AR_final file_2018-19

The laser will act as a carrier and the audio is given as a modulating signal to the solenoid, the audio signal modulated in the presence of Faraday material (TGG) and demodulated by converting polarization modulation into intensity modulation at the photo detector. The power requirement is very low as compared to the existing analog modulation techniques. The system is successfully working over the audio bandwidth. 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 radio 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 has been used in MSc practical in radio astronomy, as well as in Radio Astronomy Winter Schools. The antenna has also been used to demonstrate principles of radio astronomy to amateurs as well as for public outreach. The 21 cm 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 a very crucial line in the field of radio astronomy. A horn antenna was designed for detecting this 21 cm line from our galaxy. A primary limitation of radio astronomy 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 21 cm 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. HORN ANTENNA FOR 21 CM HYDROGEN LINE ( 162 )