I have investigated through my Master research project the suitability of the site for installation of the 25-meter Nigeria Radio Telescope (NRT) which is now under construction. This has been made by monitoring and discovering various possible sources of artificial noise causing radio frequency interference (RFI) at the proposed site for the installation of the Nigeria Radio Telescope ((NRT) under the oversight of the Centre for Basic Space Sciences (CBSS) in Nsukka (7.67oE, 6.9oN), Nigeria.
In the RFI survey, the spectrum analyzer, SPECTRAN HF 6080 was used with taking into consideration the signal power as well as their respective power densities. The panning approach was applied in obtaining the radio frequency spectra. Within the 7GHz limit of the SPECTRAN HF 6080, frequency ranges allocated for Radio Astronomy usage by International Telecommunication Union (ITU) radio chart as well as the Nigeria Communication Commission (NCC). Also other frequency ranges not designated for Radio Astronomy within the limit were investigated for finding RFI. Obtained data were manually inputted into the computer and then the plots and deductions were made.
In the resultant site spectrum, it was observed that much of the noise signals originate from the Global System of Mobile Communication (GSM) and broadcasting in the frequency range of 932 – 1822 MHz. Likely background noise sources as observed from the site may include trunk radio systems, rural telecommunication systems in 455 – 500 MHz and 845 – 866 MHz frequency ranges respectively. Understandably, there would be some noise contribution due to some natural phenomena. The effect of the variation of the seasonal weather conditions was also put into consideration. The least absorption of radio signal was observed between mid-January and late February and this corresponds with the periods of low humidity as verified from meteorological data. From the survey, the signal absorption gradually increased from March and was most significant in July. Complete disappearance of radio signals of frequency ≤ 300MHz in the wet season indicated complete absorption of such signals. RFI is moderately low as indicated by ~10dBm difference in the signal power with varying season, thus showing that the location is relatively good for the installation of the 25-meter NRT.
My research results may provide important information useful for the specification
and construction of the NRT receiver system, especially the filter system. It also brought to limelight the need to improved radio frequency usage and management in Nigeria.
