this 21cm line from our galaxy. Aprimary limitation of RadioAstronomy is noise, either man-made or naturally occurring. Hence, we require new techniques to reduce noise from our detector. The horn antenna is a high performance, high gain and low noise antenna, specially designed for detection of the 21cm Hydrogen line. The antenna is able to pick up radiation from the Hydrogen clouds in our galaxy while suppressing terrestrial interferences due to the low side lobes of the antenna. The antenna is easy to handle and is superior to a parabolic dish in terms of noise performance. The horn has enabled us to study Hydrogen line profiles from the galaxy. The spiral structure of the galaxy can be estimated. It has also made it possible to estimate the rotation curve of the galaxy. The antenna is a dual mode conical horn, and is easy to construct as compared to other antennas with similar noise performance. Software Defined Radio (SDR) receivers were used with great success with this antenna. SDR is a new advancement in radio technology. The limitation of the conventional radios, is its inability to configure the hardware. SDR can be configured to serve any purpose of the user. Such a receiver was implemented successfully for detection of Hydrogen line. Important techniques like Dicke switching were implemented with SDR. This has made the telescope low cost and hence, accessible to amateur radio enthusiasts. The antenna has proven to be very reliable. It will be used in MSc practical in radio astronomy as well as in Radio AstronomyWinter Schools.