A network monitoring and network congestion analysis can be performed based on a comparison of data packets at multiple different network nodes installed at different locations on a communication path. The invention consists in making the backing layer of such an antenna with a heat-conductive foam and enables the transmission power to be appreciably doubled. At least a portion of the exposed electrically conductive electrode material is removed while an electrically conductive veil is formed adjacent the mask layer. The substrate may be constituted of a material having properties such that, when the excitation light is irradiated to the material, the material does not produce fluorescence having a wavelength identical with the wavelength of the fluorescence produced by the fluorescent material. A triode field emission cold cathode device having randomly distributed field emission emitters is also provided.