BBC R&D

Abstract

In 1983 CCIR IWP 5/5 put forward a number of proposals for improvements to the field strength prediction methods of CCIR recommendations 370 and associated report 239, as used for international planning negotiations in the VHF and UHF Broadcast Bands. This report describes the results of studies carried out by the BBC, in conjunction with other propagation investigations, to assess the vaildity of those proposals of IWP 5/5 which relate to propagation over path lengths in excess of about 100km in the VHF Bands. It is concluded that these propasals can be supported with only one exception, relating to an addition of 7 dB to beyond-horizon oversea curves. Subsquently, the VHF proposals (excepting the one relating to the 7 dB correction) have been endorsed by CCIR Study Group 5 and adopted by the Plenary Meeting in 1986 for inclusion as modifications to Recommendation 370. Even so limitations in the existing methods are identified and further work is proposed.