Determination and analysis of radiofrequency intensities from digital television broadcasting transmitters in Kampala metropolitan, Uganda

Abstract

Digital Terrestrial Television (DTTV) broadcasting transmitters use radiofrequency electromagnetic waves to broadcast television signals to television viewers in an area of interest. The strength of a received television signal depends on the intensity of the radiofrequency radiation. In Kampala Metropolitan, Uganda, where this study has been carried out, focus has been put on radiofrequency intensities in the sub 700 MHz and the 700 MHz frequency bands. This study investigated, the spatial variation of radiofrequency intensities, the temporal variation of radiofrequency intensities and evaluation of the performance of path loss models on the distribution of radiofrequency intensities, from the digital terrestrial television broadcasting transmitters in Kampala metropolitan. The investigations and the evaluation were achieved using an Aaronia Spectran HF-6065 V4 spectrum analyzer, an Aaronia AG HyperLOG 4025 Antenna, an Aaronia GPS Logger, real time Aaronia MCS spectrum-analysis-software and a Laptop. Spatial variation of radiofrequency intensities was done in an outdoor setting for a period of two months during day hours at seven di erent measurement locations, marked on eight di erent concentric circles. It was observed that all the measurement locations have good reception of DTTV signals though their radiofrequency intensities varied at the di erent points on the same measurement location at a constant distance from the transmitter. There is a general decrease in the radiofrequency intensities in the sub 700 MHz frequency band and a slight general increase in the radiofrequency intensities in the 700 MHz frequency band. The measured Reference Signal Received Power (RSRP) values (-55 dBm to -80 dBm) for all the measurement locations where within the IEEE and FCC recommended values (-30 dBm to -110 dBm) for any DTTV signal reception. Temporal variation of radiofrequency intensities have been investigated in an indoor setting in environments like residential areas, schools, university areas and hospitals, for v three consecutive days in every environment. The mean daily and projected monthly exposure levels ranged from 0.00049 W/m²/day to 0.002542 W/m²/day and from 0.00495 W/m²/month to 0.02410 W/m²/month in the sub 700 MHz frequency band while as in the 700 MHz frequency band, it ranged from 0.00076 W/m²/day to 0.00209 W/m²/day and from 0.00769 W/m²/month to 0.07944 W/m²/month. The maximum intensities are very low when compared with the recommended International Commission on Non-Ionizing Radiation Protection (ICNIRP) safety RF intensity limits. This showed that the public is safe from these radiations. Evaluation of the performance of path loss models on the distribution of radiofrequency intensities has been achieved by performance evaluating the di erent path loss propagation models and envisaging the one most suitable for Kampala metropolitan. This was done by comparing the path loss model values with the measured eld Reference Signal Received Power (RSRP) values. The RSRP values were measured at operating frequencies of 526 MHz, 638 MHz, 730 MHz and 766 MHz for a transmitting antenna at a height of 37 m with 67.48 dBm as the transmitter power at receiving antenna heights of 1.5 m and 2.5 m. On comparing the measured path loss values with the various path loss prediction model values, results showed that Egli and Davidson models are the most accurate and reliable path loss prediction models for the distribution of DTTV RF intensities in Kampala metropolitan, since their Root Mean Square Error values were the least for both routes.