A Simplified Canceller for Interference Waves in TV Reception Caused by Sporadic-E Ionosheric Propagation

Abstract

Recently interference caused by the Sporadic-E ionosphere has caused serious TV reception problems in Japan. This ionosphere reflects the FM broadcasting waves of neighboring countries. These waves propagate over abnormally long distances and disrupt Japanese broadcasting. This paper discusses a simplified interference canceller.
The Split-Nyquist method is proposed to cancel interference. FM waves that could interfere with TV waves are intercepted by a Split-Nyquist filter or a SSB filter, notch filters may be used with either of these as necessary.
To detect these interference waves, the FFT method is proposed. One line of a TV vertical blanking interval is first converted into a digital signal, then into the frequency domain by the FFT.
A simple canceling system was produced using these concept and field experiments were conducted that produced good results.