By Rene Voyer, Communications Research Centre Dept of Communications, Ottawa, Ontario
A method of measurement was recently developed at CRC to evaluate amplitude and group delay responses of TV channels, broadcast or cable.
This method makes use of conventional test instruments or modified instruments when the channel being investigated has a bandwidth exceeding 4.2 MHz. It was adopted and used by the CABSC (Canadian Advanced Broadcast Systems Committee) during its cable TV field test program in November 1988, which was aimed at characterizing 12 MHz wide cable channels for transmission of HDTV signals. The test method has also been adopted by the ATTC (Advanced Television Test Center) for the characterization of wideband off-air channels in the VHF, 2.5 GHz and 12 GHz bands. Actual tests are underway in Washington DC. This paper describes in detail the concept of the measurement method and its implementation.