A meshed cathode structure particularly for use in high power grid-controlled transmitting tubes comprises an electrically conductive tubular current lead-in member provided with a frusto-conical support which is also electrically conductive. The periphery of the frusto-conical support is provided with circular arrays of uniformly spaced apertures and recesses, the arrays being offset circumferentially relative to one another, and the adjoining ends of two cylindrical meshed cathode components are welded respectively at mesh junction points at the apertures and recesses.
In a directly heated meshed cathode made of one metal piece in the form of a hollow cylinder, the working surface is constituted by intersecting helical filaments 3 and 4 with holes 5 therebetween, each filament 3 and 4 being formed with a stepped increase in the width from periphery to center of the cathode. A method of making the meshed cathode comprises fabrication of a tool electrode out of a plate by electroerosive cutting of grooves in the end portion of the plate with projections therebetween shaped to match the holes 5 between the filaments 3 and 4, and electroerosive broaching, using this tool electrode, of longitudinal rows of holes 5 in a hollow cylindrical blank rotatably displaced, after each pass of the tool electrode, through an angle equal to twice the angular distance between the center lines of adjacent longitudinal rows of holes 5 in the cathode. The grooves are cut out in the plate so that after each pass of the tool electrode, there are produced in the blank: full holes 5 of one longitudinal row, hole-halves 5' of two rows adjoining thereto, and corresponding sections of the filaments 3 and 4 between these holes 5.
