Transmission Lines as Frequency Modulators

A method of producing frequency modulation is described wherein an eighth-wave radio-frequency transmission line is used as a modulation device. One end of the transmission line serves as a part of the tank circuit of the oscillator while at the other end is placed a variable resistance, such as a vacuum tube. Absolute linearity may be obtained with negligible amplitude modulation. A brief description of different types of transmission lines used is also given.