Evaluation of the Signal Coverage Zone Segmentation of Broadcasting Stations in Calabar Nigeria

This research examines the coverage areas of very high frequency (VHF) and ultrahigh-frequency UHF) signal strength of terrestrial television stations (CRBC Calabar and AKBC Uyo) located within two states of proximity 99.4 km apart within the same South-South zone of Nigeria within the same climatic zone (Tropical). Measurement of the Expected Signal Strength (ESS) was carried out along the different routes and Local Government Areas (LGAs) of the states with each of the terrestrial television stations reference points about 15 and 45 km radius respectively from the base station, using Calabar and some LGAs as a case study considering the city closest to the VHF Channel 11 transmitting at radio frequencies between 54 and 216 MHz, and UHF channels at 470 and 890 MHz. A Digital cable Television Analyser (CATV) with an external television antenna of 59 (L) × 8.5 (W) × 11 (H) cm on a pole of about 9 m and a GPS receiver were used to measure the geographic coordinates, elevation and Line of Sight (LOS) of data points along the routes in a driving test. The VHF and UHF transmitters were measured radially along several routes with the transmitting stations at focus. Their corresponding distances from the transmitting stations and locations were also measured. The measurements at different locations within the 15 and 45 km of the reference points were conducted. The (CATV) has a frequency range from 40 to 890 MHz; while tuning from channel 1 through 69. The locations were segmented into primary, secondary and fringe zones for proper signal testing and collation. The analyses of channel 11 across all the LGAs show that 5% fall in the primary coverage zone with 60.4 dB μV signal strength, ≤ 60% dwells in the secondary coverage zone with ≤ 60 dB μV signal strength while ≤ 30% dwells in the fringe zone of ≤ 30 dB μV signal strength. Channel 27 shows 40% are in the fringe zone. A situation which shows over 50% of the city is unable to receive clear signals from the broadcasting stations and Channel 45 identified 97% are in the fringe zone of this signal. The highest signal strength of 60.4 dB μV was measured around the Ikot Ebong Eyo axis (72 km) and faded completely at Effio-Ette (96.2 km) and Satellite town (98.8 km). Analysis shows that Calabar city, which is the closest to the VHF Channel 11 transmitting station is not within the primary coverage area of the transmitting station because the signal strength measured is approximately 60.4 dB μV. The Path loss of the different channels (11, 27, 45), confirmed 47 dB signal loss along the line of sight with a steep regression of the signal strength with distance; and a high increasing path loss which further established the poor quality of signal strength received by the residents which further shows the area where the base station is sighted is not a primary coverage zone based on the measured data. The results obtained showed that the present configurations of the transmitters for all the television stations did not give an optimum coverage area. Only 30% of the entire landmass of the state has television signal coverage during the rainy season. Consequently, some areas in the state are completely out of television signal coverage. So there is a need to have repeater stations at certain intervals to provide reception of television signals for all the parts of the states. The overall results will enable System Engineers to know the appropriate distance(s) and locations to site additional stations for networking purposes and prepare a power budget for optimum coverage area and good quality of services for terrestrial digital channels.