A method to extend the downstream and upstream data carrying capability of an HFC CATV system. At the neighborhood level, the CATV cable (the primary channel) is divided into different segments connected by electrically active junctions. At the junctions, each segment is also connected to a secondary data channel, such as an optical fiber or ultrahigh RF frequency (1 GHz+) secondary channel, which can carry supplemental downstream narrowcast channels and upstream channels between a plurality of such CATV cable segments. At the junctions, some CATV primary channel RF signals such as broadcast channels are passed without interference, while certain primary channel downstream narrowcast RF channels and upstream narrowcast RF channels are precisely suppressed using adaptive cancelling methods. Such adaptive cancellation methods are superior to prior art lowpass, highpass, and bandpass filtering methods because they allow for more efficient use of limited CATV primary channel RF spectrum.