Today Radio Astronomy needs support from the human community for RFI free zones to set up Radio-Telescopes. In spite of best support from the government, geographical site location and other sources, man made interference is growing. The Omni directional RFI monitoring system was made for studying the various effects of RFI on the GMRT data and also locate the possible RFI sources. It consists of Four log-periodic-antennas looking towards East, West, North and South directions in the E-plane at a height of 20 meters. The output from the antennas are spectrum analyzed and stored in four files representing the four directions. The antennas are switched in a cyclic fashion throughout the time of observation. The 4-direction RFI data is thus made available for statistical and other analysis after the observation.
Figure in beside shows Omni directional RFI monitoring system tower. The 4 antennas are placed in the E-plane in orthogonal directions, viz. East, West, North and South. The computer selects the antennas sequence of North-West-South-East using the parallel port & decoder circuit. After each selection the incoming RFI power is amplified (LNA) followed by spectrum analysis and finally recorded in the file in the computer. This cyclic process is continued throughout the observation.