GB1066596A - Improvements relating to variable electrical delay lines - Google Patents

Abstract

1,066,596. Variable delay lines. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. April 27, 1964 [April 25, 1963], No. 17380/64. Heading H3U. A variable delay line comprises a coil wound on an axis, and a conductor extending axially thereof but angularly adjustable about an axis offset from the axis of the coil although parallel thereto; the distance of the conductor from the coil can thus be altered to vary the capacitance of the delay line. In Fig. 1 the coil 2 is wound on a former 1 which carries an axial strip of conducting material 8. An insulated support 6 carries a similar conductive strip 7 whose distance from the strip 8 can be altered by rotating the support 6. The members 1 and 6 can be glass or paper tubes carrying thin metal sheets, which are preferably divided into axially parallel strips to reduce eddy current losses. The member 6 can be outside the coil. The absolute delay time can be reduced by omitting the conductive material 8. Additional variation can be obtained by axial movement of the member 6 if the strip 7 does not extend the full length of the coil. The eccentricity of the member 6 can be produced by the insertion of a strip of foam rubber on one side (Fig. 3, not shown). In use, the line is fed from a generator through a, resistance equal to its characteristic impedance, and similarly terminated at its far end (Fig. 2, not shown). For use in the line circuits of a PAL colour television receiver, the line is connected in series with a fixed delay line whose delay time is slightly less than that of one scanning line.