A point-contact transistor VHF FM transmitter

In extending the upper frequency of operation of point-contact transistors to the VHF region, the device development was paralleled by an investigation of CW oscillator circuitry. This was done because a CW oscillator is a self-contained system capable of accurate analysis. It is therefore a highly suitable tool for studying the electrical characteristics of the transistor in the VHF region. The concept of frequency modulation by alpha cutoff frequency shift originated as a result of this CW oscillator circuitry study. An experimental FM transmitter operating in the commercial FM band was built to demonstrate both this frequency modulation technique and also CW oscillation in the alpha frequency cutoff region. It is the purpose of this paper to describe this transmitter and to show how a single transistor can simultaneously perform all the functions required of a complete FM transmitter.